Arithmetic evaluation: Difference between revisions
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Line 1:
{{task}}Create a program which parses and evaluates arithmetic expressions.
* An [[wp:Abstract_syntax_tree|abstract-syntax tree]] (AST) for the expression must be created from parsing the input.
* The AST must be used in evaluation, also, so the input may not be directly evaluated (e.g. by calling eval or a similar language feature.)
Line 8:
* The four symbols + - * / must be supported as binary operators with conventional precedence rules.
* Precedence-control parentheses must also be supported.
<br>
;Note:
For those who don't remember, mathematical precedence is as follows:
* Parentheses
* Multiplication/Division (left to right)
* Addition/Subtraction (left to right)
<br>
;C.f:
* [[24 game Player]].
* [[Parsing/RPN calculator algorithm]].
* [[Parsing/RPN to infix conversion]].
<br><br>
=={{header|11l}}==
[[wp:Pratt parser|Pratt parser]]
<syntaxhighlight lang="11l">T Symbol
String id
Int lbp
Int nud_bp
Int led_bp
(ASTNode -> ASTNode) nud
((ASTNode, ASTNode) -> ASTNode) led
F set_nud_bp(nud_bp, nud)
.nud_bp = nud_bp
.nud = nud
F set_led_bp(led_bp, led)
.led_bp = led_bp
.led = led
T ASTNode
Symbol& symbol
Int value
ASTNode? first_child
ASTNode? second_child
F eval()
S .symbol.id
‘(number)’
R .value
‘+’
R .first_child.eval() + .second_child.eval()
‘-’
R I .second_child == N {-.first_child.eval()} E .first_child.eval() - .second_child.eval()
‘*’
R .first_child.eval() * .second_child.eval()
‘/’
R .first_child.eval() / .second_child.eval()
‘(’
R .first_child.eval()
E
assert(0B)
R 0
[String = Symbol] symbol_table
[String] tokens
V tokeni = -1
ASTNode token_node
F advance(sid = ‘’)
I sid != ‘’
assert(:token_node.symbol.id == sid)
:tokeni++
:token_node = ASTNode()
I :tokeni == :tokens.len
:token_node.symbol = :symbol_table[‘(end)’]
R
V token = :tokens[:tokeni]
:token_node.symbol = :symbol_table[I token.is_digit() {‘(number)’} E token]
I token.is_digit()
:token_node.value = Int(token)
F expression(rbp = 0)
ASTNode t = move(:token_node)
advance()
V left = t.symbol.nud(move(t))
L rbp < :token_node.symbol.lbp
t = move(:token_node)
advance()
left = t.symbol.led(t, move(left))
R left
F parse(expr_str) -> ASTNode
:tokens = re:‘\s*(\d+|.)’.find_strings(expr_str)
:tokeni = -1
advance()
R expression()
F symbol(id, bp = 0) -> &
I !(id C :symbol_table)
V s = Symbol()
s.id = id
s.lbp = bp
:symbol_table[id] = s
R :symbol_table[id]
F infix(id, bp)
F led(ASTNode self, ASTNode left)
self.first_child = left
self.second_child = expression(self.symbol.led_bp)
R self
symbol(id, bp).set_led_bp(bp, led)
F prefix(id, bp)
F nud(ASTNode self)
self.first_child = expression(self.symbol.nud_bp)
R self
symbol(id).set_nud_bp(bp, nud)
infix(‘+’, 1)
infix(‘-’, 1)
infix(‘*’, 2)
infix(‘/’, 2)
prefix(‘-’, 3)
F nud(ASTNode self)
R self
symbol(‘(number)’).nud = nud
symbol(‘(end)’)
F nud_parens(ASTNode self)
V expr = expression()
advance(‘)’)
R expr
symbol(‘(’).nud = nud_parens
symbol(‘)’)
L(expr_str) [‘-2 / 2 + 4 + 3 * 2’,
‘2 * (3 + (4 * 5 + (6 * 7) * 8) - 9) * 10’]
print(expr_str‘ = ’parse(expr_str).eval())</syntaxhighlight>
{{out}}
<pre>
-2 / 2 + 4 + 3 * 2 = 9
2 * (3 + (4 * 5 + (6 * 7) * 8) - 9) * 10 = 7000
</pre>
=={{header|Ada}}==
Line 21 ⟶ 151:
=={{header|ALGOL 68}}==
{{works with|ALGOL 68|Revision 1 - no extensions to language used}}
{{works with|ALGOL 68G|Any - tested with release [http://sourceforge.net/projects/algol68/files/algol68g/algol68g-1.18.0/algol68g-1.18.0-9h.tiny.el5.centos.fc11.i386.rpm/download 1.18.0-9h.tiny]}}
{{wont work with|ELLA ALGOL 68|Any (with appropriate job cards) - tested with release [http://sourceforge.net/projects/algol68/files/algol68toc/algol68toc-1.8.8d/algol68toc-1.8-8d.fc9.i386.rpm/download 1.8-8d] - A68RS has not implemented forward declarations}}
<syntaxhighlight lang="algol68">INT base=10;
MODE FIXED = LONG REAL; # numbers in the format 9,999.999 #
Line 156 ⟶ 289:
);
test:(
EVAL build ast("1+1+(1+(1+(1+(1+(1+(1+(1+(1+(1+(1+(1+(1+(1+1/15)/14)/13)/12)/11)/10)/9)/8)/7)/6)/5)/4)/3)/2")));
SKIP EXIT
index error:
printf(("Stack over flow"))
)</syntaxhighlight>
{{out}}
<pre>
euler's number is about: 2.71828182845899446428546958
</pre>
=={{header|Amazing Hopper}}==
Hopper no soporta números muy grandes, por decisión de diseño, pero es posible realizar una aproximación aplicando el Límite de Euler para calcular un factorial de un número real, hecho para uno de los ejemplos.
<syntaxhighlight lang="c">
#include <basico.h>
#proto verificarconstante(_X_)
#synon _verificarconstante se verifica constante en
#proto verificarfunción(_X_)
#synon _verificarfunción se verifica función en
algoritmo
pila de trabajo 50
números (largo de datos)
decimales '13'
preparar datos(DATA_EXPRESIONES)
obtener tamaño de datos, guardar en 'largo de datos'
imprimir ("Negativos deben escribirse entre parentesis\nEjemplo: (-3)\n\n")
iterar
matrices ( pila, p, q )
cadenas (expresión)
obtener dato, copiar en 'expresión'
ir a subs ( convierte a matriz --> convierte a notación polaca \
--> evalúa expresión --> despliega resultados )
--largo de datos
mientras ' largo de datos'
terminar
subrutinas
convierte a matriz:
argumentos 'expr'
transformar(" ","",\
transformar("(-","(0-",expr)), guardar en 'expr'
l=0, #( l = len(expr) )
v="", num="", cte=""
para cada caracter (v, expr, l)
cuando ( #(typechar(v,"digit") || v==".")){
num, v, concatenar esto, guardar en 'num'
continuar
}
cuando ( #(typechar(v,"alpha") )){
cte, v, concatenar esto, guardar en 'cte'
continuar
}
cuando (num) {num, meter en 'q', num=""}
cuando (cte) {cte, meter en 'q', cte=""}
v, meter en 'q'
siguiente
cuando (num) {num, meter en 'q'}
cuando (cte) {cte, meter en 'q'}
"(", meter en 'pila'
")", meter en 'q'
// imprimir( "Q = {", q, "}\n" )
retornar
convierte a notación polaca:
l="", m=""
iterar mientras '#( not(is empty(q)) )'
sw = 1
///imprimir("P = ",p,"\nQ = ",q,"\nPILA = ",pila,NL)
extraer tope 'q' para 'l'
// ¿es un operando?
cuando ' #(not( occurs(l,"+-*^/)(%") )) ' {
si ' se verifica constante en (l) '
meter en 'p'
sino si ' se verifica función en (l) '
l, meter en 'pila'
sino
#( number(l) ), meter en 'p'
fin si
continuar
}
// es un simbolo...
// es un parentesis izquierdo?
cuando ( #( l=="(" ) ) {
l, meter en 'pila'
continuar
}
// es un operador?
cuando ( #( occurs(l,"+-*^/%")) ) {
iterar mientras ' sw '
extraer cabeza 'pila' para 'm'
cuando ' #(m=="(") '{
m,l, apilar en 'pila'
sw=0, continuar
}
cuando ' #(l=="^") '{
si ' #(m=="^") '
//m,l, apilar en 'p'
m, meter en 'p'
sino
m,l, apilar en 'pila'
sw=0
fin si, continuar
}
cuando ' #(l=="*") ' {
si ' #(occurs(m, "^*/%"))'
m, meter en 'p'
sino
m,l, apilar en 'pila'
sw=0
fin si, continuar
}
//cuando ' #(l=="/") ' {
// decisión de diseño para resto módulo
cuando ' #( occurs(l,"/%")) ' {
si ' #( occurs(m, "/^*%") )'
m, meter en 'p'
l, meter en 'pila'
sino
m,l, apilar en 'pila'
fin si
sw=0, continuar
}
cuando ' #(occurs(l, "+-"))' {
m, meter en 'p'
// saber si ya hay un símbolo "-" en pila
tmp=0
tope(pila), mover a 'tmp'
si ' #( occurs(tmp,"+-") ) '
extraer cabeza (pila)
meter en 'p'
fin si
l, meter en 'pila'
sw=0
}
reiterar
si ' #( length (pila)==0 ) '
"(", meter en 'pila'
fin si
continuar
}
// es un paréntesis derecho?
cuando( #(l==")") ) {
extraer cabeza (pila) para 'm'
iterar mientras ' #( m<>"(") '
m, meter en 'p'
extraer cabeza 'pila' para 'm'
reiterar
}
reiterar
retornar
evalúa expresión:
l = " ", a=0, b=0
iterar mientras ' #( not(is empty(p)) ) '
extraer tope 'p' para 'l'
si ' es numérico (l) '
l, meter en 'pila'
sino
si ' se verifica función en (l) '
extraer cabeza 'pila' para 'b'
seleccionar 'l'
caso ("sqrt"){ #(sqrt(b)), salir }
caso ("log"){ #(log10(b)), salir }
caso ("ln"){ #(log(b)), salir }
caso ("fact"){
si ' #(int(b)<>b) ' // límite de Euler
x=0,i=2, xb=1,
// aproximación muy burda.
#basic{
b = b + 1
x = fact(163)*(163^b)
xb = b*(b+1)
while( i<=163 )
xb = xb * ( i+b )
i+=1
wend
x/xb
}
sino // normal
#(fact(b))
fin si
salir
}
fin seleccionar
sino
extraer cabeza 'pila' para 'b'
extraer cabeza 'pila' para 'a'
seleccionar 'l'
caso ("+"){ #(a+b), salir }
caso ("-"){ #(a-b), salir }
caso ("*"){ #(a*b), salir }
// n/0 = inf, no es necesario detectar esto:
caso ("/"){ #(a/b), salir }
caso ("^"){ #(a^b), salir }
caso ("%"){ #(a%b), salir }
fin seleccionar
fin si
meter en 'pila'
fin si
reiterar
retornar
despliega resultados:
imprimir(expresión," : ", \
tomar si( #(length(pila)==1),pila, \
#(utf8("expresión mal formada!"))), NL)
retornar
verificar constante (x)
seleccionar 'x'
caso ("pi"){ M_PI, 1, salir }
caso ("e") { M_E, 1, salir }
caso ("phi"){ M_PHI, 1, salir }
// etcétera...
caso por defecto{ 0, salir }
fin seleccionar
retornar
verificar función (f)
seleccionar 'f'
caso ("sqrt"){ '1', salir }
caso ("log"){ '1', salir }
caso ("ln"){ '1', salir }
caso ("fact"){ '1', salir }
// etcétera...
caso por defecto { '0', salir }
fin seleccionar
retornar
DATA_EXPRESIONES:
datos("((30+4.5) * ( 7 / 9.67 )+3)-4*(-1)") //31.9741468459168
datos("1 + 2*(3 - 2*(3 - 2)*((2 - 4)*5 - 22/(7 + 2*(3 - 1)) - 1)) + 1") // 60!
datos("(1 - 5) * 2 / (20 + 1)") // -8/21
datos("(3 * 2) - (1 + 2) / (4") // error!
datos("(3 * 2) a - (1 + 2) / 4") // error!
datos("(6^2)*2/3") //24
datos("6^2*2/3") //24
datos("(6^2)*2/0") //inf
datos("2 * (3 + ((5) / (7 - 11)))") // 3.5
datos("1 - 5 * 2 / 20 + 1") //1,5!
datos ("(1 + 2) * 10 / 100") // 0.3
datos("1+3.78") // 4.78
datos("2.5 * 2 + 2 * pi") // 11.28
datos("1 + 2 * (3 + (4 * 5 + 6 * 7 * 8) - 9) / 10") // 71
datos("1+1+(1+(1+(1+(1+(1+(1+(1+(1+(1+(1+(1+(1+(1+1/15)/14)/13)/12)/11)/10)/9)/8)/7)/6)/5)/4)/3)/2") // 2.7182818284589946
datos("((11+15)*15)*2-(3)*4*1") // 768
datos(" 2*(-3)-(-4)+(-0.25)") //-2.25
datos(" 2-25 % 3+1") // 2
datos(" 2-(25 % 3)+1") // 2
datos(" (2-25) % (3+1)") // -3
datos(" 2- 25 % 3 % 2") // 1
datos(" 2- 25 / 3 % 2") // 1.66666
datos(" 2- ((25 / 3) % 2)") // 1.66666
datos(" 2- 25 / 3 / 2") // 2.166666
datos(" (-23) %3") // -2
datos(" (6*pi-1)^0.5-e") // 1,506591651...
datos("2^2^3^4")
datos("(4-2*phi)*pi") // 2,3999632297286
datos("( (1+sqrt(5))/2)^(2/pi)") // 1.3584562741830
datos("1-(1+ln(ln(2)))/ln(2)") // 0.0860713320559
datos("pi / (2 * ln(1+sqrt(2)))") // 1,7822139781 ....
datos("( (e^(pi/8)) * sqrt(pi)) /(4 * (2^(3/4)) * (fact(1/4))^2) ") //0,47494 93799...
datos(" fact(1/2)") // 0.906402477055...
back
</syntaxhighlight>
{{out}}
<pre>
Negativos deben escribirse entre parentesis
Ejemplo: (-3)
((30+4.5) * ( 7 / 9.67 )+3)-4*(-1) : 31.9741468459168
1 + 2*(3 - 2*(3 - 2)*((2 - 4)*5 - 22/(7 + 2*(3 - 1)) - 1)) + 1 : 60.0000000000000
(1 - 5) * 2 / (20 + 1) : -0.3809523809524
(3 * 2) - (1 + 2) / (4 : expresión mal formada!
(3 * 2) a - (1 + 2) / 4 : expresión mal formada!
(6^2)*2/3 : 24.0000000000000
6^2*2/3 : 24.0000000000000
(6^2)*2/0 : inf
2 * (3 + ((5) / (7 - 11))) : 3.5000000000000
1 - 5 * 2 / 20 + 1 : 1.5000000000000
(1 + 2) * 10 / 100 : 0.3000000000000
1+3.78 : 4.7800000000000
2.5 * 2 + 2 * pi : 11.2831853071796
1 + 2 * (3 + (4 * 5 + 6 * 7 * 8) - 9) / 10 : 71.0000000000000
1+1+(1+(1+(1+(1+(1+(1+(1+(1+(1+(1+(1+(1+(1+1/15)/14)/13)/12)/11)/10)/9)/8)/7)/6)/5)/4)/3)/2 : 2.7182818284590
((11+15)*15)*2-(3)*4*1 : 768.0000000000000
2*(-3)-(-4)+(-0.25) : -2.2500000000000
2-25 % 3+1 : 2.0000000000000
2-(25 % 3)+1 : 2.0000000000000
(2-25) % (3+1) : -3.0000000000000
2- 25 % 3 % 2 : 1.0000000000000
2- 25 / 3 % 2 : 1.6666666666667
2- ((25 / 3) % 2) : 1.6666666666667
2- 25 / 3 / 2 : -2.1666666666667
(-23) %3 : -2.0000000000000
(6*pi-1)^0.5-e : 1.5065916514856
2^2^3^4 : 16777216.0000000000000
(4-2*phi)*pi : 2.3999632297286
( (1+sqrt(5))/2)^(2/pi) : 1.3584562741830
1-(1+ln(ln(2)))/ln(2) : 0.0860713320559
pi / (2 * ln(1+sqrt(2))) : 1.7822139781915
( (e^(pi/8)) * sqrt(pi)) /(4 * (2^(3/4)) * (fact(1/4))^2) : 0.4831858606252
fact(1/2) : 0.8761319893678
</pre>
=={{header|AutoHotkey}}==
{{works with|AutoHotkey_L}}
<syntaxhighlight lang="autohotkey">/*
hand coded recursive descent parser
expr : term ( ( PLUS | MINUS ) term )* ;
term : factor ( ( MULT | DIV ) factor )* ;
factor : NUMBER | '(' expr ')';
*/
calcLexer := makeCalcLexer()
string := "((3+4)*(7*9)+3)+4"
tokens := tokenize(string, calcLexer)
msgbox % printTokens(tokens)
ast := expr()
msgbox % printTree(ast)
msgbox % expression := evalTree(ast)
filedelete expression.ahk
fileappend, % "msgbox % " expression, expression.ahk
run, expression.ahk
return
expr()
{
global tokens
ast := object(1, "expr")
if node := term()
ast._Insert(node)
loop
{
if peek("PLUS") or peek("MINUS")
{
op := getsym()
newop := object(1, op.type, 2, op.value)
node := term()
ast._Insert(newop)
ast._Insert(node)
}
Else
Break
}
return ast
}
term()
{
global tokens
tree := object(1, "term")
if node := factor()
tree._Insert(node)
loop
{
if peek("MULT") or peek("DIV")
{
op := getsym()
newop := object(1, op.type, 2, op.value)
node := factor()
tree._Insert(newop)
tree._Insert(node)
}
else
Break
}
return tree
}
factor()
{
global tokens
if peek("NUMBER")
{
token := getsym()
tree := object(1, token.type, 2, token.value)
return tree
}
else if peek("OPEN")
{
getsym()
tree := expr()
if peek("CLOSE")
{
getsym()
return tree
}
else
error("miss closing parentheses ")
}
else
error("no factor found")
}
peek(type, n=1)
{
global tokens
if (tokens[n, "type"] == type)
return 1
}
getsym(n=1)
{
global tokens
return token := tokens._Remove(n)
}
error(msg)
{
global tokens
msgbox % msg " at:`n" printToken(tokens[1])
}
printTree(ast)
{
if !ast
return
n := 0
loop
{
n += 1
if !node := ast[n]
break
if !isobject(node)
treeString .= node
else
treeString .= printTree(node)
}
return ("(" treeString ")" )
}
evalTree(ast)
{
if !ast
return
n := 1
loop
{
n += 1
if !node := ast[n]
break
if !isobject(node)
treeString .= node
else
treeString .= evalTree(node)
}
if (n == 3)
return treeString
return ("(" treeString ")" )
}
#include calclex.ahk</syntaxhighlight>
calclex.ahk<syntaxhighlight lang="autohotkey">tokenize(string, lexer)
{
stringo := string ; store original string
locationInString := 1
size := strlen(string)
tokens := object()
start:
Enum := Lexer._NewEnum()
While Enum[type, value] ; loop through regular expression lexing rules
{
if (1 == regexmatch(string, value, tokenValue))
{
token := object()
token.pos := locationInString
token.value := tokenValue
token.length := strlen(tokenValue)
token.type := type
tokens._Insert(token)
locationInString += token.length
string := substr(string, token.length + 1)
goto start
}
continue
}
if (locationInString < size)
msgbox % "unrecognized token at " substr(stringo, locationInstring)
return tokens
}
makeCalcLexer()
{
calcLexer := object()
PLUS := "\+"
MINUS := "-"
MULT := "\*"
DIV := "/"
OPEN := "\("
CLOSE := "\)"
NUMBER := "\d+"
WS := "[ \t\n]+"
END := "\."
RULES := "PLUS,MINUS,MULT,DIV,OPEN,CLOSE,NUMBER,WS,END"
loop, parse, rules, `,
{
type := A_LoopField
value := %A_LoopField%
calcLexer._Insert(type, value)
}
return calcLexer
}
printTokens(tokens)
{
loop % tokens._MaxIndex()
{
tokenString .= printToken(tokens[A_Index]) "`n`n"
}
return tokenString
}
printToken(token)
{
string := "pos= " token.pos "`nvalue= " token.value "`ntype= " token.type
return string
}</syntaxhighlight>
=={{header|BBC BASIC}}==
{{works with|BBC BASIC for Windows}}
<syntaxhighlight lang="bbcbasic"> Expr$ = "1 + 2 * (3 + (4 * 5 + 6 * 7 * 8) - 9) / 10"
PRINT "Input = " Expr$
AST$ = FNast(Expr$)
PRINT "AST = " AST$
PRINT "Value = " ;EVAL(AST$)
END
DEF FNast(RETURN in$)
LOCAL ast$, oper$
REPEAT
ast$ += FNast1(in$)
WHILE ASC(in$)=32 in$ = MID$(in$,2) : ENDWHILE
oper$ = LEFT$(in$,1)
IF oper$="+" OR oper$="-" THEN
ast$ += oper$
in$ = MID$(in$,2)
ELSE
EXIT REPEAT
ENDIF
UNTIL FALSE
= "(" + ast$ + ")"
DEF FNast1(RETURN in$)
LOCAL ast$, oper$
REPEAT
ast$ += FNast2(in$)
WHILE ASC(in$)=32 in$ = MID$(in$,2) : ENDWHILE
oper$ = LEFT$(in$,1)
IF oper$="*" OR oper$="/" THEN
ast$ += oper$
in$ = MID$(in$,2)
ELSE
EXIT REPEAT
ENDIF
UNTIL FALSE
= "(" + ast$ + ")"
DEF FNast2(RETURN in$)
LOCAL ast$
WHILE ASC(in$)=32 in$ = MID$(in$,2) : ENDWHILE
IF ASC(in$)<>40 THEN = FNnumber(in$)
in$ = MID$(in$,2)
ast$ = FNast(in$)
in$ = MID$(in$,2)
= ast$
DEF FNnumber(RETURN in$)
LOCAL ch$, num$
REPEAT
ch$ = LEFT$(in$,1)
IF INSTR("0123456789.", ch$) THEN
num$ += ch$
in$ = MID$(in$,2)
ELSE
EXIT REPEAT
ENDIF
UNTIL FALSE
= num$</syntaxhighlight>
{{out}}
<pre>
Input = 1 + 2 * (3 + (4 * 5 + 6 * 7 * 8) - 9) / 10
AST = ((1)+(2*((3)+(((4*5)+(6*7*8)))-(9))/10))
Value = 71
</pre>
=={{header|C}}==
Line 173 ⟶ 922:
=={{header|C++}}==
{{works with|g++|clang++}}
This version does not require boost.
It works by:
- converting infix strings to postfix strings using shunting yard algorithm
- converting postfix expression to list of tokens
- builds AST bottom up from list of tokens
- evaluates expression tree by performing postorder traversal.
<syntaxhighlight lang="cpp">
#include <iostream>
#include <vector>
#include <cmath>
using namespace std;
template <class T>
class stack {
private:
vector<T> st;
T sentinel;
public:
stack() { sentinel = T(); }
bool empty() { return st.empty(); }
void push(T info) { st.push_back(info); }
T& top() {
if (!st.empty()) {
return st.back();
}
return sentinel;
}
T pop() {
T ret = top();
if (!st.empty()) st.pop_back();
return ret;
}
};
//determine associativity of operator, returns true if left, false if right
bool leftAssociate(char c) {
switch (c) {
case '^': return false;
case '*': return true;
case '/': return true;
case '%': return true;
case '+': return true;
case '-': return true;
default:
break;
}
return false;
}
//determins precedence level of operator
int precedence(char c) {
switch (c) {
case '^': return 7;
case '*': return 5;
case '/': return 5;
case '%': return 5;
case '+': return 3;
case '-': return 3;
default:
break;
}
return 0;
}
//converts infix expression string to postfix expression string
string shuntingYard(string expr) {
stack<char> ops;
string output;
for (char c : expr) {
if (c == '(') {
ops.push(c);
} else if (c == '+' || c == '-' || c == '*' || c == '/' || c == '^' || c == '%') {
if (precedence(c) < precedence(ops.top()) ||
(precedence(c) == precedence(ops.top()) && leftAssociate(c))) {
output.push_back(' ');
output.push_back(ops.pop());
output.push_back(' ');
ops.push(c);
} else {
ops.push(c);
output.push_back(' ');
}
} else if (c == ')') {
while (!ops.empty()) {
if (ops.top() != '(') {
output.push_back(ops.pop());
} else {
ops.pop();
break;
}
}
} else {
output.push_back(c);
}
}
while (!ops.empty())
if (ops.top() != '(')
output.push_back(ops.pop());
else ops.pop();
cout<<"Postfix: "<<output<<endl;
return output;
}
struct Token {
int type;
union {
double num;
char op;
};
Token(double n) : type(0), num(n) { }
Token(char c) : type(1), op(c) { }
};
//converts postfix expression string to vector of tokens
vector<Token> lex(string pfExpr) {
vector<Token> tokens;
for (int i = 0; i < pfExpr.size(); i++) {
char c = pfExpr[i];
if (isdigit(c)) {
string num;
do {
num.push_back(c);
c = pfExpr[++i];
} while (i < pfExpr.size() && isdigit(c));
tokens.push_back(Token(stof(num)));
i--;
continue;
} else if (c == '+' || c == '-' || c == '*' || c == '/' || c == '^' || c == '%') {
tokens.push_back(Token(c));
}
}
return tokens;
}
//structure used for nodes of expression tree
struct node {
Token token;
node* left;
node* right;
node(Token tok) : token(tok), left(nullptr), right(nullptr) { }
};
//builds expression tree from vector of tokens
node* buildTree(vector<Token> tokens) {
cout<<"Building Expression Tree: "<<endl;
stack<node*> sf;
for (int i = 0; i < tokens.size(); i++) {
Token c = tokens[i];
if (c.type == 1) {
node* x = new node(c);
x->right = sf.pop();
x->left = sf.pop();
sf.push(x);
cout<<"Push Operator Node: "<<sf.top()->token.op<<endl;
} else
if (c.type == 0) {
sf.push(new node(c));
cout<<"Push Value Node: "<<c.num<<endl;
continue;
}
}
return sf.top();
}
//evaluate expression tree, while anotating steps being performed.
int recd = 0;
double eval(node* x) {
recd++;
if (x == nullptr) {
recd--;
return 0;
}
if (x->token.type == 0) {
for (int i = 0; i < recd; i++) cout<<" ";
cout<<"Value Node: "<<x->token.num<<endl;
recd--;
return x->token.num;
}
if (x->token.type == 1) {
for (int i = 0; i < recd; i++) cout<<" ";
cout<<"Operator Node: "<<x->token.op<<endl;
double lhs = eval(x->left);
double rhs = eval(x->right);
for (int i = 0; i < recd; i++) cout<<" ";
cout<<lhs<<" "<<x->token.op<<" "<<rhs<<endl;
recd--;
switch (x->token.op) {
case '^': return pow(lhs, rhs);
case '*': return lhs*rhs;
case '/':
if (rhs == 0) {
cout<<"Error: divide by zero."<<endl;
} else
return lhs/rhs;
case '%':
return (int)lhs % (int)rhs;
case '+': return lhs+rhs;
case '-': return lhs-rhs;
default:
break;
}
}
return 0;
}
int main() {
string expr = "3 + 4 * 2 / ( 1 - 5 ) ^ 2 ^ 3";
cout<<eval(buildTree(lex(shuntingYard(expr))))<<endl;
return 0;
}
Output:
Postfix: 3 4 2 * 1 5 - 2 3^^/+
Building Expression Tree:
Push Value Node: 3
Push Value Node: 4
Push Value Node: 2
Push Operator Node: *
Push Value Node: 1
Push Value Node: 5
Push Operator Node: -
Push Value Node: 2
Push Value Node: 3
Push Operator Node: ^
Push Operator Node: ^
Push Operator Node: /
Push Operator Node: +
Operator Node: +
Value Node: 3
Operator Node: /
Operator Node: *
Value Node: 4
Value Node: 2
4 * 2
Operator Node: ^
Operator Node: -
Value Node: 1
Value Node: 5
1 - 5
Operator Node: ^
Value Node: 2
Value Node: 3
2 ^ 3
-4 ^ 8
8 / 65536
3 + 0.00012207
3.00012
</syntaxhighlight>
{{Works with|g++|4.1.2 20061115 (prerelease) (SUSE Linux)}}
{{libheader|Boost.Spirit
<
#include <boost/spirit/tree/ast.hpp>
#include <string>
Line 291 ⟶ 1,291:
}
}
};</
=={{header|Clojure}}==
<syntaxhighlight lang="clojure">(def precedence '{* 0, / 0
+ 1, - 1})
(defn order-ops
"((A x B) y C) or (A x (B y C)) depending on precedence of x and y"
[[A x B y C & more]]
(let [ret (if (<= (precedence x)
(precedence y))
(list (list A x B) y C)
(list A x (list B y C)))]
(if more
(recur (concat ret more))
ret)))
(defn add-parens
"Tree walk to add parens. All lists are length 3 afterwards."
[s]
(clojure.walk/postwalk
#(if (seq? %)
(let [c (count %)]
(cond (even? c) (throw (Exception. "Must be an odd number of forms"))
(= c 1) (first %)
(= c 3) %
(>= c 5) (order-ops %)))
%)
s))
(defn make-ast
"Parse a string into a list of numbers, ops, and lists"
[s]
(-> (format "'(%s)" s)
(.replaceAll , "([*+-/])" " $1 ")
load-string
add-parens))
(def ops {'* *
'+ +
'- -
'/ /})
(def eval-ast
(partial clojure.walk/postwalk
#(if (seq? %)
(let [[a o b] %]
((ops o) a b))
%)))
(defn evaluate [s]
"Parse and evaluate an infix arithmetic expression"
(eval-ast (make-ast s)))
user> (evaluate "1 + 2*(3 - 2*(3 - 2)*((2 - 4)*5 - 22/(7 + 2*(3 - 1)) - 1)) + 1")
60</syntaxhighlight>
=={{header|Common Lisp}}==
The following code processes the data in a pipeline of steps which are combined in the <code>evaluate</code> function.
First, the string is converted into a sequence of tokens, represented as a list. Operator tokens are represented directly by the corresponding Lisp symbols, and the integer terms are represented by Lisp integer objects. The symbols <code>:lparen</code> and <code>:rparen</code> represent the the parentheses. So for instance the input
<code>"1*(3+2)"</code> tokenizes as <code>(1 * :lparen 3 + 2 :rparen)</code>.
Next, that sequence of tokens is then transformed by eliminating the parentheses. Subsequences of the form <code>:lparen ... :rparen</code> with a sublist containing the tokens between the <code>:lparen</code> and <code>:rparen</code>. The sequence now has an intermediate tree structure, in which parenthesized fragments like <code>1 + 2 * 3 + 4 / 9</code> still remain flat.
At this point, another processing stage parses the operator precedence, and fully parenthesizes fragments, turning <code>(1 + 2 / 3 + 5)</code> into <code>(1 + (2 / 3) + 5)</code>. The result is a Lisp-ified infix representation.
Finally, this infix representation can be easily converted to prefix, forming the final AST which is a Lisp expression.
(Lisp expressions '''are''' abstract syntax trees!) This representation evaluates directly with <code>eval</code>.
This implementation can read integers, and produce integral and rational values.
<
(labels ((whitespace-p (char)
(find char #(#\space #\newline #\return #\tab)))
Line 308 ⟶ 1,375:
finally (return (parse-integer (coerce digits 'string))))))
(consume-whitespace)
(let* ((c (peek-char nil stream nil nil)))
(
(#\(
(
(
(
(unless (or (null
(read-char stream))
(defun group-parentheses (tokens &optional (delimited nil))
Line 338 ⟶ 1,403:
(let ((token (pop tokens)))
(case token
(multiple-value-bind (group remaining-tokens)
(group-parentheses tokens t)
(setf new-tokens (cons group new-tokens)
tokens remaining-tokens)))
(if (not delimited)
(cerror "Ignore it." "Unexpected right parenthesis.")
Line 352 ⟶ 1,417:
(defun group-operations (expression)
(flet ((gop (exp) (group-operations exp)))
(if (
expression
(destructuring-bind (a &optional op1 b op2 c &rest others)
expression
(unless (member op1 '(+ - * / nil))
(error "syntax error: in expr ~a expecting operator, not ~a"
expression op1))
(unless (member op2 '(+ - * / nil))
(error "syntax error: in expr ~a expecting operator, not ~a"
expression op2))
(cond
((not
((not
(t (let ((a (gop
(if (and (
(gop `(,a
(gop `(
(defun
(if (integerp expression)
(destructuring-bind (a op b) expression
`(,op ,(infix-to-prefix a) ,(infix-to-prefix b)))))
(defun evaluate (string)
(with-input-from-string (in string)
(
(
(group-
collect token)))))))</syntaxhighlight>
Examples
Line 429 ⟶ 1,492:
=={{header|D}}==
<syntaxhighlight lang="d">import std.stdio, std.string, std.ascii, std.conv, std.array,
struct Stack(T) {
T[] data;
alias data this;
void push(T top) pure nothrow @safe { data ~= top; }
T pop(bool discard = true)() pure @nogc @safe {
immutable static exc = new immutable(Exception)("Stack Empty");
if (data.empty)
throw exc;
auto top = data[$ - 1];
static if (discard)
data.popBack;
return top;
}
}
enum Type { Num, OBkt, CBkt, Add, Sub, Mul, Div }
abstract class Visitor { void visit(XP e) pure @safe; }
final class XP {
immutable Type type
immutable string str
immutable int pos
XP LHS, RHS
this(string s=")",
auto localType = Type.Num;
foreach_reverse (immutable t; [EnumMembers!Type[1 .. $]])
if (opChar[t] == s)
localType = t;
this.type = localType;
}
override int opCmp(Object other) pure @safe {
auto rhs = cast(XP)other;
enforce(rhs !is null);
return opPrec[type] - opPrec[rhs.type];
}
void accept(Visitor v) pure @safe { v.visit(this); }
}
final class AST {
XP root
Stack!XP
string xpr, token
int xpHead, xpTail
void joinXP(XP x)
x.RHS = num.pop;
x.LHS = num.pop;
num.push(x);
}
string nextToken() pure @safe {
while (xpHead < xpr.length && xpr[xpHead] == ' ')
xpHead++
xpTail = xpHead
if (xpHead < xpr.length) {
token = xpr[xpTail .. xpTail + 1]
switch (token) {
case "(", ")", "+", "-", "*", "/": //
xpTail++
return token
default: //
if
while (xpTail < xpr.length &&
xpTail++
return xpr[xpHead .. xpTail]
} //
} //
}
if (xpTail < xpr.length)
throw new Exception("Invalid Char <" ~ xpr[xpTail] ~ ">")
return null
} //
AST parse(in string s) /*@safe*/ {
bool expectingOP
xpr = s
try {
xpHead = xpTail = 0
num = opr = null
root = null
opr.push(new XP)
while ((token = nextToken) !is null) {
XP tokenXP = new XP(token, xpHead)
if (expectingOP) {
switch (token) {
case ")":
while (opr.pop
joinXP(opr.pop
opr.pop
expectingOP = true
case "+",
while (tokenXP <=
joinXP(opr.
expectingOP = false;
break;
default:
throw new Exception("Expecting Operator or ), not <"
~ token ~ ">");
}
} else {
switch (token) {
case "+", "-", "*", "/", ")":
throw new Exception("Expecting Number or (, not <"
~ token ~ ">");
case "(":
opr.push(tokenXP)
expectingOP = false
default: //
expectingOP = true;
}
}
xpHead = xpTail
} //
while (opr.length > 1) //
joinXP(opr.pop
} catch(Exception e)
writefln("%s\n%s\n%s^", e.msg, xpr, " ".replicate(xpHead));
root = null;
}
if (num.length != 1) { // Should be one XP left.
"Parse Error...".writefln;
root = null;
} else {
root = num.pop;
}
return this;
} // End Parse.
} // End class AST.
//
void ins(
pure nothrow @safe {
s.length++;
while (s[l].length < p + v.length + 1)
s[l] ~= " ";
s[l][p .. p + v.length] = v[];
}
final class
int result, level
string
char[][] Tree
static void opCall(AST a) @safe {
if (a && a.root) {
a.root.accept(c)
bool flipflop = false
foreach
immutable c1 = c.Tree[i
if
c.Tree[i - 1][j] = mk;
if (c1 != mk && c1 != ' ' &&
(j == 0 || !isDigit(c.Tree[i][j - 1])))
flipflop = !flipflop;
}
}
foreach (const t; c.Tree)
t.writefln;
writefln("\n%s ==>\n%s = %s", a.xpr, c.resultStr, c.result);
} else
}
// Calc. the value, display AST struct and eval order.
override void visit(XP xp) @safe {
if
resultStr ~= xp.str;
result = xp.str.to!int;
} else {
xp.LHS.accept(this)
immutable int lhs = result
xp.RHS.accept(this)
switch (xp.type) {
case Type.Add: result = lhs + result
case Type.Sub: result = lhs - result
case Type.Mul: result = lhs * result
case Type.Div: result = lhs / result
default: throw new Exception("Invalid type")
}
}
level--
}
}
void main(string[] args) /*@safe*/ {
immutable exp0 = "1 + 2*(3 - 2*(3 - 2)*((2 - 4)*5" ~
immutable exp = (args.length > 1) ? args[1 .. $].join(' ') : exp0;
new AST().parse(exp).CalcVis; // Should be 60.
}</syntaxhighlight>
{{out}}
<pre> ........................................................+.
.+.. 1
1 *...
2 .-..........
3 .......*................................
*... ....................-.
2 .-. ..-... 1
3 2 ...* /...
.-. 5 22 .+..
2 4 7 *...
2 .-.
3 1
1 + 2*(3 - 2*(3 - 2)*((2 - 4)*5 - 22/(7 + 2*(3 - 1)) - 1)) + 1 ==>
((1+(2*(3-((2*(3-2))*((((2-4)*5)-(22/(7+(2*(3-1)))))-1)))))+1) = 60</pre>
=={{header|Delphi}}==
Adaptation of [[Arithmetic Evaluator/Pascal]] for run in Delphi. See [[Arithmetic_evaluation/Delphi]].
=={{header|Dyalect}}==
<syntaxhighlight lang="dyalect">type Expr = Bin(op, Expr left, Expr right) or Literal(Float val)
with Lookup
type Token(val, Char kind) with Lookup
func Token.ToString() => this.val.ToString()
func tokenize(str) {
func isSep(c) =>
c is '+' or '-' or '*' or '/' or ' ' or '\t' or '\n' or '\r' or '(' or ')' or '\0'
var idx = -1
let len = str.Length()
let tokens = []
func next() {
idx += 1
return '\0' when idx >= len
str[idx]
}
while true {
let c = next()
match c {
'\0' => { break },
'+' => tokens.Add(Token(c, '+')),
'-' => tokens.Add(Token(c, '-')),
'*' => tokens.Add(Token(c, '*')),
'/' => tokens.Add(Token(c, '/')),
'(' => tokens.Add(Token(c, '(')),
')' => tokens.Add(Token(c, ')')),
_ => {
let i = idx
while !isSep(next()) { }
idx -= 1
tokens.Add(Token(Float.Parse(str[i..idx]), 'F'))
}
}
}
tokens
}
func parse(tokens) {
var idx = -1
let len = tokens.Length()
let eol = Token(val: nil, kind: 'E')
func pop() {
idx += 1
return eol when idx == len
tokens[idx]
}
func peek() {
let t = pop()
idx -=1
t
}
func expect(kind) {
peek().kind == kind
}
var add_or_sub1
func literal() {
return false when !expect('F')
Expr.Literal(pop().val)
}
func group() {
return false when !expect('(')
pop()
var ret = add_or_sub1()
throw "Invalid group" when !expect(')')
pop()
ret
}
func mul_or_div() {
var fst = group()
fst = literal() when !fst
return fst when !expect('*') && !expect('/')
let op = pop().val
var snd = group()
snd = literal() when !snd
Expr.Bin(op, fst, snd)
}
func add_or_sub() {
let fst = mul_or_div()
return fst when !expect('+') && !expect('-')
let op = pop().val
let snd = mul_or_div()
Expr.Bin(op, fst, snd)
}
add_or_sub1 = add_or_sub
add_or_sub()
}
func exec(ast) {
match ast {
Bin(op, left, right) => {
return exec(left) + exec(right) when op == '+'
return exec(left) - exec(right) when op == '-'
return exec(left) * exec(right) when op == '*'
return exec(left) / exec(right) when op == '/'
},
Literal(value) => value
}
}
func eval(str) {
let tokens = tokenize(str)
let ast = parse(tokens)
exec(ast)
}
print( eval("(1+33.23)*7") )
print( eval("1+33.23*7") )</syntaxhighlight>
{{out}}
<pre>239.60999999999999
233.60999999999999</pre>
=={{header|E}}==
Line 621 ⟶ 1,863:
While the task requirements specify not evaluating using the language's built-in eval, they don't say that you have to write your own ''parser''...
<
def LiteralExpr := <elang:evm.makeLiteralExpr>.asType()
def arithEvaluate(expr :String) {
Line 638 ⟶ 1,880:
return evalAST(ast)
}</
Parentheses are handled by the parser.
<
# value: 3
Line 649 ⟶ 1,891:
? arithEvaluate("(1 + 2 / 2) * (5 + 5)")
# value: 20.0</
=={{header|EasyLang}}==
<syntaxhighlight lang="easylang">
subr nch
if inp_ind > len inp$[]
ch$ = strchar 0
else
ch$ = inp$[inp_ind]
inp_ind += 1
.
ch = strcode ch$
.
#
subr ntok
while ch$ = " "
nch
.
if ch >= 48 and ch <= 58
tok$ = "n"
s$ = ""
while ch >= 48 and ch <= 58 or ch$ = "."
s$ &= ch$
nch
.
tokv = number s$
elif ch = 0
tok$ = "end of text"
else
tok$ = ch$
nch
.
.
subr init0
astop$[] = [ ]
astleft[] = [ ]
astright[] = [ ]
err = 0
.
proc init s$ . .
inp$[] = strchars s$
inp_ind = 1
nch
ntok
init0
.
proc ast_print nd . .
write "AST:"
for i to len astop$[]
write " ( "
write astop$[i] & " "
write astleft[i] & " "
write astright[i]
write " )"
.
print " Start: " & nd
.
func node .
astop$[] &= ""
astleft[] &= 0
astright[] &= 0
return len astop$[]
.
#
funcdecl parse_expr .
#
func parse_factor .
if tok$ = "n"
nd = node
astop$[nd] = "n"
astleft[nd] = tokv
ntok
elif tok$ = "("
ntok
nd = parse_expr
if tok$ <> ")"
err = 1
print "error: ) expected, got " & tok$
.
ntok
else
err = 1
print "error: factor expected, got " & tok$
.
return nd
.
func parse_term .
ndx = parse_factor
while tok$ = "*" or tok$ = "/"
nd = node
astleft[nd] = ndx
astop$[nd] = tok$
ntok
astright[nd] = parse_factor
ndx = nd
.
return ndx
.
func parse_expr .
ndx = parse_term
while tok$ = "+" or tok$ = "-"
nd = node
astleft[nd] = ndx
astop$[nd] = tok$
ntok
astright[nd] = parse_term
ndx = nd
.
return ndx
.
func parse s$ .
init s$
return parse_expr
.
func eval nd .
if astop$[nd] = "n"
return astleft[nd]
.
le = eval astleft[nd]
ri = eval astright[nd]
a$ = astop$[nd]
if a$ = "+"
return le + ri
elif a$ = "-"
return le - ri
elif a$ = "*"
return le * ri
elif a$ = "/"
return le / ri
.
.
repeat
inp$ = input
until inp$ = ""
print "Inp: " & inp$
nd = parse inp$
ast_print nd
if err = 0
print "Eval: " & eval nd
.
print ""
.
input_data
4 *
4.2 * ((5.3+8)*3 + 4)
2.5 * 2 + 2 * 3.14
</syntaxhighlight>
{{out}}
<pre>
Inp: 4 * 6
AST: 2 ( n 4 0 ) ( * 1 3 ) ( n 6 0 )
Eval: 24
Inp: 4.2 * ((5.3+8)*3 + 4)
AST: 2 ( n 4.20 0 ) ( * 1 8 ) ( n 5.30 0 ) ( + 3 5 ) ( n 8 0 ) ( * 4 7 ) ( n 3 0 ) ( + 6 9 ) ( n 4 0 )
Eval: 184.38
Inp: 2.5 * 2 + 2 * 3.14
AST: 4 ( n 2.50 0 ) ( * 1 3 ) ( n 2 0 ) ( + 2 6 ) ( n 2 0 ) ( * 5 7 ) ( n 3.14 0 )
Eval: 11.28
</pre>
=={{header|Elena}}==
ELENA 6.x :
<syntaxhighlight lang="elena">import system'routines;
import extensions;
import extensions'text;
class Token
{
object _value;
int Level : rprop;
constructor new(int level)
{
_value := new StringWriter();
Level := level + 9;
}
append(ch)
{
_value.write(ch)
}
Number = _value.toReal();
}
class Node
{
object Left : prop;
object Right : prop;
int Level : rprop;
constructor new(int level)
{
Level := level
}
}
class SummaryNode : Node
{
constructor new(int level)
<= super new(level + 1);
Number = Left.Number + Right.Number;
}
class DifferenceNode : Node
{
constructor new(int level)
<= super new(level + 1);
Number = Left.Number - Right.Number;
}
class ProductNode : Node
{
constructor new(int level)
<= super new(level + 2);
Number = Left.Number * Right.Number;
}
class FractionNode : Node
{
constructor new(int level)
<= super new(level + 2);
Number = Left.Number / Right.Number;
}
class Expression
{
int Level :rprop;
object Top :prop;
constructor new(int level)
{
Level := level
}
object Right
{
get() = Top;
set(object node)
{
Top := node
}
}
get Number() => Top;
}
singleton operatorState
{
eval(ch)
{
ch =>
$40 { // (
^ weak self.newBracket().gotoStarting()
}
! {
^ weak self.newToken().append(ch).gotoToken()
}
}
}
singleton tokenState
{
eval(ch)
{
ch =>
$41 { // )
^ weak self.closeBracket().gotoToken()
}
$42 { // *
^ weak self.newProduct().gotoOperator()
}
$43 { // +
^ weak self.newSummary().gotoOperator()
}
$45 { // -
^ weak self.newDifference().gotoOperator()
}
$47 { // /
^ weak self.newFraction().gotoOperator()
}
! {
^ weak self.append(ch)
}
}
}
singleton startState
{
eval(ch)
{
ch =>
$40 { // (
^ weak self.newBracket().gotoStarting()
}
$45 { // -
^ weak self.newToken().append("0").newDifference().gotoOperator()
}
! {
^ weak self.newToken().append(ch).gotoToken()
}
}
}
class Scope
{
object _state;
int _level;
object _parser;
object _token;
object _expression;
constructor new(parser)
{
_state := startState;
_level := 0;
_expression := Expression.new(0);
_parser := parser
}
newToken()
{
_token := _parser.appendToken(_expression, _level)
}
newSummary()
{
_token := nil;
_parser.appendSummary(_expression, _level)
}
newDifference()
{
_token := nil;
_parser.appendDifference(_expression, _level)
}
newProduct()
{
_token := nil;
_parser.appendProduct(_expression, _level)
}
newFraction()
{
_token := nil;
_parser.appendFraction(_expression, _level)
}
newBracket()
{
_token := nil;
_level := _level + 10;
_parser.appendSubexpression(_expression, _level)
}
closeBracket()
{
if (_level < 10)
{ InvalidArgumentException.new("Invalid expression").raise() };
_level := _level - 10
}
append(ch)
{
if(ch >= $48 && ch < $58)
{
_token.append(ch)
}
else
{
InvalidArgumentException.new("Invalid expression").raise()
}
}
append(string s)
{
s.forEach::(ch){ self.append(ch) }
}
gotoStarting()
{
_state := startState
}
gotoToken()
{
_state := tokenState
}
gotoOperator()
{
_state := operatorState
}
get Number() => _expression;
dispatch() => _state;
}
class Parser
{
appendToken(object expression, int level)
{
var token := Token.new(level);
expression.Top := self.append(expression.Top, token);
^ token
}
appendSummary(object expression, int level)
{
var t := expression.Top;
expression.Top := self.append(/*expression.Top*/t, SummaryNode.new(level))
}
appendDifference(object expression, int level)
{
expression.Top := self.append(expression.Top, DifferenceNode.new(level))
}
appendProduct(object expression, int level)
{
expression.Top := self.append(expression.Top, ProductNode.new(level))
}
appendFraction(object expression, int level)
{
expression.Top := self.append(expression.Top, FractionNode.new(level))
}
appendSubexpression(object expression, int level)
{
expression.Top := self.append(expression.Top, Expression.new(level))
}
append(object lastNode, object newNode)
{
if(nil == lastNode)
{ ^ newNode };
if (newNode.Level <= lastNode.Level)
{ newNode.Left := lastNode; ^ newNode };
var parent := lastNode;
var current := lastNode.Right;
while (nil != current && newNode.Level > current.Level)
{ parent := current; current := current.Right };
if (nil == current)
{
parent.Right := newNode
}
else
{
newNode.Left := current; parent.Right := newNode
};
^ lastNode
}
run(text)
{
var scope := Scope.new(self);
text.forEach::(ch){ scope.eval(ch) };
^ scope.Number
}
}
public program()
{
var text := new StringWriter();
var parser := new Parser();
while (console.readLine().writeTo(text).Length > 0)
{
try
{
console.printLine("=",parser.run(text))
}
catch(Exception e)
{
console.writeLine("Invalid Expression")
};
text.clear()
}
}</syntaxhighlight>
=={{header|Elixir}}==
In Elixir AST is a built-in feature.
<syntaxhighlight lang="elixir">
defmodule Ast do
def main do
expr = IO.gets("Give an expression:\n") |> String.Chars.to_string |> String.trim
case Code.string_to_quoted(expr) do
{:ok, ast} ->
IO.puts("AST is: " <> inspect(ast))
{result, _} = Code.eval_quoted(ast)
IO.puts("Result = #{result}")
{:error, {_meta, message_info, _token}} ->
IO.puts(message_info)
end
end
end
</syntaxhighlight>
{{out}}
<pre>
>elixir -e Ast.main()
Give an expression:
2*(4 - 1)
AST is: {:*, [line: 1], [2, {:-, [line: 1], [4, 1]}]}
Result = 6
>elixir -e Ast.main()
Give an expression:
2*(4 - 1) + (
missing terminator: ) (for "(" starting at line 1)
</pre>
=={{header|Emacs Lisp}}==
<syntaxhighlight lang="lisp">#!/usr/bin/env emacs --script
;; -*- mode: emacs-lisp; lexical-binding: t -*-
;;> ./arithmetic-evaluation '(1 + 2) * 3'
(defun advance ()
(let ((rtn (buffer-substring-no-properties (point) (match-end 0))))
(goto-char (match-end 0))
rtn))
(defvar current-symbol nil)
(defun next-symbol ()
(when (looking-at "[ \t\n]+")
(goto-char (match-end 0)))
(cond
((eobp)
(setq current-symbol 'eof))
((looking-at "[0-9]+")
(setq current-symbol (string-to-number (advance))))
((looking-at "[-+*/()]")
(setq current-symbol (advance)))
((looking-at ".")
(error "Unknown character '%s'" (advance)))))
(defun accept (sym)
(when (equal sym current-symbol)
(next-symbol)
t))
(defun expect (sym)
(unless (accept sym)
(error "Expected symbol %s, but found %s" sym current-symbol))
t)
(defun p-expression ()
" expression = term { ('+' | '-') term } . "
(let ((rtn (p-term)))
(while (or (equal current-symbol "+") (equal current-symbol "-"))
(let ((op current-symbol)
(left rtn))
(next-symbol)
(setq rtn (list op left (p-term)))))
rtn))
(defun p-term ()
" term = factor { ('*' | '/') factor } . "
(let ((rtn (p-factor)))
(while (or (equal current-symbol "*") (equal current-symbol "/"))
(let ((op current-symbol)
(left rtn))
(next-symbol)
(setq rtn (list op left (p-factor)))))
rtn))
(defun p-factor ()
" factor = constant | variable | '(' expression ')' . "
(let (rtn)
(cond
((numberp current-symbol)
(setq rtn current-symbol)
(next-symbol))
((accept "(")
(setq rtn (p-expression))
(expect ")"))
(t (error "Syntax error")))
rtn))
(defun ast-build (expression)
(let (rtn)
(with-temp-buffer
(insert expression)
(goto-char (point-min))
(next-symbol)
(setq rtn (p-expression))
(expect 'eof))
rtn))
(defun ast-eval (v)
(pcase v
((pred numberp) v)
(`("+" ,a ,b) (+ (ast-eval a) (ast-eval b)))
(`("-" ,a ,b) (- (ast-eval a) (ast-eval b)))
(`("*" ,a ,b) (* (ast-eval a) (ast-eval b)))
(`("/" ,a ,b) (/ (ast-eval a) (float (ast-eval b))))
(_ (error "Unknown value %s" v))))
(dolist (arg command-line-args-left)
(let ((ast (ast-build arg)))
(princ (format " ast = %s\n" ast))
(princ (format " value = %s\n" (ast-eval ast)))
(terpri)))
(setq command-line-args-left nil)
</syntaxhighlight>
{{out}}
<pre>
$ ./arithmetic-evaluation '(1 + 2) * 3'
ast = (* (+ 1 2) 3)
value = 9
$ ./arithmetic-evaluation '1 + 2 * (3 + (4 * 5 + 6 * 7 * 8) - 9) / 10'
ast = (+ 1 (/ (* 2 (- (+ 3 (+ (* 4 5) (* (* 6 7) 8))) 9)) 10))
value = 71.0
$ ./arithmetic-evaluation '1 + 2*(3 - 2*(3 - 2)*((2 - 4)*5 - 22/(7 + 2*(3 - 1)) - 1)) + 1'
ast = (+ (+ 1 (* 2 (- 3 (* (* 2 (- 3 2)) (- (- (* (- 2 4) 5) (/ 22 (+ 7 (* 2 (- 3 1))))) 1))))) 1)
value = 60.0
$ ./arithmetic-evaluation '(1 + 2) * 10 / 100'
ast = (/ (* (+ 1 2) 10) 100)
value = 0.3
</pre>
=={{header|ERRE}}==
<syntaxhighlight lang="erre">
PROGRAM EVAL
!
! arithmetic expression evaluator
!
!$KEY
LABEL 98,100,110
DIM STACK$[50]
PROCEDURE DISEGNA_STACK
!$RCODE="LOCATE 3,1"
!$RCODE="COLOR 0,7"
PRINT(TAB(35);"S T A C K";TAB(79);)
!$RCODE="COLOR 7,0"
FOR TT=1 TO 38 DO
IF TT>=20 THEN
!$RCODE="LOCATE 3+TT-19,40"
ELSE
!$RCODE="LOCATE 3+TT,1"
END IF
IF TT=NS THEN PRINT(">";) ELSE PRINT(" ";) END IF
PRINT(RIGHT$(STR$(TT),2);"³ ";STACK$[TT];" ")
END FOR
REPEAT
GET(Z$)
UNTIL LEN(Z$)<>0
END PROCEDURE
PROCEDURE COMPATTA_STACK
IF NS>1 THEN
R=1
WHILE R<NS DO
IF INSTR(OP_LIST$,STACK$[R])=0 AND INSTR(OP_LIST$,STACK$[R+1])=0 THEN
FOR R1=R TO NS-1 DO
STACK$[R1]=STACK$[R1+1]
END FOR
NS=NS-1
END IF
R=R+1
END WHILE
END IF
DISEGNA_STACK
END PROCEDURE
PROCEDURE CALC_ARITM
L=NS1
WHILE L<=NS2 DO
IF STACK$[L]="^" THEN
IF L>=NS2 THEN GOTO 100 END IF
N1#=VAL(STACK$[L-1]) N2#=VAL(STACK$[L+1]) NOP=NOP-1
IF STACK$[L]="^" THEN
RI#=N1#^N2#
END IF
STACK$[L-1]=STR$(RI#)
N=L
WHILE N<=NS2-2 DO
STACK$[N]=STACK$[N+2]
N=N+1
END WHILE
NS2=NS2-2
L=NS1-1
END IF
L=L+1
END WHILE
L=NS1
WHILE L<=NS2 DO
IF STACK$[L]="*" OR STACK$[L]="/" THEN
IF L>=NS2 THEN GOTO 100 END IF
N1#=VAL(STACK$[L-1]) N2#=VAL(STACK$[L+1]) NOP=NOP-1
IF STACK$[L]="*" THEN RI#=N1#*N2# ELSE RI#=N1#/N2# END IF
STACK$[L-1]=STR$(RI#)
N=L
WHILE N<=NS2-2 DO
STACK$[N]=STACK$[N+2]
N=N+1
END WHILE
NS2=NS2-2
L=NS1-1
END IF
L=L+1
END WHILE
L=NS1
WHILE L<=NS2 DO
IF STACK$[L]="+" OR STACK$[L]="-" THEN
EXIT IF L>=NS2
N1#=VAL(STACK$[L-1]) N2#=VAL(STACK$[L+1]) NOP=NOP-1
IF STACK$[L]="+" THEN RI#=N1#+N2# ELSE RI#=N1#-N2# END IF
STACK$[L-1]=STR$(RI#)
N=L
WHILE N<=NS2-2 DO
STACK$[N]=STACK$[N+2]
N=N+1
END WHILE
NS2=NS2-2
L=NS1-1
END IF
L=L+1
END WHILE
100:
IF NOP<2 THEN ! operator priority
DB#=VAL(STACK$[NS1])
ELSE
IF NOP<3 THEN
DB#=VAL(STACK$[NS1+2])
ELSE
DB#=VAL(STACK$[NS1+4])
END IF
END IF
END PROCEDURE
PROCEDURE SVOLGI_PAR
NPA=NPA-1
FOR J=NS TO 1 STEP -1 DO
EXIT IF STACK$[J]="("
END FOR
IF J=0 THEN
NS1=1 NS2=NS CALC_ARITM
NERR=7
ELSE
FOR R=J TO NS-1 DO
STACK$[R]=STACK$[R+1]
END FOR
NS1=J NS2=NS-1 CALC_ARITM
IF NS1=2 THEN NS1=1 STACK$[1]=STACK$[2] END IF
NS=NS1
COMPATTA_STACK
END IF
END PROCEDURE
BEGIN
OP_LIST$="+-*/^("
NOP=0 NPA=0 NS=1 K$=""
STACK$[1]="@" ! init stack
PRINT(CHR$(12);)
INPUT(LINE,EXPRESSION$)
FOR W=1 TO LEN(EXPRESSION$) DO
LOOP
CODE=ASC(MID$(EXPRESSION$,W,1))
IF (CODE>=48 AND CODE<=57) OR CODE=46 THEN
K$=K$+CHR$(CODE)
W=W+1 IF W>LEN(EXPRESSION$) THEN GOTO 98 END IF
ELSE
EXIT IF K$=""
IF NS>1 OR (NS=1 AND STACK$[1]<>"@") THEN NS=NS+1 END IF
IF FLAG=0 THEN STACK$[NS]=K$ ELSE STACK$[NS]=STR$(VAL(K$)*FLAG) END IF
K$="" FLAG=0
EXIT
END IF
END LOOP
IF CODE=43 THEN K$="+" END IF
IF CODE=45 THEN K$="-" END IF
IF CODE=42 THEN K$="*" END IF
IF CODE=47 THEN K$="/" END IF
IF CODE=94 THEN K$="^" END IF
CASE CODE OF
43,45,42,47,94->
IF MID$(EXPRESSION$,W+1,1)="-" THEN FLAG=-1 W=W+1 END IF
IF INSTR(OP_LIST$,STACK$[NS])<>0 THEN
NERR=5
ELSE
NS=NS+1 STACK$[NS]=K$ NOP=NOP+1
IF NOP>=2 THEN
FOR J=NS TO 1 STEP -1 DO
IF STACK$[J]<>"(" THEN
CONTINUE FOR
END IF
IF J<NS-2 THEN
EXIT
ELSE
GOTO 110
END IF
END FOR
NS1=J+1 NS2=NS CALC_ARITM
NS=NS2 STACK$[NS]=K$
REGISTRO_X#=VAL(STACK$[NS-1])
END IF
END IF
110:
END ->
40->
IF NS>1 OR (NS=1 AND STACK$[1]<>"@") THEN NS=NS+1 END IF
STACK$[NS]="(" NPA=NPA+1
IF MID$(EXPRESSION$,W+1,1)="-" THEN FLAG=-1 W=W+1 END IF
END ->
41->
SVOLGI_PAR
IF NERR=7 THEN
NERR=0 NOP=0 NPA=0 NS=1
ELSE
IF NERR=0 OR NERR=1 THEN
DB#=VAL(STACK$[NS])
REGISTRO_X#=DB#
ELSE
NOP=0 NPA=0 NS=1
END IF
END IF
END ->
OTHERWISE
NERR=8
END CASE
K$=""
DISEGNA_STACK
END FOR
98:
IF K$<>"" THEN
IF NS>1 OR (NS=1 AND STACK$[1]<>"@") THEN NS=NS+1 END IF
IF FLAG=0 THEN STACK$[NS]=K$ ELSE STACK$[NS]=STR$(VAL(K$)*FLAG) END IF
END IF
DISEGNA_STACK
IF INSTR(OP_LIST$,STACK$[NS])<>0 THEN
NERR=6
ELSE
WHILE NPA<>0 DO
SVOLGI_PAR
END WHILE
IF NERR<>7 THEN NS1=1 NS2=NS CALC_ARITM END IF
END IF
NS=1 NOP=0 NPA=0
!$RCODE="LOCATE 23,1"
IF NERR>0 THEN PRINT("Internal Error #";NERR) ELSE PRINT("Value is ";DB#) END IF
END PROGRAM
</syntaxhighlight>
This solution is based on a stack: as a plus there is a power (^) operator. Unary operator "-" is accepted. Program shows the stack after every operation and you must press a key to go on (this feature can be avoided by removing the final REPEAT..UNTIL loop at the end of "DISEGNA_STACK" procedure).
=={{header|F_Sharp|F#}}==
Using FsLex and FsYacc from the F# PowerPack, we implement this with multiple source files:
<code>AbstractSyntaxTree.fs</code>:
<syntaxhighlight lang="fsharp">module AbstractSyntaxTree
type Expression =
| Int of int
| Plus of Expression * Expression
| Minus of Expression * Expression
| Times of Expression * Expression
| Divide of Expression * Expression</syntaxhighlight>
<code>Lexer.fsl</code>:
<syntaxhighlight lang="fsharp">{
module Lexer
open Parser // we need the terminal tokens from the Parser
let lexeme = Lexing.LexBuffer<_>.LexemeString
}
let intNum = '-'? ['0'-'9']+
let whitespace = ' ' | '\t'
let newline = '\n' | '\r' '\n'
rule token = parse
| intNum { INT (lexeme lexbuf |> int) }
| '+' { PLUS }
| '-' { MINUS }
| '*' { TIMES }
| '/' { DIVIDE }
| '(' { LPAREN }
| ')' { RPAREN }
| whitespace { token lexbuf }
| newline { lexbuf.EndPos <- lexbuf.EndPos.NextLine; token lexbuf }
| eof { EOF }
| _ { failwithf "unrecognized input: '%s'" <| lexeme lexbuf }</syntaxhighlight>
<code>Parser.fsy</code>:
<syntaxhighlight lang="fsharp">%{
open AbstractSyntaxTree
%}
%start Expr
// terminal tokens
%token <int> INT
%token PLUS MINUS TIMES DIVIDE LPAREN RPAREN
%token EOF
// associativity and precedences
%left PLUS MINUS
%left TIMES DIVIDE
// return type of Expr
%type <Expression> Expr
%%
Expr: INT { Int $1 }
| Expr PLUS Expr { Plus ($1, $3) }
| Expr MINUS Expr { Minus ($1, $3) }
| Expr TIMES Expr { Times ($1, $3) }
| Expr DIVIDE Expr { Divide ($1, $3) }
| LPAREN Expr RPAREN { $2 } </syntaxhighlight>
<code>Program.fs</code>:
<syntaxhighlight lang="fsharp">open AbstractSyntaxTree
open Lexer
open Parser
let parse txt =
txt
|> Lexing.LexBuffer<_>.FromString
|> Parser.Expr Lexer.token
let rec eval = function
| Int i -> i
| Plus (a,b) -> eval a + eval b
| Minus (a,b) -> eval a - eval b
| Times (a,b) -> eval a * eval b
| Divide (a,b) -> eval a / eval b
do
"((11+15)*15)*2-(3)*4*1"
|> parse
|> eval
|> printfn "%d"</syntaxhighlight>
=={{header|Factor}}==
<
IN: rosetta.arith
Line 693 ⟶ 2,918:
: evaluate ( string -- result )
expr-ast eval-ast ;</
=={{header|FreeBASIC}}==
<syntaxhighlight lang="freebasic">
'Arithmetic evaluation
'
'Create a program which parses and evaluates arithmetic expressions.
'
'Requirements
'
' * An abstract-syntax tree (AST) for the expression must be created from parsing the
' input.
' * The AST must be used in evaluation, also, so the input may not be directly evaluated
' (e.g. by calling eval or a similar language feature.)
' * The expression will be a string or list of symbols like "(1+3)*7".
' * The four symbols + - * / must be supported as binary operators with conventional
' precedence rules.
' * Precedence-control parentheses must also be supported.
'
'Standard mathematical precedence should be followed:
'
' Parentheses
' Multiplication/Division (left to right)
' Addition/Subtraction (left to right)
'
' test cases:
' 2*-3--4+-0.25 : returns -2.25
' 1 + 2 * (3 + (4 * 5 + 6 * 7 * 8) - 9) / 10 : returns 71
enum
false = 0
true = -1
end enum
enum Symbol
unknown_sym
minus_sym
plus_sym
lparen_sym
rparen_sym
number_sym
mul_sym
div_sym
unary_minus_sym
unary_plus_sym
done_sym
eof_sym
end enum
type Tree
as Tree ptr leftp, rightp
op as Symbol
value as double
end type
dim shared sym as Symbol
dim shared tokenval as double
dim shared usr_input as string
declare function expr(byval p as integer) as Tree ptr
function isdigit(byval ch as string) as long
return ch <> "" and Asc(ch) >= Asc("0") and Asc(ch) <= Asc("9")
end function
sub error_msg(byval msg as string)
print msg
system
end sub
' tokenize the input string
sub getsym()
do
if usr_input = "" then
line input usr_input
usr_input += chr(10)
endif
dim as string ch = mid(usr_input, 1, 1) ' get the next char
usr_input = mid(usr_input, 2) ' remove it from input
sym = unknown_sym
select case ch
case " ": continue do
case chr(10), "": sym = done_sym: return
case "+": sym = plus_sym: return
case "-": sym = minus_sym: return
case "*": sym = mul_sym: return
case "/": sym = div_sym: return
case "(": sym = lparen_sym: return
case ")": sym = rparen_sym: return
case else
if isdigit(ch) then
dim s as string = ""
dim dot as integer = 0
do
s += ch
if ch = "." then dot += 1
ch = mid(usr_input, 1, 1) ' get the next char
usr_input = mid(usr_input, 2) ' remove it from input
loop while isdigit(ch) orelse ch = "."
if ch = "." or dot > 1 then error_msg("bogus number")
usr_input = ch + usr_input ' prepend the char to input
tokenval = val(s)
sym = number_sym
end if
return
end select
loop
end sub
function make_node(byval op as Symbol, byval leftp as Tree ptr, byval rightp as Tree ptr) as Tree ptr
dim t as Tree ptr
t = callocate(len(Tree))
t->op = op
t->leftp = leftp
t->rightp = rightp
return t
end function
function is_binary(byval op as Symbol) as integer
select case op
case mul_sym, div_sym, plus_sym, minus_sym: return true
case else: return false
end select
end function
function prec(byval op as Symbol) as integer
select case op
case unary_minus_sym, unary_plus_sym: return 100
case mul_sym, div_sym: return 90
case plus_sym, minus_sym: return 80
case else: return 0
end select
end function
function primary as Tree ptr
dim t as Tree ptr = 0
select case sym
case minus_sym, plus_sym
dim op as Symbol = sym
getsym()
t = expr(prec(unary_minus_sym))
if op = minus_sym then return make_node(unary_minus_sym, t, 0)
if op = plus_sym then return make_node(unary_plus_sym, t, 0)
case lparen_sym
getsym()
t = expr(0)
if sym <> rparen_sym then error_msg("expecting rparen")
getsym()
return t
case number_sym
t = make_node(sym, 0, 0)
t->value = tokenval
getsym()
return t
case else: error_msg("expecting a primary")
end select
end function
function expr(byval p as integer) as Tree ptr
dim t as Tree ptr = primary()
while is_binary(sym) andalso prec(sym) >= p
dim t1 as Tree ptr
dim op as Symbol = sym
getsym()
t1 = expr(prec(op) + 1)
t = make_node(op, t, t1)
wend
return t
end function
function eval(byval t as Tree ptr) as double
if t <> 0 then
select case t->op
case minus_sym: return eval(t->leftp) - eval(t->rightp)
case plus_sym: return eval(t->leftp) + eval(t->rightp)
case mul_sym: return eval(t->leftp) * eval(t->rightp)
case div_sym: return eval(t->leftp) / eval(t->rightp)
case unary_minus_sym: return -eval(t->leftp)
case unary_plus_sym: return eval(t->leftp)
case number_sym: return t->value
case else: error_msg("unexpected tree node")
end select
end if
return 0
end function
do
getsym()
if sym = eof_sym then exit do
if sym = done_sym then continue do
dim t as Tree ptr = expr(0)
print"> "; eval(t)
if sym = eof_sym then exit do
if sym <> done_sym then error_msg("unexpected input")
loop
</syntaxhighlight>
{{out}}
<pre>
>calc
1 + 2 * (3 + (4 * 5 + 6 * 7 * 8) - 9) / 10
> 71
</pre>
=={{header|FutureBasic}}==
<syntaxhighlight lang="futurebasic">
_window = 1
begin enum 1
_expressionLabel
_expressionFld
_resultLabel
end enum
void local fn BuildUI
editmenu 1
window _window, @"Arithmetic Evaluation", (0,0,522,61)
textlabel _expressionLabel, @"Expression:", (18,23,74,16)
textfield _expressionFld,,, (98,20,300,21)
textlabel _resultLabel,, (404,23,100,16)
WindowMakeFirstResponder( _window, _expressionFld )
end fn
void local fn EvaluateExpression( string as CFStringRef )
ExpressionRef expression = fn ExpressionWithFormat( string )
textlabel _resultlabel, fn StringWithFormat( @"= %@", fn ExpressionValueWithObject( expression, NULL, NULL ) )
end fn
void local fn DoDialog( ev as long, tag as long )
select ( ev )
case _btnClick : fn EvaluateExpression( textfield(tag) )
end select
end fn
fn BuildUI
on dialog fn DoDialog
HandleEvents
</syntaxhighlight>
[[file:Arithmetic evaluation FB.png]]
=={{header|Go}}==
See [[Arithmetic Evaluator/Go]]
=={{header|Groovy}}==
Solution:
<syntaxhighlight lang="groovy">enum Op {
ADD('+', 2),
SUBTRACT('-', 2),
MULTIPLY('*', 1),
DIVIDE('/', 1);
static {
ADD.operation = { a, b -> a + b }
SUBTRACT.operation = { a, b -> a - b }
MULTIPLY.operation = { a, b -> a * b }
DIVIDE.operation = { a, b -> a / b }
}
final String symbol
final int precedence
Closure operation
private Op(String symbol, int precedence) {
this.symbol = symbol
this.precedence = precedence
}
String toString() { symbol }
static Op fromSymbol(String symbol) {
Op.values().find { it.symbol == symbol }
}
}
interface Expression {
Number evaluate();
}
class Constant implements Expression {
Number value
Constant (Number value) { this.value = value }
Constant (String str) {
try { this.value = str as BigInteger }
catch (e) { this.value = str as BigDecimal }
}
Number evaluate() { value }
String toString() { "${value}" }
}
class Term implements Expression {
Op op
Expression left, right
Number evaluate() { op.operation(left.evaluate(), right.evaluate()) }
String toString() { "(${op} ${left} ${right})" }
}
void fail(String msg, Closure cond = {true}) {
if (cond()) throw new IllegalArgumentException("Cannot parse expression: ${msg}")
}
Expression parse(String expr) {
def tokens = tokenize(expr)
def elements = groupByParens(tokens, 0)
parse(elements)
}
List tokenize(String expr) {
def tokens = []
def constStr = ""
def captureConstant = { i ->
if (constStr) {
try { tokens << new Constant(constStr) }
catch (NumberFormatException e) { fail "Invalid constant '${constStr}' near position ${i}" }
constStr = ''
}
}
for(def i = 0; i<expr.size(); i++) {
def c = expr[i]
def constSign = c in ['+','-'] && constStr.empty && (tokens.empty || tokens[-1] != ')')
def isConstChar = { it in ['.'] + ('0'..'9') || constSign }
if (c in ([')'] + Op.values()*.symbol) && !constSign) { captureConstant(i) }
switch (c) {
case ~/\s/: break
case isConstChar: constStr += c; break
case Op.values()*.symbol: tokens << Op.fromSymbol(c); break
case ['(',')']: tokens << c; break
default: fail "Invalid character '${c}' at position ${i+1}"
}
}
captureConstant(expr.size())
tokens
}
List groupByParens(List tokens, int depth) {
def deepness = depth
def tokenGroups = []
for (def i = 0; i < tokens.size(); i++) {
def token = tokens[i]
switch (token) {
case '(':
fail("'(' too close to end of expression") { i+2 > tokens.size() }
def subGroup = groupByParens(tokens[i+1..-1], depth+1)
tokenGroups << subGroup[0..-2]
i += subGroup[-1] + 1
break
case ')':
fail("Unbalanced parens, found extra ')'") { deepness == 0 }
tokenGroups << i
return tokenGroups
default:
tokenGroups << token
}
}
fail("Unbalanced parens, unclosed groupings at end of expression") { deepness != 0 }
def n = tokenGroups.size()
fail("The operand/operator sequence is wrong") { n%2 == 0 }
(0..<n).each {
def i = it
fail("The operand/operator sequence is wrong") { (i%2 == 0) == (tokenGroups[i] instanceof Op) }
}
tokenGroups
}
Expression parse(List elements) {
while (elements.size() > 1) {
def n = elements.size()
fail ("The operand/operator sequence is wrong") { n%2 == 0 }
def groupLoc = (0..<n).find { i -> elements[i] instanceof List }
if (groupLoc != null) {
elements[groupLoc] = parse(elements[groupLoc])
continue
}
def opLoc = (0..<n).find { i -> elements[i] instanceof Op && elements[i].precedence == 1 } \
?: (0..<n).find { i -> elements[i] instanceof Op && elements[i].precedence == 2 }
if (opLoc != null) {
fail ("Operator out of sequence") { opLoc%2 == 0 }
def term = new Term(left:elements[opLoc-1], op:elements[opLoc], right:elements[opLoc+1])
elements[(opLoc-1)..(opLoc+1)] = [term]
continue
}
}
return elements[0] instanceof List ? parse(elements[0]) : elements[0]
}</syntaxhighlight>
Test:
<syntaxhighlight lang="groovy">def testParse = {
def ex = parse(it)
print """
Input: ${it}
AST: ${ex}
value: ${ex.evaluate()}
"""
}
testParse('1+1+(1+(1+(1+(1+(1+(1+(1+(1+(1+(1+(1+(1+(1+1/15)/14)/13)/12)/11)/10)/9)/8)/7)/6)/5)/4)/3)/2')
assert (parse('1+1+(1+(1+(1+(1+(1+(1+(1+(1+(1+(1+(1+(1+(1+1/15)/14)/13)/12)/11)/10)/9)/8)/7)/6)/5)/4)/3)/2')
.evaluate() - Math.E).abs() < 0.0000000000001
testParse('1 + 2*(3 - 2*(3 - 2)*((2 - 4)*5 - 22/(7 + 2*(3 - 1)) - 1)) + 1')
testParse('1 - 5 * 2 / 20 + 1')
testParse('(1 - 5) * 2 / (20 + 1)')
testParse('2 * (3 + ((5) / (7 - 11)))')
testParse('(2 + 3) / (10 - 5)')
testParse('(1 + 2) * 10 / 100')
testParse('(1 + 2 / 2) * (5 + 5)')
testParse('2*-3--4+-.25')
testParse('2*(-3)-(-4)+(-.25)')
testParse('((11+15)*15)*2-(3)*4*1')
testParse('((11+15)*15)* 2 + (3) * -4 *1')
testParse('(((((1)))))')
testParse('-35')
println()
try { testParse('((11+15)*1') } catch (e) { println e }
try { testParse('((11+15)*1)))') } catch (e) { println e }
try { testParse('((11+15)*x)') } catch (e) { println e }
try { testParse('+++++') } catch (e) { println e }
try { testParse('1 /') } catch (e) { println e }
try { testParse('1++') } catch (e) { println e }
try { testParse('*1') } catch (e) { println e }
try { testParse('/ 1 /') } catch (e) { println e }</syntaxhighlight>
{{out}}
<pre style="height:30ex;overflow:scroll;">Input: 1+1+(1+(1+(1+(1+(1+(1+(1+(1+(1+(1+(1+(1+(1+1/15)/14)/13)/12)/11)/10)/9)/8)/7)/6)/5)/4)/3)/2
AST: (+ (+ 1 1) (/ (+ 1 (/ (+ 1 (/ (+ 1 (/ (+ 1 (/ (+ 1 (/ (+ 1 (/ (+ 1 (/ (+ 1 (/ (+ 1 (/ (+ 1 (/ (+ 1 (/ (+ 1 (/ (+ 1 (/ 1 15)) 14)) 13)) 12)) 11)) 10)) 9)) 8)) 7)) 6)) 5)) 4)) 3)) 2))
value: 2.7182818284589946
Input: 1 + 2*(3 - 2*(3 - 2)*((2 - 4)*5 - 22/(7 + 2*(3 - 1)) - 1)) + 1
AST: (+ (+ 1 (* 2 (- 3 (* (* 2 (- 3 2)) (- (- (* (- 2 4) 5) (/ 22 (+ 7 (* 2 (- 3 1))))) 1))))) 1)
value: 60
Input: 1 - 5 * 2 / 20 + 1
AST: (+ (- 1 (/ (* 5 2) 20)) 1)
value: 1.5
Input: (1 - 5) * 2 / (20 + 1)
AST: (/ (* (- 1 5) 2) (+ 20 1))
value: -0.3809523810
Input: 2 * (3 + ((5) / (7 - 11)))
AST: (* 2 (+ 3 (/ 5 (- 7 11))))
value: 3.50
Input: (2 + 3) / (10 - 5)
AST: (/ (+ 2 3) (- 10 5))
value: 1
Input: (1 + 2) * 10 / 100
AST: (/ (* (+ 1 2) 10) 100)
value: 0.3
Input: (1 + 2 / 2) * (5 + 5)
AST: (* (+ 1 (/ 2 2)) (+ 5 5))
value: 20
Input: 2*-3--4+-.25
AST: (+ (- (* 2 -3) -4) -0.25)
value: -2.25
Input: 2*(-3)-(-4)+(-.25)
AST: (+ (- (* 2 -3) -4) -0.25)
value: -2.25
Input: ((11+15)*15)*2-(3)*4*1
AST: (- (* (* (+ 11 15) 15) 2) (* (* 3 4) 1))
value: 768
Input: ((11+15)*15)* 2 + (3) * -4 *1
AST: (+ (* (* (+ 11 15) 15) 2) (* (* 3 -4) 1))
value: 768
Input: (((((1)))))
AST: 1
value: 1
Input: -35
AST: -35
value: -35
java.lang.IllegalArgumentException: Cannot parse expression: Unbalanced parens, unclosed groupings at end of expression
java.lang.IllegalArgumentException: Cannot parse expression: Unbalanced parens, found extra ')'
java.lang.IllegalArgumentException: Cannot parse expression: Invalid character 'x' at position 10
java.lang.IllegalArgumentException: Cannot parse expression: Invalid constant '+' near position 1
java.lang.IllegalArgumentException: Cannot parse expression: The operand/operator sequence is wrong
java.lang.IllegalArgumentException: Cannot parse expression: Invalid constant '+' near position 3
java.lang.IllegalArgumentException: Cannot parse expression: The operand/operator sequence is wrong
java.lang.IllegalArgumentException: Cannot parse expression: The operand/operator sequence is wrong</pre>
=={{header|Haskell}}==
<syntaxhighlight lang="haskell">{-# LANGUAGE FlexibleContexts #-}
import Text.Parsec
import Text.Parsec.Expr
import Text.Parsec.Combinator
import Data.Functor
import Data.Function (on)
data Exp
= Num Int
| Add Exp
Exp
| Sub Exp
Exp
| Mul Exp
Exp
| Div Exp
Exp
expr
:: Stream s m Char
=> ParsecT s u m Exp
expr = buildExpressionParser table factor
where
table =
[ [op "*" Mul AssocLeft, op "/" Div AssocLeft]
, [op "+" Add AssocLeft, op "-" Sub AssocLeft]
]
op s f = Infix (f <$ string s)
factor = (between `on` char) '(' ')' expr <|> (Num . read <$> many1 digit)
eval
:: Integral a
=> Exp -> a
eval (Num x) = fromIntegral x
eval (Add a b) = eval a + eval b
eval (Sub a b) = eval a - eval b
eval (Mul a b) = eval a * eval b
eval (Div a b) = eval a `div` eval b
solution
:: Integral a
=> String -> a
solution = either (const (error "Did not parse")) eval . parse expr ""
main :: IO ()
main = print $ solution "(1+3)*7"</syntaxhighlight>
{{Out}}
<pre>28</pre>
=={{header|Icon}} and {{header|Unicon}}==
A compact recursive descent parser using Hanson's device. This program
* handles left and right associativity and different precedences
* is ready to handle any number of infix operators without adding more functions to handle the precedences
* accepts integers, reals, and radix constants (e.g. 3r10 is 3 in base 3)
* currently accepts the Icon operators + - * / % (remainder) and ^ (exponentiation) and unary operators + and -
* string invocation is used to evaluate binary operators hence other Icon binary operators (including handle multiple character ones) can be easily added
* uses Icon style type coercion on operands
* represents the AST as a nested list eliminating unneeded parenthesis
* Notice that the code looks remarkably like a typical grammar, rather than being an opaque cryptic solution
* Does not rely on any library to silently solve 1/2 the problem; in fact, this code would probably suit being put into a library almost verbatim
<syntaxhighlight lang="icon">procedure main() #: simple arithmetical parser / evaluator
write("Usage: Input expression = Abstract Syntax Tree = Value, ^Z to end.")
repeat {
writes("Input expression : ")
if not writes(line := read()) then break
if map(line) ? { (x := E()) & pos(0) } then
write(" = ", showAST(x), " = ", evalAST(x))
else
write(" rejected")
}
end
procedure evalAST(X) #: return the evaluated AST
local x
if type(X) == "list" then {
x := evalAST(get(X))
while x := get(X)(x, evalAST(get(X) | stop("Malformed AST.")))
}
return \x | X
end
procedure showAST(X) #: return a string representing the AST
local x,s
s := ""
every x := !X do
s ||:= if type(x) == "list" then "(" || showAST(x) || ")" else x
return s
end
########
# When you're writing a big parser, a few utility recognisers are very useful
#
procedure ws() # skip optional whitespace
suspend tab(many(' \t')) | ""
end
procedure digits()
suspend tab(many(&digits))
end
procedure radixNum(r) # r sets the radix
static chars
initial chars := &digits || &lcase
suspend tab(many(chars[1 +: r]))
end
########
global token
record HansonsDevice(precedence,associativity)
procedure opinfo()
static O
initial {
O := HansonsDevice([], table(&null)) # parsing table
put(O.precedence, ["+", "-"], ["*", "/", "%"], ["^"]) # Lowest to Highest precedence
every O.associativity[!!O.precedence] := 1 # default to 1 for LEFT associativity
O.associativity["^"] := 0 # RIGHT associativity
}
return O
end
procedure E(k) #: Expression
local lex, pL
static opT
initial opT := opinfo()
/k := 1
lex := []
if not (pL := opT.precedence[k]) then # this op at this level?
put(lex, F())
else {
put(lex, E(k + 1))
while ws() & put(lex, token := =!pL) do
put(lex, E(k + opT.associativity[token]))
}
suspend if *lex = 1 then lex[1] else lex # strip useless []
end
procedure F() #: Factor
suspend ws() & ( # skip optional whitespace, and ...
(="+" & F()) | # unary + and a Factor, or ...
(="-" || V()) | # unary - and a Value, or ...
(="-" & [-1, "*", F()]) | # unary - and a Factor, or ...
2(="(", E(), ws(), =")") | # parenthesized subexpression, or ...
V() # just a value
)
end
procedure V() #: Value
local r
suspend ws() & numeric( # skip optional whitespace, and ...
=(r := 1 to 36) || ="r" || radixNum(r) | # N-based number, or ...
digits() || (="." || digits() | "") || exponent() # plain number with optional fraction
)
end
procedure exponent()
suspend tab(any('eE')) || =("+" | "-" | "") || digits() | ""
end</syntaxhighlight>
{{out|Sample Output}}
<pre>#matheval.exe
Usage: Input expression = Abstract Syntax Tree = Value, ^Z to end.
Input expression : 1
1 = 1 = 1
Input expression : -1
-1 = -1 = -1
Input expression : (-15/2.0)
(-15/2.0) = -15/2.0 = -7.5
Input expression : -(15/2.0)
-(15/2.0) = -1*(15/2.0) = -7.5
Input expression : 2+(3-4)*6/5^2^3%3
2+(3-4)*6/5^2^3%3 = 2+((3-4)*6/(5^(2^3))%3) = 2
Input expression : 1+2+3+4
1+2+3+4 = 1+2+3+4 = 10
Input expression : ((((2))))+3*5
((((2))))+3*5 = 2+(3*5) = 17
Input expression : 3r10*3
3r10*3 = 3r10*3 = 9
Input expression : ^Z</pre>
=={{header|J}}==
Note that once you get beyond a few basic arithmetic operations, what we commonly call "mathematical precedence" stops making sense, and
Nevertheless, this task deals only with simple arithmetic, so this kind of precedence is an arguably appropriate choice for this task.
The implementation here uses a shift/reduce parser to build a tree structure for evaluation (a tree structure which J happens to support for evaluation):
<
eval=:monad define
'gerund structure'=:y
Line 801 ⟶ 3,678:
coerase tmp
r
)</
example use:
<
2.2</
You can also display the syntax tree, for example:
<syntaxhighlight lang
┌─────────────────────────────────────────────────────┬───────────────────┐
│┌───┬───────┬───┬───────┬───┬─┬───────┬───┬───────┬─┐│┌───────┬─┬───────┐│
││┌─┐│┌─────┐│┌─┐│┌─────┐│┌─┐│(│┌─────┐│┌─┐│┌─────┐│)│││┌─┬─┬─┐│4│┌─┬─┬─┐││
│││$│││┌─┬─┐│││*│││┌─┬─┐│││%││ ││┌─┬─┐│││-│││┌─┬─┐││ ││││1│2│3││ ││6│7│8│││
││└─┘│││0│2│││└─┘│││0│3│││└─┘│ │││0│4│││└─┘│││0│5│││ │││└─┴─┴─┘│ │└─┴─┴─┘││
││ ││└─┴─┘││ ││└─┴─┘││ │ ││└─┴─┘││ ││└─┴─┘││ ││└───────┴─┴───────┘│
││ │└─────┘│ │└─────┘│ │ │└─────┘│ │└─────┘│ ││ │
│└───┴───────┴───┴───────┴───┴─┴───────┴───┴───────┴─┘│ │
└─────────────────────────────────────────────────────┴───────────────────┘</syntaxhighlight>
At the top level, the first box is a list of terminals, and the second box represents their parsed structure within the source sentence, with numbers indexing the respective terminals. Within the list of terminals - each terminal is contained with a box. Operators are strings inside of boxes (the leading $ "operator" in this example is not really an operator - it's just a placeholder that was used to help in the parsing). Punctuation is simply the punctuation string (left or right parenthesis - these are also not really operators and are just placeholders which were used during parsing). Numeric values are a box inside of a box where the inner box carries two further boxes. The first indicates syntactic data type ('0' for arrays - here that means numbers) and the second carries the value.
=={{header|Java}}==
Uses the [[Arithmetic/Rational/Java|BigRational class]] to handle arbitrary-precision numbers (rational numbers since basic arithmetic will result in rational values).
<syntaxhighlight lang="java">import java.util.Stack;
public class ArithmeticEvaluation {
public interface Expression {
BigRational eval();
}
public enum Parentheses {LEFT}
public enum BinaryOperator {
ADD('+', 1),
SUB('-', 1),
MUL('*', 2),
DIV('/', 2);
public final char symbol;
public final int precedence;
BinaryOperator(char symbol, int precedence) {
this.symbol = symbol;
this.precedence = precedence;
}
public BigRational eval(BigRational leftValue, BigRational rightValue) {
switch (this) {
case ADD:
return leftValue.add(rightValue);
case SUB:
return leftValue.subtract(rightValue);
case MUL:
return leftValue.multiply(rightValue);
case DIV:
return leftValue.divide(rightValue);
}
throw new IllegalStateException();
}
public static BinaryOperator forSymbol(char symbol) {
for (BinaryOperator operator : values()) {
if (operator.symbol == symbol) {
return operator;
}
}
throw new IllegalArgumentException(String.valueOf(symbol));
}
}
public static class Number implements Expression {
private final BigRational number;
public Number(BigRational number) {
this.number = number;
}
@Override
public BigRational eval() {
return number;
}
@Override
public String toString() {
return number.toString();
}
}
public static class BinaryExpression implements Expression {
public final Expression leftOperand;
public final BinaryOperator operator;
public final Expression rightOperand;
public BinaryExpression(Expression leftOperand, BinaryOperator operator, Expression rightOperand) {
this.leftOperand = leftOperand;
this.operator = operator;
this.rightOperand = rightOperand;
}
@Override
public BigRational eval() {
BigRational leftValue = leftOperand.eval();
BigRational rightValue = rightOperand.eval();
return operator.eval(leftValue, rightValue);
}
@Override
public String toString() {
return "(" + leftOperand + " " + operator.symbol + " " + rightOperand + ")";
}
}
private static void createNewOperand(BinaryOperator operator, Stack<Expression> operands) {
Expression rightOperand = operands.pop();
Expression leftOperand = operands.pop();
operands.push(new BinaryExpression(leftOperand, operator, rightOperand));
}
public static Expression parse(String input) {
int curIndex = 0;
boolean afterOperand = false;
Stack<Expression> operands = new Stack<>();
Stack<Object> operators = new Stack<>();
while (curIndex < input.length()) {
int startIndex = curIndex;
char c = input.charAt(curIndex++);
if (Character.isWhitespace(c))
continue;
if (afterOperand) {
if (c == ')') {
Object operator;
while (!operators.isEmpty() && ((operator = operators.pop()) != Parentheses.LEFT))
createNewOperand((BinaryOperator) operator, operands);
continue;
}
afterOperand = false;
BinaryOperator operator = BinaryOperator.forSymbol(c);
while (!operators.isEmpty() && (operators.peek() != Parentheses.LEFT) && (((BinaryOperator) operators.peek()).precedence >= operator.precedence))
createNewOperand((BinaryOperator) operators.pop(), operands);
operators.push(operator);
continue;
}
if (c == '(') {
operators.push(Parentheses.LEFT);
continue;
}
afterOperand = true;
while (curIndex < input.length()) {
c = input.charAt(curIndex);
if (((c < '0') || (c > '9')) && (c != '.'))
break;
curIndex++;
}
operands.push(new Number(BigRational.valueOf(input.substring(startIndex, curIndex))));
}
while (!operators.isEmpty()) {
Object operator = operators.pop();
if (operator == Parentheses.LEFT)
throw new IllegalArgumentException();
createNewOperand((BinaryOperator) operator, operands);
}
Expression expression = operands.pop();
if (!operands.isEmpty())
throw new IllegalArgumentException();
return expression;
}
public static void main(String[] args) {
String[] testExpressions = {
"2+3",
"2+3/4",
"2*3-4",
"2*(3+4)+5/6",
"2 * (3 + (4 * 5 + (6 * 7) * 8) - 9) * 10",
"2*-3--4+-.25"};
for (String testExpression : testExpressions) {
Expression expression = parse(testExpression);
System.out.printf("Input: \"%s\", AST: \"%s\", value=%s%n", testExpression, expression, expression.eval());
}
}
}</syntaxhighlight>
{{out}}
<pre>Input: "2+3", AST: "(2 + 3)", value=5
Input: "2+3/4", AST: "(2 + (3 / 4))", value=11/4
Input: "2*3-4", AST: "((2 * 3) - 4)", value=2
Input: "2*(3+4)+5/6", AST: "((2 * (3 + 4)) + (5 / 6))", value=89/6
Input: "2 * (3 + (4 * 5 + (6 * 7) * 8) - 9) * 10", AST: "((2 * ((3 + ((4 * 5) + ((6 * 7) * 8))) - 9)) * 10)", value=7000
Input: "2*-3--4+-.25", AST: "(((2 * -3) - -4) + -1/4)", value=-9/4</pre>
=={{header|JavaScript}}==
Numbers must have a digit before the decimal point, so 0.1 not .1.
Spaces are removed, expressions like <code>5--1</code> are treated as <code>5 - -1</code>
<syntaxhighlight lang="javascript">function evalArithmeticExp(s) {
s = s.replace(/\s/g,'').replace(/^\+/,'');
var rePara = /\([^\(\)]*\)/;
var exp = s.match(rePara);
while (exp = s.match(rePara)) {
s = s.replace(exp[0], evalExp(exp[0]));
}
return evalExp(s);
function evalExp(s) {
s = s.replace(/[\(\)]/g,'');
var reMD = /\d+\.?\d*\s*[\*\/]\s*[+-]?\d+\.?\d*/;
var reM = /\*/;
var reAS = /-?\d+\.?\d*\s*[\+-]\s*[+-]?\d+\.?\d*/;
var reA = /\d\+/;
var exp;
while (exp = s.match(reMD)) {
s = exp[0].match(reM)? s.replace(exp[0], multiply(exp[0])) : s.replace(exp[0], divide(exp[0]));
}
while (exp = s.match(reAS)) {
s = exp[0].match(reA)? s.replace(exp[0], add(exp[0])) : s.replace(exp[0], subtract(exp[0]));
}
return '' + s;
function multiply(s, b) {
b = s.split('*');
return b[0] * b[1];
}
function divide(s, b) {
b = s.split('/');
return b[0] / b[1];
}
function add(s, b) {
s = s.replace(/^\+/,'').replace(/\++/,'+');
b = s.split('+');
return Number(b[0]) + Number(b[1]);
}
function subtract(s, b) {
s = s.replace(/\+-|-\+/g,'-');
if (s.match(/--/)) {
return add(s.replace(/--/,'+'));
}
b = s.split('-');
return b.length == 3? -1 * b[1] - b[2] : b[0] - b[1];
}
}
}</syntaxhighlight>
{{out|Sample Output}}
<pre>evalArithmeticExp('2+3') // 5
evalArithmeticExp('2+3/4') // 2.75
evalArithmeticExp('2*3-4') // 2
evalArithmeticExp('2*(3+4)+5/6') // 14.833333333333334
evalArithmeticExp('2 * (3 + (4 * 5 + (6 * 7) * 8) - 9) * 10') // 7000
evalArithmeticExp('2*-3--4+-0.25' // -2.25</pre>
=={{header|jq}}==
[[Category:PEG]]
This entry highlights the use of a [[:Category:PEG|PEG]] grammar expressed in jq.
=== PEG operations ===
<syntaxhighlight lang="jq">def star(E): (E | star(E)) // .;
def plus(E): E | (plus(E) // . );
def optional(E): E // .;
def amp(E): . as $in | E | $in;
def neg(E): select( [E] == [] );</syntaxhighlight>
=== Helper functions ===
<syntaxhighlight lang="jq">def literal($s):
select(.remainder | startswith($s))
| .result += [$s]
| .remainder |= .[$s | length :] ;
def box(E):
((.result = null) | E) as $e
| .remainder = $e.remainder
| .result += [$e.result] # the magic sauce
;
# Consume a regular expression rooted at the start of .remainder, or emit empty;
# on success, update .remainder and set .match but do NOT update .result
def consume($re):
# on failure, match yields empty
(.remainder | match("^" + $re)) as $match
| .remainder |= .[$match.length :]
| .match = $match.string ;
def parseNumber($re):
consume($re)
| .result = .result + [.match|tonumber] ;</syntaxhighlight>
=== PEG Grammar ===
The PEG grammar for arithmetic expressions follows the one given at the Raku entry.<syntaxhighlight lang="jq">def Expr:
def ws: consume(" *");
def Number: ws | parseNumber( "-?[0-9]+([.][0-9]*)?" );
def Sum:
def Parenthesized: ws | consume("[(]") | ws | box(Sum) | ws | consume("[)]");
def Factor: Parenthesized // Number;
def Product: box(Factor | star( ws | (literal("*") // literal("/")) | Factor));
Product | ws | star( (literal("+") // literal("-")) | Product);
Sum;</syntaxhighlight>
=== Evaluation ===
<syntaxhighlight lang="jq"># Left-to-right evaluation
def eval:
if type == "array" then
if length == 0 then null
else .[-1] |= eval
| if length == 1 then .[0]
else (.[:-2] | eval) as $v
| if .[-2] == "*" then $v * .[-1]
elif .[-2] == "/" then $v / .[-1]
elif .[-2] == "+" then $v + .[-1]
elif .[-2] == "-" then $v - .[-1]
else tostring|error
end
end
end
else .
end;
def eval(String):
{remainder: String}
| Expr.result
| eval;</syntaxhighlight>
=== Example ===
eval("2 * (3 -1) + 2 * 5")
produces: 14
=={{header|Jsish}}==
From Javascript entry.
<syntaxhighlight lang="javascript">/* Arithmetic evaluation, in Jsish */
function evalArithmeticExp(s) {
s = s.replace(/\s/g,'').replace(/^\+/,'');
var rePara = /\([^\(\)]*\)/;
var exp;
function evalExp(s) {
s = s.replace(/[\(\)]/g,'');
var reMD = /[0-9]+\.?[0-9]*\s*[\*\/]\s*[+-]?[0-9]+\.?[0-9]*/;
var reM = /\*/;
var reAS = /-?[0-9]+\.?[0-9]*\s*[\+-]\s*[+-]?[0-9]+\.?[0-9]*/;
var reA = /[0-9]\+/;
var exp;
function multiply(s, b=0) {
b = s.split('*');
return b[0] * b[1];
}
function divide(s, b=0) {
b = s.split('/');
return b[0] / b[1];
}
function add(s, b=0) {
s = s.replace(/^\+/,'').replace(/\++/,'+');
b = s.split('+');
return Number(b[0]) + Number(b[1]);
}
function subtract(s, b=0) {
s = s.replace(/\+-|-\+/g,'-');
if (s.match(/--/)) {
return add(s.replace(/--/,'+'));
}
b = s.split('-');
return b.length == 3 ? -1 * b[1] - b[2] : b[0] - b[1];
}
while (exp = s.match(reMD)) {
s = exp[0].match(reM) ? s.replace(exp[0], multiply(exp[0]).toString()) : s.replace(exp[0], divide(exp[0]).toString());
}
while (exp = s.match(reAS)) {
s = exp[0].match(reA)? s.replace(exp[0], add(exp[0]).toString()) : s.replace(exp[0], subtract(exp[0]).toString());
}
return '' + s;
}
while (exp = s.match(rePara)) {
s = s.replace(exp[0], evalExp(exp[0]));
}
return evalExp(s);
}
if (Interp.conf('unitTest')) {
; evalArithmeticExp('2+3');
; evalArithmeticExp('2+3/4');
; evalArithmeticExp('2*3-4');
; evalArithmeticExp('2*(3+4)+5/6');
; evalArithmeticExp('2 * (3 + (4 * 5 + (6 * 7) * 8) - 9) * 10');
; evalArithmeticExp('2*-3--4+-0.25');
}
/*
=!EXPECTSTART!=
evalArithmeticExp('2+3') ==> 5
evalArithmeticExp('2+3/4') ==> 2.75
evalArithmeticExp('2*3-4') ==> 2
evalArithmeticExp('2*(3+4)+5/6') ==> 14.8333333333333
evalArithmeticExp('2 * (3 + (4 * 5 + (6 * 7) * 8) - 9) * 10') ==> 7000
evalArithmeticExp('2*-3--4+-0.25') ==> -2.25
=!EXPECTEND!=
*/</syntaxhighlight>
{{out}}
<pre>prompt$ jsish --U arithmeticEvaluation.jsi
evalArithmeticExp('2+3') ==> 5
evalArithmeticExp('2+3/4') ==> 2.75
evalArithmeticExp('2*3-4') ==> 2
evalArithmeticExp('2*(3+4)+5/6') ==> 14.8333333333333
evalArithmeticExp('2 * (3 + (4 * 5 + (6 * 7) * 8) - 9) * 10') ==> 7000
evalArithmeticExp('2*-3--4+-0.25') ==> -2.25</pre>
=={{header|Julia}}==
Julia's homoiconic nature and strong metaprogramming facilities make AST/Expression parsing and creation as accessible and programmatic as other language features
<syntaxhighlight lang="julia">julia> expr="2 * (3 -1) + 2 * 5"
"2 * (3 -1) + 2 * 5"
julia> parsed = parse(expr) #Julia provides low-level access to language parser for AST/Expr creation
:(+(*(2,-(3,1)),*(2,5)))
julia> t = typeof(parsed)
Expr
julia> names(t) #shows type fields
(:head,:args,:typ)
julia> parsed.args #Inspect our 'Expr' type innards
3-element Any Array:
:+
:(*(2,-(3,1)))
:(*(2,5))
julia> typeof(parsed.args[2]) #'Expr' types can nest
Expr
julia> parsed.args[2].args
3-element Any Array:
:*
2
:(-(3,1))
julia> parsed.args[2].args[3].args #Will nest until lowest level of AST
3-element Any Array:
:-
3
1
julia> eval(parsed)
14
julia> eval(parse("1 - 5 * 2 / 20 + 1"))
1.5
julia> eval(parse("2 * (3 + ((5) / (7 - 11)))"))
3.5</syntaxhighlight>
=={{header|Kotlin}}==
{{trans|JavaScript}}
<syntaxhighlight lang="scala">// version 1.2.10
/* if string is empty, returns zero */
fun String.toDoubleOrZero() = this.toDoubleOrNull() ?: 0.0
fun multiply(s: String): String {
val b = s.split('*').map { it.toDoubleOrZero() }
return (b[0] * b[1]).toString()
}
fun divide(s: String): String {
val b = s.split('/').map { it.toDoubleOrZero() }
return (b[0] / b[1]).toString()
}
fun add(s: String): String {
var t = s.replace(Regex("""^\+"""), "").replace(Regex("""\++"""), "+")
val b = t.split('+').map { it.toDoubleOrZero() }
return (b[0] + b[1]).toString()
}
fun subtract(s: String): String {
var t = s.replace(Regex("""(\+-|-\+)"""), "-")
if ("--" in t) return add(t.replace("--", "+"))
val b = t.split('-').map { it.toDoubleOrZero() }
return (if (b.size == 3) -b[1] - b[2] else b[0] - b[1]).toString()
}
fun evalExp(s: String): String {
var t = s.replace(Regex("""[()]"""), "")
val reMD = Regex("""\d+\.?\d*\s*[*/]\s*[+-]?\d+\.?\d*""")
val reM = Regex( """\*""")
val reAS = Regex("""-?\d+\.?\d*\s*[+-]\s*[+-]?\d+\.?\d*""")
val reA = Regex("""\d\+""")
while (true) {
val match = reMD.find(t)
if (match == null) break
val exp = match.value
val match2 = reM.find(exp)
t = if (match2 != null)
t.replace(exp, multiply(exp))
else
t.replace(exp, divide(exp))
}
while (true) {
val match = reAS.find(t)
if (match == null) break
val exp = match.value
val match2 = reA.find(exp)
t = if (match2 != null)
t.replace(exp, add(exp))
else
t.replace(exp, subtract(exp))
}
return t
}
fun evalArithmeticExp(s: String): Double {
var t = s.replace(Regex("""\s"""), "").replace("""^\+""", "")
val rePara = Regex("""\([^()]*\)""")
while(true) {
val match = rePara.find(t)
if (match == null) break
val exp = match.value
t = t.replace(exp, evalExp(exp))
}
return evalExp(t).toDoubleOrZero()
}
fun main(arsg: Array<String>) {
listOf(
"2+3",
"2+3/4",
"2*3-4",
"2*(3+4)+5/6",
"2 * (3 + (4 * 5 + (6 * 7) * 8) - 9) * 10",
"2*-3--4+-0.25",
"-4 - 3",
"((((2))))+ 3 * 5",
"1 + 2 * (3 + (4 * 5 + 6 * 7 * 8) - 9) / 10",
"1 + 2*(3 - 2*(3 - 2)*((2 - 4)*5 - 22/(7 + 2*(3 - 1)) - 1)) + 1"
).forEach { println("$it = ${evalArithmeticExp(it)}") }
}</syntaxhighlight>
{{out}}
<pre>
2+3 = 5.0
2+3/4 = 2.75
2*3-4 = 2.0
2*(3+4)+5/6 = 14.833333333333334
2 * (3 + (4 * 5 + (6 * 7) * 8) - 9) * 10 = 7000.0
2*-3--4+-0.25 = -2.25
-4 - 3 = -7.0
((((2))))+ 3 * 5 = 17.0
1 + 2 * (3 + (4 * 5 + 6 * 7 * 8) - 9) / 10 = 71.0
1 + 2*(3 - 2*(3 - 2)*((2 - 4)*5 - 22/(7 + 2*(3 - 1)) - 1)) + 1 = 60.0
</pre>
=={{header|Liberty BASIC}}==
<syntaxhighlight lang="lb">
'[RC] Arithmetic evaluation.bas
'Buld the tree (with linked nodes, in array 'cause LB has no pointers)
'applying shunting yard algorythm.
'Then evaluate tree
global stack$ 'operator/brakets stack
stack$=""
maxStack = 100
dim stack(maxStack) 'nodes stack
global SP 'stack pointer
SP = 0
'-------------------
global maxNode,curFree
global FirstOp,SecondOp,isNumber,NodeCont
global opList$
opList$ = "+-*/^"
maxNode=100
FirstOp=1 'pointers to other nodes; 0 means no pointer
SecondOp=2
isNumber=3 'like, 1 is number, 0 is operator
NodeCont=4 'number if isNumber; or mid$("+-*/^", i, 1) for 1..5 operator
dim node(NodeCont, maxNode)
'will be used from 1, 0 plays null pointer (no link)
curFree=1 'first free node
'-------------------
in$ = " 1 + 2 ^ 3 * 4 - 12 / 6 "
print "Input: "
print in$
'read tokens
token$ = "#"
while 1
i=i+1
token$ = word$(in$, i)
if token$ = "" then i=i-1: exit while
select case
case token$ = "("
'If the token is a left parenthesis, then push it onto the stack.
call stack.push token$
case token$ = ")"
'If the token is a right parenthesis:
'Until the token at the top of the stack is a left parenthesis, pop operators off the stack onto the output queue.
'Pop the left parenthesis from the stack, but not onto the output queue.
'If the stack runs out without finding a left parenthesis, then there are mismatched parentheses.
while stack.peek$() <> "("
'if stack is empty
if stack$="" then print "Error: no matching '(' for token ";i: end
'add operator node to tree
child2=node.pop()
child1=node.pop()
call node.push addOpNode(child1,child2,stack.pop$())
wend
discard$=stack.pop$() 'discard "("
case isOperator(token$)
'If the token is an operator, o1, then:
'while there is an operator token, o2, at the top of the stack, and
'either o1 is left-associative and its precedence is equal to that of o2,
'or o1 has precedence less than that of o2,
' pop o2 off the stack, onto the output queue;
'push o1 onto the stack
op1$=token$
while(isOperator(stack.peek$()))
op2$=stack.peek$()
if (op2$<>"^" and precedence(op1$) = precedence(op2$)) _
OR (precedence(op1$) < precedence(op2$)) then
'"^" is the only right-associative operator
'add operator node to tree
child2=node.pop()
child1=node.pop()
call node.push addOpNode(child1,child2,stack.pop$())
else
exit while
end if
wend
call stack.push op1$
case else 'number
'actually, wrohg operator could end up here, like say %
'If the token is a number, then
'add leaf node to tree (number)
call node.push addNumNode(val(token$))
end select
wend
'When there are no more tokens to read:
'While there are still operator tokens in the stack:
' If the operator token on the top of the stack is a parenthesis, then there are mismatched parentheses.
' Pop the operator onto the output queue.
while stack$<>""
if stack.peek$() = "(" then print "no matching ')'": end
'add operator node to tree
child2=node.pop()
child1=node.pop()
call node.push addOpNode(child1,child2,stack.pop$())
wend
root = node.pop()
'call dumpNodes
print "Tree:"
call drawTree root, 1, 0, 3
locate 1, 10
print "Result: ";evaluate(root)
end
'------------------------------------------
function isOperator(op$)
isOperator = instr(opList$, op$)<>0 AND len(op$)=1
end function
function precedence(op$)
if isOperator(op$) then
precedence = 1 _
+ (instr("+-*/^", op$)<>0) _
+ (instr("*/^", op$)<>0) _
+ (instr("^", op$)<>0)
end if
end function
'------------------------------------------
sub stack.push s$
stack$=s$+"|"+stack$
end sub
function stack.pop$()
'it does return empty on empty stack or queue
stack.pop$=word$(stack$,1,"|")
stack$=mid$(stack$,instr(stack$,"|")+1)
end function
function stack.peek$()
'it does return empty on empty stack or queue
stack.peek$=word$(stack$,1,"|")
end function
'---------------------------------------
sub node.push s
stack(SP)=s
SP=SP+1
end sub
function node.pop()
'it does return -999999 on empty stack
if SP<1 then pop=-999999: exit function
SP=SP-1
node.pop=stack(SP)
end function
'=======================================
sub dumpNodes
for i = 1 to curFree-1
print i,
for j = 1 to 4
print node(j, i),
next
print
next
print
end sub
function evaluate(node)
if node=0 then exit function
if node(isNumber, node) then
evaluate = node(NodeCont, node)
exit function
end if
'else operator
op1 = evaluate(node(FirstOp, node))
op2 = evaluate(node(SecondOp, node))
select case node(NodeCont, node) 'opList$, "+-*/^"
case 1
evaluate = op1+op2
case 2
evaluate = op1-op2
case 3
evaluate = op1*op2
case 4
evaluate = op1/op2
case 5
evaluate = op1^op2
end select
end function
sub drawTree node, level, leftRight, offsetY
if node=0 then exit sub
call drawTree node(FirstOp, node), level+1, leftRight-1/2^level, offsetY
'print node
'count on 80 char maiwin
x = 40*(1+leftRight)
y = level+offsetY
locate x, y
'print x, y,">";
if node(isNumber, node) then
print node(NodeCont, node)
else
print mid$(opList$, node(NodeCont, node),1)
end if
call drawTree node(SecondOp, node), level+1, leftRight+1/2^level, offsetY
end sub
function addNumNode(num)
'returns new node
newNode=curFree
curFree=curFree+1
node(isNumber,newNode)=1
node(NodeCont,newNode)=num
addNumNode = newNode
end function
function addOpNode(firstChild, secondChild, op$)
'returns new node
'FirstOrSecond ignored if parent is 0
newNode=curFree
curFree=curFree+1
node(isNumber,newNode)=0
node(NodeCont,newNode)=instr(opList$, op$)
node(FirstOp,newNode)=firstChild
node(SecondOp,newNode)=secondChild
addOpNode = newNode
end function
</syntaxhighlight>
{{out}}
<pre>
Input:
1 + 2 ^ 3 * 4 - 12 / 6
Tree:
-
+ /
1 * 12 6
^ 4
2 3
Result: 31
</pre>
=={{header|Lua}}==
<syntaxhighlight lang="lua">require"lpeg"
P, R, C, S, V = lpeg.P, lpeg.R, lpeg.C, lpeg.S, lpeg.V
Line 851 ⟶ 4,556:
end
print(eval{expression:match(io.read())})</syntaxhighlight>
=={{header|M2000 Interpreter}}==
There is a function called EVAL which has many variants, one of them is the Expression Evaluation (when we pass a string as parameter).
All visible variables can be used, and all known functions, internal and user (if they are visible at that point). Global variables and functions are always visible.
<syntaxhighlight lang="m2000 interpreter">
y=100
Module CheckEval {
A$="1 + 2 * (3 + (4 * 5 + 6 * 7 * 8) - 9) / 10"
Print Eval(A$)
x=10
Print Eval("x+5")=x+5
Print Eval("A$=A$")=True
Try {
Print Eval("y") ' error: y is uknown here
}
}
Call CheckEval
</syntaxhighlight>
New version of the task program. Based on BBC Basic. Exclude the final use of Eval() function (we use it for test only)
The Ast is a stack object which have strings and numbers. String are operators. This stack has all members in a RPN form. So it is easy to extract numbers and push them to reg (a stack also), and process the operators as they pop from the stack. There is no unary operator.
So the Ast isn't a tree here, it is a flat list.
<syntaxhighlight lang="m2000 interpreter">
Module CheckAst {
class EvalAst {
private:
Function Ast(&in$) {
object Ast=stack, op=stack
Do
stack Ast {stack .Ast1(&in$)}
in$=Trim$(in$)
oper$=left$(in$,1)
if Instr("+-", oper$)>0 else exit
if len(oper$)>0 then stack op {push oper$}
in$=Mid$(in$, 2)
until len(in$)=0
stack Ast {stack op} // dump op to end of stack Ast
=Ast
}
Function Ast1(&in$) {
object Ast=stack, op=stack
Do
stack Ast {stack .Ast2(&in$)}
in$=Trim$(in$)
oper$=left$(in$,1)
if Instr("*/", oper$)>0 else exit
if len(oper$)>0 then stack op {push oper$}
in$=Mid$(in$, 2)
until len(in$)=0
stack Ast {stack op}
=Ast
}
Function Ast2(&in$) {
in$=Trim$(in$)
if Asc(in$)<>40 then =.GetNumber(&in$) : exit
in$=Mid$(in$, 2)
=.Ast(&in$)
in$=Mid$(in$, 2)
}
Function GetNumber (&in$) {
Def ch$, num$
Do
ch$=left$(in$,1)
if instr("0123456789", ch$)>0 else exit
num$+=ch$
in$=Mid$(in$, 2)
until len(in$)=0
=stack:=val(num$)
}
public:
value () {
=.Ast(![])
}
}
Ast=EvalAst()
Expr$ = "1+2 * (3 + (4 * 5 + 6 * 7 * 8) - 9) / 10"
// Expr$="1/2+(4-3)/2+1/2"
print "Result through eval$:";eval(Expr$)
print "Expr :";Expr$
mres=Ast(&Expr$)
print "RPN :";array(stack(mres))#str$()
reg=stack
stack mres {
while not empty
if islet then
read op$
stack reg {
select case op$
case "+"
push number+number
case "-"
shift 2:push number-number
case "*"
push number*number
case "/"
shift 2:push number/number // shif 2 swap top 2 values
end select
}
else
read v
stack reg {push v}
end if
end while
}
if len(reg)<>1 then Error "Wrong Evaluation"
print "Result :";stackitem(reg)
}
CheckAst
</syntaxhighlight>
{{out}}
<pre>
Result through eval$:71
Expr : 1+2 * (3 + (4 * 5 + 6 * 7 * 8) - 9) / 10
RPN : 1 2 3 4 5 * 6 7 8 * * + 9 - + 10 / * +
Result :71
</pre>
=={{header|Mathematica}} / {{header|Wolfram Language}}==
<syntaxhighlight lang="mathematica">(*parsing:*)
parse[string_] :=
Module[{e},
StringCases[string,
"+" | "-" | "*" | "/" | "(" | ")" |
DigitCharacter ..] //. {a_String?DigitQ :>
e[ToExpression@a], {x___, PatternSequence["(", a_e, ")"],
y___} :> {x, a,
y}, {x :
PatternSequence[] |
PatternSequence[___, "(" | "+" | "-" | "*" | "/"],
PatternSequence[op : "+" | "-", a_e], y___} :> {x, e[op, a],
y}, {x :
PatternSequence[] | PatternSequence[___, "(" | "+" | "-"],
PatternSequence[a_e, op : "*" | "/", b_e], y___} :> {x,
e[op, a, b],
y}, {x :
PatternSequence[] | PatternSequence[___, "(" | "+" | "-"],
PatternSequence[a_e, b_e], y___} :> {x, e["*", a, b],
y}, {x : PatternSequence[] | PatternSequence[___, "("],
PatternSequence[a_e, op : "+" | "-", b_e],
y : PatternSequence[] |
PatternSequence[")" | "+" | "-", ___]} :> {x, e[op, a, b],
y}} //. {e -> List, {a_Integer} :> a, {a_List} :> a}]
(*evaluation*)
evaluate[a_Integer] := a;
evaluate[{"+", a_}] := evaluate[a];
evaluate[{"-", a_}] := -evaluate[a];
evaluate[{"+", a_, b_}] := evaluate[a] + evaluate[b];
evaluate[{"-", a_, b_}] := evaluate[a] - evaluate[b];
evaluate[{"*", a_, b_}] := evaluate[a]*evaluate[b];
evaluate[{"/", a_, b_}] := evaluate[a]/evaluate[b];
evaluate[string_String] := evaluate[parse[string]]</syntaxhighlight>
Example use:
<syntaxhighlight lang="mathematica">parse["-1+2(3+4*-5/6)"]
evaluate["-1+2(3+4*-5/6)"]</syntaxhighlight>
{{out}}
<pre>{"+", {"-", 1}, {"*", 2, {"-", 3, {"/", {"*", 4, {"-", 5}}, 6}}}}
35/3</pre>
=={{header|MiniScript}}==
<syntaxhighlight lang="miniscript">Expr = {}
Expr.eval = 0
BinaryExpr = new Expr
BinaryExpr.eval = function()
if self.op == "+" then return self.lhs.eval + self.rhs.eval
if self.op == "-" then return self.lhs.eval - self.rhs.eval
if self.op == "*" then return self.lhs.eval * self.rhs.eval
if self.op == "/" then return self.lhs.eval / self.rhs.eval
end function
binop = function(lhs, op, rhs)
e = new BinaryExpr
e.lhs = lhs
e.op = op
e.rhs = rhs
return e
end function
parseAtom = function(inp)
tok = inp.pull
if tok >= "0" and tok <= "9" then
e = new Expr
e.eval = val(tok)
while inp and inp[0] >= "0" and inp[0] <= "9"
e.eval = e.eval * 10 + val(inp.pull)
end while
else if tok == "(" then
e = parseAddSub(inp)
inp.pull // swallow closing ")"
return e
else
print "Unexpected token: " + tok
exit
end if
return e
end function
parseMultDiv = function(inp)
next = @parseAtom
e = next(inp)
while inp and (inp[0] == "*" or inp[0] == "/")
e = binop(e, inp.pull, next(inp))
end while
return e
end function
parseAddSub = function(inp)
next = @parseMultDiv
e = next(inp)
while inp and (inp[0] == "+" or inp[0] == "-")
e = binop(e, inp.pull, next(inp))
end while
return e
end function
while true
s = input("Enter expression: ").replace(" ","")
if not s then break
inp = split(s, "")
ast = parseAddSub(inp)
print ast.eval
end while
</syntaxhighlight>
{{out}}
<pre>Enter expression: 200*42
8400
Enter expression: 2+2+2
6
Enter expression: 2 + 3 * 4
14
Enter expression: (2+3)*4
20
Enter expression:
</pre>
=={{header|Nim}}==
{{works with|Nim|0.19.0}}
This implementation uses a Pratt parser.
<syntaxhighlight lang="nim">import strutils
import os
#--
# Lexer
#--
type
TokenKind = enum
tokNumber
tokPlus = "+", tokMinus = "-", tokStar = "*", tokSlash = "/"
tokLPar, tokRPar
tokEnd
Token = object
case kind: TokenKind
of tokNumber: value: float
else: discard
proc lex(input: string): seq[Token] =
# Here we go through the entire input string and collect all the tokens into
# a sequence.
var pos = 0
while pos < input.len:
case input[pos]
of '0'..'9':
# Digits consist of three parts: the integer part, the delimiting decimal
# point, and the decimal part.
var numStr = ""
while pos < input.len and input[pos] in Digits:
numStr.add(input[pos])
inc(pos)
if pos < input.len and input[pos] == '.':
numStr.add('.')
inc(pos)
while pos < input.len and input[pos] in Digits:
numStr.add(input[pos])
inc(pos)
result.add(Token(kind: tokNumber, value: numStr.parseFloat()))
of '+': inc(pos); result.add(Token(kind: tokPlus))
of '-': inc(pos); result.add(Token(kind: tokMinus))
of '*': inc(pos); result.add(Token(kind: tokStar))
of '/': inc(pos); result.add(Token(kind: tokSlash))
of '(': inc(pos); result.add(Token(kind: tokLPar))
of ')': inc(pos); result.add(Token(kind: tokRPar))
of ' ': inc(pos)
else: raise newException(ArithmeticError,
"Unexpected character '" & input[pos] & '\'')
# We append an 'end' token to the end of our token sequence, to mark where the
# sequence ends.
result.add(Token(kind: tokEnd))
#--
# Parser
#--
type
ExprKind = enum
exprNumber
exprBinary
Expr = ref object
case kind: ExprKind
of exprNumber: value: float
of exprBinary:
left, right: Expr
operator: TokenKind
proc `$`(ex: Expr): string =
# This proc returns a lisp representation of the expression.
case ex.kind
of exprNumber: $ex.value
of exprBinary: '(' & $ex.operator & ' ' & $ex.left & ' ' & $ex.right & ')'
var
# The input to the program is provided via command line parameters.
tokens = lex(commandLineParams().join(" "))
pos = 0
# This table stores the precedence level of each infix operator. For tokens
# this does not apply to, the precedence is set to 0.
const Precedence: array[low(TokenKind)..high(TokenKind), int] = [
tokNumber: 0,
tokPlus: 1,
tokMinus: 1,
tokStar: 2,
tokSlash: 2,
tokLPar: 0,
tokRPar: 0,
tokEnd: 0
]
# We use a Pratt parser, so the two primary components are the prefix part, and
# the infix part. We start with a prefix token, and when we're done, we continue
# with an infix token.
proc parse(prec = 0): Expr
proc parseNumber(token: Token): Expr =
result = Expr(kind: exprNumber, value: token.value)
proc parseParen(token: Token): Expr =
result = parse()
if tokens[pos].kind != tokRPar:
raise newException(ArithmeticError, "Unbalanced parenthesis")
inc(pos)
proc parseBinary(left: Expr, token: Token): Expr =
result = Expr(kind: exprBinary, left: left, right: parse(),
operator: token.kind)
proc parsePrefix(token: Token): Expr =
case token.kind
of tokNumber: result = parseNumber(token)
of tokLPar: result = parseParen(token)
else: discard
proc parseInfix(left: Expr, token: Token): Expr =
case token.kind
of tokPlus, tokMinus, tokStar, tokSlash: result = parseBinary(left, token)
else: discard
proc parse(prec = 0): Expr =
# This procedure is the heart of a Pratt parser, it puts the whole expression
# together into one abstract syntax tree, properly dealing with precedence.
var token = tokens[pos]
inc(pos)
result = parsePrefix(token)
while prec < Precedence[tokens[pos].kind]:
token = tokens[pos]
if token.kind == tokEnd:
# When we hit the end token, we're done.
break
inc(pos)
result = parseInfix(result, token)
let ast = parse()
proc `==`(ex: Expr): float =
# This proc recursively evaluates the given expression.
result =
case ex.kind
of exprNumber: ex.value
of exprBinary:
case ex.operator
of tokPlus: ==ex.left + ==ex.right
of tokMinus: ==ex.left - ==ex.right
of tokStar: ==ex.left * ==ex.right
of tokSlash: ==ex.left / ==ex.right
else: 0.0
# In the end, we print out the result.
echo ==ast</syntaxhighlight>
=={{header|OCaml}}==
<
| Const of float
| Sum of expression * expression (* e1 + e2 *)
Line 864 ⟶ 4,965:
| Quot of expression * expression (* e1 / e2 *)
let rec eval
| Const c -> c
| Sum (f, g) -> eval f +. eval g
Line 896 ⟶ 4,996:
let parse_expression = parser [< e = parse_expr; _ = Stream.empty >] -> e
let read_expression s = parse_expression(lexer(Stream.of_string s))</
Using the function <code>read_expression</code> in an interactive loop:
<
while true do
print_string "Expression: ";
Line 908 ⟶ 5,008:
let res = eval expr in
Printf.printf " = %g\n%!" res;
done</
Compile with:
ocamlopt -pp camlp4o arith_eval.ml -o arith_eval.opt
=={{header|ooRexx}}==
<syntaxhighlight lang="oorexx">
expressions = .array~of("2+3", "2+3/4", "2*3-4", "2*(3+4)+5/6", "2 * (3 + (4 * 5 + (6 * 7) * 8) - 9) * 10", "2*-3--4+-.25")
loop input over expressions
expression = createExpression(input)
if expression \= .nil then
say 'Expression "'input'" parses to "'expression~string'" and evaluates to "'expression~evaluate'"'
end
-- create an executable expression from the input, printing out any
-- errors if they are raised.
::routine createExpression
use arg inputString
-- signal on syntax
return .ExpressionParser~parseExpression(inputString)
syntax:
condition = condition('o')
say condition~errorText
say condition~message
return .nil
-- a base class for tree nodes in the tree
-- all nodes return some sort of value. This can be constant,
-- or the result of additional evaluations
::class evaluatornode
-- all evaluation is done here
::method evaluate abstract
-- node for numeric values in the tree
::class constant
::method init
expose value
use arg value
::method evaluate
expose value
return value
::method string
expose value
return value
-- node for a parenthetical group on the tree
::class parens
::method init
expose subexpression
use arg subexpression
::method evaluate
expose subexpression
return subexpression~evaluate
::method string
expose subexpression
return "("subexpression~string")"
-- base class for binary operators
::class binaryoperator
::method init
expose left right
-- the left and right sides are set after the left and right sides have
-- been resolved.
left = .nil
right = .nil
-- base operation
::method evaluate
expose left right
return self~operation(left~evaluate, right~evaluate)
-- the actual operation of the node
::method operation abstract
::method symbol abstract
::method precedence abstract
-- display an operator as a string value
::method string
expose left right
return '('left~string self~symbol right~string')'
::attribute left
::attribute right
::class addoperator subclass binaryoperator
::method operation
use arg left, right
return left + right
::method symbol
return "+"
::method precedence
return 1
::class subtractoperator subclass binaryoperator
::method operation
use arg left, right
return left - right
::method symbol
return "-"
::method precedence
return 1
::class multiplyoperator subclass binaryoperator
::method operation
use arg left, right
return left * right
::method symbol
return "*"
::method precedence
return 2
::class divideoperator subclass binaryoperator
::method operation
use arg left, right
return left / right
::method symbol
return "/"
::method precedence
return 2
-- a class to parse the expression and build an evaluation tree
::class expressionParser
-- create a resolved operand from an operator instance and the top
-- two entries on the operand stack.
::method createNewOperand class
use strict arg operator, operands
-- the operands are a stack, so they are in inverse order current
operator~right = operands~pull
operator~left = operands~pull
-- this goes on the top of the stack now
operands~push(operator)
::method parseExpression class
use strict arg inputString
-- stacks for managing the operands and pending operators
operands = .queue~new
operators = .queue~new
-- this flags what sort of item we expect to find at the current
-- location
afterOperand = .false
loop currentIndex = 1 to inputString~length
char = inputString~subChar(currentIndex)
-- skip over whitespace
if char == ' ' then iterate currentIndex
-- If the last thing we parsed was an operand, then
-- we expect to see either a closing paren or an
-- operator to appear here
if afterOperand then do
if char == ')' then do
loop while \operators~isempty
operator = operators~pull
-- if we find the opening paren, replace the
-- top operand with a paren group wrapper
-- and stop popping items
if operator == '(' then do
operands~push(.parens~new(operands~pull))
leave
end
-- collapse the operator stack a bit
self~createNewOperand(operator, operands)
end
-- done with this character
iterate currentIndex
end
afterOperand = .false
operator = .nil
if char == "+" then operator = .addoperator~new
else if char == "-" then operator = .subtractoperator~new
else if char == "*" then operator = .multiplyoperator~new
else if char == "/" then operator = .divideoperator~new
if operator \= .nil then do
loop while \operators~isEmpty
top = operators~peek
-- start of a paren group stops the popping
if top == '(' then leave
-- or the top operator has a lower precedence
if top~precedence < operator~precedence then leave
-- process this pending one
self~createNewOperand(operators~pull, operands)
end
-- this new operator is now top of the stack
operators~push(operator)
-- and back to the top
iterate currentIndex
end
raise syntax 98.900 array("Invalid expression character" char)
end
-- if we've hit an open paren, add this to the operator stack
-- as a phony operator
if char == '(' then do
operators~push('(')
iterate currentIndex
end
-- not an operator, so we have an operand of some type
afterOperand = .true
startindex = currentIndex
-- allow a leading minus sign on this
if inputString~subchar(currentIndex) == '-' then
currentIndex += 1
-- now scan for the end of numbers
loop while currentIndex <= inputString~length
-- exit for any non-numeric value
if \inputString~matchChar(currentIndex, "0123456789.") then leave
currentIndex += 1
end
-- extract the string value
operand = inputString~substr(startIndex, currentIndex - startIndex)
if \operand~datatype('Number') then
raise syntax 98.900 array("Invalid numeric operand '"operand"'")
-- back this up to the last valid character
currentIndex -= 1
-- add this to the operand stack as a tree element that returns a constant
operands~push(.constant~new(operand))
end
loop while \operators~isEmpty
operator = operators~pull
if operator == '(' then
raise syntax 98.900 array("Missing closing ')' in expression")
self~createNewOperand(operator, operands)
end
-- our entire expression should be the top of the expression tree
expression = operands~pull
if \operands~isEmpty then
raise syntax 98.900 array("Invalid expression")
return expression
</syntaxhighlight>
{{out}}
<pre>
Expression "2+3" parses to "(2 + 3)" and evaluates to "5"
Expression "2+3/4" parses to "(2 + (3 / 4))" and evaluates to "2.75"
Expression "2*3-4" parses to "((2 * 3) - 4)" and evaluates to "2"
Expression "2*(3+4)+5/6" parses to "((2 * ((3 + 4))) + (5 / 6))" and evaluates to "14.8333333"
Expression "2 * (3 + (4 * 5 + (6 * 7) * 8) - 9) * 10" parses to "((2 * (((3 + (((4 * 5) + (((6 * 7)) * 8)))) - 9))) * 10)" and evaluates to 7000"
Expression "2*-3--4+-.25" parses to "(((2 * -3) - -4) + -.25)" and evaluates to "-2.25"
</pre>
=={{header|Oz}}==
Line 920 ⟶ 5,267:
The <code>Do</code> procedure automatically threads the input state through a sequence of procedure calls.
<
fun {Expr X0 ?X}
Line 1,007 ⟶ 5,354:
{Inspector.configure widgetShowStrings true}
{Inspect AST}
{Inspect {Eval AST}}</
To improve performance, the number of choice points should be limited, for example by reading numbers deterministically instead.
Line 1,016 ⟶ 5,363:
=={{header|Perl}}==
<
# Evaluates an arithmetic expression like "(1+3)*7" and returns
# its value.
Line 1,076 ⟶ 5,423:
my ($op, @operands) = @$ast;
$_ = ev_ast($_) foreach @operands;
return $ops{$op}->(@operands);}}</
=={{header|
This is really just a simplification of the one in the heart of Phix,
which of course by now is thousands of lines spread over several files,
plus this as asked for has an AST, whereas Phix uses cross-linked flat IL.
See also [[Arithmetic_evaluation/Phix]] for a translation of the D entry.
<!--<syntaxhighlight lang="phix">(phixonline)-->
<span style="color: #000080;font-style:italic;">-- demo\rosetta\Arithmetic_evaluation.exw</span>
<span style="color: #008080;">with</span> <span style="color: #008080;">javascript_semantics</span>
<span style="color: #004080;">sequence</span> <span style="color: #000000;">opstack</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">{}</span> <span style="color: #000080;font-style:italic;">-- atom elements are literals,
-- sequence elements are subexpressions
-- on completion length(opstack) should be 1</span>
<span style="color: #004080;">object</span> <span style="color: #000000;">token</span>
<span style="color: #008080;">constant</span> <span style="color: #000000;">op_p_p</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">1</span> <span style="color: #000080;font-style:italic;">-- 1: expressions stored as op,p1,p2
-- p_op_p -- 0: expressions stored as p1,op,p2
-- p_p_op -- -1: expressions stored as p1,p2,op</span>
<span style="color: #004080;">object</span> <span style="color: #000000;">op</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">0</span> <span style="color: #000080;font-style:italic;">-- 0 if none, else "+", "-", "*", "/", "^", "%", or "u-"</span>
<span style="color: #004080;">string</span> <span style="color: #000000;">s</span> <span style="color: #000080;font-style:italic;">-- the expression being parsed</span>
<span style="color: #004080;">integer</span> <span style="color: #000000;">ch</span>
<span style="color: #004080;">integer</span> <span style="color: #000000;">sidx</span>
<span style="color: #008080;">procedure</span> <span style="color: #000000;">err</span><span style="color: #0000FF;">(</span><span style="color: #004080;">string</span> <span style="color: #000000;">msg</span><span style="color: #0000FF;">)</span>
<span style="color: #7060A8;">printf</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"%s\n%s^ %s\n\nPressEnter..."</span><span style="color: #0000FF;">,{</span><span style="color: #000000;">s</span><span style="color: #0000FF;">,</span><span style="color: #7060A8;">repeat</span><span style="color: #0000FF;">(</span><span style="color: #008000;">' '</span><span style="color: #0000FF;">,</span><span style="color: #000000;">sidx</span><span style="color: #0000FF;">-</span><span style="color: #000000;">1</span><span style="color: #0000FF;">),</span><span style="color: #000000;">msg</span><span style="color: #0000FF;">})</span>
<span style="color: #0000FF;">{}</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">wait_key</span><span style="color: #0000FF;">()</span>
<span style="color: #7060A8;">abort</span><span style="color: #0000FF;">(</span><span style="color: #000000;">0</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">procedure</span>
<span style="color: #008080;">procedure</span> <span style="color: #000000;">nxtch</span><span style="color: #0000FF;">(</span><span style="color: #004080;">object</span> <span style="color: #000000;">msg</span><span style="color: #0000FF;">=</span><span style="color: #008000;">"eof"</span><span style="color: #0000FF;">)</span>
<span style="color: #000000;">sidx</span> <span style="color: #0000FF;">+=</span> <span style="color: #000000;">1</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">sidx</span><span style="color: #0000FF;">></span><span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">s</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">then</span>
<span style="color: #008080;">if</span> <span style="color: #004080;">string</span><span style="color: #0000FF;">(</span><span style="color: #000000;">msg</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">then</span> <span style="color: #000000;">err</span><span style="color: #0000FF;">(</span><span style="color: #000000;">msg</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #000000;">ch</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">-</span><span style="color: #000000;">1</span>
<span style="color: #008080;">else</span>
<span style="color: #000000;">ch</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">s</span><span style="color: #0000FF;">[</span><span style="color: #000000;">sidx</span><span style="color: #0000FF;">]</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">procedure</span>
<span style="color: #008080;">procedure</span> <span style="color: #000000;">skipspaces</span><span style="color: #0000FF;">()</span>
<span style="color: #008080;">while</span> <span style="color: #7060A8;">find</span><span style="color: #0000FF;">(</span><span style="color: #000000;">ch</span><span style="color: #0000FF;">,{</span><span style="color: #008000;">' '</span><span style="color: #0000FF;">,</span><span style="color: #008000;">'\t'</span><span style="color: #0000FF;">,</span><span style="color: #008000;">'\r'</span><span style="color: #0000FF;">,</span><span style="color: #008000;">'\n'</span><span style="color: #0000FF;">})!=</span><span style="color: #000000;">0</span> <span style="color: #008080;">do</span> <span style="color: #000000;">nxtch</span><span style="color: #0000FF;">(</span><span style="color: #000000;">0</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">end</span> <span style="color: #008080;">while</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">procedure</span>
<span style="color: #008080;">procedure</span> <span style="color: #000000;">get_token</span><span style="color: #0000FF;">()</span>
<span style="color: #004080;">atom</span> <span style="color: #000000;">n</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">fraction</span>
<span style="color: #004080;">integer</span> <span style="color: #000000;">dec</span>
<span style="color: #000000;">skipspaces</span><span style="color: #0000FF;">()</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">ch</span><span style="color: #0000FF;">=-</span><span style="color: #000000;">1</span> <span style="color: #008080;">then</span> <span style="color: #000000;">token</span> <span style="color: #0000FF;">=</span> <span style="color: #008000;">"eof"</span> <span style="color: #008080;">return</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">ch</span><span style="color: #0000FF;">>=</span><span style="color: #008000;">'0'</span> <span style="color: #008080;">and</span> <span style="color: #000000;">ch</span><span style="color: #0000FF;"><=</span><span style="color: #008000;">'9'</span> <span style="color: #008080;">then</span>
<span style="color: #000000;">n</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">ch</span><span style="color: #0000FF;">-</span><span style="color: #008000;">'0'</span>
<span style="color: #008080;">while</span> <span style="color: #000000;">1</span> <span style="color: #008080;">do</span>
<span style="color: #000000;">nxtch</span><span style="color: #0000FF;">(</span><span style="color: #000000;">0</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">ch</span><span style="color: #0000FF;"><</span><span style="color: #008000;">'0'</span> <span style="color: #008080;">or</span> <span style="color: #000000;">ch</span><span style="color: #0000FF;">></span><span style="color: #008000;">'9'</span> <span style="color: #008080;">then</span> <span style="color: #008080;">exit</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #000000;">n</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">n</span><span style="color: #0000FF;">*</span><span style="color: #000000;">10</span><span style="color: #0000FF;">+</span><span style="color: #000000;">ch</span><span style="color: #0000FF;">-</span><span style="color: #008000;">'0'</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">while</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">ch</span><span style="color: #0000FF;">=</span><span style="color: #008000;">'.'</span> <span style="color: #008080;">then</span>
<span style="color: #000000;">dec</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">1</span>
<span style="color: #000000;">fraction</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">0</span>
<span style="color: #008080;">while</span> <span style="color: #000000;">1</span> <span style="color: #008080;">do</span>
<span style="color: #000000;">nxtch</span><span style="color: #0000FF;">(</span><span style="color: #000000;">0</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">ch</span><span style="color: #0000FF;"><</span><span style="color: #008000;">'0'</span> <span style="color: #008080;">or</span> <span style="color: #000000;">ch</span><span style="color: #0000FF;">></span><span style="color: #008000;">'9'</span> <span style="color: #008080;">then</span> <span style="color: #008080;">exit</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #000000;">fraction</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">fraction</span><span style="color: #0000FF;">*</span><span style="color: #000000;">10</span> <span style="color: #0000FF;">+</span> <span style="color: #000000;">ch</span><span style="color: #0000FF;">-</span><span style="color: #008000;">'0'</span>
<span style="color: #000000;">dec</span> <span style="color: #0000FF;">*=</span> <span style="color: #000000;">10</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">while</span>
<span style="color: #000000;">n</span> <span style="color: #0000FF;">+=</span> <span style="color: #000000;">fraction</span><span style="color: #0000FF;">/</span><span style="color: #000000;">dec</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #000080;font-style:italic;">-- if find(ch,"eE") then -- you get the idea
-- end if</span>
<span style="color: #000000;">token</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">n</span>
<span style="color: #008080;">return</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #008080;">if</span> <span style="color: #7060A8;">find</span><span style="color: #0000FF;">(</span><span style="color: #000000;">ch</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"+-/*()^%"</span><span style="color: #0000FF;">)=</span><span style="color: #000000;">0</span> <span style="color: #008080;">then</span> <span style="color: #000000;">err</span><span style="color: #0000FF;">(</span><span style="color: #008000;">"syntax error"</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #000000;">token</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">s</span><span style="color: #0000FF;">[</span><span style="color: #000000;">sidx</span><span style="color: #0000FF;">..</span><span style="color: #000000;">sidx</span><span style="color: #0000FF;">]</span>
<span style="color: #000000;">nxtch</span><span style="color: #0000FF;">(</span><span style="color: #000000;">0</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">return</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">procedure</span>
<span style="color: #008080;">procedure</span> <span style="color: #000000;">Match</span><span style="color: #0000FF;">(</span><span style="color: #004080;">string</span> <span style="color: #000000;">t</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">token</span><span style="color: #0000FF;">!=</span><span style="color: #000000;">t</span> <span style="color: #008080;">then</span> <span style="color: #000000;">err</span><span style="color: #0000FF;">(</span><span style="color: #000000;">t</span><span style="color: #0000FF;">&</span><span style="color: #008000;">" expected"</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #000000;">get_token</span><span style="color: #0000FF;">()</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">procedure</span>
<span style="color: #008080;">procedure</span> <span style="color: #000000;">PopFactor</span><span style="color: #0000FF;">()</span>
<span style="color: #004080;">object</span> <span style="color: #000000;">p1</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">p2</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">opstack</span><span style="color: #0000FF;">[$]</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">op</span><span style="color: #0000FF;">=</span><span style="color: #008000;">"u-"</span> <span style="color: #008080;">then</span>
<span style="color: #000000;">p1</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">0</span>
<span style="color: #008080;">else</span>
<span style="color: #000000;">opstack</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">opstack</span><span style="color: #0000FF;">[</span><span style="color: #000000;">1</span><span style="color: #0000FF;">..$-</span><span style="color: #000000;">1</span><span style="color: #0000FF;">]</span>
<span style="color: #000000;">p1</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">opstack</span><span style="color: #0000FF;">[$]</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">op_p_p</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span> <span style="color: #008080;">then</span>
<span style="color: #000000;">opstack</span><span style="color: #0000FF;">[$]</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">{</span><span style="color: #000000;">op</span><span style="color: #0000FF;">,</span><span style="color: #000000;">p1</span><span style="color: #0000FF;">,</span><span style="color: #000000;">p2</span><span style="color: #0000FF;">}</span> <span style="color: #000080;font-style:italic;">-- op_p_p</span>
<span style="color: #008080;">elsif</span> <span style="color: #000000;">op_p_p</span><span style="color: #0000FF;">=</span><span style="color: #000000;">0</span> <span style="color: #008080;">then</span>
<span style="color: #000000;">opstack</span><span style="color: #0000FF;">[$]</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">{</span><span style="color: #000000;">p1</span><span style="color: #0000FF;">,</span><span style="color: #000000;">op</span><span style="color: #0000FF;">,</span><span style="color: #000000;">p2</span><span style="color: #0000FF;">}</span> <span style="color: #000080;font-style:italic;">-- p_op_p</span>
<span style="color: #008080;">else</span> <span style="color: #000080;font-style:italic;">-- -1</span>
<span style="color: #000000;">opstack</span><span style="color: #0000FF;">[$]</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">{</span><span style="color: #000000;">p1</span><span style="color: #0000FF;">,</span><span style="color: #000000;">p2</span><span style="color: #0000FF;">,</span><span style="color: #000000;">op</span><span style="color: #0000FF;">}</span> <span style="color: #000080;font-style:italic;">-- p_p_op</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #000000;">op</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">0</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">procedure</span>
<span style="color: #008080;">procedure</span> <span style="color: #000000;">PushFactor</span><span style="color: #0000FF;">(</span><span style="color: #004080;">atom</span> <span style="color: #000000;">t</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">op</span><span style="color: #0000FF;">!=</span><span style="color: #000000;">0</span> <span style="color: #008080;">then</span> <span style="color: #000000;">PopFactor</span><span style="color: #0000FF;">()</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #000000;">opstack</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">append</span><span style="color: #0000FF;">(</span><span style="color: #000000;">opstack</span><span style="color: #0000FF;">,</span><span style="color: #000000;">t</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">procedure</span>
<span style="color: #008080;">procedure</span> <span style="color: #000000;">PushOp</span><span style="color: #0000FF;">(</span><span style="color: #004080;">string</span> <span style="color: #000000;">t</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">op</span><span style="color: #0000FF;">!=</span><span style="color: #000000;">0</span> <span style="color: #008080;">then</span> <span style="color: #000000;">PopFactor</span><span style="color: #0000FF;">()</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #000000;">op</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">t</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">procedure</span>
<span style="color: #008080;">forward</span> <span style="color: #008080;">procedure</span> <span style="color: #000000;">Expr</span><span style="color: #0000FF;">(</span><span style="color: #004080;">integer</span> <span style="color: #000000;">p</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">procedure</span> <span style="color: #000000;">Factor</span><span style="color: #0000FF;">()</span>
<span style="color: #008080;">if</span> <span style="color: #004080;">atom</span><span style="color: #0000FF;">(</span><span style="color: #000000;">token</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">then</span>
<span style="color: #000000;">PushFactor</span><span style="color: #0000FF;">(</span><span style="color: #000000;">token</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">ch</span><span style="color: #0000FF;">!=-</span><span style="color: #000000;">1</span> <span style="color: #008080;">then</span>
<span style="color: #000000;">get_token</span><span style="color: #0000FF;">()</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #008080;">elsif</span> <span style="color: #000000;">token</span><span style="color: #0000FF;">=</span><span style="color: #008000;">"+"</span> <span style="color: #008080;">then</span> <span style="color: #000080;font-style:italic;">-- (ignore)</span>
<span style="color: #000000;">nxtch</span><span style="color: #0000FF;">()</span>
<span style="color: #000000;">Factor</span><span style="color: #0000FF;">()</span>
<span style="color: #008080;">elsif</span> <span style="color: #000000;">token</span><span style="color: #0000FF;">=</span><span style="color: #008000;">"-"</span> <span style="color: #008080;">then</span>
<span style="color: #000000;">get_token</span><span style="color: #0000FF;">()</span>
<span style="color: #000080;font-style:italic;">-- Factor()</span>
<span style="color: #000000;">Expr</span><span style="color: #0000FF;">(</span><span style="color: #000000;">3</span><span style="color: #0000FF;">)</span> <span style="color: #000080;font-style:italic;">-- makes "-3^2" yield -9 (ie -(3^2)) not 9 (ie (-3)^2).</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">op</span><span style="color: #0000FF;">!=</span><span style="color: #000000;">0</span> <span style="color: #008080;">then</span> <span style="color: #000000;">PopFactor</span><span style="color: #0000FF;">()</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #008080;">if</span> <span style="color: #004080;">integer</span><span style="color: #0000FF;">(</span><span style="color: #000000;">opstack</span><span style="color: #0000FF;">[$])</span> <span style="color: #008080;">then</span>
<span style="color: #000000;">opstack</span><span style="color: #0000FF;">[$]</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">-</span><span style="color: #000000;">opstack</span><span style="color: #0000FF;">[$]</span>
<span style="color: #008080;">else</span>
<span style="color: #000000;">PushOp</span><span style="color: #0000FF;">(</span><span style="color: #008000;">"u-"</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #008080;">elsif</span> <span style="color: #000000;">token</span><span style="color: #0000FF;">=</span><span style="color: #008000;">"("</span> <span style="color: #008080;">then</span>
<span style="color: #000000;">get_token</span><span style="color: #0000FF;">()</span>
<span style="color: #000000;">Expr</span><span style="color: #0000FF;">(</span><span style="color: #000000;">0</span><span style="color: #0000FF;">)</span>
<span style="color: #000000;">Match</span><span style="color: #0000FF;">(</span><span style="color: #008000;">")"</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">else</span>
<span style="color: #000000;">err</span><span style="color: #0000FF;">(</span><span style="color: #008000;">"syntax error"</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">procedure</span>
<span style="color: #008080;">constant</span> <span style="color: #0000FF;">{</span><span style="color: #000000;">operators</span><span style="color: #0000FF;">,</span>
<span style="color: #000000;">precedence</span><span style="color: #0000FF;">,</span>
<span style="color: #000000;">associativity</span><span style="color: #0000FF;">}</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">columnize</span><span style="color: #0000FF;">({{</span><span style="color: #008000;">"^"</span><span style="color: #0000FF;">,</span><span style="color: #000000;">3</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">},</span>
<span style="color: #0000FF;">{</span><span style="color: #008000;">"%"</span><span style="color: #0000FF;">,</span><span style="color: #000000;">2</span><span style="color: #0000FF;">,</span><span style="color: #000000;">1</span><span style="color: #0000FF;">},</span>
<span style="color: #0000FF;">{</span><span style="color: #008000;">"*"</span><span style="color: #0000FF;">,</span><span style="color: #000000;">2</span><span style="color: #0000FF;">,</span><span style="color: #000000;">1</span><span style="color: #0000FF;">},</span>
<span style="color: #0000FF;">{</span><span style="color: #008000;">"/"</span><span style="color: #0000FF;">,</span><span style="color: #000000;">2</span><span style="color: #0000FF;">,</span><span style="color: #000000;">1</span><span style="color: #0000FF;">},</span>
<span style="color: #0000FF;">{</span><span style="color: #008000;">"+"</span><span style="color: #0000FF;">,</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #000000;">1</span><span style="color: #0000FF;">},</span>
<span style="color: #0000FF;">{</span><span style="color: #008000;">"-"</span><span style="color: #0000FF;">,</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #000000;">1</span><span style="color: #0000FF;">},</span>
<span style="color: #0000FF;">$})</span>
<span style="color: #008080;">procedure</span> <span style="color: #000000;">Expr</span><span style="color: #0000FF;">(</span><span style="color: #004080;">integer</span> <span style="color: #000000;">p</span><span style="color: #0000FF;">)</span>
<span style="color: #000080;font-style:italic;">--
-- Parse an expression, using precedence climbing.
--
-- p is the precedence level we should parse to, eg/ie
-- 4: Factor only (may as well just call Factor)
-- 3: "" and ^
-- 2: "" and *,/,%
-- 1: "" and +,-
-- 0: full expression (effectively the same as 1)
-- obviously, parentheses override any setting of p.
--</span>
<span style="color: #004080;">integer</span> <span style="color: #000000;">k</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">thisp</span>
<span style="color: #000000;">Factor</span><span style="color: #0000FF;">()</span>
<span style="color: #008080;">while</span> <span style="color: #000000;">1</span> <span style="color: #008080;">do</span>
<span style="color: #000000;">k</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">find</span><span style="color: #0000FF;">(</span><span style="color: #000000;">token</span><span style="color: #0000FF;">,</span><span style="color: #000000;">operators</span><span style="color: #0000FF;">)</span> <span style="color: #000080;font-style:italic;">-- *,/,+,-</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">k</span><span style="color: #0000FF;">=</span><span style="color: #000000;">0</span> <span style="color: #008080;">then</span> <span style="color: #008080;">exit</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #000000;">thisp</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">precedence</span><span style="color: #0000FF;">[</span><span style="color: #000000;">k</span><span style="color: #0000FF;">]</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">thisp</span><span style="color: #0000FF;"><</span><span style="color: #000000;">p</span> <span style="color: #008080;">then</span> <span style="color: #008080;">exit</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #000000;">get_token</span><span style="color: #0000FF;">()</span>
<span style="color: #000000;">Expr</span><span style="color: #0000FF;">(</span><span style="color: #000000;">thisp</span><span style="color: #0000FF;">+</span><span style="color: #000000;">associativity</span><span style="color: #0000FF;">[</span><span style="color: #000000;">k</span><span style="color: #0000FF;">])</span>
<span style="color: #000000;">PushOp</span><span style="color: #0000FF;">(</span><span style="color: #000000;">operators</span><span style="color: #0000FF;">[</span><span style="color: #000000;">k</span><span style="color: #0000FF;">])</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">while</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">procedure</span>
<span style="color: #008080;">function</span> <span style="color: #000000;">evaluate</span><span style="color: #0000FF;">(</span><span style="color: #004080;">object</span> <span style="color: #000000;">s</span><span style="color: #0000FF;">)</span>
<span style="color: #004080;">object</span> <span style="color: #000000;">lhs</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">rhs</span>
<span style="color: #004080;">string</span> <span style="color: #000000;">op</span>
<span style="color: #008080;">if</span> <span style="color: #004080;">atom</span><span style="color: #0000FF;">(</span><span style="color: #000000;">s</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">then</span>
<span style="color: #008080;">return</span> <span style="color: #000000;">s</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">op_p_p</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span> <span style="color: #008080;">then</span> <span style="color: #000080;font-style:italic;">-- op_p_p</span>
<span style="color: #0000FF;">{</span><span style="color: #000000;">op</span><span style="color: #0000FF;">,</span><span style="color: #000000;">lhs</span><span style="color: #0000FF;">,</span><span style="color: #000000;">rhs</span><span style="color: #0000FF;">}</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">s</span>
<span style="color: #008080;">elsif</span> <span style="color: #000000;">op_p_p</span><span style="color: #0000FF;">=</span><span style="color: #000000;">0</span> <span style="color: #008080;">then</span> <span style="color: #000080;font-style:italic;">-- p_op_p</span>
<span style="color: #0000FF;">{</span><span style="color: #000000;">lhs</span><span style="color: #0000FF;">,</span><span style="color: #000000;">op</span><span style="color: #0000FF;">,</span><span style="color: #000000;">rhs</span><span style="color: #0000FF;">}</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">s</span>
<span style="color: #008080;">else</span> <span style="color: #000080;font-style:italic;">-- -1 -- p_p_op</span>
<span style="color: #0000FF;">{</span><span style="color: #000000;">lhs</span><span style="color: #0000FF;">,</span><span style="color: #000000;">rhs</span><span style="color: #0000FF;">,</span><span style="color: #000000;">op</span><span style="color: #0000FF;">}</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">s</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #008080;">if</span> <span style="color: #004080;">sequence</span><span style="color: #0000FF;">(</span><span style="color: #000000;">lhs</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">then</span> <span style="color: #000000;">lhs</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">evaluate</span><span style="color: #0000FF;">(</span><span style="color: #000000;">lhs</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #008080;">if</span> <span style="color: #004080;">sequence</span><span style="color: #0000FF;">(</span><span style="color: #000000;">rhs</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">then</span> <span style="color: #000000;">rhs</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">evaluate</span><span style="color: #0000FF;">(</span><span style="color: #000000;">rhs</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">op</span><span style="color: #0000FF;">=</span><span style="color: #008000;">"+"</span> <span style="color: #008080;">then</span>
<span style="color: #008080;">return</span> <span style="color: #000000;">lhs</span><span style="color: #0000FF;">+</span><span style="color: #000000;">rhs</span>
<span style="color: #008080;">elsif</span> <span style="color: #000000;">op</span><span style="color: #0000FF;">=</span><span style="color: #008000;">"-"</span> <span style="color: #008080;">then</span>
<span style="color: #008080;">return</span> <span style="color: #000000;">lhs</span><span style="color: #0000FF;">-</span><span style="color: #000000;">rhs</span>
<span style="color: #008080;">elsif</span> <span style="color: #000000;">op</span><span style="color: #0000FF;">=</span><span style="color: #008000;">"*"</span> <span style="color: #008080;">then</span>
<span style="color: #008080;">return</span> <span style="color: #000000;">lhs</span><span style="color: #0000FF;">*</span><span style="color: #000000;">rhs</span>
<span style="color: #008080;">elsif</span> <span style="color: #000000;">op</span><span style="color: #0000FF;">=</span><span style="color: #008000;">"/"</span> <span style="color: #008080;">then</span>
<span style="color: #008080;">return</span> <span style="color: #000000;">lhs</span><span style="color: #0000FF;">/</span><span style="color: #000000;">rhs</span>
<span style="color: #008080;">elsif</span> <span style="color: #000000;">op</span><span style="color: #0000FF;">=</span><span style="color: #008000;">"^"</span> <span style="color: #008080;">then</span>
<span style="color: #008080;">return</span> <span style="color: #7060A8;">power</span><span style="color: #0000FF;">(</span><span style="color: #000000;">lhs</span><span style="color: #0000FF;">,</span><span style="color: #000000;">rhs</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">elsif</span> <span style="color: #000000;">op</span><span style="color: #0000FF;">=</span><span style="color: #008000;">"%"</span> <span style="color: #008080;">then</span>
<span style="color: #008080;">return</span> <span style="color: #7060A8;">remainder</span><span style="color: #0000FF;">(</span><span style="color: #000000;">lhs</span><span style="color: #0000FF;">,</span><span style="color: #000000;">rhs</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">elsif</span> <span style="color: #000000;">op</span><span style="color: #0000FF;">=</span><span style="color: #008000;">"u-"</span> <span style="color: #008080;">then</span>
<span style="color: #008080;">return</span> <span style="color: #0000FF;">-</span><span style="color: #000000;">rhs</span>
<span style="color: #008080;">else</span>
<span style="color: #0000FF;">?</span><span style="color: #000000;">9</span><span style="color: #0000FF;">/</span><span style="color: #000000;">0</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">function</span>
<span style="color: #000000;">s</span> <span style="color: #0000FF;">=</span> <span style="color: #008000;">"3+4+5+6*7/1*5^2^3"</span> <span style="color: #000080;font-style:italic;">-- 16406262</span>
<span style="color: #000000;">sidx</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">0</span>
<span style="color: #000000;">nxtch</span><span style="color: #0000FF;">()</span>
<span style="color: #000000;">get_token</span><span style="color: #0000FF;">()</span>
<span style="color: #000000;">Expr</span><span style="color: #0000FF;">(</span><span style="color: #000000;">0</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">op</span><span style="color: #0000FF;">!=</span><span style="color: #000000;">0</span> <span style="color: #008080;">then</span> <span style="color: #000000;">PopFactor</span><span style="color: #0000FF;">()</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #008080;">if</span> <span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">opstack</span><span style="color: #0000FF;">)!=</span><span style="color: #000000;">1</span> <span style="color: #008080;">then</span> <span style="color: #000000;">err</span><span style="color: #0000FF;">(</span><span style="color: #008000;">"some error"</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #7060A8;">printf</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"expression: \"%s\"\n"</span><span style="color: #0000FF;">,{</span><span style="color: #000000;">s</span><span style="color: #0000FF;">})</span>
<span style="color: #7060A8;">puts</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"AST (flat): "</span><span style="color: #0000FF;">)</span>
<span style="color: #0000FF;">?</span><span style="color: #000000;">opstack</span><span style="color: #0000FF;">[</span><span style="color: #000000;">1</span><span style="color: #0000FF;">]</span>
<span style="color: #7060A8;">puts</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"AST (tree):\n"</span><span style="color: #0000FF;">)</span>
<span style="color: #7060A8;">ppEx</span><span style="color: #0000FF;">(</span><span style="color: #000000;">opstack</span><span style="color: #0000FF;">[</span><span style="color: #000000;">1</span><span style="color: #0000FF;">],{</span><span style="color: #004600;">pp_Nest</span><span style="color: #0000FF;">,</span><span style="color: #000000;">9999</span><span style="color: #0000FF;">})</span>
<span style="color: #7060A8;">puts</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"result: "</span><span style="color: #0000FF;">)</span>
<span style="color: #0000FF;">?</span><span style="color: #000000;">evaluate</span><span style="color: #0000FF;">(</span><span style="color: #000000;">opstack</span><span style="color: #0000FF;">[</span><span style="color: #000000;">1</span><span style="color: #0000FF;">])</span>
<span style="color: #0000FF;">{}</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">wait_key</span><span style="color: #0000FF;">()</span>
<!--</syntaxhighlight>-->
I added a flag (for this task) to store the ast nodes as op_p_p, p_op_p, or p_p_op, whichever you prefer.
{{out}}
For "3+4+5+6*7/1*5^2^3", the fully parenthesised Phix equivalent being ((3+4)+5)+(((6*7)/1)*power(5,power(2,3)))
<pre>
with op_p_p:
AST (flat): {"+",{"+",{"+",3,4},5},{"*",{"/",{"*",6,7},1},{"^",5,{"^",2,3}}}}
AST (tree):
{"+",
{"+",
{"+",
3,
4},
5},
{"*",
{"/",
{"*",
6,
7},
1},
{"^",
5,
{"^",
2,
3}}}}
result: 16406262
with p_op_p:
AST (flat): {{{3,"+",4},"+",5},"+",{{{6,"*",7},"/",1},"*",{5,"^",{2,"^",3}}}}
AST (tree):
{{{3,
"+",
4},
"+",
5},
"+",
{{{6,
"*",
7},
"/",
1},
"*",
{5,
"^",
{2,
"^",
3}}}}
result: 16406262
and lastly with p_p_op:
16406262
AST (flat): {{{3,4,"+"},5,"+"},{{{6,7,"*"},1,"/"},{5,{2,3,"^"},"^"},"*"},"+"}
AST (tree):
{{{3,
4,
"+"},
5,
{{{6,
7,
"*"},
1,
"/"},
{5,
{2,
3,
"^"},
"^"},
"*"},
"+"}
result: 16406262
</pre>
=={{header|Picat}}==
<syntaxhighlight lang="picat">main =>
print("Enter an expression: "),
Str =
Exp = parse_term(Str),
Res is Exp,
</syntaxhighlight>
=={{header|PicoLisp}}==
Line 1,130 ⟶ 5,736:
(numbers and transient symbols). From that, a recursive descendent parser can
build an expression tree, resulting in directly executable Lisp code.
<
(let *L (str Str "")
(aggregate) ) )
Line 1,152 ⟶ 5,758:
((= "+" X) (term))
((= "-" X) (list '- (term)))
((= "(" X) (prog1 (aggregate) (pop '*L)))
{{out}}
<
-> (+ (+ 1 2) (/ (* 3 (- 4)) (+ 1 2)))
: (ast "(1+2+3)*-4/(1+2)")
-> (/ (* (+ (+ 1 2) 3) (- 4)) (+ 1 2))</
=={{header|Pop11}}==
<
/* Uncomment the following to parse data from standard input
Line 1,310 ⟶ 5,916:
;;; Test it
arith_eval(do_expr()) =></
=={{header|Prolog}}==
{{works with|SWI Prolog 8.1.19}}
<
numeric(X) :- 48 =< X, X =< 57.
not_numeric(X) :- 48 > X ; X > 57.
Line 1,357 ⟶ 5,963:
% Solution
calculator(String, Value) :-
lex1(Codes, Tokens1),
lex2(Tokens1, Tokens2),
parse(Tokens2, Expression),
Line 1,363 ⟶ 5,970:
% Example use
% calculator("(3+50)*7-9", X).</
=={{header|Python}}==
Line 1,369 ⟶ 5,976:
<br>A subsequent example uses Pythons' ast module to generate the abstract syntax tree.
<
class AstNode(object):
Line 1,484 ⟶ 6,091:
expr = raw_input("Expression:")
astTree = Lex( expr, Yaccer())
print expr, '=',astTree.eval()</
===ast standard library module===
Python comes with its own [http://docs.python.org/3.1/library/ast.html#module-ast ast] module as part of its standard libraries. The module compiles Python source into an AST tree that can in turn be compiled to bytecode then executed.
<
>>>
>>> expr="2 * (3 -1) + 2 * 5"
>>> node = ast.parse(expr, mode='eval')
>>> print(ast.dump(node).replace(',', ',\n'))
op=Mult(),
right=BinOp(left=Num(n=3),
op=Sub(),
right=Num(n=1))),
op=Add(),
right=BinOp(left=Num(n=2),
op=Mult(),
right=Num(n=5))))
>>> code_object = compile(node, filename='<string>', mode='eval')
>>> eval(code_object)
Line 1,503 ⟶ 6,118:
>>> code_object = compile(node, filename='<string>', mode='eval')
>>> eval(code_object)
16</
=={{header|
<syntaxhighlight lang="racket">#lang racket
(require parser-tools/yacc
parser-tools/lex
(prefix-in ~ parser-tools/lex-sre))
(define-tokens value-tokens (NUM))
(define-empty-tokens op-tokens (OPEN CLOSE + - * / EOF NEG))
(define lex
(lexer [(eof) 'EOF]
[whitespace (lex input-port)]
[(~or "+" "-" "*" "/") (string->symbol lexeme)]
["(" 'OPEN]
[")" 'CLOSE]
[(~: (~+ numeric) (~? (~: #\. (~* numeric))))
(token-NUM (string->number lexeme))]))
(define parse
(parser [start E] [end EOF]
[tokens value-tokens op-tokens]
[precs (left - +) (left * /) (left NEG)]
[grammar (E [(NUM) $1]
[(E + E) (+ $1 $3)]
[(E - E) (- $1 $3)]
[(E * E) (* $1 $3)]
[(E / E) (/ $1 $3)]
[(- E) (prec NEG) (- $2)]
[(OPEN E CLOSE) $2])]))
(define (calc str)
(define i (open-input-string str))
(displayln (parse (λ () (lex i)))))
(calc "(1 + 2 * 3) - (1+2)*-3")</syntaxhighlight>
=={{header|Raku}}==
(formerly Perl 6)
{{Works with|rakudo|2018.03}}
<syntaxhighlight lang="raku" line>sub ev (Str $s --> Numeric) {
grammar expr {
token TOP { ^ <sum> $ }
token sum { <product> (('+' || '-') <product>)* }
token product { <factor> (('*' || '/') <factor>)* }
token factor { <unary_minus>? [ <parens> || <literal> ] }
token unary_minus { '-' }
token parens { '(' <sum> ')' }
token literal { \d+ ['.' \d+]? || '.' \d+ }
}
my sub minus ($b) { $b ?? -1 !! +1 }
my sub
[+] flat product($x<product>), map
{ minus($^y[0] eq '-') * product $^y<product> },
|($x[0] or [])
}
my sub product ($x) {
[*] flat factor($x<factor>), map
{ factor($^y<factor>) ** minus($^y[0] eq '/') },
|($x[0] or [])
}
my sub factor ($x) {
minus($x<unary_minus>) * ($x<parens>
?? sum $x<parens><sum>
!! $x<literal>)
}
expr.parse([~] split /\s+/, $s);
$/ or fail 'No parse.';
sum $/<sum>;
}
# Testing:
say ev '5'; # 5
say ev '1 + 2 - 3 * 4 / 5'; # 0.6
say ev '1 + 5*3.4 - .5 -4 / -2 * (3+4) -6'; # 25.5
say ev '((11+15)*15)* 2 + (3) * -4 *1'; # 768</syntaxhighlight>
=={{header|REXX}}==
Several additional operators are supported as well as several forms of exponentiated numbers:
:::* '''^''' exponentiation, as well as '''**'''
:::* '''//''' remainder division
:::* '''%''' integer division
:::* '''<big>÷</big>''' in addition to '''<big>/</big>'''
:::* '''&''' for logical '''AND'''
:::* '''|''' for logical '''OR'''
:::* '''&&''' for logical '''XOR'''
:::* '''||''' for concatenation
:::* '''[ ] { }''' as grouping symbols, as well as '''( )'''
:::* 12.3e+44 ("single" precision)
:::* 12.3E+44 ("single" precision)
:::* 12.3D+44 ("double" precision)
:::* 12.3Q+44 ("extended" or "quad" precision)
<syntaxhighlight lang="rexx">/*REXX program evaluates an infix─type arithmetic expression and displays the result.*/
nchars = '0123456789.eEdDqQ' /*possible parts of a number, sans ± */
e='***error***'; $=" "; doubleOps= '&|*/'; z= /*handy─dandy variables.*/
parse arg x 1 ox1; if x='' then call serr "no input was specified."
x=space(x); L=length(x); x=translate(x, '()()', "[]{}")
j=0
do forever; j=j+1; if j>L then leave; _=substr(x, j, 1); _2=getX()
newT=pos(_,' ()[]{}^÷')\==0; if newT then do; z=z _ $; iterate; end
possDouble=pos(_,doubleOps)\==0 /*is _ a possible double operator?*/
if possDouble then do /* " this " " " " */
if _2==_ then do /*yupper, it's one of a double operator*/
_=_ || _ /*create and use a double char operator*/
x=overlay($, x, Nj) /*blank out 2nd symbol.*/
end
z=z _ $; iterate
end
if _=='+' | _=="-" then do; p_=word(z, max(1,words(z))) /*last Z token. */
if p_=='(' then z=z 0 /*handle a unary ± */
z=z _ $; iterate
end
lets=0; sigs=0; #=_
do j=j+1 to L; _=substr(x,j,1) /*build a valid number.*/
if lets==1 & sigs==0 then if _=='+' | _=="-" then do; sigs=1
#=# || _
iterate
end
if pos(_,nchars)==0 then leave
lets=lets+datatype(_,'M') /*keep track of the number of exponents*/
#=# || translate(_,'EEEEE', "eDdQq") /*keep building the number. */
end /*j*/
j=j-1
if \datatype(#,'N') then call serr "invalid number: " #
z=z # $
end /*forever*/
_=word(z,1); if _=='+' | _=="-" then z=0 z /*handle the unary cases. */
x='(' space(z) ")"; tokens=words(x) /*force stacking for the expression. */
do i=1 for tokens; @.i=word(x,i); end /*i*/ /*assign input tokens. */
L=max(20,length(x)) /*use 20 for the minimum display width.*/
op= ')(-+/*^'; Rop=substr(op,3); p.=; s.=; n=length(op); epr=; stack=
do i=1 for n; _=substr(op,i,1); s._=(i+1)%2; p._=s._ + (i==n); end /*i*/
/* [↑] assign the operator priorities.*/
do #=1 for tokens; ?=@.# /*process each token from the @. list.*/
if ?=='**' then ?="^" /*convert to REXX-type exponentiation. */
select /*@.# is: ( operator ) operand*/
when ?=='(' then stack="(" stack
when isOp(?) then do /*is the token an operator ? */
!=word(stack,1) /*get token from stack.*/
do while !\==')' & s.!>=p.?; epr=epr ! /*addition.*/
stack=subword(stack, 2) /*del token from stack*/
!= word(stack, 1) /*get token from stack*/
end /*while*/
stack=? stack /*add token to stack*/
end
when ?==')' then do; !=word(stack, 1) /*get token from stack*/
do while !\=='('; epr=epr ! /*append to expression*/
stack=subword(stack, 2) /*del token from stack*/
!= word(stack, 1) /*get token from stack*/
end /*while*/
stack=subword(stack, 2) /*del token from stack*/
end
otherwise epr=epr ? /*add operand to epr.*/
end /*select*/
end /*#*/
epr=space(epr stack); tokens=words(epr); x=epr; z=; stack=
do i=1 for tokens; @.i=word(epr,i); end /*i*/ /*assign input tokens.*/
Dop='/ // % ÷'; Bop="& | &&" /*division operands; binary operands.*/
Aop='- + * ^ **' Dop Bop; Lop=Aop "||" /*arithmetic operands; legal operands.*/
do #=1 for tokens; ?=@.#; ??=? /*process each token from @. list. */
w=words(stack); b=word(stack, max(1, w ) ) /*stack count; the last entry. */
a=word(stack, max(1, w-1) ) /*stack's "first" operand. */
division =wordpos(?, Dop)\==0 /*flag: doing a division operation. */
arith =wordpos(?, Aop)\==0 /*flag: doing arithmetic operation. */
bitOp =wordpos(?, Bop)\==0 /*flag: doing binary mathematics. */
if datatype(?, 'N') then do; stack=stack ?; iterate; end
if wordpos(?,Lop)==0 then do; z=e "illegal operator:" ?; leave; end
if w<2 then do; z=e "illegal epr expression."; leave; end
if ?=='^' then ??="**" /*REXXify ^ ──► ** (make it legal).*/
if ?=='÷' then ??="/" /*REXXify ÷ ──► / (make it legal).*/
if division & b=0 then do; z=e "division by zero" b; leave; end
if bitOp & \isBit(a) then do; z=e "token isn't logical: " a; leave; end
if bitOp & \isBit(b) then do; z=e "token isn't logical: " b; leave; end
select /*perform an arithmetic operation. */
when ??=='+' then y = a + b
when ??=='-' then y = a - b
when ??=='*' then y = a * b
when ??=='/' | ??=="÷" then y = a / b
when ??=='//' then y = a // b
when ??=='%' then y = a % b
when ??=='^' | ??=="**" then y = a ** b
when ??=='||' then y = a || b
otherwise z=e 'invalid operator:' ?; leave
end /*select*/
if datatype(y, 'W') then y=y/1 /*normalize the number with ÷ by 1. */
_=subword(stack, 1, w-2); stack=_ y /*rebuild the stack with the answer. */
end /*#*/
if word(z, 1)==e then stack= /*handle the special case of errors. */
z=space(z stack) /*append any residual entries. */
say 'answer──►' z /*display the answer (result). */
parse source upper . how . /*invoked via C.L. or REXX program ? */
if how=='COMMAND' | \datatype(z, 'W') then exit /*stick a fork in it, we're all done. */
return z /*return Z ──► invoker (the RESULT). */
/*──────────────────────────────────────────────────────────────────────────────────────*/
isBit: return arg(1)==0 | arg(1) == 1 /*returns 1 if 1st argument is binary*/
isOp: return pos(arg(1), rOp) \== 0 /*is argument 1 a "real" operator? */
serr: say; say e arg(1); say; exit 13 /*issue an error message with some text*/
/*──────────────────────────────────────────────────────────────────────────────────────*/
getX: do Nj=j+1 to length(x); _n=substr(x, Nj, 1); if _n==$ then iterate
return substr(x, Nj, 1) /* [↑] ignore any blanks in expression*/
end /*Nj*/
return $ /*reached end-of-tokens, return $. */</syntaxhighlight>
To view a version of the above REXX program, see this version which has much more whitespace: ──► [[Arithmetic_evaluation/REXX]]. <br>
<br>
'''output''' when using the input of: <tt> + 1+2.0-003e-00*[4/6] </tt>
<pre>
answer──► 1
</pre>
=={{header|RPL}}==
This expression evaluator generates the AST through an RPN converter based on the shunting-yard algorithm.
<code>LEXER</code> is defined at [[Parsing/Shunting-yard algorithm#RPL|Parsing/Shunting-yard algorithm]]
{{works with|HP|48}}
≪ '''IF''' OVER '''THEN'''
"^*/+-" DUP 5 PICK POS SWAP ROT POS
{ 4 3 3 2 2 } { 1 0 0 0 0 }
→ o2 o1 prec rasso
≪ '''IF''' o2 '''THEN'''
prec o1 GET prec o2 GET
'''IF''' rasso o1 GET '''THEN''' < '''ELSE''' ≤ '''END'''
'''ELSE''' 0 '''END'''
≫
'''ELSE''' DROP 0 '''END'''
≫ ‘<span style="color:blue>POPOP?</span>’ STO
<span style="color:grey>@ ''( op → Boolean )''</span>
≪ { } "" → infix postfix token
≪ 0
1 infix SIZE '''FOR''' j
infix j GET 'token' STO
1 SF
'''CASE'''
"^*/+-" token →STR POS '''THEN'''
1 CF
'''WHILE''' token <span style="color:blue>POPOP?</span> '''REPEAT'''
'postfix' ROT STO+ 1 - '''END'''
token SWAP 1 + '''END'''
"(" token == '''THEN'''
token SWAP 1 + '''END'''
")" token == '''THEN'''
'''WHILE''' DUP 1 FS? AND '''REPEAT'''
'''IF''' OVER "(" ≠ '''THEN'''
'postfix' ROT STO+
'''ELSE''' SWAP DROP 1 CF '''END'''
1 -
'''END'''
'''END'''
1 FS? '''THEN''' 'postfix' token STO+ '''END'''
'''END'''
'''NEXT'''
'''WHILE''' DUP '''REPEAT'''
'postfix' ROT STO+ 1 - '''END'''
DROP
≫ ≫ ‘<span style="color:blue>→RPN</span>’ STO
<span style="color:grey>@ ''( { infixed tokens } → { postfixed tokens )''</span>
≪ DUP SIZE → len
≪ '''IF''' len '''THEN'''
DUP len GET SWAP
'''IF''' len 1 ≠ '''THEN''' 1 len 1 - SUB '''ELSE''' DROP { } '''END'''
'''IF''' OVER TYPE '''THEN'''
<span style="color:blue>→AST</span> <span style="color:blue>→AST</span>
4 ROLLD ROT ROT 3 →LIST SWAP
'''END'''
'''ELSE''' "Err" SWAP '''END'''
≫ ≫ ‘<span style="color:blue>→AST</span>’ STO
<span style="color:grey>@ ''( { postfixed tokens } → { AST } )''</span>
≪ DUP 1 GET
'''IF''' DUP TYPE '''THEN''' <span style="color:blue>AST→N</span> '''END'''
OVER 3 GET
'''IF''' DUP TYPE '''THEN''' <span style="color:blue>AST→N</span> '''END'''
ROT 2 GET "≪" SWAP + "≫" + STR→ EVAL
≫ ‘<span style="color:blue>AST→N</span>' STO
<span style="color:grey>@ ''( { AST } → value )''</span>
≪ <span style="color:blue>LEXER</span> <span style="color:blue>→RPN</span>
<span style="color:blue>→AST</span> DROP DUP <span style="color:grey>@ DUP is just here to leave the AST in the stack</span>
<span style="color:blue>AST→N</span>
≫ ‘<span style="color:blue>AEVAL</span>’ STO
"3 + 4 * 2 / ( 1 - 5 ) ^ 2 ^ 3" <span style="color:blue>AEVAL</span>
{{out}}
<pre>
2: { 3 "+" { { 4 "*" 2 } "/" { { 1 "-" 5 } "^" { 2 "^" 3 } } } }
1: 3.00012207031
</pre>
=={{header|Ruby}}==
Function to convert infix arithmetic expression to binary tree. The resulting tree knows how to print and evaluate itself. Assumes expression is well-formed (matched parens, all operators have 2 operands). Algorithm: http://www.seas.gwu.edu/~csci131/fall96/exp_to_tree.html
<syntaxhighlight lang="ruby">$op_priority = {"+" => 0, "-" => 0, "*" => 1, "/" => 1}
class TreeNode
OP_FUNCTION = {
"+" => lambda {|x, y| x + y},
"-" => lambda {|x, y| x - y},
"*" => lambda {|x, y| x * y},
"/" => lambda {|x, y| x / y}}
attr_accessor :info, :left, :right
def initialize(info)
@info = info
end
def leaf?
@left.nil? and @right.nil?
end
def to_s(order)
if leaf?
@info
else
left_s, right_s = @left.to_s(order), @right.to_s(order)
strs = case order
when :prefix then [@info, left_s, right_s]
when :infix then [left_s, @info, right_s]
when :postfix then [left_s, right_s, @info]
else []
end
"(" + strs.join(" ") + ")"
end
end
def eval
if !leaf? and operator?(@info)
OP_FUNCTION[@info].call(@left.eval, @right.eval)
else
@info.to_f
end
end
end
def tokenize(exp)
exp
.gsub('(', ' ( ')
.gsub(')', ' ) ')
.gsub('+', ' + ')
.gsub('-', ' - ')
.gsub('*', ' * ')
.gsub('/', ' / ')
.split(' ')
end
def operator?(token)
$op_priority.has_key?(token)
end
def pop_connect_push(op_stack, node_stack)
temp = op_stack.pop
temp.right = node_stack.pop
temp.left = node_stack.pop
node_stack.push(temp)
end
def infix_exp_to_tree(exp)
tokens = tokenize(exp)
op_stack, node_stack = [], []
tokens.each do |token|
if operator?(token)
# clear stack of higher priority operators
until (op_stack.empty? or
op_stack.last.info == "(" or
$op_priority[op_stack.last.info] < $op_priority[token])
pop_connect_push(op_stack, node_stack)
end
op_stack.push(TreeNode.new(token))
elsif token == "("
op_stack.push(TreeNode.new(token))
elsif token == ")"
while op_stack.last.info != "("
pop_connect_push(op_stack, node_stack)
end
# throw away the '('
op_stack.pop
else
node_stack.push(TreeNode.new(token))
end
end
until op_stack.empty?
pop_connect_push(op_stack, node_stack)
end
node_stack.last
end</syntaxhighlight>
Testing:
<syntaxhighlight lang="ruby">exp = "1 + 2 - 3 * (4 / 6)"
puts("Original: " + exp)
tree = infix_exp_to_tree(exp)
puts("Prefix: " + tree.to_s(:prefix))
puts("Infix: " + tree.to_s(:infix))
puts("Postfix: " + tree.to_s(:postfix))
puts("Result: " + tree.eval.to_s)</syntaxhighlight>
{{out}}
<pre>Original: 1 + 2 - 3 * (4 / 6)
Prefix: (- (+ 1 2) (* 3 (/ 4 6)))
Infix: ((1 + 2) - (3 * (4 / 6)))
Postfix: ((1 2 +) (3 (4 6 /) *) -)
Result: 1.0</pre>
=={{header|Rust}}==
<syntaxhighlight lang="rust">//! Simple calculator parser and evaluator
/// Binary operator
#[derive(Debug)]
pub enum Operator {
Add,
Substract,
Multiply,
Divide
}
/// A node in the tree
#[derive(Debug)]
pub enum Node {
Value(f64),
Binary(Operator, Box<Node>,Box<Node>),
}
/// parse a string into a node
pub fn parse(txt :&str) -> Option<Node> {
let chars = txt.chars().filter(|c| *c != ' ').collect();
parse_expression(&chars, 0).map(|(_,n)| n)
}
/// parse an expression into a node, keeping track of the position in the character vector
fn parse_expression(chars: &Vec<char>, pos: usize) -> Option<(usize,Node)> {
match parse_start(chars, pos) {
Some((new_pos, first)) => {
match parse_operator(chars, new_pos) {
Some((new_pos2,op)) => {
if let Some((new_pos3, second)) = parse_expression(chars, new_pos2) {
Some((new_pos3, combine(op, first, second)))
} else {
None
}
},
None => Some((new_pos,first)),
}
},
None => None,
}
}
/// combine nodes to respect associativity rules
fn combine(op: Operator, first: Node, second: Node) -> Node {
match second {
Node::Binary(op2,v21,v22) => if precedence(&op)>=precedence(&op2) {
Node::Binary(op2,Box::new(combine(op,first,*v21)),v22)
} else {
Node::Binary(op,Box::new(first),Box::new(Node::Binary(op2,v21,v22)))
},
_ => Node::Binary(op,Box::new(first),Box::new(second)),
}
}
/// a precedence rank for operators
fn precedence(op: &Operator) -> usize {
match op{
Operator::Multiply | Operator::Divide => 2,
_ => 1
}
}
/// try to parse from the start of an expression (either a parenthesis or a value)
fn parse_start(chars: &Vec<char>, pos: usize) -> Option<(usize,Node)> {
match start_parenthesis(chars, pos){
Some (new_pos) => {
let r = parse_expression(chars, new_pos);
end_parenthesis(chars, r)
},
None => parse_value(chars, pos),
}
}
/// match a starting parentheseis
fn start_parenthesis(chars: &Vec<char>, pos: usize) -> Option<usize>{
if pos<chars.len() && chars[pos] == '(' {
Some(pos+1)
} else {
None
}
}
/// match an end parenthesis, if successful will create a sub node contained the wrapped expression
fn end_parenthesis(chars: &Vec<char>, wrapped :Option<(usize,Node)>) -> Option<(usize,Node)>{
match wrapped {
Some((pos, node)) => if pos<chars.len() && chars[pos] == ')' {
Some((pos+1,Node::SubNode(Box::new(node))))
} else {
None
},
None => None,
}
}
/// parse a value: an decimal with an optional minus sign
fn parse_value(chars: &Vec<char>, pos: usize) -> Option<(usize,Node)>{
let mut new_pos = pos;
if new_pos<chars.len() && chars[new_pos] == '-' {
new_pos = new_pos+1;
}
while new_pos<chars.len() && (chars[new_pos]=='.' || (chars[new_pos] >= '0' && chars[new_pos] <= '9')) {
new_pos = new_pos+1;
}
if new_pos>pos {
if let Ok(v) = dbg!(chars[pos..new_pos].iter().collect::<String>()).parse() {
Some((new_pos,Node::Value(v)))
} else {
None
}
} else {
None
}
}
/// parse an operator
fn parse_operator(chars: &Vec<char>, pos: usize) -> Option<(usize,Operator)> {
if pos<chars.len() {
let ops_with_char = vec!(('+',Operator::Add),('-',Operator::Substract),('*',Operator::Multiply),('/',Operator::Divide));
for (ch,op) in ops_with_char {
if chars[pos] == ch {
return Some((pos+1, op));
}
}
}
None
}
/// eval a string
pub fn eval(txt :&str) -> f64 {
match parse(txt) {
Some(t) => eval_term(&t),
None => panic!("Cannot parse {}",txt),
}
}
/// eval a term, recursively
fn eval_term(t: &Node) -> f64 {
match t {
Node::Value(v) => *v,
Node::SubNode(t) => eval_term(t),
Node::Binary(Operator::Add,t1,t2) => eval_term(t1) + eval_term(t2),
Node::Binary(Operator::Substract,t1,t2) => eval_term(t1) - eval_term(t2),
Node::Binary(Operator::Multiply,t1,t2) => eval_term(t1) * eval_term(t2),
Node::Binary(Operator::Divide,t1,t2) => eval_term(t1) / eval_term(t2),
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_eval(){
assert_eq!(2.0,eval("2"));
assert_eq!(4.0,eval("2+2"));
assert_eq!(11.0/4.0, eval("2+3/4"));
assert_eq!(2.0, eval("2*3-4"));
assert_eq!(3.0, eval("1+2*3-4"));
assert_eq!(89.0/6.0, eval("2*(3+4)+5/6"));
assert_eq!(14.0, eval("2 * (3 -1) + 2 * 5"));
assert_eq!(7000.0, eval("2 * (3 + (4 * 5 + (6 * 7) * 8) - 9) * 10"));
assert_eq!(-9.0/4.0, eval("2*-3--4+-.25"));
assert_eq!(1.5, eval("1 - 5 * 2 / 20 + 1"));
assert_eq!(3.5, eval("2 * (3 + ((5) / (7 - 11)))"));
}
}
</syntaxhighlight>
=={{header|Scala}}==
This code shows a bit of Scala's parser classes. The error handling of parser errors
is practically non-existent, to avoid obscuring the code.
<syntaxhighlight lang="scala">
package org.rosetta.arithmetic_evaluator.scala
object ArithmeticParser extends scala.util.parsing.combinator.RegexParsers {
def readExpression(input: String) : Option[()=>Int] = {
parseAll(expr, input) match {
case Success(result, _) =>
Some(result)
case other =>
println(other)
None
}
}
private def
(term<~"-")~expr ^^ { case l~r => () => l() - r() } |
term
}
private def
(factor<~"*")~term ^^ { case l~r => () => l() * r() } |
(factor<~"/")~term ^^ { case l~r => () => l() / r() } |
factor
}
private def factor : Parser[()=>Int] = {
"("~>expr<~")" |
"\\d+".r ^^ { x => () => x.toInt } |
failure("Expected a value")
}
}
object Main {
def main(args: Array[String]) {
println("""Please input the expressions. Type "q" to quit.""")
var input: String = ""
do {
input = readLine("> ")
if (input != "q") {
ArithmeticParser.readExpression(input).foreach(f => println(f()))
}
} while (input != "q")
}
}
</syntaxhighlight>
Example:
Line 1,612 ⟶ 6,794:
This example was made rather more complex by the requirement of generating an AST tree. With a Scala distribution there are many examples of arithmetic parsers, as small as half a dozen lines.
=={{header|Scheme}}==
This works in three stages: string->tokens turns the input string into a list of tokens, parse converts this into an AST, which is eventually evaluated into a number result. Only positive integers are read, though output can be a rational, positive or negative.
The parse function uses a recursive-descent parser to follow the precedence rules.
<syntaxhighlight lang="scheme">
(import (scheme base)
(scheme char)
(scheme cxr)
(scheme write)
(srfi 1 lists))
;; convert a string into a list of tokens
(define (string->tokens str)
(define (next-token chars)
(cond ((member (car chars) (list #\+ #\- #\* #\/) char=?)
(values (cdr chars)
(cdr (assq (car chars) ; convert char for op into op procedure, using a look up list
(list (cons #\+ +) (cons #\- -) (cons #\* *) (cons #\/ /))))))
((member (car chars) (list #\( #\)) char=?)
(values (cdr chars)
(if (char=? (car chars) #\()
'open
'close)))
(else ; read a multi-digit positive integer
(let loop ((rem chars)
(res 0))
(if (and (not (null? rem))
(char-numeric? (car rem)))
(loop (cdr rem)
(+ (* res 10)
(- (char->integer (car rem))
(char->integer #\0))))
(values rem
res))))))
;
(let loop ((chars (remove char-whitespace? (string->list str)))
(tokens '()))
(if (null? chars)
(reverse tokens)
(let-values (((remaining-chars token) (next-token chars)))
(loop remaining-chars
(cons token tokens))))))
;; turn list of tokens into an AST
;; -- using recursive descent parsing to obey laws of precedence
(define (parse tokens)
(define (parse-factor tokens)
(if (number? (car tokens))
(values (car tokens) (cdr tokens))
(let-values (((expr rem) (parse-expr (cdr tokens))))
(values expr (cdr rem)))))
(define (parse-term tokens)
(let-values (((left-expr rem) (parse-factor tokens)))
(if (and (not (null? rem))
(member (car rem) (list * /)))
(let-values (((right-expr remr) (parse-term (cdr rem))))
(values (list (car rem) left-expr right-expr)
remr))
(values left-expr rem))))
(define (parse-part tokens)
(let-values (((left-expr rem) (parse-term tokens)))
(if (and (not (null? rem))
(member (car rem) (list + -)))
(let-values (((right-expr remr) (parse-part (cdr rem))))
(values (list (car rem) left-expr right-expr)
remr))
(values left-expr rem))))
(define (parse-expr tokens)
(let-values (((expr rem) (parse-part tokens)))
(values expr rem)))
;
(let-values (((expr rem) (parse-expr tokens)))
(if (null? rem)
expr
(error "Misformed expression"))))
;; evaluate the AST, returning a number
(define (eval-expression ast)
(cond ((number? ast)
ast)
((member (car ast) (list + - * /))
((car ast)
(eval-expression (cadr ast))
(eval-expression (caddr ast))))
(else
(error "Misformed expression"))))
;; parse and evaluate the given string
(define (interpret str)
(eval-expression (parse (string->tokens str))))
;; running some examples
(for-each
(lambda (str)
(display
(string-append str
" => "
(number->string (interpret str))))
(newline))
'("1 + 2" "20+4*5" "1/2+5*(6-3)" "(1+3)/4-1" "(1 - 5) * 2 / (20 + 1)"))
</syntaxhighlight>
{{out}}
<pre>
1 + 2 => 3
20+4*5 => 40
1/2+5*(6-3) => 31/2
(1+3)/4-1 => 0
(1 - 5) * 2 / (20 + 1) => -8/21
</pre>
=={{header|Sidef}}==
{{trans|JavaScript}}
<syntaxhighlight lang="ruby">func evalArithmeticExp(s) {
func evalExp(s) {
func operate(s, op) {
s.split(op).map{|c| Number(c) }.reduce(op)
}
func add(s) {
operate(s.sub(/^\+/,'').sub(/\++/,'+'), '+')
}
func subtract(s) {
s.gsub!(/(\+-|-\+)/,'-')
if (s ~~ /--/) {
return(add(s.sub(/--/,'+')))
}
var b = s.split('-')
b.len == 3 ? (-1*Number(b[1]) - Number(b[2]))
: operate(s, '-')
}
s.gsub!(/[()]/,'').gsub!(/-\+/, '-')
var reM = /\*/
var reMD = %r"(\d+\.?\d*\s*[*/]\s*[+-]?\d+\.?\d*)"
var reA = /\d\+/
var reAS = /(-?\d+\.?\d*\s*[+-]\s*[+-]?\d+\.?\d*)/
while (var match = reMD.match(s)) {
match[0] ~~ reM
? s.sub!(reMD, operate(match[0], '*').to_s)
: s.sub!(reMD, operate(match[0], '/').to_s)
}
while (var match = reAS.match(s)) {
match[0] ~~ reA
? s.sub!(reAS, add(match[0]).to_s)
: s.sub!(reAS, subtract(match[0]).to_s)
}
return s
}
var rePara = /(\([^\(\)]*\))/
s.split!.join!('').sub!(/^\+/,'')
while (var match = s.match(rePara)) {
s.sub!(rePara, evalExp(match[0]))
}
return Number(evalExp(s))
}</syntaxhighlight>
Testing the function:
<syntaxhighlight lang="ruby">for expr,res in [
['2+3' => 5],
['-4-3' => -7],
['-+2+3/4' => -1.25],
['2*3-4' => 2],
['2*(3+4)+2/4' => 2/4 + 14],
['2*-3--4+-0.25' => -2.25],
['2 * (3 + (4 * 5 + (6 * 7) * 8) - 9) * 10' => 7000],
] {
var num = evalArithmeticExp(expr)
assert_eq(num, res)
"%-45s == %10g\n".printf(expr, num)
}</syntaxhighlight>
=={{header|Standard ML}}==
This implementation uses a [https://en.wikipedia.org/wiki/Recursive_descent_parser recursive descent parser]. It first lexes the input. The parser builds a Abstract Syntax Tree (AST) and the evaluator evaluates it. The parser uses sub categories.
The parsing is a little bit tricky because the grammar is left recursive.
<syntaxhighlight lang="sml">(* AST *)
datatype expression =
Con of int (* constant *)
| Add of expression * expression (* addition *)
| Mul of expression * expression (* multiplication *)
| Sub of expression * expression (* subtraction *)
| Div of expression * expression (* division *)
(* Evaluator *)
fun eval (Con x) = x
| eval (Add (x, y)) = (eval x) + (eval y)
| eval (Mul (x, y)) = (eval x) * (eval y)
| eval (Sub (x, y)) = (eval x) - (eval y)
| eval (Div (x, y)) = (eval x) div (eval y)
(* Lexer *)
datatype token =
CON of int
| ADD
| MUL
| SUB
| DIV
| LPAR
| RPAR
fun lex nil = nil
| lex (#"+" :: cs) = ADD :: lex cs
| lex (#"*" :: cs) = MUL :: lex cs
| lex (#"-" :: cs) = SUB :: lex cs
| lex (#"/" :: cs) = DIV :: lex cs
| lex (#"(" :: cs) = LPAR :: lex cs
| lex (#")" :: cs) = RPAR :: lex cs
| lex (#"~" :: cs) = if null cs orelse not (Char.isDigit (hd cs)) then raise Domain
else lexDigit (0, cs, ~1)
| lex (c :: cs) = if Char.isDigit c then lexDigit (0, c :: cs, 1)
else raise Domain
and lexDigit (a, cs, s) = if null cs orelse not (Char.isDigit (hd cs)) then CON (a*s) :: lex cs
else lexDigit (a * 10 + (ord (hd cs))- (ord #"0") , tl cs, s)
(* Parser *)
exception Error of string
fun match (a,ts) t = if null ts orelse hd ts <> t
then raise Error "match"
else (a, tl ts)
fun extend (a,ts) p f = let val (a',tr) = p ts in (f(a,a'), tr) end
fun parseE ts = parseE' (parseM ts)
and parseE' (e, ADD :: ts) = parseE' (extend (e, ts) parseM Add)
| parseE' (e, SUB :: ts) = parseE' (extend (e, ts) parseM Sub)
| parseE' s = s
and parseM ts = parseM' (parseP ts)
and parseM' (e, MUL :: ts) = parseM' (extend (e, ts) parseP Mul)
| parseM' (e, DIV :: ts) = parseM' (extend (e, ts) parseP Div)
| parseM' s = s
and parseP (CON c :: ts) = (Con c, ts)
| parseP (LPAR :: ts) = match (parseE ts) RPAR
| parseP _ = raise Error "parseP"
(* Test *)
fun lex_parse_eval (str:string) =
case parseE (lex (explode str)) of
(exp, nil) => eval exp
| _ => raise Error "not parseable stuff at the end"</syntaxhighlight>
=={{header|Tailspin}}==
<syntaxhighlight lang="tailspin">
def ops: ['+','-','*','/'];
data binaryExpression <{left: <node>, op: <?($ops <[<=$::raw>]>)>, right: <node>}>
data node <binaryExpression|"1">
composer parseArithmetic
(<WS>?) <addition|multiplication|term> (<WS>?)
rule addition: {left:<addition|multiplication|term> (<WS>?) op:<'[+-]'> (<WS>?) right:<multiplication|term>}
rule multiplication: {left:<multiplication|term> (<WS>?) op:<'[*/]'> (<WS>?) right:<term>}
rule term: <INT"1"|parentheses>
rule parentheses: (<'\('> <WS>?) <addition|multiplication|term> (<WS>? <'\)'>)
end parseArithmetic
templates evaluateArithmetic
<´node´ {op: <='+'>}> ($.left -> evaluateArithmetic) + ($.right -> evaluateArithmetic) !
<´node´ {op: <='-'>}> ($.left -> evaluateArithmetic) - ($.right -> evaluateArithmetic) !
<´node´ {op: <='*'>}> ($.left -> evaluateArithmetic) * ($.right -> evaluateArithmetic) !
<´node´ {op: <='/'>}> ($.left -> evaluateArithmetic) ~/ ($.right -> evaluateArithmetic) !
otherwise $ !
end evaluateArithmetic
def ast: '(100 - 5 * (2+3*4) + 2) / 2' -> parseArithmetic;
'$ast;
' -> !OUT::write
'$ast -> evaluateArithmetic;
' -> !OUT::write
</syntaxhighlight>
{{out}}
<pre>
{left={left={left=100"1", op=-, right={left=5"1", op=*, right={left=2"1", op=+, right={left=3"1", op=*, right=4"1"}}}}, op=+, right=2"1"}, op=/, right=2"1"}
16"1"
</pre>
If we don't need to get the AST, we could just evaluate right away:
<syntaxhighlight lang="tailspin">
composer calculator
(<WS>?) <addition|multiplication|term> (<WS>?)
rule addition: [<addition|multiplication|term> (<WS>?) <'[+-]'> (<WS>?) <multiplication|term>] ->
\(when <?($(2) <='+'>)> do $(1) + $(3) !
otherwise $(1) - $(3) !
\)
rule multiplication: [<multiplication|term> (<WS>?) <'[*/]'> (<WS>?) <term>] ->
\(when <?($(2) <='*'>)> do $(1) * $(3) !
otherwise $(1) ~/ $(3) !
\)
rule term: <INT|parentheses>
rule parentheses: (<'\('> <WS>?) <addition|multiplication|term> (<WS>? <'\)'>)
end calculator
'(100 - 5 * (2+3*4) + 2) / 2' -> calculator -> !OUT::write
'
' -> !OUT::write
</syntaxhighlight>
{{out}}
<pre>16</pre>
=={{header|Tcl}}==
{{works with|Tcl|8.5}}
The code below delivers the AST for an expression
in a form that it can be immediately eval-led,
using Tcl's prefix operators.
<syntaxhighlight lang="tcl">namespace import tcl::mathop::*
proc ast str {
Line 1,659 ⟶ 7,162:
} \n] {
puts "$test ..... [eval $test] ..... [eval [eval $test]]"
}</
{{out}}
<pre>
ast 2-2 ..... - 2 2 ..... 0
ast 1-2-3 ..... - [- 1 2] 3 ..... -4
Line 1,670 ⟶ 7,174:
</pre>
=={{header|TXR}}==
Use TXR text pattern matching to parse expression to a Lisp AST, then evaluate with <code>eval</code>:
<syntaxhighlight lang="txr">@(next :args)
@(define space)@/ */@(end)
@(define mulop (nod))@\
@(local op)@\
@(space)@\
@(cases)@\
@{op /[*]/}@(bind nod @(intern op *user-package*))@\
@(or)@\
@{op /\//}@(bind (nod) @(list 'trunc))@\
@(end)@\
@(space)@\
@(end)
@(define addop (nod))@\
@(local op)@(space)@{op /[+\-]/}@(space)@\
@(bind nod @(intern op *user-package*))@\
@(end)
@(define number (nod))@\
@(local n)@(space)@{n /[0-9]+/}@(space)@\
@(bind nod @(int-str n 10))@\
@(end)
@(define factor (nod))@(cases)(@(expr nod))@(or)@(number nod)@(end)@(end)
@(define term (nod))@\
@(local op nod1 nod2)@\
@(cases)@\
@(factor nod1)@\
@(cases)@(mulop op)@(term nod2)@(bind nod (op nod1 nod2))@\
@(or)@(bind nod nod1)@\
@(end)@\
@(or)@\
@(addop op)@(factor nod1)@\
@(bind nod (op nod1))@\
@(end)@\
@(end)
@(define expr (nod))@\
@(local op nod1 nod2)@\
@(term nod1)@\
@(cases)@(addop op)@(expr nod2)@(bind nod (op nod1 nod2))@\
@(or)@(bind nod nod1)@\
@(end)@\
@(end)
@(cases)
@ {source (expr e)}
@ (output)
source: @source
AST: @(format nil "~s" e)
value: @(eval e nil)
@ (end)
@(or)
@ (maybe)@(expr e)@(end)@bad
@ (output)
erroneous suffix "@bad"
@ (end)
@(end)</syntaxhighlight>
Run:
<pre>$ txr expr-ast.txr '3 + 3/4 * (2 + 2) + (4*4)'
source: 3 + 3/4 * (2 + 2) + (4*4)
AST: (+ 3 (+ (trunc 3 (* 4 (+ 2 2))) (* 4 4)))
value: 19</pre>
=={{header|Ursala}}==
with no error checking other than removal of spaces
<
#import nat
#import flo
Line 1,691 ⟶ 7,260:
traverse = *^ ~&v?\%ep ^H\~&vhthPX '+-*/'-$<plus,minus,times,div>@dh
evaluate = traverse+ parse+ lex</
test program:
<
test = evaluate*t
Line 1,710 ⟶ 7,279:
5-3*2
(1+1)*(2+3)
(2-4)/(3+5*(8-1))]-</
{{out}}
<pre>
<
Line 1,726 ⟶ 7,295:
1.000000e+01,
-5.263158e-02></pre>
=={{header|Wren}}==
{{trans|Kotlin}}
{{libheader|Wren-pattern}}
<syntaxhighlight lang="wren">import "./pattern" for Pattern
/* if string is empty, returns zero */
var toDoubleOrZero = Fn.new { |s|
var n = Num.fromString(s)
return n ? n : 0
}
var multiply = Fn.new { |s|
var b = s.split("*").map { |t| toDoubleOrZero.call(t) }.toList
return (b[0] * b[1]).toString
}
var divide = Fn.new { |s|
var b = s.split("/").map { |t| toDoubleOrZero.call(t) }.toList
return (b[0] / b[1]).toString
}
var add = Fn.new { |s|
var p1 = Pattern.new("/+", Pattern.start)
var p2 = Pattern.new("+1/+")
var t = p1.replaceAll(s, "")
t = p2.replaceAll(t, "+")
var b = t.split("+").map { |u| toDoubleOrZero.call(u) }.toList
return (b[0] + b[1]).toString
}
var subtract = Fn.new { |s|
var p = Pattern.new("[/+-|-/+]")
var t = p.replaceAll(s, "-")
if (t.contains("--")) return add.call(t.replace("--", "+"))
var b = t.split("-").map { |u| toDoubleOrZero.call(u) }.toList
return ((b.count == 3) ? -b[1] - b[2] : b[0] - b[1]).toString
}
var evalExp = Fn.new { |s|
var p = Pattern.new("[(|)|/s]")
var t = p.replaceAll(s, "")
var i = "*/"
var pMD = Pattern.new("+1/f/i~/n+1/f", Pattern.within, i)
var pM = Pattern.new("*")
var pAS = Pattern.new("~-+1/f+1/n+1/f")
var pA = Pattern.new("/d/+")
while (true) {
var match = pMD.find(t)
if (!match) break
var exp = match.text
var match2 = pM.find(exp)
t = match2 ? t.replace(exp, multiply.call(exp)) : t.replace(exp, divide.call(exp))
}
while (true) {
var match = pAS.find(t)
if (!match) break
var exp = match.text
var match2 = pA.find(exp)
t = match2 ? t.replace(exp, add.call(exp)) : t.replace(exp, subtract.call(exp))
}
return t
}
var evalArithmeticExp = Fn.new { |s|
var p1 = Pattern.new("/s")
var p2 = Pattern.new("/+", Pattern.start)
var t = p1.replaceAll(s, "")
t = p2.replaceAll(t, "")
var i = "()"
var pPara = Pattern.new("(+0/I)", Pattern.within, i)
while (true) {
var match = pPara.find(t)
if (!match) break
var exp = match.text
t = t.replace(exp, evalExp.call(exp))
}
return toDoubleOrZero.call(evalExp.call(t))
}
[
"2+3",
"2+3/4",
"2*3-4",
"2*(3+4)+5/6",
"2 * (3 + (4 * 5 + (6 * 7) * 8) - 9) * 10",
"2*-3--4+-0.25",
"-4 - 3",
"((((2))))+ 3 * 5",
"1 + 2 * (3 + (4 * 5 + 6 * 7 * 8) - 9) / 10",
"1 + 2*(3 - 2*(3 - 2)*((2 - 4)*5 - 22/(7 + 2*(3 - 1)) - 1)) + 1"
].each { |s| System.print("%(s) = %(evalArithmeticExp.call(s))") }</syntaxhighlight>
{{out}}
<pre>
2+3 = 5
2+3/4 = 2.75
2*3-4 = 2
2*(3+4)+5/6 = 14.833333333333
2 * (3 + (4 * 5 + (6 * 7) * 8) - 9) * 10 = 7000
2*-3--4+-0.25 = -2.25
-4 - 3 = -7
((((2))))+ 3 * 5 = 17
1 + 2 * (3 + (4 * 5 + 6 * 7 * 8) - 9) / 10 = 71
1 + 2*(3 - 2*(3 - 2)*((2 - 4)*5 - 22/(7 + 2*(3 - 1)) - 1)) + 1 = 60
</pre>
=={{header|XPL0}}==
<syntaxhighlight lang "XPL0">def \Node\ Left, Data, Right;
def IntSize = 4;
int Stack(16);
int SP; \stack pointer
proc Push(N);
int N;
[Stack(SP):= N; SP:= SP+1];
func Pop;
[SP:= SP-1; return Stack(SP)];
func Precedence(Op);
int Op;
case Op of
^+, ^-: return 2;
^*, ^/: return 3;
^^: return 4
other [];
proc PostOrder(Node); \Traverse tree at Node in postorder, and
int Node, Top; \ return its evaluation on the stack
[if Node # 0 then
[PostOrder(Node(Left));
PostOrder(Node(Right));
case Node(Data) of
^+: [Top:= Pop; Push(Pop+Top)];
^-: [Top:= Pop; Push(Pop-Top)];
^*: [Top:= Pop; Push(Pop*Top)];
^/: [Top:= Pop; Push(Pop/Top)]
other Push(Node(Data) - ^0); \convert ASCII to binary
];
];
char Str;
int Token, Op1, Op2, Node;
[Str:= "3 + 4 * 2 / ( 1 - 5 ) "; \RPN: 342*15-/+
Text(0, Str);
\Convert infix expression to RPN (postfix) using shunting-yard algorithm
SP:= 0;
OpenO(8); \discard (overwrite) arguments in RPi's command line
loop [repeat Token:= Str(0); Str:= Str+1;
until Token # ^ ; \strip out space characters
case Token of
^+, ^-, ^*, ^/, ^^:
[Op1:= Token;
loop [if SP <= 0 then quit; \stack is empty
Op2:= Stack(SP-1);
if Op2 = ^( then quit;
if Precedence(Op2) < Precedence(Op1) then quit;
if Precedence(Op2) = Precedence(Op1) then
if Op1 = ^^ then quit;
ChOut(8, Pop);
];
Push(Op1);
];
^(: Push(Token);
^): [while SP > 0 and Stack(SP-1) # ^( do
ChOut(8, Pop);
Pop; \discard left parenthesis
];
$A0: quit \terminating space with its MSB set
other ChOut(8, Token); \output the single-digit number
];
while SP > 0 do ChOut(8, Pop); \output any remaining operators
\Build AST from RPN expression
OpenI(8); \(for safety)
loop [Token:= ChIn(8);
if Token = $1A\EOF\ then quit
else if Token >= ^0 and Token <= ^9 then
[Node:= Reserve(3*IntSize);
Node(Data):= Token;
Node(Left):= 0;
Node(Right):= 0;
Push(Node);
]
else \must be an operator
[Node:= Reserve(3*IntSize);
Node(Data):= Token;
Node(Right):= Pop;
Node(Left):= Pop;
Push(Node);
];
];
\Evaluate expression in AST
PostOrder(Pop);
Text(0, "= ");
IntOut(0, Pop);
]</syntaxhighlight>
{{out}}
<pre>
t.txt"a</pre>
=={{header|zkl}}==
In zkl, the compiler stack is part of the language and is written in zkl so ...
<syntaxhighlight lang="zkl">Compiler.Parser.parseText("(1+3)*7").dump();
Compiler.Parser.parseText("1+3*7").dump();</syntaxhighlight>
The ASTs look like
{{out}}
<pre>
class RootClass# Input source: "<text>"
Attributes: static createReturnsSelf
...
{ Block(Class) <Line 1>
Exp(
(,1,+,3,),*,7
)
}
class RootClass# Input source: "<text>"
...
{ Block(Class) <Line 1>
Exp(
1,+,3,*,7
)
}
</pre>
Evaluating them is just moving up the stack:
<syntaxhighlight lang="zkl">Compiler.Compiler.compileText("(1+3)*7").__constructor(); vm.regX;
Compiler.Compiler.compileText("1+3*7").__constructor(); vm.regX;</syntaxhighlight>
{{out}}
<pre>
28
22
</pre>
=={{header|ZX Spectrum Basic}}==
<syntaxhighlight lang="zxbasic">10 PRINT "Use integer numbers and signs"'"+ - * / ( )"''
20 LET s$="": REM last symbol
30 LET pc=0: REM parenthesis counter
40 LET i$="1+2*(3+(4*5+6*7*8)-9)/10"
50 PRINT "Input = ";i$
60 FOR n=1 TO LEN i$
70 LET c$=i$(n)
80 IF c$>="0" AND c$<="9" THEN GO SUB 170: GO TO 130
90 IF c$="+" OR c$="-" THEN GO SUB 200: GO TO 130
100 IF c$="*" OR c$="/" THEN GO SUB 200: GO TO 130
110 IF c$="(" OR c$=")" THEN GO SUB 230: GO TO 130
120 GO TO 300
130 NEXT n
140 IF pc>0 THEN PRINT FLASH 1;"Parentheses not paired.": BEEP 1,-25: STOP
150 PRINT "Result = ";VAL i$
160 STOP
170 IF s$=")" THEN GO TO 300
180 LET s$=c$
190 RETURN
200 IF (NOT (s$>="0" AND s$<="9")) AND s$<>")" THEN GO TO 300
210 LET s$=c$
220 RETURN
230 IF c$="(" AND ((s$>="0" AND s$<="9") OR s$=")") THEN GO TO 300
240 IF c$=")" AND ((NOT (s$>="0" AND s$<="9")) OR s$="(") THEN GO TO 300
250 LET s$=c$
260 IF c$="(" THEN LET pc=pc+1: RETURN
270 LET pc=pc-1
280 IF pc<0 THEN GO TO 300
290 RETURN
300 PRINT FLASH 1;"Invalid symbol ";c$;" detected in pos ";n: BEEP 1,-25
310 STOP
</syntaxhighlight>
{{omit from|gnuplot}}
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