Parsing/RPN calculator algorithm: Difference between revisions
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{{
;Task:
Create a stack-based evaluator for an expression in [[wp:Reverse Polish notation|<u>r</u>everse <u>P</u>olish <u>n</u>otation (RPN)]] that also shows the changes in the stack as each individual token is processed ''as a table''.
* Assume an input of a correct, space separated, string of tokens of an RPN expression
* Test with the RPN expression generated from the [[Parsing/Shunting-yard algorithm]] task: <
<big><big><code> 3 4 2 * 1 5 - 2 3 ^ ^ / + </code></big></big>
* Print or display the output here
;Notes:
* <big><b> '''^''' </b></big> means exponentiation in the expression above.
* <big><b> '''/''' </b></big> means division.
;See also:
* [[Parsing/Shunting-yard algorithm]] for a method of generating an RPN from an infix expression.
* Several solutions to [[24 game/Solve]] make use of RPN evaluators (although tracing how they work is not a part of that task).
* [[Parsing/RPN to infix conversion]].
* [[Arithmetic evaluation]].
<br><br>
=={{header|
{{trans|Python}}
<syntaxhighlight lang="11l">[Float] a
[String = ((Float, Float) -> Float)] b
b[‘+’] = (x, y) -> y + x
b[‘-’] = (x, y) -> y - x
b[‘*’] = (x, y) -> y * x
b[‘/’] = (x, y) -> y / x
b[‘^’] = (x, y) -> y ^ x
L(c) ‘3 4 2 * 1 5 - 2 3 ^ ^ / +’.split(‘ ’)
I c C b
V first = a.pop()
V second = a.pop()
a.append(b[c](first, second))
E
a.append(Float(c))
print(c‘ ’a)</syntaxhighlight>
{{out}}
<pre>
3 [3]
4 [3, 4]
2 [3, 4, 2]
* [3, 8]
1 [3, 8, 1]
5 [3, 8, 1, 5]
- [3, 8, -4]
2 [3, 8, -4, 2]
3 [3, 8, -4, 2, 3]
^ [3, 8, -4, 8]
^ [3, 8, 65536]
/ [3, 0.00012207]
+ [3.00012207]
</pre>
=={{header|360 Assembly}}==
{{trans|FORTRAN}}
For concision, only integer arithmetic is handled, but input numbers can be of any length. The formal task is not completed, but the spirit of it is.
<syntaxhighlight lang="360asm">* RPN calculator RC 25/01/2019
REVPOL CSECT
USING REVPOL,R13 base register
B 72(R15) skip savearea
DC 17F'0' savearea
STM R14,R12,12(R13) save previous context
ST R13,4(R15) link backward
ST R15,8(R13) link forward
LR R13,R15 set addressability
XPRNT TEXT,L'TEXT print expression !?
L R4,0 js=0 offset in stack
LA R5,0 ns=0 number of stack items
LA R6,0 jt=0 offset in text
LA R7,TEXT r7=@text
MVC CC,0(R7) cc first char of token
DO WHILE=(CLI,CC,NE,X'00') do while cc<>'0'x
MVC CTOK,=CL5' ' ctok=''
MVC CTOK(1),CC ctok=cc
CLI CC,C' ' if cc=' '
BE ITERATE then goto iterate
IF CLI,CC,GE,C'0',AND,CLI,CC,LE,C'9' THEN
MVC DEED,=C'Load' deed='Load'
XDECI R2,0(R7) r2=cint(text); r1=@text
ST R2,STACK(R4) stack(js)=cc
SR R1,R7 lt length of token
BCTR R1,0 lt-1
EX R1,MVCV MVC CTOK("R1"),0(R7)
AR R6,R1 jt+=lt-1
AR R7,R1 @text+=lt-1
LA R4,4(R4) js+=4
LA R5,1(R5) ns++
ELSE , else
MVC DEED,=C'Exec' deed='Exec'
LA R9,STACK-8(R4) @stack(j-1)
IF CLI,CC,EQ,C'+' THEN if cc='+' then
L R1,STACK-8(R4) stack(j-1)
A R1,STACK-4(R4) stack(j-1)+stack(j)
ST R1,0(R9) stack(j-1)=stack(j-1)+stack(j)
ENDIF , endif
IF CLI,CC,EQ,C'-' THEN if cc='-' then
L R1,STACK-8(R4) stack(j-1)
S R1,STACK-4(R4) stack(j-1)-stack(j)
ST R1,0(R9) stack(j-1)=stack(j-1)-stack(j)
ENDIF , endif
IF CLI,CC,EQ,C'*' THEN if cc='*' then
L R3,STACK-8(R4) stack(j-1)
M R2,STACK-4(R4) stack(j-1)*stack(j)
ST R3,0(R9) stack(j-1)=stack(j-1)*stack(j)
ENDIF , endif
IF CLI,CC,EQ,C'/' THEN if cc='/' then
L R2,STACK-8(R4) stack(j-1)
SRDA R2,32 for sign propagation
D R2,STACK-4(R4) stack(j-1)/stack(j)
ST R3,0(R9) stack(j-1)=stack(j-1)/stack(j)
ENDIF , endif
IF CLI,CC,EQ,C'^' THEN if cc='^' then
LA R3,1 r3=1
L R0,STACK-4(R4) r0=stack(j) [loop count]
EXPONENT M R2,STACK-8(R4) r3=r3*stack(j-1)
BCT R0,EXPONENT if r0--<>0 then goto exponent
ST R3,0(R9) stack(j-1)=stack(j-1)^stack(j)
ENDIF , endif
S R4,=F'4' js-=4
BCTR R5,0 ns--
ENDIF , endif
MVC PG,=CL80' ' clean buffer
MVC PG(4),DEED output deed
MVC PG+5(5),CTOK output cc
MVC PG+11(6),=C'Stack:' output
LA R2,1 i=1
LA R3,STACK @stack
LA R9,PG+18 @buffer
DO WHILE=(CR,R2,LE,R5) do i=1 to ns
L R1,0(R3) stack(i)
XDECO R1,XDEC edit stack(i)
MVC 0(5,R9),XDEC+7 output stack(i)
LA R2,1(R2) i=i+1
LA R3,4(R3) @stack+=4
LA R9,6(R9) @buffer+=6
ENDDO , enddo
XPRNT PG,L'PG print
ITERATE LA R6,1(R6) jt++
LA R7,1(R7) @text++
MVC CC,0(R7) cc next char
ENDDO , enddo
L R1,STACK stack(1)
XDECO R1,XDEC edit stack(1)
MVC XDEC(4),=C'Val=' output
XPRNT XDEC,L'XDEC print stack(1)
L R13,4(0,R13) restore previous savearea pointer
LM R14,R12,12(R13) restore previous context
XR R15,R15 rc=0
BR R14 exit
MVCV MVC CTOK(0),0(R7) patern mvc
TEXT DC C'3 4 2 * 1 5 - 2 3 ^ ^ / +',X'00'
STACK DS 16F stack(16)
DEED DS CL4
CC DS C
CTOK DS CL5
PG DS CL80
XDEC DS CL12
YREGS
END REVPOL</syntaxhighlight>
{{out}}
<pre>
3 4 2 * 1 5 - 2 3 ^ ^ / +
Load 3 Stack: 3
Load 4 Stack: 3 4
Load 2 Stack: 3 4 2
Exec * Stack: 3 8
Load 1 Stack: 3 8 1
Load 5 Stack: 3 8 1 5
Exec - Stack: 3 8 -4
Load 2 Stack: 3 8 -4 2
Load 3 Stack: 3 8 -4 2 3
Exec ^ Stack: 3 8 -4 8
Exec ^ Stack: 3 8 65536
Exec / Stack: 3 0
Exec + Stack: 3
Val= 3
</pre>
=={{header|Action!}}==
{{libheader|Action! Tool Kit}}
<syntaxhighlight lang="action!">INCLUDE "D2:REAL.ACT" ;from the Action! Tool Kit
DEFINE PTR="CARD"
DEFINE BUFFER_SIZE="60"
DEFINE ENTRY_SIZE="6"
DEFINE MAX_SIZE="10"
BYTE ARRAY stack(BUFFER_SIZE)
BYTE stackSize=[0]
BYTE FUNC IsEmpty()
IF stackSize=0 THEN
RETURN (1)
FI
RETURN (0)
PTR FUNC GetPtr(BYTE i)
RETURN (stack+i*ENTRY_SIZE)
PROC Push(REAL POINTER v)
REAL POINTER p
IF stackSize=MAX_SIZE THEN
PrintE("Error: stack is full!")
Break()
FI
p=GetPtr(stackSize)
RealAssign(v,p)
stackSize==+1
RETURN
PROC Pop(REAL POINTER v)
REAL POINTER p
IF IsEmpty() THEN
PrintE("Error: stack is empty!")
Break()
FI
stackSize==-1
p=GetPtr(stackSize)
RealAssign(p,v)
RETURN
PROC PrintStack()
INT i
REAL POINTER p
FOR i=0 TO stackSize-1
DO
p=GetPtr(i)
PrintR(p) Put(32)
OD
PutE()
RETURN
BYTE FUNC GetToken(CHAR ARRAY s BYTE start CHAR ARRAY t)
BYTE pos
pos=start
WHILE pos<=s(0) AND s(pos)#'
DO
pos==+1
OD
SCopyS(t,s,start,pos-1)
RETURN (pos)
PROC MyPower(REAL POINTER base,exp,res)
INT i,expI
REAL tmp
expI=RealToInt(exp)
IF expI<0 THEN Break() FI
IntToReal(1,res)
FOR i=1 TO expI
DO
RealMult(res,base,tmp)
RealAssign(tmp,res)
OD
RETURN
PROC Process(CHAR ARRAY s)
DEFINE Pop21="Pop(v2) Pop(v1)"
CHAR ARRAY t(100)
BYTE i,j
CHAR c
REAL v1,v2,v3
i=1
WHILE i<=s(0)
DO
WHILE i<=s(0) AND s(i)='
DO i==+1 OD
IF i>s(0) THEN EXIT FI
i=GetToken(s,i,t)
IF SCompare(t,"+")=0 THEN
Pop21 RealAdd(v1,v2,v3)
Print("calc +: ")
ELSEIF SCompare(t,"-")=0 THEN
Pop21 RealSub(v1,v2,v3)
Print("calc -: ")
ELSEIF SCompare(t,"*")=0 THEN
Pop21 RealMult(v1,v2,v3)
Print("calc *: ")
ELSEIF SCompare(t,"/")=0 THEN
Pop21 RealDiv(v1,v2,v3)
Print("calc /: ")
ELSEIF SCompare(t,"^")=0 THEN
Pop21 MyPower(v1,v2,v3)
Print("calc ^: ")
ELSE
ValR(t,v3)
PrintF("push %S: ",t)
FI
Push(v3)
PrintStack()
OD
RETURN
PROC Test(CHAR ARRAY s)
PrintE(s) PutE()
Process(s)
RETURN
PROC Main()
Put(125) PutE() ;clear the screen
Test("3 4 2 * 1 5 - 2 3 ^ ^ / +")
RETURN</syntaxhighlight>
{{out}}
[https://gitlab.com/amarok8bit/action-rosetta-code/-/raw/master/images/RPN_calculator_algorithm.png Screenshot from Atari 8-bit computer]
<pre>
3 4 2 * 1 5 - 2 3 ^ ^ / +
push 3: 3
push 4: 3 4
push 2: 3 4 2
calc *: 3 8
push 1: 3 8 1
push 5: 3 8 1 5
calc -: 3 8 -4
push 2: 3 8 -4 2
push 3: 3 8 -4 2 3
calc ^: 3 8 -4 8
calc ^: 3 8 65536
calc /: 3 1.22070312E-04
calc +: 3.00012207
</pre>
=={{header|Ada}}==
<syntaxhighlight lang="ada">with Ada.Text_IO, Ada.Containers.Vectors;
procedure RPN_Calculator is
package IIO is new Ada.Text_IO.Float_IO(Float);
package Float_Vec is new Ada.Containers.Vectors
(Index_Type => Positive, Element_Type => Float);
Stack: Float_Vec.Vector;
Input: String := Ada.Text_IO.Get_Line;
Cursor: Positive := Input'First;
New_Cursor: Positive;
begin
loop
-- read spaces
while Cursor <= Input'Last and then Input(Cursor)=' ' loop
Cursor := Cursor + 1;
end loop;
exit when Cursor > Input'Last;
New_Cursor := Cursor;
while New_Cursor <= Input'Last and then Input(New_Cursor) /= ' ' loop
New_Cursor := New_Cursor + 1;
end loop;
-- try to read a number and push it to the stack
declare
Last: Positive;
Value: Float;
X, Y: Float;
begin
IIO.Get(From => Input(Cursor .. New_Cursor - 1),
Item => Value,
Last => Last);
Stack.Append(Value);
Cursor := New_Cursor;
exception -- if reading the number fails, try to read an operator token
when others =>
Y := Stack.Last_Element; Stack.Delete_Last; -- pick two elements
X := Stack.Last_Element; Stack.Delete_Last; -- from the stack
case Input(Cursor) is
when '+' => Stack.Append(X+Y);
when '-' => Stack.Append(X-Y);
when '*' => Stack.Append(X*Y);
when '/' => Stack.Append(X/Y);
when '^' => Stack.Append(X ** Integer(Float'Rounding(Y)));
when others => raise Program_Error with "unecpected token '"
& Input(Cursor) & "' at column" & Integer'Image(Cursor);
end case;
Cursor := New_Cursor;
end;
for I in Stack.First_Index .. Stack.Last_Index loop
Ada.Text_IO.Put(" ");
IIO.Put(Stack.Element(I), Aft => 5, Exp => 0);
end loop;
Ada.Text_IO.New_Line;
end loop;
Ada.Text_IO.Put("Result = ");
IIO.Put(Item => Stack.Last_Element, Aft => 5, Exp => 0);
end RPN_Calculator;</syntaxhighlight>
{{out}}
<pre>3 4 2 * 1 5 - 2 3 ^ ^ / +
3.00000
3.00000 4.00000
3.00000 4.00000 2.00000
3.00000 8.00000
3.00000 8.00000 1.00000
3.00000 8.00000 1.00000 5.00000
3.00000 8.00000 -4.00000
3.00000 8.00000 -4.00000 2.00000
3.00000 8.00000 -4.00000 2.00000 3.00000
3.00000 8.00000 -4.00000 8.00000
3.00000 8.00000 65536.00000
3.00000 0.00012
3.00012
Result = 3.00012</pre>
=={{header|ALGOL 68}}==
{{works with|ALGOL 68G|Any - tested with release 2.8.win32}}
<syntaxhighlight lang="algol68"># RPN Expression evaluator - handles numbers and + - * / ^ #
# the right-hand operand for ^ is converted to an integer #
# expression terminator #
CHAR end of expression character = REPR 12;
# evaluates the specified rpn expression #
PROC evaluate = ( STRING rpn expression )VOID:
BEGIN
[ 256 ]REAL stack;
INT stack pos := 0;
# pops an element off the stack #
PROC pop = REAL:
BEGIN
stack pos -:= 1;
stack[ stack pos + 1 ]
END; # pop #
INT rpn pos := LWB rpn expression;
# evaluate tokens from the expression until we get the end of expression #
WHILE
# get the next token from the string #
STRING token type;
REAL value;
# skip spaces #
WHILE rpn expression[ rpn pos ] = " "
DO
rpn pos +:= 1
OD;
# handle the token #
IF rpn expression[ rpn pos ] = end of expression character
THEN
# no more tokens #
FALSE
ELSE
# have a token #
IF rpn expression[ rpn pos ] >= "0"
AND rpn expression[ rpn pos ] <= "9"
THEN
# have a number #
# find where the nmumber is in the expression #
INT number start = rpn pos;
WHILE ( rpn expression[ rpn pos ] >= "0"
AND rpn expression[ rpn pos ] <= "9"
)
OR rpn expression[ rpn pos ] = "."
DO
rpn pos +:= 1
OD;
# read the number from the expression #
FILE number f;
associate( number f
, LOC STRING := rpn expression[ number start : rpn pos - 1 ]
);
get( number f, ( value ) );
close( number f );
token type := "number"
ELSE
# must be an operator #
CHAR op = rpn expression[ rpn pos ];
rpn pos +:= 1;
REAL arg1 := pop;
REAL arg2 := pop;
token type := op;
value := IF op = "+"
THEN
# add the top two stack elements #
arg1 + arg2
ELIF op = "-"
THEN
# subtract the top two stack elements #
arg2 - arg1
ELIF op = "*"
THEN
# multiply the top two stack elements #
arg2 * arg1
ELIF op = "/"
THEN
# divide the top two stack elements #
arg2 / arg1
ELIF op = "^"
THEN
# raise op2 to the power of op1 #
arg2 ^ ENTIER arg1
ELSE
# unknown operator #
print( ( "Unknown operator: """ + op + """", newline ) );
0
FI
FI;
TRUE
FI
DO
# push the new value on the stack and show the new stack #
stack[ stack pos +:= 1 ] := value;
print( ( ( token type + " " )[ 1 : 8 ] ) );
FOR element FROM LWB stack TO stack pos
DO
print( ( " ", fixed( stack[ element ], 8, 4 ) ) )
OD;
print( ( newline ) )
OD;
print( ( "Result is: ", fixed( stack[ stack pos ], 12, 8 ), newline ) )
END; # evaluate #
main: (
# get the RPN expresson from the user #
STRING rpn expression;
print( ( "Enter expression: " ) );
read( ( rpn expression, newline ) );
# add a space to terminate the final token and an expression terminator #
rpn expression +:= " " + end of expression character;
# execute the expression #
evaluate( rpn expression )
)</syntaxhighlight>
{{out}}
<pre>
Enter expression: 3 4 2 * 1 5 - 2 3 ^ ^ / +
number +3.0000
number +3.0000 +4.0000
number +3.0000 +4.0000 +2.0000
* +3.0000 +8.0000
number +3.0000 +8.0000 +1.0000
number +3.0000 +8.0000 +1.0000 +5.0000
- +3.0000 +8.0000 -4.0000
number +3.0000 +8.0000 -4.0000 +2.0000
number +3.0000 +8.0000 -4.0000 +2.0000 +3.0000
^ +3.0000 +8.0000 -4.0000 +8.0000
^ +3.0000 +8.0000 +65536.0
/ +3.0000 +0.0001
+ +3.0001
Result is: +3.00012207
</pre>
=={{header|ANTLR}}==
[[File:Rpn.png|left|rpnC]]
[[File:rpnCNum.png|left|rpnC]]
[[File:RpnCop.png|left|rpnC]]
<br clear=both>
===Java===
<syntaxhighlight lang="java">
grammar rpnC ;
//
// rpn Calculator
//
// Nigel Galloway - April 7th., 2012
//
@members {
Stack<Double> s = new Stack<Double>();
}
rpn : (WS* (num|op) (WS | WS* NEWLINE {System.out.println(s.pop());}))*;
num : '-'? Digit+ ('.' Digit+)? {s.push(Double.parseDouble($num.text));};
Digit : '0'..'9';
op : '-' {double x = s.pop(); s.push(s.pop() - x);}
| '/' {double x = s.pop(); s.push(s.pop() / x);}
| '*' {s.push(s.pop() * s.pop());}
| '^' {double x = s.pop(); s.push(Math.pow(s.pop(), x));}
| '+' {s.push(s.pop() + s.pop());};
WS : (' ' | '\t'){skip()};
NEWLINE : '\r'? '\n';
</syntaxhighlight>
Produces:
<pre>
>java Test
3 4 2 * 1 5 - 2 3 ^ ^ / +
^Z
3.0001220703125
</pre>
=={{header|AutoHotkey}}==
{{works with|AutoHotkey_L}}
Output is in clipboard.
<syntaxhighlight lang="ahk">evalRPN("3 4 2 * 1 5 - 2 3 ^ ^ / +")
evalRPN(s){
stack := []
out := "For RPN expression: '" s "'`r`n`r`nTOKEN`t`tACTION`t`t`tSTACK`r`n"
Loop Parse, s
If A_LoopField is number
t .= A_LoopField
else
{
If t
stack.Insert(t)
, out .= t "`tPush num onto top of stack`t" stackShow(stack) "`r`n"
, t := ""
If InStr("+-/*^", l := A_LoopField)
{
a := stack.Remove(), b := stack.Remove()
stack.Insert( l = "+" ? b + a
:l = "-" ? b - a
:l = "*" ? b * a
:l = "/" ? b / a
:l = "^" ? b **a
:0 )
out .= l "`tApply op " l " to top of stack`t" stackShow(stack) "`r`n"
}
}
r := stack.Remove()
out .= "`r`n The final output value is: '" r "'"
clipboard := out
return r
}
StackShow(stack){
for each, value in stack
out .= A_Space value
return subStr(out, 2)
}</syntaxhighlight>
{{out}}
<pre>For RPN expression: '3 4 2 * 1 5 - 2 3 ^ ^ / +'
TOKEN ACTION STACK
3 Push num onto top of stack 3
4 Push num onto top of stack 3 4
2 Push num onto top of stack 3 4 2
* Apply op * to top of stack 3 8
1 Push num onto top of stack 3 8 1
5 Push num onto top of stack 3 8 1 5
- Apply op - to top of stack 3 8 -4
2 Push num onto top of stack 3 8 -4 2
3 Push num onto top of stack 3 8 -4 2 3
^ Apply op ^ to top of stack 3 8 -4 8
^ Apply op ^ to top of stack 3 8 65536
/ Apply op / to top of stack 3 0.000122
+ Apply op + to top of stack 3.000122
The final output value is: '3.000122'</pre>
=={{header|BASIC}}==
==={{header|ANSI BASIC}}===
{{works with|Decimal BASIC}}
<syntaxhighlight lang="basic">1000 DECLARE EXTERNAL SUB rpn
1010 PUBLIC NUMERIC R(64) ! stack
1020 PUBLIC STRING expn$ ! for keyboard input
1030 PUBLIC NUMERIC i, lenn, n, true, false ! global values
1040 LET true = -1
1050 LET false = 0
1060 DO
1070 PRINT "enter an RPN expression:"
1080 INPUT expn$
1090 IF LEN( expn$ ) = 0 THEN EXIT DO
1100 PRINT "expn: ";expn$
1110 CALL rpn( expn$ )
1120 LOOP
1130 END
1140 !
1150 ! interpret reverse polish (postfix) expression
1160 EXTERNAL SUB rpn( expn$ )
1170 DECLARE EXTERNAL FUNCTION is_digit, get_number
1180 DECLARE EXTERNAL SUB print_stack
1190 DECLARE STRING ch$
1200 LET expn$ = expn$ & " " ! must terminate line with space
1210 LET lenn = LEN( expn$ )
1220 LET i = 0
1230 LET n = 1
1240 LET R(n) = 0.0 ! push zero for unary operations
1250 DO
1260 IF i >= lenn THEN EXIT DO ! at end of line
1270 LET i = i + 1
1280 IF expn$(i:i) <> " " THEN ! skip white spaces
1290 IF is_digit( expn$(i:i) ) = true THEN ! push number onto stack
1300 LET n = n + 1
1310 LET R(n) = get_number
1320 CALL print_stack
1330 ELSEIF expn$(i:i) = "+" then ! add and pop stack
1340 IF n < 2 THEN
1350 PRINT "stack underflow"
1360 ELSE
1370 LET R(n-1) = R(n-1) + R(n)
1380 LET n = n - 1
1390 CALL print_stack
1400 END IF
1410 ELSEIF expn$(i:i) = "-" then ! subtract and pop stack
1420 IF n < 2 THEN
1430 PRINT "stack underflow"
1440 ELSE
1450 LET R(n-1) = R(n-1) - R(n)
1460 LET n = n - 1
1470 CALL print_stack
1480 END IF
1490 ELSEIF expn$(i:i) = "*" then ! multiply and pop stack
1500 IF n < 2 THEN
1510 PRINT "stack underflow"
1520 ELSE
1530 LET R(n-1) = R(n-1) * R(n)
1540 LET n = n - 1
1550 CALL print_stack
1560 END IF
1570 ELSEIF expn$(i:i) = "/" THEN ! divide and pop stack
1580 IF n < 2 THEN
1590 PRINT "stack underflow"
1600 ELSE
1610 LET R(n-1) = R(n-1) / R(n)
1620 LET n = n - 1
1630 CALL print_stack
1640 END IF
1650 ELSEIF expn$(i:i) = "^" THEN ! raise to power and pop stack
1660 IF n < 2 THEN
1670 PRINT "stack underflow"
1680 ELSE
1690 LET R(n-1) = R(n-1) ^ R(n)
1700 LET n = n - 1
1710 CALL print_stack
1720 END IF
1730 ELSE
1740 PRINT REPEAT$( " ", i+5 ); "^ error"
1750 EXIT DO
1760 END IF
1770 END IF
1780 LOOP
1790 PRINT "result: "; R(n) ! end of main program
1800 END SUB
1810 !
1820 ! extract a number from a string
1830 EXTERNAL FUNCTION get_number
1840 DECLARE EXTERNAL FUNCTION is_digit
1850 LET i1 = i ! start of number substring
1860 DO ! get integer part
1870 LET i = i + 1
1880 IF is_digit( expn$(i:i) ) = false THEN
1890 IF expn$(i:i) = "." THEN
1900 LET i = i + 1
1910 DO WHILE is_digit( expn$(i:i) ) = true ! get fractional part
1920 LET i = i + 1
1930 LOOP
1940 END IF
1950 EXIT DO
1960 END IF
1970 LOOP
1980 LET get_number = VAL( expn$(i1:i - 1) )
1990 END FUNCTION
2000 !
2010 ! check for digit character
2020 EXTERNAL FUNCTION is_digit( ch$ )
2030 IF "0" <= ch$ AND ch$ <= "9" THEN
2040 LET is_digit = true
2050 ELSE
2060 LET is_digit = false
2070 END IF
2080 END FUNCTION
2090 !
2100 EXTERNAL SUB print_stack
2110 PRINT expn$(i:i);" ";
2120 FOR ptr=n TO 2 STEP -1
2130 PRINT USING "-----%.####":R(ptr);
2140 NEXT ptr
2150 PRINT
2160 END SUB</syntaxhighlight>
{{out}}
<pre>
enter an RPN expression:
? 3 4 2 * 1 5 - 2 3 ^ ^ / +
expn: 3 4 2 * 1 5 - 2 3 ^ ^ / +
3.0000
4.0000 3.0000
2.0000 4.0000 3.0000
* 8.0000 3.0000
1.0000 8.0000 3.0000
5.0000 1.0000 8.0000 3.0000
- -4.0000 8.0000 3.0000
2.0000 -4.0000 8.0000 3.0000
3.0000 2.0000 -4.0000 8.0000 3.0000
^ 8.0000 -4.0000 8.0000 3.0000
^ 65536.0000 8.0000 3.0000
/ 0.0001 3.0000
+ 3.0001
result: 3.0001220703125
enter an RPN expression:
?
</pre>
==={{header|BBC BASIC}}===
<syntaxhighlight lang="bbcbasic"> @% = &60B
RPN$ = "3 4 2 * 1 5 - 2 3 ^ ^ / +"
DIM Stack(1000)
SP% = 0
FOR i% = 1 TO LEN(RPN$)
Token$ = MID$(RPN$,i%,1)
IF Token$ <> " " THEN
PRINT Token$ " :";
CASE Token$ OF
WHEN "+": PROCpush(FNpop + FNpop)
WHEN "-": PROCpush(-FNpop + FNpop)
WHEN "*": PROCpush(FNpop * FNpop)
WHEN "/": n = FNpop : PROCpush(FNpop / n)
WHEN "^": n = FNpop : PROCpush(FNpop ^ n)
WHEN "0","1","2","3","4","5","6","7","8","9":
PROCpush(VALMID$(RPN$,i%))
WHILE ASCMID$(RPN$,i%)>=48 AND ASCMID$(RPN$,1)<=57
i% += 1
ENDWHILE
ENDCASE
FOR j% = SP%-1 TO 0 STEP -1 : PRINT Stack(j%); : NEXT
PRINT
ENDIF
NEXT i%
END
DEF PROCpush(n)
IF SP% > DIM(Stack(),1) ERROR 100, "Stack full"
Stack(SP%) = n
SP% += 1
ENDPROC
DEF FNpop
IF SP% = 0 ERROR 100, "Stack empty"
SP% -= 1
= Stack(SP%)</syntaxhighlight>
{{out}}
<pre>
3 : 3
4 : 4 3
2 : 2 4 3
* : 8 3
1 : 1 8 3
5 : 5 1 8 3
- : -4 8 3
2 : 2 -4 8 3
3 : 3 2 -4 8 3
^ : 8 -4 8 3
^ : 65536 8 3
/ : 0.00012207 3
+ : 3.00012
</pre>
==={{header|FreeBASIC}}===
<syntaxhighlight lang="freebasic">#define NULL 0
type node
'implement the stack as a linked list
n as double
p as node ptr
end type
function spctok( byref s as string ) as string
'returns everything in the string up to the first space
'modifies the original string to begin at the fist non-space char after the first space
dim as string r
dim as double i = 1
while mid(s,i,1)<>" " and i<=len(s)
r += mid(s,i,1)
i+=1
wend
do
i+=1
loop until mid(s,i,1)<>" " or i >= len(s)
s = right(s,len(s)-i+1)
return r
end function
sub print_stack( byval S as node ptr )
'display everything on the stack
print "Stack <--- ";
while S->p <> NULL
S = S->p
print S->n;" ";
wend
print
end sub
sub push( byval S as node ptr, v as double )
'push a value onto the stack
dim as node ptr x
x = allocate(sizeof(node))
x->n = v
x->p = S->p
S->p = x
end sub
function pop( byval S as node ptr ) as double
'pop a value from the stack
if s->P = NULL then return -99999
dim as double r = S->p->n
dim as node ptr junk = S->p
S->p = S->p->p
deallocate(junk)
return r
end function
dim as string s = "3 4 2 * 1 5 - 2 3 ^ ^ / +", c
dim as node StackHead
while len(s) > 0
c = spctok(s)
print "Token: ";c;" ";
select case c
case "+"
push(@StackHead, pop(@StackHead) + pop(@StackHead))
print "Operation + ";
case "-"
push(@StackHead, -(pop(@StackHead) - pop(@StackHead)))
print "Operation - ";
case "/"
push(@StackHead, 1./(pop(@StackHead) / pop(@StackHead)))
print "Operation / ";
case "*"
push(@StackHead, pop(@StackHead) * pop(@StackHead))
print "Operation * ";
case "^"
push(@StackHead, pop(@StackHead) ^ pop(@StackHead))
print "Operation ^ ";
case else
push(@StackHead, val(c))
print "Operation push ";
end select
print_stack(@StackHead)
wend</syntaxhighlight>
{{out}}<pre>
Token: 3 Operation push Stack <--- 3
Token: 4 Operation push Stack <--- 4 3
Token: 2 Operation push Stack <--- 2 4 3
Token: * Operation * Stack <--- 8 3
Token: 1 Operation push Stack <--- 1 8 3
Token: 5 Operation push Stack <--- 5 1 8 3
Token: - Operation - Stack <--- -4 8 3
Token: 2 Operation push Stack <--- 2 -4 8 3
Token: 3 Operation push Stack <--- 3 2 -4 8 3
Token: ^ Operation ^ Stack <--- 8 -4 8 3
Token: ^ Operation ^ Stack <--- 65536 8 3
Token: / Operation / Stack <--- 0.0001220703125 3
Token: + Operation + Stack <--- 3.0001220703125
</pre>
=== {{header|GW-BASIC}} ===
{{trans|QuickBASIC}}
Supports multi-digit numbers and negative numbers.
{{works with|BASICA}}
<syntaxhighlight lang="gwbasic">
10 REM Parsing/RPN calculator algorithm
20 MAX.INDEX% = 63
30 REM Stack
40 REM TOP.INDEX% - top index of the stack
50 DIM ELEMS(MAX.INDEX%)
60 EXPR$ = "3 4 2 * 1 5 - 2 3 ^ ^ / +": GOSUB 200
70 END
190 REM ** Evaluate the expression in RPN
200 GOSUB 1000
210 PRINT "Input", "Operation", "Stack after"
220 REM SP% - start position of token, DP% - position of delimiter
230 DP% = 0
240 REM Loop: do ... until DP% = 0
250 SP% = DP% + 1
260 DP% = INSTR(DP% + 1, EXPR$, " ")
270 IF DP% = 0 THEN TOKEN$ = MID$(EXPR$, SP%, LEN(EXPR$) - SP% + 1) ELSE TE% = DP% - 1: TOKEN$ = MID$(EXPR$, SP%, DP% - SP%)
280 PRINT TOKEN$,
290 IF TOKEN$ <> "*" THEN 350
300 PRINT "Operate",
310 GOSUB 1060: SECOND = POP
320 GOSUB 1060: FIRST = POP
330 X = FIRST * SECOND: GOSUB 1160
340 GOTO 610
350 IF TOKEN$ <> "/" THEN 410
360 PRINT "Operate",
370 GOSUB 1060: SECOND = POP
380 GOSUB 1060: FIRST = POP
390 X = FIRST / SECOND: GOSUB 1160
400 GOTO 610
410 IF TOKEN$ <> "-" THEN 470
420 PRINT "Operate",
430 GOSUB 1060: SECOND = POP
440 GOSUB 1060: FIRST = POP
450 X = FIRST - SECOND: GOSUB 1160
460 GOTO 610
470 IF TOKEN$ <> "+" THEN 530
480 PRINT "Operate",
490 GOSUB 1060: SECOND = POP
500 GOSUB 1060: FIRST = POP
510 X = FIRST + SECOND: GOSUB 1160
520 GOTO 610
530 IF TOKEN$ <> "^" THEN 590
540 PRINT "Operate",
550 GOSUB 1060: SECOND = POP
560 GOSUB 1060: FIRST = POP
570 X = FIRST ^ SECOND: GOSUB 1160
580 GOTO 610
590 PRINT "Push",
600 X = VAL(TOKEN$): GOSUB 1160
610 GOSUB 1100
620 IF DP% <> 0 THEN 250
630 GOSUB 1060:
640 PRINT "Final answer: "; POP
650 GOSUB 1030
660 IF NOT EMPTY% THEN PRINT "Error, too many operands: "; : GOSUB 1100: STOP
670 RETURN
980 REM ** Operations on the stack
990 REM ** Make the stack empty
1000 TOP.INDEX% = MAX.INDEX% + 1
1010 RETURN
1020 REM ** Is the stack empty?
1030 EMPTY% = TOP.INDEX% > MAX.INDEX%
1040 RETURN
1050 REM ** Pop from the stack
1060 GOSUB 1030
1070 IF NOT EMPTY% THEN POP = ELEMS(TOP.INDEX%): TOP.INDEX% = TOP.INDEX% + 1 ELSE PRINT "The stack is empty.": STOP
1080 RETURN
1090 REM ** Print the stack
1100 FOR PTR% = TOP.INDEX% TO MAX.INDEX%
1110 PRINT USING "######.###"; ELEMS(PTR%);
1120 NEXT PTR%
1130 PRINT
1140 RETURN
1150 REM ** Push to the stack
1160 IF TOP.INDEX% > 0 THEN TOP.INDEX% = TOP.INDEX% - 1: ELEMS(TOP.INDEX%) = X ELSE PRINT "The stack is full.": STOP
1170 RETURN
</syntaxhighlight>
{{out}}
<pre>
Input Operation Stack after
3 Push 3.000
4 Push 4.000 3.000
2 Push 2.000 4.000 3.000
* Operate 8.000 3.000
1 Push 1.000 8.000 3.000
5 Push 5.000 1.000 8.000 3.000
- Operate -4.000 8.000 3.000
2 Push 2.000 -4.000 8.000 3.000
3 Push 3.000 2.000 -4.000 8.000 3.000
^ Operate 8.000 -4.000 8.000 3.000
^ Operate 65536.000 8.000 3.000
/ Operate 0.000 3.000
+ Operate 3.000
Final answer: 3.000122
</pre>
==={{header|Liberty BASIC}}===
{{works with|Just BASIC}}
<syntaxhighlight lang="lb">
global stack$
expr$ = "3 4 2 * 1 5 - 2 3 ^ ^ / +"
print "Expression:"
print expr$
print
print "Input","Operation","Stack after"
stack$=""
token$ = "#"
i = 1
token$ = word$(expr$, i)
token2$ = " "+token$+" "
do
print "Token ";i;": ";token$,
select case
'operation
case instr("+-*/^",token$)<>0
print "operate",
op2$=pop$()
op1$=pop$()
if op1$="" then
print "Error: stack empty for ";i;"-th token: ";token$
end
end if
op1=val(op1$)
op2=val(op2$)
select case token$
case "+"
res = op1+op2
case "-"
res = op1-op2
case "*"
res = op1*op2
case "/"
res = op1/op2
case "^"
res = op1^op2
end select
call push str$(res)
'default:number
case else
print "push",
call push token$
end select
print "Stack: ";reverse$(stack$)
i = i+1
token$ = word$(expr$, i)
token2$ = " "+token$+" "
loop until token$ =""
res$=pop$()
print
print "Result:" ;res$
extra$=pop$()
if extra$<>"" then
print "Error: extra things on a stack: ";extra$
end if
end
'---------------------------------------
function reverse$(s$)
reverse$ = ""
token$="#"
while token$<>""
i=i+1
token$=word$(s$,i,"|")
reverse$ = token$;" ";reverse$
wend
end function
'---------------------------------------
sub push s$
stack$=s$+"|"+stack$ 'stack
end sub
function pop$()
'it does return empty on empty stack
pop$=word$(stack$,1,"|")
stack$=mid$(stack$,instr(stack$,"|")+1)
end function
</syntaxhighlight>
{{out}}
<pre>
Expression:
3 4 2 * 1 5 - 2 3 ^ ^ / +
Input Operation Stack after
Token 1: 3 push Stack: 3
Token 2: 4 push Stack: 3 4
Token 3: 2 push Stack: 3 4 2
Token 4: * operate Stack: 3 8
Token 5: 1 push Stack: 3 8 1
Token 6: 5 push Stack: 3 8 1 5
Token 7: - operate Stack: 3 8 -4
Token 8: 2 push Stack: 3 8 -4 2
Token 9: 3 push Stack: 3 8 -4 2 3
Token 10: ^ operate Stack: 3 8 -4 8
Token 11: ^ operate Stack: 3 8 65536
Token 12: / operate Stack: 3 0.12207031e-3
Token 13: + operate Stack: 3.00012207
Result:3.00012207
</pre>
==={{header|QuickBASIC}}===
{{trans|Java|In fact, stack and tokenizing had to be implemented. Converting string to numbers is based on the <code>VAL</code> function in BASIC.}}
Supports multi-digit numbers and negative numbers.
<syntaxhighlight lang="qbasic">
' Parsing/RPN calculator algorithm
DECLARE SUB MakeEmpty (S AS ANY)
DECLARE SUB Push (X AS SINGLE, S AS ANY)
DECLARE SUB PrintStack (S AS ANY)
DECLARE SUB EvalRPN (Expr$)
DECLARE FUNCTION Empty% (S AS ANY)
DECLARE FUNCTION Pop! (S AS ANY)
CONST MAXINDEX = 63
TYPE TNumStack
TopIndex AS INTEGER
Elems(MAXINDEX) AS SINGLE
END TYPE
EvalRPN ("3 4 2 * 1 5 - 2 3 ^ ^ / +")
END
FUNCTION Empty% (S AS TNumStack)
Empty% = S.TopIndex > MAXINDEX
END FUNCTION
SUB EvalRPN (Expr$)
DIM S AS TNumStack
MakeEmpty S
PRINT "Input", "Operation", "Stack after"
' SP% - start position of token
' DP% - position of delimiter
DP% = 0
DO
SP% = DP% + 1
DP% = INSTR(DP% + 1, Expr$, " ")
IF DP% <> 0 THEN
TE% = DP% - 1
Token$ = MID$(Expr$, SP%, DP% - SP%)
ELSE
Token$ = MID$(Expr$, SP%, LEN(Expr$) - SP% + 1)
END IF
PRINT Token$,
IF Token$ = "*" THEN
PRINT "Operate",
Second = Pop(S): First = Pop(S)
Push First * Second, S
ELSEIF Token$ = "/" THEN
PRINT "Operate",
Second = Pop(S): First = Pop(S)
Push First / Second, S
ELSEIF Token$ = "-" THEN
PRINT "Operate",
Second = Pop(S): First = Pop(S)
Push First - Second, S
ELSEIF Token$ = "+" THEN
PRINT "Operate",
Second = Pop(S): First = Pop(S)
Push First + Second, S
ELSEIF Token$ = "^" THEN
PRINT "Operate",
Second = Pop(S): First = Pop(S)
Push First ^ Second, S
ELSE
PRINT "Push",
Push VAL(Token$), S
END IF
PrintStack S
LOOP UNTIL DP% = 0
PRINT "Final answer: "; Pop(S)
IF NOT Empty(S) THEN
PRINT "Error, too many operands: ";
PrintStack S
STOP
END IF
END SUB
SUB MakeEmpty (S AS TNumStack)
S.TopIndex = MAXINDEX + 1
END SUB
FUNCTION Pop (S AS TNumStack)
IF Empty%(S) THEN
PRINT "The stack is empty."
STOP
ELSE
Pop = S.Elems(S.TopIndex)
S.TopIndex = S.TopIndex + 1
END IF
END FUNCTION
SUB PrintStack (S AS TNumStack)
FOR Ptr% = S.TopIndex% TO MAXINDEX
PRINT USING "######.###"; S.Elems(Ptr%);
NEXT Ptr%
PRINT
END SUB
SUB Push (X AS SINGLE, S AS TNumStack)
IF S.TopIndex = 0 THEN
PRINT "The stack is full."
STOP
ELSE
S.TopIndex = S.TopIndex - 1
S.Elems(S.TopIndex) = X
END IF
END SUB
</syntaxhighlight>
{{out}}
<pre>
Input Operation Stack after
3 Push 3.000
4 Push 4.000 3.000
2 Push 2.000 4.000 3.000
* Operate 8.000 3.000
1 Push 1.000 8.000 3.000
5 Push 5.000 1.000 8.000 3.000
- Operate -4.000 8.000 3.000
2 Push 2.000 -4.000 8.000 3.000
3 Push 3.000 2.000 -4.000 8.000 3.000
^ Operate 8.000 -4.000 8.000 3.000
^ Operate 65536.000 8.000 3.000
/ Operate 0.000 3.000
+ Operate 3.000
Final answer: 3.000122
</pre>
==={{header|Run BASIC}}===
<syntaxhighlight lang="runbasic">prn$ = "3 4 2 * 1 5 - 2 3 ^ ^ / + "
j = 0
while word$(prn$,i + 1," ") <> ""
i = i + 1
n$ = word$(prn$,i," ")
if n$ < "0" or n$ > "9" then
num1 = val(word$(stack$,s," "))
num2 = val(word$(stack$,s-1," "))
n = op(n$,num2,num1)
s = s - 1
stack$ = stk$(stack$,s -1,str$(n))
print "Push Opr ";n$;" to stack: ";stack$
else
s = s + 1
stack$ = stack$ + n$ + " "
print "Push Num ";n$;" to stack: ";stack$
end if
wend
function stk$(stack$,s,a$)
for i = 1 to s
stk$ = stk$ + word$(stack$,i," ") + " "
next i
stk$ = stk$ + a$ + " "
end function
FUNCTION op(op$,a,b)
if op$ = "*" then op = a * b
if op$ = "/" then op = a / b
if op$ = "^" then op = a ^ b
if op$ = "+" then op = a + b
if op$ = "-" then op = a - b
end function</syntaxhighlight>
<pre>Push Num 3 to stack: 3
Push Num 4 to stack: 3 4
Push Num 2 to stack: 3 4 2
Push Opr * to stack: 3 8
Push Num 1 to stack: 3 8 1
Push Num 5 to stack: 3 8 1 5
Push Opr - to stack: 3 8 -4
Push Num 2 to stack: 3 8 -4 2
Push Num 3 to stack: 3 8 -4 2 3
Push Opr ^ to stack: 3 8 -4 8
Push Opr ^ to stack: 3 8 65536
Push Opr / to stack: 3 1.22070312e-4
Push Opr + to stack: 3.00012207</pre>
==={{header|Sinclair ZX81 BASIC}}===
If you only have 1k of RAM, this program will correctly evaluate the test expression with fewer than 10 bytes to spare. (I know that because I tried running it with the first line modified to allow a stack depth of 7, i.e. allocating space for two more 40-bit floats, and it crashed with an "out of memory" error code before it could print the result of the final addition.) If we desperately needed a few extra bytes there are ways they could be shaved out of the current program; but this version works, and editing a program that takes up almost all your available RAM isn't very comfortable, and to make it really useful for practical purposes you would still want to have 2k or more anyway.
The ZX81 character set doesn't include <code>^</code>, so we have to use <code>**</code> instead. Note that this is not two separate stars, although that's what it looks like: you have to enter it by typing <code>SHIFT</code>+<code>H</code>.
No attempt is made to check for invalid syntax, stack overflow or underflow, etc.
<syntaxhighlight lang="basic"> 10 DIM S(5)
20 LET P=1
30 INPUT E$
40 LET I=0
50 LET I=I+1
60 IF E$(I)=" " THEN GOTO 110
70 IF I<LEN E$ THEN GOTO 50
80 LET W$=E$
90 GOSUB 150
100 STOP
110 LET W$=E$( TO I-1)
120 LET E$=E$(I+1 TO )
130 GOSUB 150
140 GOTO 40
150 IF W$="+" OR W$="-" OR W$="*" OR W$="/" OR W$="**" THEN GOTO 250
160 LET S(P)=VAL W$
170 LET P=P+1
180 PRINT W$;
190 PRINT ":";
200 FOR I=P-1 TO 1 STEP -1
210 PRINT " ";S(I);
220 NEXT I
230 PRINT
240 RETURN
250 IF W$="**" THEN LET S(P-2)=ABS S(P-2)
260 LET S(P-2)=VAL (STR$ S(P-2)+W$+STR$ S(P-1))
270 LET P=P-1
280 GOTO 180</syntaxhighlight>
{{in}}
<pre>3 4 2 * 1 5 - 2 3 ** ** / +</pre>
{{out}}
<pre>3: 3
4: 4 3
2: 2 4 3
*: 8 3
1: 1 8 3
5: 5 1 8 3
-: -4 8 3
2: 2 -4 8 3
3: 3 2 -4 8 3
**: 8 -4 8 3
**: 65536 8 3
/: .00012207031 3
+: 3.0001221</pre>
==={{header|VBA}}===
{{trans|Liberty BASIC}}
<syntaxhighlight lang="vba">Global stack$
Function RPN(expr$)
Debug.Print "Expression:"
Debug.Print expr$
Debug.Print "Input", "Operation", "Stack after"
stack$ = ""
token$ = "#"
i = 1
token$ = Split(expr$)(i - 1) 'split is base 0
token2$ = " " + token$ + " "
Do
Debug.Print "Token "; i; ": "; token$,
'operation
If InStr("+-*/^", token$) <> 0 Then
Debug.Print "operate",
op2$ = pop$()
op1$ = pop$()
If op1$ = "" Then
Debug.Print "Error: stack empty for "; i; "-th token: "; token$
End
End If
op1 = Val(op1$)
op2 = Val(op2$)
Select Case token$
Case "+"
res = CDbl(op1) + CDbl(op2)
Case "-"
res = CDbl(op1) - CDbl(op2)
Case "*"
res = CDbl(op1) * CDbl(op2)
Case "/"
res = CDbl(op1) / CDbl(op2)
Case "^"
res = CDbl(op1) ^ CDbl(op2)
End Select
Call push2(str$(res))
'default:number
Else
Debug.Print "push",
Call push2(token$)
End If
Debug.Print "Stack: "; reverse$(stack$)
i = i + 1
If i > Len(Join(Split(expr, " "), "")) Then
token$ = ""
Else
token$ = Split(expr$)(i - 1) 'base 0
token2$ = " " + token$ + " "
End If
Loop Until token$ = ""
Debug.Print
Debug.Print "Result:"; pop$()
'extra$ = pop$()
If stack <> "" Then
Debug.Print "Error: extra things on a stack: "; stack$
End If
End
End Function
'---------------------------------------
Function reverse$(s$)
reverse$ = ""
token$ = "#"
While token$ <> ""
i = i + 1
token$ = Split(s$, "|")(i - 1) 'split is base 0
reverse$ = token$ & " " & reverse$
Wend
End Function
'---------------------------------------
Sub push2(s$)
stack$ = s$ + "|" + stack$ 'stack
End Sub
Function pop$()
'it does return empty on empty stack
pop$ = Split(stack$, "|")(0)
stack$ = Mid$(stack$, InStr(stack$, "|") + 1)
End Function</syntaxhighlight>
{{out}}
<pre>?RPN("3 4 2 * 1 5 - 2 3 ^ ^ / +")
Expression:
3 4 2 * 1 5 - 2 3 ^ ^ / +
Input Operation Stack after
Token 1 : 3 push Stack: 3
Token 2 : 4 push Stack: 3 4
Token 3 : 2 push Stack: 3 4 2
Token 4 : * operate Stack: 3 8
Token 5 : 1 push Stack: 3 8 1
Token 6 : 5 push Stack: 3 8 1 5
Token 7 : - operate Stack: 3 8 -4
Token 8 : 2 push Stack: 3 8 -4 2
Token 9 : 3 push Stack: 3 8 -4 2 3
Token 10 : ^ operate Stack: 3 8 -4 8
Token 11 : ^ operate Stack: 3 8 65536
Token 12 : / operate Stack: 3 .0001220703125
Token 13 : + operate Stack: 3.0001220703125
Result: 3.0001220703125</pre>
==={{header|Xojo}}===
{{trans|VBA}}
<syntaxhighlight lang="xojo">
Function RPN(expr As String) As String
Dim tokenArray() As String
Dim stack() As String
Dim Wert1 As Double
Dim Wert2 As Double
'Initialize array (removed later)
ReDim tokenArray(1)
ReDim stack(1)
tokenArray = Split(expr, " ")
Dim i As integer
i = 0
While i <= tokenArray.Ubound
If tokenArray(i) = "+" Then
Wert2 = Val(stack.pop)
Wert1 = Val(stack.pop)
stack.Append(Str(Wert1+Wert2))
ElseIf tokenArray(i) = "-" Then
Wert2 = Val(stack.pop)
Wert1 = Val(stack.pop)
stack.Append(Str(Wert1-Wert2))
ElseIf tokenArray(i) = "*" Then
Wert2 = Val(stack.pop)
Wert1 = Val(stack.pop)
stack.Append(Str(Wert1*Wert2))
ElseIf tokenArray(i) = "/" Then
Wert2 = Val(stack.pop)
Wert1 = Val(stack.pop)
stack.Append(Str(Wert1/Wert2))
ElseIf tokenArray(i) = "^" Then
Wert2 = Val(stack.pop)
Wert1 = Val(stack.pop)
stack.Append(Str(pow(Wert1,Wert2)))
Else
stack.Append(tokenArray(i))
End If
i = i +1
Wend
Return stack(2)
End Function</syntaxhighlight>
{{out}}
<pre>?RPN("3 4 2 * 1 5 - 2 3 ^ ^ / +")
Expression:
3 4 2 * 1 5 - 2 3 ^ ^ / +
Input Operation Stack after
Token 1 : 3 push Stack: 3
Token 2 : 4 push Stack: 3 4
Token 3 : 2 push Stack: 3 4 2
Token 4 : * operate Stack: 3 8
Token 5 : 1 push Stack: 3 8 1
Token 6 : 5 push Stack: 3 8 1 5
Token 7 : - operate Stack: 3 8 -4
Token 8 : 2 push Stack: 3 8 -4 2
Token 9 : 3 push Stack: 3 8 -4 2 3
Token 10 : ^ operate Stack: 3 8 -4 8
Token 11 : ^ operate Stack: 3 8 65536
Token 12 : / operate Stack: 3 .000122
Token 13 : + operate Stack: 3.000122
Result: 3.000122</pre>
=={{header|Bracmat}}==
<syntaxhighlight lang="bracmat">( ( show
= line a
. \n:?line
& whl
' (!arg:%?a ?arg&!a " " !line:?line)
& put$(str$!line)
)
& :?stack
& map
$ ( (
= a b
. show$(!arg !stack)
& ( !arg
: ( "+"
| "-"
| "*"
| "/"
| "^"
)
& !stack:%?a %?b ?stack
& ( !arg:"+"&!a+!b
| !arg:"-"&-1*!a+!b
| !arg:"*"&!a*!b
| !arg:"/"&!a*!b^-1
| !a^!b
)
| !arg
)
!stack
: ?stack
)
. vap$((=.!arg).get'(,STR)." ")
)
& out$!stack
)</syntaxhighlight>
Input from keyboard:
<pre>3 4 2 * 1 5 - 2 3 ^ ^ / +</pre>
Output:
<pre>3
3 4
3 4 2
3 4 2 *
3 8 1
3 8 1 5
3 8 1 5 -
3 8 -4 2
3 8 -4 2 3
3 8 -4 2 3 ^
3 8 -4 9 ^
3 8 1/6561 /
3 1/52488 +
157465/52488
{!} 157465/52488</pre>
=={{header|C}}==
<syntaxhighlight lang="c">#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
void die(const char *msg)
{
fprintf(stderr, "%s", msg);
abort();
}
#define MAX_D 256
double stack[MAX_D];
int depth;
void push(double v)
{
if (depth >= MAX_D) die("stack overflow\n");
stack[depth++] = v;
}
double pop()
{
if (!depth) die("stack underflow\n");
return stack[--depth];
}
double rpn(char *s)
{
double a, b;
int i;
char *e, *w = " \t\n\r\f";
for (s = strtok(s, w); s; s = strtok(0, w)) {
a = strtod(s, &e);
if (e > s) printf(" :"), push(a);
#define binop(x) printf("%c:", *s), b = pop(), a = pop(), push(x)
else if (*s == '+') binop(a + b);
else if (*s == '-') binop(a - b);
else if (*s == '*') binop(a * b);
else if (*s == '/') binop(a / b);
else if (*s == '^') binop(pow(a, b));
#undef binop
else {
fprintf(stderr, "'%c': ", *s);
die("unknown oeprator\n");
}
for (i = depth; i-- || 0 * putchar('\n'); )
printf(" %g", stack[i]);
}
if (depth != 1) die("stack leftover\n");
return pop();
}
int main(void)
{
char s[] = " 3 4 2 * 1 5 - 2 3 ^ ^ / + ";
printf("%g\n", rpn(s));
return 0;
}</syntaxhighlight>
It's also possible to parse RPN string backwards and recursively; good luck printing out your token stack ''as a table'': there isn't one.
<syntaxhighlight lang="c">#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
#include <math.h>
#define die(msg) fprintf(stderr, msg"\n"), abort();
double get(const char *s, const char *e, char **new_e)
{
const char *t;
double a, b;
for (e--; e >= s && isspace(*e); e--);
for (t = e; t > s && !isspace(t[-1]); t--);
if (t < s) die("underflow");
#define get2(expr) b = get(s, t, (char **)&t), a = get(s, t, (char **)&t), a = expr
a = strtod(t, (char **)&e);
if (e <= t) {
if (t[0] == '+') get2(a + b);
else if (t[0] == '-') get2(a - b);
else if (t[0] == '*') get2(a * b);
else if (t[0] == '/') get2(a / b);
else if (t[0] == '^') get2(pow(a, b));
else {
fprintf(stderr, "'%c': ", t[0]);
die("unknown token");
}
}
#undef get2
*(const char **)new_e = t;
return a;
}
double rpn(const char *s)
{
const char *e = s + strlen(s);
double v = get(s, e, (char**)&e);
while (e > s && isspace(e[-1])) e--;
if (e == s) return v;
fprintf(stderr, "\"%.*s\": ", e - s, s);
die("front garbage");
}
int main(void)
{
printf("%g\n", rpn("3 4 2 * 1 5 - 2 3 ^ ^ / +"));
return 0;
}</syntaxhighlight>
=={{header|C sharp|C#}}==
<syntaxhighlight lang="csharp">using System;
using System.Collections.Generic;
using System.Linq;
using System.Globalization;
using System.Threading;
namespace RPNEvaluator
{
class RPNEvaluator
{
static void Main(string[] args)
{
Thread.CurrentThread.CurrentCulture = CultureInfo.InvariantCulture;
string rpn = "3 4 2 * 1 5 - 2 3 ^ ^ / +";
Console.WriteLine("{0}\n", rpn);
decimal result = CalculateRPN(rpn);
Console.WriteLine("\nResult is {0}", result);
}
static decimal CalculateRPN(string rpn)
{
string[] rpnTokens = rpn.Split(' ');
Stack<decimal> stack = new Stack<decimal>();
decimal number = decimal.Zero;
foreach (string token in rpnTokens)
{
if (decimal.TryParse(token, out number))
{
stack.Push(number);
}
else
{
switch (token)
{
case "^":
case "pow":
{
number = stack.Pop();
stack.Push((decimal)Math.Pow((double)stack.Pop(), (double)number));
break;
}
case "ln":
{
stack.Push((decimal)Math.Log((double)stack.Pop(), Math.E));
break;
}
case "sqrt":
{
stack.Push((decimal)Math.Sqrt((double)stack.Pop()));
break;
}
case "*":
{
stack.Push(stack.Pop() * stack.Pop());
break;
}
case "/":
{
number = stack.Pop();
stack.Push(stack.Pop() / number);
break;
}
case "+":
{
stack.Push(stack.Pop() + stack.Pop());
break;
}
case "-":
{
number = stack.Pop();
stack.Push(stack.Pop() - number);
break;
}
default:
Console.WriteLine("Error in CalculateRPN(string) Method!");
break;
}
}
PrintState(stack);
}
return stack.Pop();
}
static void PrintState(Stack<decimal> stack)
{
decimal[] arr = stack.ToArray();
for (int i = arr.Length - 1; i >= 0; i--)
{
Console.Write("{0,-8:F3}", arr[i]);
}
Console.WriteLine();
}
}
}</syntaxhighlight>
{{out}}
<pre>
3 4 2 * 1 5 - 2 3 ^ ^ / +
3.000
3.000 4.000
3.000 4.000 2.000
3.000 8.000
3.000 8.000 1.000
3.000 8.000 1.000 5.000
3.000 8.000 -4.000
3.000 8.000 -4.000 2.000
3.000 8.000 -4.000 2.000 3.000
3.000 8.000 -4.000 8.000
3.000 8.000 65536.000
3.000 0.000
3.000
Result is 3.0001220703125
</pre>
=={{header|C++}}==
<syntaxhighlight lang="cpp">#include <vector>
#include <string>
#include <sstream>
#include <iostream>
#include <cmath>
#include <algorithm>
#include <iterator>
#include <cstdlib>
double rpn(const std::string &expr){
std::istringstream iss(expr);
std::vector<double> stack;
std::cout << "Input\tOperation\tStack after" << std::endl;
std::string token;
while (iss >> token) {
std::cout << token << "\t";
double tokenNum;
if (std::istringstream(token) >> tokenNum) {
std::cout << "Push\t\t";
stack.push_back(tokenNum);
} else {
std::cout << "Operate\t\t";
double secondOperand = stack.back();
stack.pop_back();
double firstOperand = stack.back();
stack.pop_back();
if (token == "*")
stack.push_back(firstOperand * secondOperand);
else if (token == "/")
stack.push_back(firstOperand / secondOperand);
else if (token == "-")
stack.push_back(firstOperand - secondOperand);
else if (token == "+")
stack.push_back(firstOperand + secondOperand);
else if (token == "^")
stack.push_back(std::pow(firstOperand, secondOperand));
else { //just in case
std::cerr << "Error" << std::endl;
std::exit(1);
}
}
std::copy(stack.begin(), stack.end(), std::ostream_iterator<double>(std::cout, " "));
std::cout << std::endl;
}
return stack.back();
}
int main() {
std::string s = " 3 4 2 * 1 5 - 2 3 ^ ^ / + ";
std::cout << "Final answer: " << rpn(s) << std::endl;
return 0;
}</syntaxhighlight>
{{out}}
<pre>
Input Operation Stack after
3 Push 3
4 Push 3 4
2 Push 3 4 2
* Operate 3 8
1 Push 3 8 1
5 Push 3 8 1 5
- Operate 3 8 -4
2 Push 3 8 -4 2
3 Push 3 8 -4 2 3
^ Operate 3 8 -4 8
^ Operate 3 8 65536
/ Operate 3 0.00012207
+ Operate 3.00012
Final answer: 3.00012
</pre>
=={{header|Ceylon}}==
<syntaxhighlight lang="text">import ceylon.collection {
ArrayList
}
shared void run() {
value ops = map {
"+" -> plus<Float>,
"*" -> times<Float>,
"-" -> ((Float a, Float b) => a - b),
"/" -> ((Float a, Float b) => a / b),
"^" -> ((Float a, Float b) => a ^ b)
};
void printTableRow(String|Float token, String description, {Float*} stack) {
print("``token.string.padTrailing(8)````description.padTrailing(30)````stack``");
}
function calculate(String input) {
value stack = ArrayList<Float>();
value tokens = input.split().map((String element)
=> if(ops.keys.contains(element)) then element else parseFloat(element));
print("Token Operation Stack");
for(token in tokens.coalesced) {
if(is Float token) {
stack.push(token);
printTableRow(token, "push", stack);
} else if(exists op = ops[token], exists first = stack.pop(), exists second = stack.pop()) {
value result = op(second, first);
stack.push(result);
printTableRow(token, "perform ``token`` on ``formatFloat(second, 1, 1)`` and ``formatFloat(first, 1, 1)``", stack);
} else {
throw Exception("bad syntax");
}
}
return stack.pop();
}
print(calculate("3 4 2 * 1 5 - 2 3 ^ ^ / +"));
}</syntaxhighlight>
{{out}}
<pre>Token Operation Stack
3.0 push { 3.0 }
4.0 push { 3.0, 4.0 }
2.0 push { 3.0, 4.0, 2.0 }
* perform * on 4.0 and 2.0 { 3.0, 8.0 }
1.0 push { 3.0, 8.0, 1.0 }
5.0 push { 3.0, 8.0, 1.0, 5.0 }
- perform - on 1.0 and 5.0 { 3.0, 8.0, -4.0 }
2.0 push { 3.0, 8.0, -4.0, 2.0 }
3.0 push { 3.0, 8.0, -4.0, 2.0, 3.0 }
^ perform ^ on 2.0 and 3.0 { 3.0, 8.0, -4.0, 8.0 }
^ perform ^ on -4.0 and 8.0 { 3.0, 8.0, 65536.0 }
/ perform / on 8.0 and 65536.0 { 3.0, 1.220703125E-4 }
+ perform + on 3.0 and 0.0 { 3.0001220703125 }
3.0001220703125
</pre>
=={{header|Clojure}}==
This would be a lot simpler and generic if we were allowed to use something other than ^ for exponentiation. ^ isn't a legal clojure symbol.
<syntaxhighlight lang="clojure">
(ns rosettacode.parsing-rpn-calculator-algorithm
(:require clojure.math.numeric-tower
clojure.string
clojure.pprint))
(def operators
"the only allowable operators for our calculator"
{"+" +
"-" -
"*" *
"/" /
"^" clojure.math.numeric-tower/expt})
(defn rpn
"takes a string and returns a lazy-seq of all the stacks"
[string]
(letfn [(rpn-reducer [stack item] ; this takes a stack and one item and makes a new stack
(if (contains? operators item)
(let [operand-1 (peek stack) ; if we used lists instead of vectors, we could use destructuring, but stacks would look backwards
stack-1 (pop stack)] ;we're assuming that all the operators are binary
(conj (pop stack-1)
((operators item) (peek stack-1) operand-1)))
(conj stack (Long. item))))] ; if it wasn't an operator, we'll assume it's a long. Could choose bigint, or even read-line
(reductions rpn-reducer [] (clojure.string/split string #"\s+")))) ;reductions is like reduce only shows all the intermediate steps
(let [stacks (rpn "3 4 2 * 1 5 - 2 3 ^ ^ / +")] ;bind it so we can output the answer separately.
(println "stacks: ")
(clojure.pprint/pprint stacks)
(print "answer:" (->> stacks last first)))
</syntaxhighlight>
{{out}}
stacks:
([]
[3]
[3 4]
[3 4 2]
[3 8]
[3 8 1]
[3 8 1 5]
[3 8 -4]
[3 8 -4 2]
[3 8 -4 2 3]
[3 8 -4 8]
[3 8 65536]
[3 1/8192]
[24577/8192])
answer: 24577/8192
=={{header|CLU}}==
<syntaxhighlight lang="clu">% Split string by whitespace
split = iter (expr: string) yields (string)
own whitespace: string := " \r\n\t"
cur: array[char] := array[char]$[]
for c: char in string$chars(expr) do
if string$indexc(c, whitespace) = 0 then
array[char]$addh(cur, c)
else
if array[char]$empty(cur) then continue end
yield(string$ac2s(cur))
cur := array[char]$[]
end
end
if ~array[char]$empty(cur) then
yield(string$ac2s(cur))
end
end split
% Tokenize a RPN expression
token = oneof[number: real, op: char]
tokens = iter (expr: string) yields (token) signals (parse_error(string))
own operators: string := "+-*/^"
for t: string in split(expr) do
if string$size(t) = 1 cand string$indexc(t[1], operators)~=0 then
yield(token$make_op(t[1]))
else
yield(token$make_number(real$parse(t)))
except when bad_format:
signal parse_error(t)
end
end
end
end tokens
% Print the stack
print_stack = proc (stack: array[real])
po: stream := stream$primary_output()
for num: real in array[real]$elements(stack) do
stream$puts(po, f_form(num, 5, 5) || " ")
end
stream$putl(po, "")
end print_stack
% Evaluate an expression, printing the stack at each point
evaluate_rpn = proc (expr: string) returns (real) signals (parse_error(string), bounds)
stack: array[real] := array[real]$[]
for t: token in tokens(expr) do
tagcase t
tag number (n: real): array[real]$addh(stack, n)
tag op (f: char):
r: real := array[real]$remh(stack)
l: real := array[real]$remh(stack)
n: real
if f='+' then n := l+r
elseif f='-' then n := l-r
elseif f='*' then n := l*r
elseif f='/' then n := l/r
elseif f='^' then n := l**r
end
array[real]$addh(stack, n)
end
print_stack(stack)
end resignal parse_error
return(array[real]$reml(stack))
end evaluate_rpn
start_up = proc ()
po: stream := stream$primary_output()
expr: string := "3 4 2 * 1 5 - 2 3 ^ ^ / +"
stream$putl(po, "Expression: " || expr)
stream$putl(po, "Result: " || f_form(evaluate_rpn(expr), 5, 5))
end start_up</syntaxhighlight>
{{out}}
<pre>Expression: 3 4 2 * 1 5 - 2 3 ^ ^ / +
3.00000
3.00000 4.00000
3.00000 4.00000 2.00000
3.00000 8.00000
3.00000 8.00000 1.00000
3.00000 8.00000 1.00000 5.00000
3.00000 8.00000 -4.00000
3.00000 8.00000 -4.00000 2.00000
3.00000 8.00000 -4.00000 2.00000 3.00000
3.00000 8.00000 -4.00000 8.00000
3.00000 8.00000 65535.99240
3.00000 0.00012
3.00012
Result: 3.00012</pre>
=={{header|COBOL}}==
<syntaxhighlight lang="cobol">
IDENTIFICATION DIVISION.
PROGRAM-ID. RPN.
AUTHOR. Bill Gunshannon.
INSTALLATION.
DATE-WRITTEN. 9 Feb 2020.
************************************************************
** Program Abstract:
** Create a stack-based evaluator for an expression in
** reverse Polish notation (RPN) that also shows the
** changes in the stack as each individual token is
** processed as a table.
************************************************************
DATA DIVISION.
WORKING-STORAGE SECTION.
01 LineIn PIC X(25).
01 IP PIC 99
VALUE 1.
01 CInNum PIC XXXX.
01 Stack PIC S999999V9999999
OCCURS 50 times.
01 SP PIC 99
VALUE 1.
01 Operator PIC X.
01 Value1 PIC S999999V9999999.
01 Value2 PIC S999999V9999999.
01 Result PIC S999999V9999999.
01 Idx PIC 99.
01 FormatNum PIC ZZZZZZ9.9999999.
01 Zip PIC X.
PROCEDURE DIVISION.
Main-Program.
DISPLAY "Enter the RPN Equation: "
WITH NO ADVANCING.
ACCEPT LineIn.
PERFORM UNTIL IP GREATER THAN
FUNCTION STORED-CHAR-LENGTH(LineIn)
UNSTRING LineIn DELIMITED BY SPACE INTO CInNum
WITH POINTER IP
MOVE CInNum TO Operator
PERFORM Do-Operation
PERFORM Show-Stack
END-PERFORM.
DISPLAY "End Result: " FormatNum
STOP RUN.
Do-Operation.
EVALUATE Operator
WHEN "+"
PERFORM Pop
Compute Result = Value2 + Value1
PERFORM Push
WHEN "-"
PERFORM Pop
Compute Result = Value2 - Value1
PERFORM Push
WHEN "*"
PERFORM Pop
Compute Result = Value2 * Value1
PERFORM Push
WHEN "/"
PERFORM Pop
Compute Result = Value2 / Value1
PERFORM Push
WHEN "^"
PERFORM Pop
Compute Result = Value2 ** Value1
PERFORM Push
WHEN NUMERIC
MOVE Operator TO Result
PERFORM Push
END-EVALUATE.
Show-Stack.
DISPLAY "STACK: " WITH NO ADVANCING.
MOVE 1 TO Idx.
PERFORM UNTIL (Idx = SP)
MOVE Stack(Idx) TO FormatNum
IF Stack(Idx) IS NEGATIVE
THEN
DISPLAY " -" FUNCTION TRIM(FormatNum)
WITH NO ADVANCING
ELSE
DISPLAY FormatNum WITH NO ADVANCING
END-IF
ADD 1 to Idx
END-PERFORM.
DISPLAY " ".
Push.
MOVE Result TO Stack(SP)
ADD 1 TO SP.
Pop.
SUBTRACT 1 FROM SP
MOVE Stack(SP) TO Value1
SUBTRACT 1 FROM SP
MOVE Stack(SP) TO Value2.
END-PROGRAM.
</syntaxhighlight>
{{out}}
<pre>
Enter the RPN Equation: 3 4 2 * 1 5 - 2 3 ^ ^ / +
STACK: 3.0000000
STACK: 3.0000000 4.0000000
STACK: 3.0000000 4.0000000 2.0000000
STACK: 3.0000000 8.0000000
STACK: 3.0000000 8.0000000 1.0000000
STACK: 3.0000000 8.0000000 1.0000000 5.0000000
STACK: 3.0000000 8.0000000 -4.0000000
STACK: 3.0000000 8.0000000 -4.0000000 2.0000000
STACK: 3.0000000 8.0000000 -4.0000000 2.0000000 3.0000000
STACK: 3.0000000 8.0000000 -4.0000000 8.0000000
STACK: 3.0000000 8.0000000 65536.0000000
STACK: 3.0000000 0.0001220
STACK: 3.0001220
End Result: 3.0001220
</pre>
=={{header|Common Lisp}}==
<syntaxhighlight lang="lisp">(setf (symbol-function '^) #'expt) ; Make ^ an alias for EXPT
(defun print-stack (token stack)
(format T "~a: ~{~a ~}~%" token (reverse stack)))
(defun rpn (tokens &key stack verbose )
(cond
((and (not tokens) (not stack)) 0)
((not tokens) (car stack))
(T
(let* ((current (car tokens))
(next-stack (if (numberp current)
(cons current stack)
(let* ((arg2 (car stack))
(arg1 (cadr stack))
(fun (car tokens)))
(cons (funcall fun arg1 arg2) (cddr stack))))))
(when verbose
(print-stack current next-stack))
(rpn (cdr tokens) :stack next-stack :verbose verbose)))))</syntaxhighlight>
{{Out}}
<pre>>(defparameter *tokens* '(3 4 2 * 1 5 - 2 3 ^ ^ / +))
*TOKENS*
> (rpn *tokens*)
24577/8192
> (rpn *tokens* :verbose T)
3: 3
4: 3 4
2: 3 4 2
*: 3 8
1: 3 8 1
5: 3 8 1 5
-: 3 8 -4
2: 3 8 -4 2
3: 3 8 -4 2 3
^: 3 8 -4 8
^: 3 8 65536
/: 3 1/8192
+: 24577/8192
24577/8192</pre>
=={{header|D}}==
{{trans|Go}}
<syntaxhighlight lang="d">import std.stdio, std.string, std.conv, std.typetuple;
void main() {
auto input = "3 4 2 * 1 5 - 2 3 ^ ^ / +";
writeln("For postfix expression: ", input);
writeln("\nToken Action Stack");
real[] stack;
foreach (tok; input.split()) {
auto action = "Apply op to top of stack";
switch (tok) {
foreach (o; TypeTuple!("+", "-", "*", "/", "^")) {
case o:
mixin("stack[$ - 2]" ~
(o == "^" ? "^^" : o) ~ "=stack[$ - 1];");
stack.length--;
break;
}
break;
default:
action = "Push num onto top of stack";
stack ~= to!real(tok);
}
writefln("%3s %-26s %s", tok, action, stack);
}
writeln("\nThe final value is ", stack[0]);
}</syntaxhighlight>
{{out}}
<pre>For postfix expression: 3 4 2 * 1 5 - 2 3 ^ ^ / +
Token Action Stack
3 Push num onto top of stack [3]
4 Push num onto top of stack [3, 4]
2 Push num onto top of stack [3, 4, 2]
* Apply op to top of stack [3, 8]
1 Push num onto top of stack [3, 8, 1]
5 Push num onto top of stack [3, 8, 1, 5]
- Apply op to top of stack [3, 8, -4]
2 Push num onto top of stack [3, 8, -4, 2]
3 Push num onto top of stack [3, 8, -4, 2, 3]
^ Apply op to top of stack [3, 8, -4, 8]
^ Apply op to top of stack [3, 8, 65536]
/ Apply op to top of stack [3, 0.00012207]
+ Apply op to top of stack [3.00012]
The final value is 3.00012</pre>
=={{header|Delphi}}==
{{works with|Delphi|6.0}}
{{libheader|SysUtils,StdCtrls}}
This is a good example of creating s simple object to create a stakc for use in parsing the data.
<syntaxhighlight lang="Delphi">
{This code normally exists in a library, but is presented here for clarity}
function ExtractToken(S: string; Sep: char; var P: integer): string;
{Extract token from S, starting at P up to but not including Sep}
{Terminates with P pointing past Sep or past end of string}
var C: char;
begin
Result:='';
while P<=Length(S) do
begin
C:=S[P]; Inc(P);
if C=Sep then break
else Result:=Result+C;
end;
end;
{Create stack object to handle parsing}
type TRealStack = class(TObject)
private
Data: array of double;
protected
public
function GetStackStr: string;
procedure Push(D: double);
function Pop: double;
end;
procedure TRealStack.Push(D: double);
{Push double on stack}
begin
SetLength(Data,Length(Data)+1);
Data[High(Data)]:=D;
end;
function TRealStack.Pop: double;
{Pop double off stack, raises exception if stack empty}
begin
if Length(Data)<1 then raise exception.Create('Stack Empty');
Result:=Data[High(Data)];
SetLength(Data,Length(Data)-1);
end;
function TRealStack.GetStackStr: string;
{Get string representation of stack data}
var I: integer;
begin
Result:='';
for I:=0 to High(Data) do
begin
if I<>0 then Result:=Result+', ';
Result:=Result+FloatToStrF(Data[I],ffGeneral,18,4);
end;
end;
procedure RPNParser(Memo: TMemo; S: string);
{Parse RPN string and display all operations}
var I: integer;
var Stack: TRealStack;
var Token: string;
var D: double;
function HandleOperator(S: string): boolean;
{Handle numerical operator command}
var Arg1,Arg2: double;
begin
Result:=False;
{Empty comand string? }
if Length(S)>1 then exit;
{Invalid command? }
if not (S[1] in ['+','-','*','/','^']) then exit;
{Get arguments off stack}
Arg1:=Stack.Pop; Arg2:=Stack.Pop;
Result:=True;
{Decode command}
case S[1] of
'+': Stack.Push(Arg2 + Arg1);
'-': Stack.Push(Arg2 - Arg1);
'*': Stack.Push(Arg2 * Arg1);
'/': Stack.Push(Arg2 / Arg1);
'^': Stack.Push(Power(Arg2,Arg1));
else Result:=False;
end;
end;
begin
Stack:=TRealStack.Create;
try
I:=1;
while true do
begin
{Extract one token from string}
Token:=ExtractToken(S,' ',I);
{Exit if no more data}
if Token='' then break;
{If token is a number convert it to a double otherwise, process an operator}
if Token[1] in ['0'..'9'] then Stack.Push(StrToFloat(Token))
else if not HandleOperator(Token) then raise Exception.Create('Illegal Token: '+Token);
Memo.Lines.Add(Token+' ['+Stack.GetStackStr+']');
end;
finally Stack.Free; end;
end;
procedure ShowRPNParser(Memo: TMemo);
var S: string;
begin
S:='3 4 2 * 1 5 - 2 3 ^ ^ / + ';
RPNParser(Memo,S);
end;
</syntaxhighlight>
{{out}}
<pre>
3 [3]
4 [3, 4]
2 [3, 4, 2]
* [3, 8]
1 [3, 8, 1]
5 [3, 8, 1, 5]
- [3, 8, -4]
2 [3, 8, -4, 2]
3 [3, 8, -4, 2, 3]
^ [3, 8, -4, 8]
^ [3, 8, 65536]
/ [3, 0.0001220703125]
+ [3.0001220703125]
Elapsed Time: 16.409 ms.
</pre>
=={{header|EchoLisp}}==
<syntaxhighlight lang="scheme">
;; RPN (postfix) evaluator
(lib 'hash)
(define OPS (make-hash))
(hash-set OPS "^" expt)
(hash-set OPS "*" *)
(hash-set OPS "/" //) ;; float divide
(hash-set OPS "+" +)
(hash-set OPS "-" -)
(define (op? op) (hash-ref OPS op))
;; algorithm : https://en.wikipedia.org/wiki/Reverse_Polish_notation#Postfix_algorithm
(define (calculator rpn S)
(for ((token rpn))
(if (op? token)
(let [(op2 (pop S)) (op1 (pop S))]
(unless (and op1 op2) (error "cannot calculate expression at:" token))
(push S ((op? token) op1 op2))
(writeln op1 token op2 "→" (stack-top S)))
(push S (string->number token))))
(pop S))
(define (task rpn)
(define S (stack 'S))
(calculator (text-parse rpn) S ))
</syntaxhighlight>
{{out}}
<pre>
(task "3 4 2 * 1 5 - 2 3 ^ ^ / +")
4 * 2 → 8
1 - 5 → -4
2 ^ 3 → 8
-4 ^ 8 → 65536
8 / 65536 → 0.0001220703125
3 + 0.0001220703125 → 3.0001220703125
→ 3.0001220703125
;; RATIONAL CALCULATOR
(hash-set OPS "/" /) ;; rational divide
(task "3 4 2 * 1 5 - 2 3 ^ ^ / +")
4 * 2 → 8
1 - 5 → -4
2 ^ 3 → 8
-4 ^ 8 → 65536
8 / 65536 → 1/8192
3 + 1/8192 → 24577/8192
→ 24577/8192
</pre>
=={{header|Ela}}==
<syntaxhighlight lang="ela">open string generic monad io
type OpType = Push | Operate
deriving Show
type Op = Op (OpType typ) input stack
deriving Show
parse str = split " " str
eval stack [] = []
eval stack (x::xs) = op :: eval nst xs
where (op, nst) = conv x stack
conv "+"@x = operate x (+)
conv "-"@x = operate x (-)
conv "*"@x = operate x (*)
conv "/"@x = operate x (/)
conv "^"@x = operate x (**)
conv x = \stack ->
let n = gread x::stack in
(Op Push x n, n)
operate input fn (x::y::ys) =
let n = (y `fn` x) :: ys in
(Op Operate input n, n)
print_line (Op typ input stack) = do
putStr input
putStr "\t"
put typ
putStr "\t\t"
putLn stack
print ((Op typ input stack)@x::xs) lv = print_line x `seq` print xs (head stack)
print [] lv = lv
print_result xs = do
putStrLn "Input\tOperation\tStack after"
res <- return $ print xs 0
putStrLn ("Result: " ++ show res)
res = parse "3 4 2 * 1 5 - 2 3 ^ ^ / +" |> eval []
print_result res ::: IO</syntaxhighlight>
{{out}}
<pre>Input Operation Stack after
3 Push [3]
4 Push [4,3]
2 Push [2,4,3]
* Operate [8,3]
1 Push [1,8,3]
5 Push [5,1,8,3]
- Operate [-4,8,3]
2 Push [2,-4,8,3]
3 Push [3,2,-4,8,3]
^ Operate [8,-4,8,3]
^ Operate [65536,8,3]
/ Operate [0.0001220703f,3]
+ Operate [3.000122f]
Result: 3.000122f</pre>
=={{header|Erlang}}==
<syntaxhighlight lang="erlang">-module(rpn).
-export([eval/1]).
parse(Expression) ->
parse(string:tokens(Expression," "),[]).
parse([],Expression) ->
lists:reverse(Expression);
parse(["+"|Xs],Expression) ->
parse(Xs,[fun erlang:'+'/2|Expression]);
parse(["-"|Xs],Expression) ->
parse(Xs,[fun erlang:'-'/2|Expression]);
parse(["*"|Xs],Expression) ->
parse(Xs,[fun erlang:'*'/2|Expression]);
parse(["/"|Xs],Expression) ->
parse(Xs,[fun erlang:'/'/2|Expression]);
parse(["^"|Xs],Expression) ->
parse(Xs,[fun math:pow/2|Expression]);
parse([X|Xs],Expression) ->
{N,_} = string:to_integer(X),
parse(Xs,[N|Expression]).
%% The expression should be entered as a string of numbers and
%% operators separated by spaces. No error handling is included if
%% another string format is used.
eval(Expression) ->
eval(parse(Expression),[]).
eval([],[N]) ->
N;
eval([N|Exp],Stack) when is_number(N) ->
NewStack = [N|Stack],
print(NewStack),
eval(Exp,NewStack);
eval([F|Exp],[X,Y|Stack]) ->
NewStack = [F(Y,X)|Stack],
print(NewStack),
eval(Exp,NewStack).
print(Stack) ->
lists:map(fun (X) when is_integer(X) -> io:format("~12.12b ",[X]);
(X) when is_float(X) -> io:format("~12f ",[X]) end, Stack),
io:format("~n").</syntaxhighlight>
{{out}}
<pre>145> rpn:eval("3 4 2 * 1 5 - 2 3 ^ ^ / +").
3
4 3
2 4 3
8 3
1 8 3
5 1 8 3
-4 8 3
2 -4 8 3
3 2 -4 8 3
8.000000 -4 8 3
65536.000000 8 3
0.000122 3
3.000122
3.0001220703125</pre>
=={{header|F_Sharp|F#}}==
{{trans|OCaml}}
<p>As interactive script</p>
<syntaxhighlight lang="fsharp">let reduce op = function
| b::a::r -> (op a b)::r
| _ -> failwith "invalid expression"
let interprete s = function
| "+" -> "add", reduce ( + ) s
| "-" -> "subtr", reduce ( - ) s
| "*" -> "mult", reduce ( * ) s
| "/" -> "divide", reduce ( / ) s
| "^" -> "exp", reduce ( ** ) s
| str -> "push", (System.Double.Parse str) :: s
let interp_and_show s inp =
let op,s'' = interprete s inp
printf "%5s%8s " inp op
List.iter (printf " %-6.3F") (List.rev s'')
printf "\n";
s''
let eval str =
printfn "Token Action Stack";
let ss = str.ToString().Split() |> Array.toList
List.fold interp_and_show [] ss</syntaxhighlight>
{{out}}
<pre>> eval "3 4 2 * 1 5 - 2 3 ^ ^ / +";;
Token Action Stack
3 push 3.000
4 push 3.000 4.000
2 push 3.000 4.000 2.000
* mult 3.000 8.000
1 push 3.000 8.000 1.000
5 push 3.000 8.000 1.000 5.000
- subtr 3.000 8.000 -4.000
2 push 3.000 8.000 -4.000 2.000
3 push 3.000 8.000 -4.000 2.000 3.000
^ exp 3.000 8.000 -4.000 8.000
^ exp 3.000 8.000 65536.000
/ divide 3.000 0.000
+ add 3.000
val it : float list = [3.00012207]</pre>
=={{header|Factor}}==
Factor <i>is</i> a stack-based evaluator for an expression in reverse Polish notation. In the listener:
<syntaxhighlight lang="factor">IN: scratchpad 3 4 2 * 1 5 - 2 3 ^ ^ / +
--- Data stack:
3+1/8192</syntaxhighlight>
To show intermediate steps:
<syntaxhighlight lang="factor">{ 3 4 2 * 1 5 - 2 3 ^ ^ / + }
[ dup pprint bl 1quotation call get-datastack . ] each</syntaxhighlight>
{{out}}
<pre>
3 { 3 }
4 { 3 4 }
2 { 3 4 2 }
* { 3 8 }
1 { 3 8 1 }
5 { 3 8 1 5 }
- { 3 8 -4 }
2 { 3 8 -4 2 }
3 { 3 8 -4 2 3 }
^ { 3 8 -4 8 }
^ { 3 8 65536 }
/ { 3 1/8192 }
+ { 3+1/8192 }
</pre>
=={{header|Forth}}==
{{works with|gforth|0.7.3}}
Forth is stack-based, so evaluation is direct:
<syntaxhighlight lang="forth">: ^ over swap 1 ?do over * loop nip ;
s" 3 4 2 * 1 5 - 2 3 ^ ^ / +" evaluate .</syntaxhighlight>
To show intermediate steps:
<syntaxhighlight lang="forth">: ^ over swap 1 ?do over * loop nip ;
: detail
begin
cr ." stack: " .s
bl word count dup
0<> while
." , read: " 2dup type evaluate
repeat
2drop
;
detail 3 4 2 * 1 5 - 2 3 ^ ^ / +</syntaxhighlight>
{{out}}
<pre>stack: <0> , read: 3
stack: <1> 3 , read: 4
stack: <2> 3 4 , read: 2
stack: <3> 3 4 2 , read: *
stack: <2> 3 8 , read: 1
stack: <3> 3 8 1 , read: 5
stack: <4> 3 8 1 5 , read: -
stack: <3> 3 8 -4 , read: 2
stack: <4> 3 8 -4 2 , read: 3
stack: <5> 3 8 -4 2 3 , read: ^
stack: <4> 3 8 -4 8 , read: ^
stack: <3> 3 8 65536 , read: /
stack: <2> 3 0 , read: +
stack: <1> 3 ok</pre>
=={{header|Fortran}}==
Since the project is to demonstrate the workings of the scheme to evaluate a RPN text sequence, and the test example contains only single-digit numbers and single-character operators, there is no need to escalate to reading full integers or floating-point numbers, the code for which would swamp the details of the RPN evaluator. As a result, it is easy to scan the text via a DO-loop that works one character at a time since there is no backstepping, probing ahead, nor multi-symbol items that must be combined into a single "token" with states that must be remembered from one character to the next. With multi-character tokens, the scan would be changed to invocations of NEXTTOKEN that would lurch ahead accordingly.
The method is simple (the whole point of RPN) and the function prints a schedule of actions at each step. Possibly this semi-tabular output is what is meant by "as a table". Conveniently, all the operators take two operands and return one, so the SP accountancy can be shared. Unlike ! for example.
The source style is essentially F77 except for the trivial use of the PARAMETER statement, and CYCLE to GO TO the end of the loop when a space is encountered. With the introduction of unfixed-format source style came also the possible use of semicolons to cram more than one statement part on a line so that the CASE and its action statement can be spread across the page rather than use two lines in alternation: for this case a tabular layout results that is easier to read and check. Because the F90 MODULE protocol is not used, the function's type should be declared in the calling routine but the default type suffices.<syntaxhighlight lang="fortran"> REAL FUNCTION EVALRP(TEXT) !Evaluates a Reverse Polish string.
Caution: deals with single digits only.
CHARACTER*(*) TEXT !The RPN string.
INTEGER SP,STACKLIMIT !Needed for the evaluation.
PARAMETER (STACKLIMIT = 6) !This should do.
REAL*8 STACK(STACKLIMIT) !Though with ^ there's no upper limit.
INTEGER L,D !Assistants for the scan.
CHARACTER*4 DEED !A scratchpad for the annotation.
CHARACTER*1 C !The character of the moment.
WRITE (6,1) TEXT !A function that writes messages... Improper.
1 FORMAT ("Evaluation of the Reverse Polish string ",A,// !Still, it's good to see stuff.
1 "Char Token Action SP:Stack...") !Such as a heading for the trace.
SP = 0 !Commence with the stack empty.
STACK = -666 !This value should cause trouble.
DO L = 1,LEN(TEXT) !Step through the text.
C = TEXT(L:L) !Grab a character.
IF (C.LE." ") CYCLE !Boring.
D = ICHAR(C) - ICHAR("0") !Uncouth test to check for a digit.
IF (D.GE.0 .AND. D.LE.9) THEN !Is it one?
DEED = "Load" !Yes. So, load its value.
SP = SP + 1 !By going up one.
IF (SP.GT.STACKLIMIT) STOP "Stack overflow!" !Or, maybe not.
STACK(SP) = D !And stashing the value.
ELSE !Otherwise, it must be an operator.
IF (SP.LT.2) STOP "Stack underflow!" !They all require two operands.
DEED = "XEQ" !So, I'm about to do so.
SELECT CASE(C) !Which one this time?
CASE("+"); STACK(SP - 1) = STACK(SP - 1) + STACK(SP) !A + B = B + A, so it is easy.
CASE("-"); STACK(SP - 1) = STACK(SP - 1) - STACK(SP) !A is in STACK(SP - 1), B in STACK(SP)
CASE("*"); STACK(SP - 1) = STACK(SP - 1)*STACK(SP) !Again, order doesn't count.
CASE("/"); STACK(SP - 1) = STACK(SP - 1)/STACK(SP) !But for division, A/B becomes A B /
CASE("^"); STACK(SP - 1) = STACK(SP - 1)**STACK(SP) !So, this way around.
CASE DEFAULT !This should never happen!
STOP "Unknown operator!" !If the RPN script is indeed correct.
END SELECT !So much for that operator.
SP = SP - 1 !All of them take two operands and make one.
END IF !So much for that item.
WRITE (6,2) L,C,DEED,SP,STACK(1:SP) !Reveal the state now.
2 FORMAT (I4,A6,A7,I4,":",66F14.6) !Aligned with the heading of FORMAT 1.
END DO !On to the next symbol.
EVALRP = STACK(1) !The RPN string being correct, this is the result.
END !Simple enough!
PROGRAM HSILOP
REAL V
V = EVALRP("3 4 2 * 1 5 - 2 3 ^ ^ / +") !The specified example.
WRITE (6,*) "Result is...",V
END</syntaxhighlight>
Output...
<pre>
Evaluation of the Reverse Polish string 3 4 2 * 1 5 - 2 3 ^ ^ / +
Char Token Action SP:Stack...
1 3 Load 1: 3.000000
3 4 Load 2: 3.000000 4.000000
5 2 Load 3: 3.000000 4.000000 2.000000
7 * XEQ 2: 3.000000 8.000000
9 1 Load 3: 3.000000 8.000000 1.000000
11 5 Load 4: 3.000000 8.000000 1.000000 5.000000
13 - XEQ 3: 3.000000 8.000000 -4.000000
15 2 Load 4: 3.000000 8.000000 -4.000000 2.000000
17 3 Load 5: 3.000000 8.000000 -4.000000 2.000000 3.000000
19 ^ XEQ 4: 3.000000 8.000000 -4.000000 8.000000
21 ^ XEQ 3: 3.000000 8.000000 65536.000000
23 / XEQ 2: 3.000000 0.000122
25 + XEQ 1: 3.000122
Result is... 3.000122</pre>
=={{header|FunL}}==
<syntaxhighlight lang="funl">def evaluate( expr ) =
stack = []
for token <- expr.split( '''\s+''' )
case number( token )
Some( n ) ->
stack = n : stack
println( "push $token: ${stack.reversed()}" )
None ->
case {'+': (+), '-': (-), '*': (*), '/': (/), '^': (^)}.>get( token )
Some( op ) ->
stack = op( stack.tail().head(), stack.head() ) : stack.tail().tail()
println( "perform $token: ${stack.reversed()}" )
None -> error( "unrecognized operator '$token'" )
stack.head()
res = evaluate( '3 4 2 * 1 5 - 2 3 ^ ^ / +' )
println( res + (if res is Integer then '' else " or ${float(res)}") )</syntaxhighlight>
{{out}}
<pre>
push 3: [3]
push 4: [3, 4]
push 2: [3, 4, 2]
perform *: [3, 8]
push 1: [3, 8, 1]
push 5: [3, 8, 1, 5]
perform -: [3, 8, -4]
push 2: [3, 8, -4, 2]
push 3: [3, 8, -4, 2, 3]
perform ^: [3, 8, -4, 8]
perform ^: [3, 8, 65536]
perform /: [3, 1/8192]
perform +: [24577/8192]
24577/8192 or 3.0001220703125
</pre>
=={{header|Go}}==
No error checking.
<syntaxhighlight lang="go">package main
import (
"fmt"
"math"
"strconv"
"strings"
)
var input = "3 4 2 * 1 5 - 2 3 ^ ^ / +"
func main() {
fmt.Printf("For postfix %q\n", input)
fmt.Println("\nToken Action Stack")
var stack []float64
for _, tok := range strings.Fields(input) {
action := "Apply op to top of stack"
switch tok {
case "+":
stack[len(stack)-2] += stack[len(stack)-1]
stack = stack[:len(stack)-1]
case "-":
stack[len(stack)-2] -= stack[len(stack)-1]
stack = stack[:len(stack)-1]
case "*":
stack[len(stack)-2] *= stack[len(stack)-1]
stack = stack[:len(stack)-1]
case "/":
stack[len(stack)-2] /= stack[len(stack)-1]
stack = stack[:len(stack)-1]
case "^":
stack[len(stack)-2] =
math.Pow(stack[len(stack)-2], stack[len(stack)-1])
stack = stack[:len(stack)-1]
default:
action = "Push num onto top of stack"
f, _ := strconv.ParseFloat(tok, 64)
stack = append(stack, f)
}
fmt.Printf("%3s %-26s %v\n", tok, action, stack)
}
fmt.Println("\nThe final value is", stack[0])
}</syntaxhighlight>
{{out}}
<pre>
For postfix "3 4 2 * 1 5 - 2 3 ^ ^ / +"
Token Action Stack
3 Push num onto top of stack [3]
4 Push num onto top of stack [3 4]
2 Push num onto top of stack [3 4 2]
* Apply op to top of stack [3 8]
1 Push num onto top of stack [3 8 1]
5 Push num onto top of stack [3 8 1 5]
- Apply op to top of stack [3 8 -4]
2 Push num onto top of stack [3 8 -4 2]
3 Push num onto top of stack [3 8 -4 2 3]
^ Apply op to top of stack [3 8 -4 8]
^ Apply op to top of stack [3 8 65536]
/ Apply op to top of stack [3 0.0001220703125]
+ Apply op to top of stack [3.0001220703125]
The final value is 3.0001220703125
</pre>
=={{header|Groovy}}==
<syntaxhighlight lang="groovy">def evaluateRPN(expression) {
def stack = [] as Stack
def binaryOp = { action -> return { action.call(stack.pop(), stack.pop()) } }
def actions = [
'+': binaryOp { a, b -> b + a },
'-': binaryOp { a, b -> b - a },
'*': binaryOp { a, b -> b * a },
'/': binaryOp { a, b -> b / a },
'^': binaryOp { a, b -> b ** a }
]
expression.split(' ').each { item ->
def action = actions[item] ?: { item as BigDecimal }
stack.push(action.call())
println "$item: $stack"
}
assert stack.size() == 1 : "Unbalanced Expression: $expression ($stack)"
stack.pop()
}</syntaxhighlight>
Test
<syntaxhighlight lang="groovy">println evaluateRPN('3 4 2 * 1 5 - 2 3 ^ ^ / +')</syntaxhighlight>
{{out}}
<pre>3: [3]
4: [3, 4]
2: [3, 4, 2]
*: [3, 8]
1: [3, 8, 1]
5: [3, 8, 1, 5]
-: [3, 8, -4]
2: [3, 8, -4, 2]
3: [3, 8, -4, 2, 3]
^: [3, 8, -4, 8]
^: [3, 8, 65536]
/: [3, 0.0001220703125]
+: [3.0001220703125]
3.0001220703125</pre>
=={{header|Haskell}}==
Pure RPN calculator
<syntaxhighlight lang="haskell">calcRPN :: String -> [Double]
calcRPN = foldl interprete [] . words
interprete s x
| x `elem` ["+","-","*","/","^"] = operate x s
| otherwise = read x:s
where
operate op (x:y:s) = case op of
"+" -> x + y:s
"-" -> y - x:s
"*" -> x * y:s
"/" -> y / x:s
"^" -> y ** x:s</syntaxhighlight>
<pre>λ> calcRPN "3 4 +"
[7.0]
λ> calcRPN "3 4 2 * 1 5 - 2 3 ^ ^ / +"
[3.0001220703125]
</pre>
'''Calculation logging'''
''Pure logging''. Log as well as a result could be used as a data.
<syntaxhighlight lang="haskell">calcRPNLog :: String -> ([Double],[(String, [Double])])
calcRPNLog input = mkLog $ zip commands $ tail result
where result = scanl interprete [] commands
commands = words input
mkLog [] = ([], [])
mkLog res = (snd $ last res, res)</syntaxhighlight>
<pre>λ> calcRPNLog "3 4 +"
([7.0],[("3",[3.0]),("4",[4.0,3.0]),("+",[7.0])])
λ> mapM_ print $ snd $ calcRPNLog "3 4 2 * 1 5 - 2 3 ^ ^ / +"
("3",[3.0])
("4",[4.0,3.0])
("2",[2.0,4.0,3.0])
("*",[8.0,3.0])
("1",[1.0,8.0,3.0])
("5",[5.0,1.0,8.0,3.0])
("-",[-4.0,8.0,3.0])
("2",[2.0,-4.0,8.0,3.0])
("3",[3.0,2.0,-4.0,8.0,3.0])
("^",[8.0,-4.0,8.0,3.0])
("^",[65536.0,8.0,3.0])
("/",[1.220703125e-4,3.0])
("+",[3.0001220703125])</pre>
''Logging as a side effect.'' Calculator returns result in IO context:
<syntaxhighlight lang="haskell">import Control.Monad (foldM)
calcRPNIO :: String -> IO [Double]
calcRPNIO = foldM (verbose interprete) [] . words
verbose f s x = write (x ++ "\t" ++ show res ++ "\n") >> return res
where res = f s x</syntaxhighlight>
<pre>λ> calcRPNIO "3 4 +"
3 [3.0]
4 [4.0,3.0]
+ [7.0]
[7.0]
λ> calcRPNIO "3 4 2 * 1 5 - 2 3 ^ ^ / +"
3 [3.0]
4 [4.0,3.0]
2 [2.0,4.0,3.0]
* [8.0,3.0]
1 [1.0,8.0,3.0]
5 [5.0,1.0,8.0,3.0]
- [-4.0,8.0,3.0]
2 [2.0,-4.0,8.0,3.0]
3 [3.0,2.0,-4.0,8.0,3.0]
^ [8.0,-4.0,8.0,3.0]
^ [65536.0,8.0,3.0]
/ [1.220703125e-4,3.0]
+ [3.0001220703125]
[3.0001220703125]</pre>
Or even more general (requires <tt>FlexibleInstances</tt> and <tt>TypeFamilies</tt> extensions).
Some universal definitions:
<syntaxhighlight lang="haskell">class Monad m => Logger m where
write :: String -> m ()
instance Logger IO where write = putStr
instance a ~ String => Logger (Writer a) where write = tell
verbose2 f x y = write (show x ++ " " ++
show y ++ " ==> " ++
show res ++ "\n") >> return res
where res = f x y</syntaxhighlight>
The use case:
<syntaxhighlight lang="haskell">calcRPNM :: Logger m => String -> m [Double]
calcRPNM = foldM (verbose interprete) [] . words</syntaxhighlight>
{{out}} in REPL
<pre>λ> calcRPNM "3 4 2 * 1 5 - 2 3 ^ ^ / +"
[] "3" ==> [3.0]
[3.0] "4" ==> [4.0,3.0]
[4.0,3.0] "2" ==> [2.0,4.0,3.0]
[2.0,4.0,3.0] "*" ==> [8.0,3.0]
[8.0,3.0] "1" ==> [1.0,8.0,3.0]
[1.0,8.0,3.0] "5" ==> [5.0,1.0,8.0,3.0]
[5.0,1.0,8.0,3.0] "-" ==> [-4.0,8.0,3.0]
[-4.0,8.0,3.0] "2" ==> [2.0,-4.0,8.0,3.0]
[2.0,-4.0,8.0,3.0] "3" ==> [3.0,2.0,-4.0,8.0,3.0]
[3.0,2.0,-4.0,8.0,3.0] "^" ==> [8.0,-4.0,8.0,3.0]
[8.0,-4.0,8.0,3.0] "^" ==> [65536.0,8.0,3.0]
[65536.0,8.0,3.0] "/" ==> [1.220703125e-4,3.0]
[1.220703125e-4,3.0] "+" ==> [3.0001220703125]
[3.0001220703125]
λ> runWriter $ calcRPNM "3 4 +"
([7.0],"[] \"3\" ==> [3.0]\n[3.0] \"4\" ==> [4.0,3.0]\n[4.0,3.0] \"+\" ==> [7.0]\n")</pre>
=={{header|Icon}} and {{header|Unicon}}==
<syntaxhighlight lang="icon">procedure main()
EvalRPN("3 4 2 * 1 5 - 2 3 ^ ^ / +")
end
link printf
invocable all
procedure EvalRPN(expr) #: evaluate (and trace stack) an RPN string
stack := []
expr ? until pos(0) do {
tab(many(' ')) # consume previous seperator
token := tab(upto(' ')|0) # get token
if token := numeric(token) then { # ... numeric
push(stack,token)
printf("pushed numeric %i : %s\n",token,list2string(stack))
}
else { # ... operator
every b|a := pop(stack) # pop & reverse operands
case token of {
"+"|"-"|"*"|"^" : push(stack,token(a,b))
"/" : push(stack,token(real(a),b))
default : runerr(205,token)
}
printf("applied operator %s : %s\n",token,list2string(stack))
}
}
end
procedure list2string(L) #: format list as a string
every (s := "[ ") ||:= !L || " "
return s || "]"
end</syntaxhighlight>
{{libheader|Icon Programming Library}}
[http://www.cs.arizona.edu/icon/library/src/procs/printf.icn printf.icn provides formatting]
{{out}}
<pre>pushed numeric 3 : [ 3 ]
pushed numeric 4 : [ 4 3 ]
pushed numeric 2 : [ 2 4 3 ]
applied operator * : [ 8 3 ]
pushed numeric 1 : [ 1 8 3 ]
pushed numeric 5 : [ 5 1 8 3 ]
applied operator - : [ -4 8 3 ]
pushed numeric 2 : [ 2 -4 8 3 ]
pushed numeric 3 : [ 3 2 -4 8 3 ]
applied operator ^ : [ 8 -4 8 3 ]
applied operator ^ : [ 65536 8 3 ]
applied operator / : [ 0.0001220703125 3 ]
applied operator + : [ 3.0001220703125 ]</pre>
=={{header|J}}==
This task's operations are all dyadic - having two arguments.
So on each step we may either "shift" a number to the stack
or "reduce" two topmost stack items to one.
Our implementation will be a monadic verb: it will take a single argument, which contains both the accumulated stack and the tokens to be processed. First, create initial state of the input:
<syntaxhighlight lang="j"> a: , <;._1 ' ' , '3 4 2 * 1 5 - 2 3 ^ ^ / +'
┌┬─┬─┬─┬─┬─┬─┬─┬─┬─┬─┬─┬─┬─┐
││3│4│2│*│1│5│-│2│3│^│^│/│+│
└┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┘</syntaxhighlight>
As an example, let's also add monadic operation _ which inverses the sign of the stack top element.
We're going to read tokens from input one by one.
Each time we read a token, we're checking if it's a number - in this case we put the number to the stack - or an operation - in this case we apply the operation to the stack.
The monad which returns 1 (true) for a token representing an operation and 0 (false) otherwise is "isOp".
The dyad, which moves an input token to the stack, is "doShift". Applying the operation to the stack is "doApply".
There are 6 operations - one monadic "_" and five dyadic "+", "-", "*", "/", "^".
For operation, we need to translate input token into operation and apply it to the stack.
The dyad which converts the input token to the operation is "dispatch". It uses two miscellaneous adverbs, one for monadic operations - "mo" - and another for dyadic - "dy".
The RPN driver is the monad "consume", which handles one token.
The output is the state of the program after the token was consumed - stack in the 0th box, and remaining input afterwards.
As a side effect, "consume" is going to print the resulting stack,
so running "consume" once for each token will produce intermediate states of the stack.
<syntaxhighlight lang="j"> isOp=: '_+-*/^' e.~ {.@>@{.
mo=: 1 :'(}: , u@{:) @ ['
dy=: 1 :'(_2&}. , u/@(_2&{.)) @ ['
dispatch=: (-mo)`(+dy)`(-dy)`(*dy)`(%dy)`(^dy)@.('_+-*/^' i. {.@>@])
doShift=: (<@, ".@>@{.) , }.@]
doApply=: }.@] ,~ [ <@dispatch {.@]
consume=: [: ([ smoutput@>@{.) >@{. doShift`doApply@.(isOp@]) }.
consume ^: (<:@#) a: , <;._1 ' ' , '3 4 2 * 1 5 - 2 3 ^ ^ / +'
3
3 4
3 4 2
3 8
3 8 1
3 8 1 5
3 8 _4
3 8 _4 2
3 8 _4 2 3
3 8 _4 8
3 8 65536
3 0.00012207
3.00012
┌───────┐
│3.00012│
└───────┘
consume ^: (<:@#) a: , <;._1 ' ' , '3 _ 4 +'
3
_3
_3 4
1
┌─┐
│1│
└─┘</syntaxhighlight>
=== Alternate Implementation ===
<syntaxhighlight lang="j">rpn=: 3 :0
queue=. |.3 :'|.3 :y 0'::]each;: y
op=. 1 :'2 (u~/@:{.,}.)S:0 ,@]'
ops=. +op`(-op)`(*op)`(%op)`(^op)`(,&;)
choose=. ((;:'+-*/^')&i.@[)
,ops@.choose/queue
)</syntaxhighlight>
Example use:
<syntaxhighlight lang="j"> rpn '3 4 2 * 1 5 - 2 3 ^ ^ / +'
3.00012</syntaxhighlight>
To see intermediate result stacks, use this variant (the only difference is the definition of 'op'):
<syntaxhighlight lang="j">rpnD=: 3 :0
queue=. |.3 :'|.3 :y 0'::]each;: y
op=. 1 :'2 (u~/@:{.,}.)S:0 ,@([smoutput)@]'
ops=. +op`(-op)`(*op)`(%op)`(^op)`(,&;)
choose=. ((;:'+-*/^')&i.@[)
,ops@.choose/queue
)</syntaxhighlight>
In other words:
<syntaxhighlight lang="j"> rpnD '3 4 2 * 1 5 - 2 3 ^ ^ / +'
┌─────┐
│2 4 3│
└─────┘
5 1 8 3
3 2 _4 8 3
8 _4 8 3
65536 8 3
0.00012207 3
3.00012</syntaxhighlight>
Note that the seed stack is boxed while computed stacks are not.
Note that top of stack here is on the left.
Note also that adjacent constants are bundled in the parsing phase.
Finally, note that the result of rpn (and of rpnD - lines previous to the last line in the rpnD example here are output and not a part of the result) is the final state of the stack - in the general case it may not contain exactly one value.
=={{header|Java}}==
{{works with|Java|1.5+}}
Supports multi-digit numbers and negative numbers.
<syntaxhighlight lang="java5">
import java.util.LinkedList;
public class RPN{
public static void main(String[] args) {
evalRPN("3 4 2 * 1 5 - 2 3 ^ ^ / +");
}
private static void evalRPN(String expr){
LinkedList<Double> stack = new LinkedList<Double>();
System.out.println("Input\tOperation\tStack after");
for (String token : expr.split("\\s")){
System.out.print(token + "\t");
if (token.equals("*")) {
System.out.print("Operate\t\t");
double secondOperand = stack.pop();
double firstOperand = stack.pop();
stack.push(firstOperand * secondOperand);
} else if (token.equals("/")) {
System.out.print("Operate\t\t");
double secondOperand = stack.pop();
double firstOperand = stack.pop();
stack.push(firstOperand / secondOperand);
} else if (token.equals("-")) {
System.out.print("Operate\t\t");
double secondOperand = stack.pop();
double firstOperand = stack.pop();
stack.push(firstOperand - secondOperand);
} else if (token.equals("+")) {
System.out.print("Operate\t\t");
double secondOperand = stack.pop();
double firstOperand = stack.pop();
stack.push(firstOperand + secondOperand);
} else if (token.equals("^")) {
System.out.print("Operate\t\t");
double secondOperand = stack.pop();
double firstOperand = stack.pop();
stack.push(Math.pow(firstOperand, secondOperand));
} else {
System.out.print("Push\t\t");
try {
stack.push(Double.parseDouble(token+""));
} catch (NumberFormatException e) {
System.out.println("\nError: invalid token " + token);
return;
}
}
System.out.println(stack);
}
if (stack.size() > 1) {
System.out.println("Error, too many operands: " + stack);
return;
}
System.out.println("Final answer: " + stack.pop());
}
}
</syntaxhighlight>
{{out}}
<pre>Input Operation Stack after
3 Push [3.0]
4 Push [4.0, 3.0]
2 Push [2.0, 4.0, 3.0]
* Operate [8.0, 3.0]
1 Push [1.0, 8.0, 3.0]
5 Push [5.0, 1.0, 8.0, 3.0]
- Operate [-4.0, 8.0, 3.0]
2 Push [2.0, -4.0, 8.0, 3.0]
3 Push [3.0, 2.0, -4.0, 8.0, 3.0]
^ Operate [8.0, -4.0, 8.0, 3.0]
^ Operate [65536.0, 8.0, 3.0]
/ Operate [1.220703125E-4, 3.0]
+ Operate [3.0001220703125]
Final answer: 3.0001220703125</pre>
=={{header|JavaScript}}==
<syntaxhighlight lang="javascript">
const e = '3 4 2 * 1 5 - 2 3 ^ ^ / +';
const s = [], tokens = e.split(' ');
for (const t of tokens) {
const n = Number(t);
if (!isNaN(n)) {
s.push(n);
} else {
if (s.length < 2) {
throw new Error(`${t}: ${s}: insufficient operands.`);
}
const o2 = s.pop(), o1 = s.pop();
switch (t) {
case '+': s.push(o1 + o2); break;
case '-': s.push(o1 - o2); break;
case '*': s.push(o1 * o2); break;
case '/': s.push(o1 / o2); break;
case '^': s.push(Math.pow(o1, o2)); break;
default: throw new Error(`Unrecognized operator: [${t}]`);
}
}
console.log(`${t}: ${s}`);
}
if (s.length > 1) {
throw new Error(`${s}: insufficient operators.`);
}
</syntaxhighlight>
{{out}}
<pre>
3: 3
4: 3,4
2: 3,4,2
*: 3,8
1: 3,8,1
5: 3,8,1,5
-: 3,8,-4
2: 3,8,-4,2
3: 3,8,-4,2,3
^: 3,8,-4,8
^: 3,8,65536
/: 3,0.0001220703125
+: 3.0001220703125
</pre>
=={{header|jq}}==
{{works with|jq}}
'''Also works with gojq, the Go implementation of jq, and with jackson-jq and fq.'''
<syntaxhighlight lang=jq>
# Input: an array representing a stack, with .[-1] being its top.
# Output: the updated array after applying `op`
def rpn(op):
def two: .[-2:];
def update($x): (.[:-2] + [$x]);
if length<=1 then .
elif op == "+" then update(two | add)
elif op == "*" then update(two | (.[0] * .[1]))
elif op == "/" then update(two | (.[0] / .[1]))
elif op == "-" then update(two | (.[0] - .[1]))
elif op == "^" then update(two | (pow(.[0]; .[1])))
else ("ignoring unrecognized op \(op)" | debug) as $debug | .
end;
def eval:
foreach .[] as $item ([];
if ($item | type) == "number" then . + [$item]
else rpn($item)
end;
"\($item) => \(.)" ) ;
"3 4 2 * 1 5 - 2 3 ^ ^ / +"
| split(" ") | map( (try tonumber) // .)
| eval
</syntaxhighlight>
''Invocation:'' jq -nr -f rpn.jq
{{output}}
<pre>
3 => [3]
4 => [3,4]
2 => [3,4,2]
* => [3,8]
1 => [3,8,1]
5 => [3,8,1,5]
- => [3,8,-4]
2 => [3,8,-4,2]
3 => [3,8,-4,2,3]
^ => [3,8,-4,8]
^ => [3,8,65536]
/ => [3,0.0001220703125]
+ => [3.0001220703125]
</pre>
=={{header|Julia}}==
(This code takes advantage of the fact that all of the operands and functions in the specified RPN syntax are valid Julia expressions, so we can use the built-in <code>parse</code> and <code>eval</code> functions to turn them into numbers and the corresponding Julia functions.)
<syntaxhighlight lang="julia">function rpn(s)
stack = Any[]
for op in map(eval, map(parse, split(s)))
if isa(op, Function)
arg2 = pop!(stack)
arg1 = pop!(stack)
push!(stack, op(arg1, arg2))
else
push!(stack, op)
end
println("$op: ", join(stack, ", "))
end
length(stack) != 1 && error("invalid RPN expression $s")
return stack[1]
end
rpn("3 4 2 * 1 5 - 2 3 ^ ^ / +")</syntaxhighlight>
{{out}}
<pre>3: 3
4: 3, 4
2: 3, 4, 2
*: 3, 8
1: 3, 8, 1
5: 3, 8, 1, 5
-: 3, 8, -4
2: 3, 8, -4, 2
3: 3, 8, -4, 2, 3
^: 3, 8, -4, 8
^: 3, 8, 65536
/: 3, 0.0001220703125
+: 3.0001220703125</pre>
(The return value is also <code>3.0001220703125</code>.)
=={{header|Kotlin}}==
<syntaxhighlight lang="scala">// version 1.1.2
fun rpnCalculate(expr: String) {
if (expr.isEmpty()) throw IllegalArgumentException("Expresssion cannot be empty")
println("For expression = $expr\n")
println("Token Action Stack")
val tokens = expr.split(' ').filter { it != "" }
val stack = mutableListOf<Double>()
for (token in tokens) {
val d = token.toDoubleOrNull()
if (d != null) {
stack.add(d)
println(" $d Push num onto top of stack $stack")
}
else if ((token.length > 1) || (token !in "+-*/^")) {
throw IllegalArgumentException("$token is not a valid token")
}
else if (stack.size < 2) {
throw IllegalArgumentException("Stack contains too few operands")
}
else {
val d1 = stack.removeAt(stack.lastIndex)
val d2 = stack.removeAt(stack.lastIndex)
stack.add(when (token) {
"+" -> d2 + d1
"-" -> d2 - d1
"*" -> d2 * d1
"/" -> d2 / d1
else -> Math.pow(d2, d1)
})
println(" $token Apply op to top of stack $stack")
}
}
println("\nThe final value is ${stack[0]}")
}
fun main(args: Array<String>) {
val expr = "3 4 2 * 1 5 - 2 3 ^ ^ / +"
rpnCalculate(expr)
}</syntaxhighlight>
{{out}}
<pre>
For expression = 3 4 2 * 1 5 - 2 3 ^ ^ / +
Token Action Stack
3.0 Push num onto top of stack [3.0]
4.0 Push num onto top of stack [3.0, 4.0]
2.0 Push num onto top of stack [3.0, 4.0, 2.0]
* Apply op to top of stack [3.0, 8.0]
1.0 Push num onto top of stack [3.0, 8.0, 1.0]
5.0 Push num onto top of stack [3.0, 8.0, 1.0, 5.0]
- Apply op to top of stack [3.0, 8.0, -4.0]
2.0 Push num onto top of stack [3.0, 8.0, -4.0, 2.0]
3.0 Push num onto top of stack [3.0, 8.0, -4.0, 2.0, 3.0]
^ Apply op to top of stack [3.0, 8.0, -4.0, 8.0]
^ Apply op to top of stack [3.0, 8.0, 65536.0]
/ Apply op to top of stack [3.0, 1.220703125E-4]
+ Apply op to top of stack [3.0001220703125]
The final value is 3.0001220703125
</pre>
==[[header|Lambdatalk]]==
<syntaxhighlight lang="scheme">
{calc 3 4 2 * 1 5 - 2 3 pow pow / +}
->
3:
4: 3
2: 4 3
*: 2 4 3
1: 8 3
5: 1 8 3
-: 5 1 8 3
2: -4 8 3
3: 2 -4 8 3
pow: 3 2 -4 8 3
pow: 8 -4 8 3
/: 65536 8 3
+: 0.0001220703125 3
-> 3.0001220703125
where
{def calc
{def calc.r
{lambda {:x :s}
{if {empty? :x}
then -> {car :s}
else {car :x}: {disp :s}{br}
{calc.r {cdr :x}
{if {unop? {car :x}}
then {cons {{car :x} {car :s}} {cdr :s}}
else {if {binop? {car :x}}
then {cons {{car :x} {car {cdr :s}} {car :s}} {cdr {cdr :s}}}
else {cons {car :x} :s}} }}}}}
{lambda {:s}
{calc.r {list :s} nil}}}
using the unop? & binop? functions to test unary and binary operators
{def unop?
{lambda {:op}
{or {W.equal? :op sqrt} // n sqrt sqrt(n)
{W.equal? :op exp} // n exp exp(n)
{W.equal? :op log} // n log log(n)
{W.equal? :op cos} // n cos cos(n)
... and so // ...
}}}
{def binop?
{lambda {:op}
{or {W.equal? :op +} // m n + m+n
{W.equal? :op -} // m n - m-n
{W.equal? :op *} // m n * m*n
{W.equal? :op /} // m n / m/n
{W.equal? :op %} // m n % m%n
{W.equal? :op pow} // m n pow m^n
... and so on // ...
}}}
and the list, empty? and disp functions to create
a list from a string, test its emptynes and display it.
{def list
{lambda {:s}
{if {W.empty? {S.rest :s}}
then {cons {S.first :s} nil}
else {cons {S.first :s} {list {S.rest :s}}}}}}
{def empty?
{lambda {:x}
{W.equal? :x nil}}}
{def disp
{lambda {:l}
{if {empty? :l}
then
else {car :l} {disp {cdr :l}}}}}
Note that everything is exclusively built on 5 lambdatalk primitives:
- "cons, car, cdr", to create lists,
- "W.equal?" which test the equality between two words,
- and the "or" boolean function.
</syntaxhighlight>
=={{header|Lua}}==
<syntaxhighlight lang="lua">
local stack = {}
function push( a ) table.insert( stack, 1, a ) end
function pop()
if #stack == 0 then return nil end
return table.remove( stack, 1 )
end
function writeStack()
for i = #stack, 1, -1 do
io.write( stack[i], " " )
end
print()
end
function operate( a )
local s
if a == "+" then
push( pop() + pop() )
io.write( a .. "\tadd\t" ); writeStack()
elseif a == "-" then
s = pop(); push( pop() - s )
io.write( a .. "\tsub\t" ); writeStack()
elseif a == "*" then
push( pop() * pop() )
io.write( a .. "\tmul\t" ); writeStack()
elseif a == "/" then
s = pop(); push( pop() / s )
io.write( a .. "\tdiv\t" ); writeStack()
elseif a == "^" then
s = pop(); push( pop() ^ s )
io.write( a .. "\tpow\t" ); writeStack()
elseif a == "%" then
s = pop(); push( pop() % s )
io.write( a .. "\tmod\t" ); writeStack()
else
push( tonumber( a ) )
io.write( a .. "\tpush\t" ); writeStack()
end
end
function calc( s )
local t, a = "", ""
print( "\nINPUT", "OP", "STACK" )
for i = 1, #s do
a = s:sub( i, i )
if a == " " then operate( t ); t = ""
else t = t .. a
end
end
if a ~= "" then operate( a ) end
print( string.format( "\nresult: %.13f", pop() ) )
end
--[[ entry point ]]--
calc( "3 4 2 * 1 5 - 2 3 ^ ^ / +" )
calc( "22 11 *" )</syntaxhighlight>
{{out}}
<pre>
INPUT OP STACK
3 push 3
4 push 3 4
2 push 3 4 2
* mul 3 8
1 push 3 8 1
5 push 3 8 1 5
- sub 3 8 -4
2 push 3 8 -4 2
3 push 3 8 -4 2 3
^ pow 3 8 -4 8
^ pow 3 8 65536
/ div 3 0.0001220703125
+ add 3.0001220703125
result: 3.0001220703125
INPUT OP STACK
22 push 22
11 push 22 11
* mul 242
result: 242.0000000000000</pre>
=={{header|M2000 Interpreter}}==
<syntaxhighlight lang="m2000 interpreter">
Module Rpn_Calc {
Rem Form 80,60
function rpn_calc(a$) {
def m=0
dim token$()
token$()=piece$(a$," ")
l=len(token$())
dim type(l)=0, reg(l)
where=-1
for i=0 to l-1
c=val(token$(i),"",m)
if m>-1 then
where++
reg(where)=c
else
reg(where-1)=eval(str$(reg(where-1))+token$(i)+str$(reg(where)))
where--
end if
inf=each(reg(),1, where+1)
while inf
export$<=token$(i)+" ["+str$(inf^,"")+"] "+ str$(array(inf))+{
}
token$(i)=" "
end while
next i
=reg(0)
}
Global export$
document export$
example1=rpn_calc("3 4 2 * 1 5 - 2 3 ^ ^ / +")
example2=rpn_calc("1 2 + 3 4 + ^ 5 6 + ^")
Print example1, example2
Rem Print #-2, Export$
ClipBoard Export$
}
Rpn_Calc
</syntaxhighlight>
{{out}}
<pre style="height:30ex;overflow:scroll">
3 [0] 3
4 [0] 3
[1] 4
2 [0] 3
[1] 4
[2] 2
* [0] 3
[1] 8
1 [0] 3
[1] 8
[2] 1
5 [0] 3
[1] 8
[2] 1
[3] 5
- [0] 3
[1] 8
[2] -4
2 [0] 3
[1] 8
[2] -4
[3] 2
3 [0] 3
[1] 8
[2] -4
[3] 2
[4] 3
^ [0] 3
[1] 8
[2] -4
[3] 8
^ [0] 3
[1] 8
[2] 65536
/ [0] 3
[1] .0001220703125
+ [0] 3.0001220703125
1 [0] 1
2 [0] 1
[1] 2
+ [0] 3
3 [0] 3
[1] 3
4 [0] 3
[1] 3
[2] 4
+ [0] 3
[1] 7
^ [0] 2187
5 [0] 2187
[1] 5
6 [0] 2187
[1] 5
[2] 6
+ [0] 2187
[1] 11
^ [0] 5.47440108942022E+36
</pre >
=={{header|Mathematica}}/{{header|Wolfram Language}}==
(This code takes advantage of the fact that all of the operands and functions in the specified RPN syntax can be used to form valid Mathematica expressions, so we can use the built-in ToExpression function to turn them into numbers and the corresponding Mathematica functions. Note that we need to add braces around arguments, otherwise "-4^8" would be parsed as "-(4^8)" instead of "(-4)^8".)
<syntaxhighlight lang="mathematica">calc[rpn_] :=
Module[{tokens = StringSplit[rpn], s = "(" <> ToString@InputForm@# <> ")" &, op, steps},
op[o_, x_, y_] := ToExpression[s@x <> o <> s@y];
steps = FoldList[Switch[#2, _?DigitQ, Append[#, FromDigits[#2]],
_, Append[#[[;; -3]], op[#2, #[[-2]], #[[-1]]]]
] &, {}, tokens][[2 ;;]];
Grid[Transpose[{# <> ":" & /@ tokens,
StringRiffle[ToString[#, InputForm] & /@ #] & /@ steps}]]];
Print[calc["3 4 2 * 1 5 - 2 3 ^ ^ / +"]];</syntaxhighlight>
{{out}}
<pre>3: 3
4: 3 4
2: 3 4 2
*: 3 8
1: 3 8 1
5: 3 8 1 5
-: 3 8 -4
2: 3 8 -4 2
3: 3 8 -4 2 3
^: 3 8 -4 8
^: 3 8 65536
/: 3 1/8192
+: 24577/8192</pre>
=={{header|Maxima}}==
<syntaxhighlight lang="maxima">rmod(i, j) := mod(j, i)$
rpow(x, y) := y^x$
rpn(sexpr) := (
operands: [],
expr: charlist(sexpr),
for token in expr do (
if token = "+" then (
push(pop(operands) + pop(operands), operands)
)
elseif token = "-" then (
push(-1 * (pop(operands) - pop(operands)), operands)
)
elseif token = "*" then (
push(pop(operands) * pop(operands), operands)
)
elseif token = "/" then (
push(1 / (pop(operands) / pop(operands)), operands)
)
elseif token = "%" then (
push(rmod(pop(operands), pop(operands)), operands)
)
elseif token = "^" then (
push(rpow(pop(operands), pop(operands)), operands)
)
elseif token # " " then (
push(parse_string(token), operands)
),
if token # " " then (
print(token, " : ", operands)
)
),
pop(operands)
)$
rpn("3 4 2 * 1 5 - 2 3 ^ ^ / +"), numer;</syntaxhighlight>
===Output===
<syntaxhighlight lang="text">(%i5) ev(rpn("3 4 2 * 1 5 - 2 3 ^ ^ / +"),numer)
3 : [3]
4 : [4, 3]
2 : [2, 4, 3]
* : [8, 3]
1 : [1, 8, 3]
5 : [5, 1, 8, 3]
- : [- 4, 8, 3]
2 : [2, - 4, 8, 3]
3 : [3, 2, - 4, 8, 3]
^ : [8, - 4, 8, 3]
^ : [65536, 8, 3]
/ : [1.220703125e-4, 3]
+ : [3.0001220703125]
(%o5) 3.0001220703125</syntaxhighlight>
=={{header|MiniScript}}==
<syntaxhighlight lang="miniscript">RPN = function(inputText)
tokens = inputText.split
stack = []
while tokens
tok = tokens.pull
if "+-*/^".indexOf(tok) != null then
b = stack.pop
a = stack.pop
if tok == "+" then stack.push a + b
if tok == "-" then stack.push a - b
if tok == "*" then stack.push a * b
if tok == "/" then stack.push a / b
if tok == "^" then stack.push a ^ b
else
stack.push val(tok)
end if
print tok + " --> " + stack
end while
return stack[0]
end function
print RPN("3 4 2 * 1 5 - 2 3 ^ ^ / +")</syntaxhighlight>
{{out}}
<pre>3 --> [3]
4 --> [3, 4]
2 --> [3, 4, 2]
* --> [3, 8]
1 --> [3, 8, 1]
5 --> [3, 8, 1, 5]
- --> [3, 8, -4]
2 --> [3, 8, -4, 2]
3 --> [3, 8, -4, 2, 3]
^ --> [3, 8, -4, 8]
^ --> [3, 8, 65536]
/ --> [3, 0.000122]
+ --> [3.000122]
3.000122</pre>
=={{header|N/t/roff}}==
===Classically-oriented version===
This implementation does not take advantage of GNU TROFF's ability to handle numerical registers of more than 2 characters.
{{works with|GNU TROFF|1.22.2}}
<syntaxhighlight lang="n/t/roff">.ig
RPN parser implementation in TROFF
..
.\" \(*A stack implementation
.nr Ac 0
.af Ac 1
.de APUSH
.if (\\n(Ac>=0)&(\\n(Ac<27) \{ \
. nr Ac +1
. af Ac A
. nr A\\n(Ac \\$1
. af Ac 1
\}
..
.de APOP
.if (\\n(Ac>0)&(\\n(Ac<27) \{ \
. af Ac A
. rr A\\n(Ac \\$1
. af Ac 1
. nr Ac -1
..
.\" Facility to print entire stack
.de L2
.af Ac 1
.if \\n(Li<=\\n(Ac \{ \
. af Li A
\\n(A\\n(Li
. af Li 1
. nr Li +1
. L2
\}
..
.de APRINT
.nr Li 1
.L2
.br
..
.\" Integer exponentiation algorithm
.de L1
.if \\n(Li<\\$2 \{ \
. nr Rs \\n(Rs*\\$1
. nr Li +1
. L1 \\$1 \\$2
\}
..
.de EXP
.nr Li 0
.nr Rs 1
.L1 \\$1 \\$2
..
.\" RPN Parser
.de REAP
.af Ac A
.nr O2 \\n(A\\n(Ac
.af Ac 1
.nr Ai \\n(Ac-1
.af Ai A
.nr O1 \\n(A\\n(Ai
.APOP
.APOP
..
.de RPNPUSH
.ie '\\$1'+' \{ \
. REAP
. nr Rs \\n(O1+\\n(O2
\}
.el \{ \
. ie '\\$1'-' \{ \
. REAP
. nr Rs \\n(O1-\\n(O2
\}
. el \{ \
. ie '\\$1'*' \{ \
. REAP
. nr Rs \\n(O1*\\n(O2
\}
. el \{ \
. ie '\\$1'/' \{ \
. REAP
. nr Rs \\n(O1/\\n(O2
\}
. el \{ \
. ie '\\$1'%' \{ \
. REAP
. nr Rs \\n(O1%\\n(O2
\}
. el \{ \
. ie '\\$1'^' \{ \
. REAP
. EXP \\n(O1 \\n(O2
\}
. el .nr Rs \\$1
\}
\}
\}
\}
\}
.APUSH \\n(Rs
.APRINT
..
.de RPNPRINT
.if \\n(Ac>1 .tm ERROR (rpn.roff): Malformed input expression. Evaluation stack size: \\n(Ac > 1 .
\\n(AA
..
.de RPNPARSE
.RPNPUSH \\$1
.ie \\n(.$>1 \{ \
. shift
. RPNPARSE \\$@
\}
.el .RPNPRINT
..
.RPNPARSE 3 4 2 * 1 5 - 2 3 ^ ^ / + \" Our input expression</syntaxhighlight>
====Output====
<syntaxhighlight lang="text"> 3
3 4
3 4 2
3 8
3 8 1
3 8 1 5
3 8 ‐4
3 8 ‐4 2
3 8 ‐4 2 3
3 8 ‐4 8
3 8 16
3 0
3
3</syntaxhighlight>
===Modern version===
This version sees great improvement on syntax, stacks can now be as big as they want, and modern GNU Troff constructs are used.
{{works with|GNU Troff|1.22.2}}
<syntaxhighlight lang="n/t/roff">.ig
===========================
Array implementation
===========================
..
.de end
..
.de array
. nr \\$1.c 0 1
. de \\$1.push end
. nr \\$1..\\\\n+[\\$1.c] \\\\$1
. end
. de \\$1.pop end
. if \\\\n[\\$1.c]>0 \{ \
. rr \\$1..\\\\n[\\$1.c]
. nr \\$1.c -1\
. \}
. end
. de \\$1.dump end
. nr i 0 1
. rm ou
. while \\\\n+i<=\\\\n[\\$1.c] \{ \
. as ou "\\\\n[\\$1..\\\\ni]
. \}
. tm \\\\*(ou
. rr i
. end
..
.ig
==========================
End array implementation
==========================
..
.array stack
.de hyper3
. nr rs 1
. nr i 0 1
. while \\n+i<=\\$2 .nr rs \\n(rs*\\$1
. rr i
..
.de pop2
. nr O2 \\n[\\$1..\\n[\\$1.c]]
. \\$1.pop
. nr O1 \\n[\\$1..\\n[\\$1.c]]
. \\$1.pop
..
.de rpn
. ie '\\$1'+' \{ \
. pop2 stack
. nr rs \\n(O1+\\n(O2
. \}
. el \{ \
. ie '\\$1'-' \{ \
. pop2 stack
. nr rs \\n(O1-\\n(O2
. \}
. el \{ \
. ie '\\$1'*' \{ \
. pop2 stack
. nr rs \\n(O1*\\n(O2
. \}
. el \{ \
. ie '\\$1'/' \{ \
. pop2 stack
. nr rs \\n(O1/\\n(O2
. \}
. el \{ \
. ie '\\$1'%' \{ \
. pop2 stack
. nr rs \\n(O1%\\n(O2
. \}
. el \{ \
. ie '\\$1'^' \{ \
. pop2 stack
. hyper3 \\n(O1 \\n(O2
. \}
. el .nr rs \\$1
. \}\}\}\}\}
.
. stack.push \\n(rs
. stack.dump
.
. if \\n(.$>1 \{ \
. shift
. rpn \\$@
. \}
..
.rpn 3 4 2 * 1 5 - 2 3 ^ ^ / +
.stack.dump</syntaxhighlight>
====Output====
<syntaxhighlight lang="text">3
3 4
3 4 2
3 8
3 8 1
3 8 1 5
3 8 -4
3 8 -4 2
3 8 -4 2 3
3 8 -4 8
3 8 16
3 0
3
3</syntaxhighlight>
=={{header|NetRexx}}==
{{trans|Java}}
<syntaxhighlight lang="netrexx">/* NetRexx */
options replace format comments java crossref symbols nobinary
numeric digits 20
rpnDefaultExpression = '3 4 2 * 1 5 - 2 3 ^ ^ / +'
EODAD = '.*'
parse arg rpnString
if rpnString = '.' then rpnString = rpnDefaultExpression
if rpnString = '' then do
say 'Enter numbers or operators [to stop enter' EODAD']:'
loop label rpnloop forever
rpnval = ask
if rpnval == EODAD then leave rpnloop
rpnString = rpnString rpnval
end rpnloop
end
rpnString = rpnString.space(1)
say rpnString':' evaluateRPN(rpnString)
return
-- -----------------------------------------------------------------------------
method evaluateRPN(rpnString) public static returns Rexx
stack = LinkedList()
op = 0
L = 'L'
R = 'R'
rpnString = rpnString.strip('b')
say 'Input\tOperation\tStack after'
loop label rpn while rpnString.length > 0
parse rpnString token rest
rpnString = rest.strip('b')
say token || '\t\-'
select label tox case token
when '*' then do
say 'Operate\t\t\-'
op[R] = Rexx stack.pop()
op[L] = Rexx stack.pop()
stack.push(op[L] * op[R])
end
when '/' then do
say 'Operate\t\t\-'
op[R] = Rexx stack.pop()
op[L] = Rexx stack.pop()
stack.push(op[L] / op[R])
end
when '+' then do
say 'Operate\t\t\-'
op[R] = Rexx stack.pop()
op[L] = Rexx stack.pop()
stack.push(op[L] + op[R])
end
when '-' then do
say 'Operate\t\t\-'
op[R] = Rexx stack.pop()
op[L] = Rexx stack.pop()
stack.push(op[L] - op[R])
end
when '^' then do
say 'Operate\t\t\-'
op[R] = Rexx stack.pop()
op[L] = Rexx stack.pop()
-- If exponent is a whole number use Rexx built-in exponentiation operation, otherwise use Math.pow()
op[R] = op[R] + 0
if op[R].datatype('w') then stack.push(op[L] ** op[R])
else stack.push(Rexx Math.pow(op[L], op[R]))
end
otherwise do
if token.datatype('n') then do
say 'Push\t\t\-'
stack.push(token)
end
else do
say 'Error\t\t\-'
end
end
end tox
calc = Rexx
say stack.toString
end rpn
say
calc = stack.toString
return calc
</syntaxhighlight>
{{out}}
<pre>
Input Operation Stack after
3 Push [3]
4 Push [4, 3]
2 Push [2, 4, 3]
* Operate [8, 3]
1 Push [1, 8, 3]
5 Push [5, 1, 8, 3]
- Operate [-4, 8, 3]
2 Push [2, -4, 8, 3]
3 Push [3, 2, -4, 8, 3]
^ Operate [8, -4, 8, 3]
^ Operate [65536, 8, 3]
/ Operate [0.0001220703125, 3]
+ Operate [3.0001220703125]
3 4 2 * 1 5 - 2 3 ^ ^ / +: [3.0001220703125]
</pre>
=={{header|Nim}}==
{{trans|Python}}
<syntaxhighlight lang="nim">import math, rdstdin, strutils, tables
type Stack = seq[float]
proc opPow(s: var Stack) =
let b = s.pop
let a = s.pop
s.add a.pow b
proc opMul(s: var Stack) =
let b = s.pop
let a = s.pop
s.add a * b
proc opDiv(s: var Stack) =
let b = s.pop
let a = s.pop
s.add a / b
proc opAdd(s: var Stack) =
let b = s.pop
let a = s.pop
s.add a + b
proc opSub(s: var Stack) =
let b = s.pop
let a = s.pop
s.add a - b
proc opNum(s: var Stack; num: float) =
s.add num
let ops = toTable({"^": opPow,
"*": opMul,
"/": opDiv,
"+": opAdd,
"-": opSub})
proc getInput(inp = ""): seq[string] =
var inp = inp
if inp.len == 0:
inp = readLineFromStdin "Expression: "
result = inp.strip.split
proc rpnCalc(tokens: seq[string]): seq[seq[string]] =
var s: Stack
result = @[@["TOKEN","ACTION","STACK"]]
for token in tokens:
var action = ""
if ops.hasKey token:
action = "Apply op to top of stack"
ops[token](s)
else:
action = "Push num onto top of stack"
s.opNum token.parseFloat
result.add(@[token, action, s.join(" ")])
let rpn = "3 4 2 * 1 5 - 2 3 ^ ^ / +"
echo "For RPN expression: ", rpn
let rp = rpnCalc rpn.getInput
var maxColWidths = newSeq[int](rp[0].len)
for i in 0 .. rp[0].high:
for x in rp:
maxColWidths[i] = max(maxColWidths[i], x[i].len + 3)
for x in rp:
for i, y in x:
stdout.write y.alignLeft(maxColWidths[i])
echo ""</syntaxhighlight>
{{out}}
<pre>For RPN expression: 3 4 2 * 1 5 - 2 3 ^ ^ / +
TOKEN ACTION STACK
3 Push num onto top of stack 3.0
4 Push num onto top of stack 3.0 4.0
2 Push num onto top of stack 3.0 4.0 2.0
* Apply op to top of stack 3.0 8.0
1 Push num onto top of stack 3.0 8.0 1.0
5 Push num onto top of stack 3.0 8.0 1.0 5.0
- Apply op to top of stack 3.0 8.0 -4.0
2 Push num onto top of stack 3.0 8.0 -4.0 2.0
3 Push num onto top of stack 3.0 8.0 -4.0 2.0 3.0
^ Apply op to top of stack 3.0 8.0 -4.0 8.0
^ Apply op to top of stack 3.0 8.0 65536.0
/ Apply op to top of stack 3.0 0.0001220703125
+ Apply op to top of stack 3.0001220703125 </pre>
=={{header|Objeck}}==
<syntaxhighlight lang="objeck">
use IO;
use Struct;
bundle Default {
class RpnCalc {
function : Main(args : String[]) ~ Nil {
Caculate("3 4 2 * 1 5 - 2 3 ^ ^ / +");
}
function : native : Caculate(rpn : String) ~ Nil {
rpn->PrintLine();
tokens := rpn->Split(" ");
stack := FloatVector->New();
each(i : tokens) {
token := tokens[i]->Trim();
if(token->Size() > 0) {
if(token->Get(0)->IsDigit()) {
stack->AddBack(token->ToFloat());
}
else {
right := stack->Get(stack->Size() - 1); stack->RemoveBack();
left := stack->Get(stack->Size() - 1); stack->RemoveBack();
select(token->Get(0)) {
label '+': {
stack->AddBack(left + right);
}
label '-': {
stack->AddBack(left - right);
}
label '*': {
stack->AddBack(left * right);
}
label '/': {
stack->AddBack(left / right);
}
label '^': {
stack->AddBack(right->Power(left));
}
};
};
PrintStack(stack);
};
};
Console->Print("result: ")->PrintLine(stack->Get(0));
}
function : PrintStack(stack : FloatVector) ~ Nil {
" ["->Print();
each(i : stack) {
stack->Get(i)->Print();
if(i + 1< stack->Size()) {
", "->Print();
};
};
']'->PrintLine();
}
}
}
</syntaxhighlight>
{{out}}
<pre>
3 4 2 * 1 5 - 2 3 ^ ^ / +
[3]
[3, 4]
[3, 4, 2]
[3, 8]
[3, 8, 1]
[3, 8, 1, 5]
[3, 8, -4]
[3, 8, -4, 2]
[3, 8, -4, 2, 3]
[3, 8, -4, 8]
[3, 8, 65536]
[3, 0.00012207]
[3.00012]
result: 3.00012
</pre>
=={{header|OCaml}}==
<syntaxhighlight lang="ocaml">(* binop : ('a -> 'a -> 'a) -> 'a list -> 'a list *)
let binop op = function
| b::a::r -> (op a b)::r
| _ -> failwith "invalid expression"
(* interp : float list -> string -> string * float list *)
let interp s = function
| "+" -> "add", binop ( +. ) s
| "-" -> "subtr", binop ( -. ) s
| "*" -> "mult", binop ( *. ) s
| "/" -> "divide", binop ( /. ) s
| "^" -> "exp", binop ( ** ) s
| str -> "push", (float_of_string str) :: s
(* interp_and_show : float list -> string -> float list *)
let interp_and_show s inp =
let op,s' = interp s inp in
Printf.printf "%s\t%s\t" inp op;
List.(iter (Printf.printf "%F ") (rev s'));
print_newline ();
s'
(* rpn_eval : string -> float list *)
let rpn_eval str =
Printf.printf "Token\tAction\tStack\n";
let ss = Str.(split (regexp_string " ") str) in
List.fold_left interp_and_show [] ss</syntaxhighlight>
Evaluation of the test expression:
<pre>
# rpn_eval "3 4 2 * 1 5 - 2 3 ^ ^ / +";;
Token Action Stack
3 push 3.
4 push 3. 4.
2 push 3. 4. 2.
* mult 3. 8.
1 push 3. 8. 1.
5 push 3. 8. 1. 5.
- subtr 3. 8. -4.
2 push 3. 8. -4. 2.
3 push 3. 8. -4. 2. 3.
^ exp 3. 8. -4. 8.
^ exp 3. 8. 65536.
/ divide 3. 0.0001220703125
+ add 3.00012207031
- : float list = [3.0001220703125]
</pre>
=={{header|Oforth}}==
Oforth uses RPN and natively parse RPN.
<syntaxhighlight lang="oforth">"3 4 2 * 1 5 - 2 3 ^ ^ / +" eval println</syntaxhighlight>
{{out}}
<pre>
3
</pre>
To show the changes in the stack, we can use .l after evaluating each word :
<syntaxhighlight lang="oforth">: rpn(s) { s words apply(#[ eval .l ]) }
rpn("3 4 2 * 1 5 - 2 3 ^ ^ / +")</syntaxhighlight>
{{out}}
<pre>
3 |
3 | 4 |
3 | 4 | 2 |
3 | 8 |
3 | 8 | 1 |
3 | 8 | 1 | 5 |
3 | 8 | -4 |
3 | 8 | -4 | 2 |
3 | 8 | -4 | 2 | 3 |
3 | 8 | -4 | 8 |
3 | 8 | 65536 |
3 | 0 |
3 |
</pre>
=={{header|ooRexx}}==
<syntaxhighlight lang="oorexx">/* ooRexx *************************************************************
* 10.11.2012 Walter Pachl translated from PL/I via REXX
**********************************************************************/
fid='rpl.txt'
ex=linein(fid)
Say 'Input:' ex
/* ex=' 3 4 2 * 1 5 - 2 3 ^ ^ / +' */
Numeric Digits 15
expr=''
st=.circularqueue~new(100)
Say 'Stack contents:'
do While ex<>''
Parse Var ex ch +1 ex
expr=expr||ch;
if ch<>' ' then do
If pos(ch,'0123456789')>0 Then /* a digit goes onto stack */
st~push(ch)
Else Do /* an operator */
op=st~pull /* get top element */
select /* and modify the (now) top el*/
when ch='+' Then st~push(st~pull + op)
when ch='-' Then st~push(st~pull - op)
when ch='*' Then st~push(st~pull * op)
when ch='/' Then st~push(st~pull / op)
when ch='^' Then st~push(st~pull ** op)
end;
Say st~string(' ','L') /* show stack in LIFO order */
end
end
end
Say 'The reverse polish expression = 'expr
Say 'The evaluated expression = 'st~pull</syntaxhighlight>
{{out}}
<pre>
Input: 3 4 2 * 1 5 - 2 3 ^ ^ / +
Stack contents:
3 8
3 8 -4
3 8 -4 8
3 8 65536
3 0.0001220703125
3.0001220703125
The reverse polish expression = 3 4 2 * 1 5 - 2 3 ^ ^ / +
The evaluated expression = 3.0001220703125
</pre>
=={{header|PARI/GP}}==
Due to the nature of the language, it is not trivial to process an expression as a simple space-separated string. Though, this could be done if one calls an external shell program such as <code>sed</code> and pipes the result back hither.
<syntaxhighlight lang="parigp">estack = [];
epush(x) = {
estack = vector(#estack + 1, i, if(i <= #estack, estack[i], x));
return(#estack);
};
epop() = {
local(val = estack[#estack]);
estack = vector(#estack - 1, i, estack[i]);
return(val);
};
registerRPNToken(t) = {
local(o1, o2);
if(type(t) == "t_STR",
if(t == "+", o2 = epop(); o1 = epop(); epush(o1 + o2),
if(t == "-", o2 = epop(); o1 = epop(); epush(o1 - o2),
if(t == "*", o2 = epop(); o1 = epop(); epush(o1 * o2),
if(t == "/", o2 = epop(); o1 = epop(); epush(o1 / o2),
if(t == "%", o2 = epop(); o1 = epop(); epush(o1 % o2),
if(t == "^", o2 = epop(); o1 = epop(); epush(o1 ^ o2)
)))))),
if(type(t) == "t_INT" || type(t) == "t_REAL" || type(t) == "t_FRAC",
epush(t))
);
print(estack);
};
parseRPN(s) = {
estack = [];
for(i = 1, #s, registerRPNToken(s[i]));
if(#estack > 1, error("Malformed postfix expression."));
return(estack[1]);
};
parseRPN([3, 4, 2, "*", 1, 5, "-", 2, 3, "^", "^", "/", "+"]); \\ Our input expression</syntaxhighlight>
===Output===
<syntaxhighlight lang="text">[3]
[3, 4]
[3, 4, 2]
[3, 8]
[3, 8, 1]
[3, 8, 1, 5]
[3, 8, -4]
[3, 8, -4, 2]
[3, 8, -4, 2, 3]
[3, 8, -4, 8]
[3, 8, 65536]
[3, 1/8192]
[24577/8192]</syntaxhighlight>
Whenever possible, PARI/GP tries to manipulate and return results in the simplest form it can. In this case, it deems fractions the most suitable form of output. Nonetheless, converting the fraction <code>24577/8192</code> yields <code>3.0001220703125</code> as expected.
=={{header|Perl}}==
<syntaxhighlight lang="perl">use strict;
use warnings;
use feature 'say';
my $number = '[+-]?(?:\.\d+|\d+(?:\.\d*)?)';
my $operator = '[-+*/^]';
my @tests = ('3 4 2 * 1 5 - 2 3 ^ ^ / +');
for (@tests) {
while (
s/ \s* ((?<left>$number)) # 1st operand
\s+ ((?<right>$number)) # 2nd operand
\s+ ((?<op>$operator)) # operator
(?:\s+|$) # more to parse, or done?
/
' '.evaluate().' ' # substitute results of evaluation
/ex
) {}
say;
}
sub evaluate {
(my $a = "($+{left})$+{op}($+{right})") =~ s/\^/**/;
say $a;
eval $a;
}</syntaxhighlight>
{{out}}
<pre>(4)*(2)
(1)-(5)
(2)**(3)
(-4)**(8)
(8)/(65536)
(3)+(0.0001220703125)
3.0001220703125</pre>
=={{header|Phix}}==
<!--<syntaxhighlight lang="phix">(phixonline)-->
<span style="color: #008080;">with</span> <span style="color: #008080;">javascript_semantics</span>
<span style="color: #008080;">procedure</span> <span style="color: #000000;">evalRPN</span><span style="color: #0000FF;">(</span><span style="color: #004080;">string</span> <span style="color: #000000;">s</span><span style="color: #0000FF;">)</span>
<span style="color: #004080;">sequence</span> <span style="color: #000000;">stack</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">{},</span>
<span style="color: #000000;">ops</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">split</span><span style="color: #0000FF;">(</span><span style="color: #000000;">s</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">for</span> <span style="color: #000000;">i</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span> <span style="color: #008080;">to</span> <span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">ops</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">do</span>
<span style="color: #004080;">string</span> <span style="color: #000000;">op</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">ops</span><span style="color: #0000FF;">[</span><span style="color: #000000;">i</span><span style="color: #0000FF;">]</span>
<span style="color: #008080;">switch</span> <span style="color: #000000;">op</span>
<span style="color: #008080;">case</span> <span style="color: #008000;">"+"</span><span style="color: #0000FF;">:</span> <span style="color: #000000;">stack</span><span style="color: #0000FF;">[-</span><span style="color: #000000;">2</span><span style="color: #0000FF;">]</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">stack</span><span style="color: #0000FF;">[-</span><span style="color: #000000;">2</span><span style="color: #0000FF;">]+</span><span style="color: #000000;">stack</span><span style="color: #0000FF;">[-</span><span style="color: #000000;">1</span><span style="color: #0000FF;">];</span> <span style="color: #000000;">stack</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">stack</span><span style="color: #0000FF;">[</span><span style="color: #000000;">1</span><span style="color: #0000FF;">..-</span><span style="color: #000000;">2</span><span style="color: #0000FF;">]</span>
<span style="color: #008080;">case</span> <span style="color: #008000;">"-"</span><span style="color: #0000FF;">:</span> <span style="color: #000000;">stack</span><span style="color: #0000FF;">[-</span><span style="color: #000000;">2</span><span style="color: #0000FF;">]</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">stack</span><span style="color: #0000FF;">[-</span><span style="color: #000000;">2</span><span style="color: #0000FF;">]-</span><span style="color: #000000;">stack</span><span style="color: #0000FF;">[-</span><span style="color: #000000;">1</span><span style="color: #0000FF;">];</span> <span style="color: #000000;">stack</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">stack</span><span style="color: #0000FF;">[</span><span style="color: #000000;">1</span><span style="color: #0000FF;">..-</span><span style="color: #000000;">2</span><span style="color: #0000FF;">]</span>
<span style="color: #008080;">case</span> <span style="color: #008000;">"*"</span><span style="color: #0000FF;">:</span> <span style="color: #000000;">stack</span><span style="color: #0000FF;">[-</span><span style="color: #000000;">2</span><span style="color: #0000FF;">]</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">stack</span><span style="color: #0000FF;">[-</span><span style="color: #000000;">2</span><span style="color: #0000FF;">]*</span><span style="color: #000000;">stack</span><span style="color: #0000FF;">[-</span><span style="color: #000000;">1</span><span style="color: #0000FF;">];</span> <span style="color: #000000;">stack</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">stack</span><span style="color: #0000FF;">[</span><span style="color: #000000;">1</span><span style="color: #0000FF;">..-</span><span style="color: #000000;">2</span><span style="color: #0000FF;">]</span>
<span style="color: #008080;">case</span> <span style="color: #008000;">"/"</span><span style="color: #0000FF;">:</span> <span style="color: #000000;">stack</span><span style="color: #0000FF;">[-</span><span style="color: #000000;">2</span><span style="color: #0000FF;">]</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">stack</span><span style="color: #0000FF;">[-</span><span style="color: #000000;">2</span><span style="color: #0000FF;">]/</span><span style="color: #000000;">stack</span><span style="color: #0000FF;">[-</span><span style="color: #000000;">1</span><span style="color: #0000FF;">];</span> <span style="color: #000000;">stack</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">stack</span><span style="color: #0000FF;">[</span><span style="color: #000000;">1</span><span style="color: #0000FF;">..-</span><span style="color: #000000;">2</span><span style="color: #0000FF;">]</span>
<span style="color: #008080;">case</span> <span style="color: #008000;">"^"</span><span style="color: #0000FF;">:</span> <span style="color: #000000;">stack</span><span style="color: #0000FF;">[-</span><span style="color: #000000;">2</span><span style="color: #0000FF;">]</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">power</span><span style="color: #0000FF;">(</span><span style="color: #000000;">stack</span><span style="color: #0000FF;">[-</span><span style="color: #000000;">2</span><span style="color: #0000FF;">],</span><span style="color: #000000;">stack</span><span style="color: #0000FF;">[-</span><span style="color: #000000;">1</span><span style="color: #0000FF;">]);</span> <span style="color: #000000;">stack</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">stack</span><span style="color: #0000FF;">[</span><span style="color: #000000;">1</span><span style="color: #0000FF;">..-</span><span style="color: #000000;">2</span><span style="color: #0000FF;">]</span>
<span style="color: #008080;">default</span> <span style="color: #0000FF;">:</span> <span style="color: #000000;">stack</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">append</span><span style="color: #0000FF;">(</span><span style="color: #000000;">stack</span><span style="color: #0000FF;">,</span><span style="color: #7060A8;">scanf</span><span style="color: #0000FF;">(</span><span style="color: #000000;">op</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"%d"</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: #008080;">end</span> <span style="color: #008080;">switch</span>
<span style="color: #0000FF;">?{</span><span style="color: #000000;">op</span><span style="color: #0000FF;">,</span><span style="color: #000000;">stack</span><span style="color: #0000FF;">}</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">for</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">procedure</span>
<span style="color: #000000;">evalRPN</span><span style="color: #0000FF;">(</span><span style="color: #008000;">"3 4 2 * 1 5 - 2 3 ^ ^ / +"</span><span style="color: #0000FF;">)</span>
<!--</syntaxhighlight>-->
{{out}}
<pre>
{"3",{3}}
{"4",{3,4}}
{"2",{3,4,2}}
{"*",{3,8}}
{"1",{3,8,1}}
{"5",{3,8,1,5}}
{"-",{3,8,-4}}
{"2",{3,8,-4,2}}
{"3",{3,8,-4,2,3}}
{"^",{3,8,-4,8}}
{"^",{3,8,65536}}
{"/",{3,0.0001220703}}
{"+",{3.00012207}}
</pre>
=={{header|PHP}}==
<syntaxhighlight lang="php">
<?php
function rpn($postFix){
$stack = Array();
echo "Input\tOperation\tStack\tafter\n" ;
$token = explode(" ", trim($postFix));
$count = count($token);
for($i = 0 ; $i<$count;$i++)
{
echo $token[$i] ." \t";
$tokenNum = "";
if (is_numeric($token[$i])) {
echo "Push";
array_push($stack,$token[$i]);
}
else
{
echo "Operate";
$secondOperand = end($stack);
array_pop($stack);
$firstOperand = end($stack);
array_pop($stack);
if ($token[$i] == "*")
array_push($stack,$firstOperand * $secondOperand);
else if ($token[$i] == "/")
array_push($stack,$firstOperand / $secondOperand);
else if ($token[$i] == "-")
array_push($stack,$firstOperand - $secondOperand);
else if ($token[$i] == "+")
array_push($stack,$firstOperand + $secondOperand);
else if ($token[$i] == "^")
array_push($stack,pow($firstOperand,$secondOperand));
else {
die("Error");
}
}
echo "\t\t" . implode(" ", $stack) . "\n";
}
return end($stack);
}
echo "Compute Value: " . rpn("3 4 2 * 1 5 - 2 3 ^ ^ / + ");
?>
</syntaxhighlight>
{{out}}
<pre>
Input Operation Stack after
3 Push 3
4 Push 3 4
2 Push 3 4 2
* Operate 3 8
1 Push 3 8 1
5 Push 3 8 1 5
- Operate 3 8 -4
2 Push 3 8 -4 2
3 Push 3 8 -4 2 3
^ Operate 3 8 -4 8
^ Operate 3 8 65536
/ Operate 3 0.0001220703125
+ Operate 3.0001220703125
Compute Value: 3.0001220703125
</pre>
=={{header|PicoLisp}}==
This is an integer-only calculator:
<syntaxhighlight lang="picolisp">(de rpnCalculator (Str)
(let (^ ** Stack) # Define '^' from the built-in '**'
(prinl "Token Stack")
(for Token (str Str "*+-/\^")
(if (num? Token)
(push 'Stack @)
(set (cdr Stack)
((intern Token) (cadr Stack) (pop 'Stack)) ) )
(prin Token)
(space 6)
(println Stack) )
(println (car Stack)) ) )</syntaxhighlight>
Test (note that the top-of-stack is in the left-most position):
<syntaxhighlight lang="picolisp">: (rpnCalculator "3 4 2 * 1 5 - 2 3 \^ \^ / +")
Token Stack
3 (3)
4 (4 3)
2 (2 4 3)
* (8 3)
1 (1 8 3)
5 (5 1 8 3)
- (-4 8 3)
2 (2 -4 8 3)
3 (3 2 -4 8 3)
^ (8 -4 8 3)
^ (65536 8 3)
/ (0 3)
+ (3)
3
-> 3</syntaxhighlight>
=={{header|PL/I}}==
<syntaxhighlight lang="pl/i">Calculator: procedure options (main); /* 14 Sept. 2012 */
declare expression character (100) varying initial ('');
declare ch character (1);
declare (stack controlled, operand) float (18);
declare in file input;
open file (in) title ('/CALCULAT.DAT,type(text),recsize(100)');
on endfile (in) go to done;
put ('Stack contents:');
main_loop:
do forever;
get file (in) edit (ch) (a(1));
expression = expression || ch;
if ch = ' ' then iterate;
select (ch);
when ('0', '1', '2', '3', '4', '5', '6', '7', '8', '9')
do; allocate stack; stack = ch; iterate main_loop; end;
when ('+') do; operand = stack; free stack; stack = stack + operand; end;
when ('-') do; operand = stack; free stack; stack = stack - operand; end;
when ('*') do; operand = stack; free stack; stack = stack * operand; end;
when ('/') do; operand = stack; free stack; stack = stack / operand; end;
when ('^') do; operand = stack; free stack; stack = stack ** operand; end;
end;
call show_stack;
end;
done:
put skip list ('The reverse polish expression = ' || expression);
put skip list ('The evaluated expression = ' || stack);
end Calculator;</syntaxhighlight>
<pre>
Stack contents:
3.0000000000 8.0000000000
3.0000000000 8.0000000000 -4.0000000000
3.0000000000 8.0000000000 -4.0000000000 8.0000000000
3.0000000000 8.0000000000 65536.0000000000
3.0000000000 0.0001220703
3.0001220703
The reverse polish expression = 3 4 2 * 1 5 - 2 3 ^ ^ / +
The evaluated expression = 3.00012207031250000E+0000
</pre>
The procedure to display the stack:
<pre>
/* As the stack is push-down pop-up, need to pop it to see what's inside. */
show_stack: procedure;
declare ts float (18) controlled;
do while (allocation(stack) > 0);
allocate ts; ts = stack; free stack;
end;
put skip;
do while (allocation(ts) > 0);
allocate stack; stack = ts; free ts; put edit (stack) (f(18,10));
end;
end show_stack;</pre>
=={{header|PL/SQL}}==
<syntaxhighlight lang="plsql">create or replace function rpn_calc(str varchar2) return number as
type num_aa is table of number index by pls_integer;
type num_stack is record (a num_aa, top pls_integer default 0);
ns num_stack;
pos1 integer := 1;
pos2 integer;
token varchar2(100);
op2 number;
procedure push(s in out nocopy num_stack, x number) is
begin
s.top := s.top + 1;
s.a(s.top) := x;
end;
function pop(s in out nocopy num_stack) return number is
x number;
begin
x := s.a(s.top);
s.top := s.top - 1;
return x;
end;
procedure print_stack(s num_stack) is -- for debugging only; remove from final version
ps varchar2(4000);
begin
for i in 1 .. s.top loop
ps := ps || s.a(i) || ' ';
end loop;
dbms_output.put_line('Stack: ' || rtrim(ps));
end;
begin
while pos1 <= length(str) loop
pos2 := instr(str || ' ', ' ', pos1);
token := substr(str, pos1, pos2 - pos1);
pos1 := pos2 + 1;
case token
when '+' then push(ns, pop(ns) + pop(ns));
when '-' then op2 := pop(ns); push(ns, pop(ns) - op2);
when '*' then push(ns, pop(ns) * pop(ns));
when '/' then op2 := pop(ns); push(ns, pop(ns) / op2);
when '^' then op2 := pop(ns); push(ns, power(pop(ns), op2));
else push(ns, to_number(token));
end case;
print_stack(ns); -- for debugging purposes only
end loop;
return pop(ns);
end rpn_calc;
/</syntaxhighlight>
Testing:
<syntaxhighlight lang="plsql">begin
dbms_output.put_line(chr(10) || 'Result: ' || rpn_calc('3 4 2 * 1 5 - 2 3 ^ ^ / +'));
end;
/</syntaxhighlight>
Output:
<pre>
Stack: 3
Stack: 3 4
Stack: 3 4 2
Stack: 3 8
Stack: 3 8 1
Stack: 3 8 1 5
Stack: 3 8 -4
Stack: 3 8 -4 2
Stack: 3 8 -4 2 3
Stack: 3 8 -4 8
Stack: 3 8 65536
Stack: 3 .0001220703125
Stack: 3.0001220703125
Result: 3.0001220703125
PL/SQL procedure successfully completed.
</pre>
=={{header|PowerShell}}==
<syntaxhighlight lang="powershell">
function Invoke-Rpn
{
<#
.SYNOPSIS
A stack-based evaluator for an expression in reverse Polish notation.
.DESCRIPTION
A stack-based evaluator for an expression in reverse Polish notation.
All methods in the Math and Decimal classes are available.
.PARAMETER Expression
A space separated, string of tokens.
.PARAMETER DisplayState
This switch shows the changes in the stack as each individual token is processed as a table.
.EXAMPLE
Invoke-Rpn -Expression "3 4 Max"
.EXAMPLE
Invoke-Rpn -Expression "3 4 Log2"
.EXAMPLE
Invoke-Rpn -Expression "3 4 2 * 1 5 - 2 3 ^ ^ / +"
.EXAMPLE
Invoke-Rpn -Expression "3 4 2 * 1 5 - 2 3 ^ ^ / +" -DisplayState
#>
[CmdletBinding()]
Param
(
[Parameter(Mandatory=$true)]
[AllowEmptyString()]
[string]
$Expression,
[Parameter(Mandatory=$false)]
[switch]
$DisplayState
)
Begin
{
function Out-State ([System.Collections.Stack]$Stack)
{
$array = $Stack.ToArray()
[Array]::Reverse($array)
$array | ForEach-Object -Process { Write-Host ("{0,-8:F3}" -f $_) -NoNewline } -End { Write-Host }
}
function New-RpnEvaluation
{
$stack = New-Object -Type System.Collections.Stack
$shortcuts = @{
"+" = "Add"; "-" = "Subtract"; "/" = "Divide"; "*" = "Multiply"; "%" = "Remainder"; "^" = "Pow"
}
:ARGUMENT_LOOP foreach ($argument in $args)
{
if ($DisplayState -and $stack.Count)
{
Out-State $stack
}
if ($shortcuts[$argument])
{
$argument = $shortcuts[$argument]
}
try
{
$stack.Push([decimal]$argument)
continue
}
catch
{
}
$argCountList = $argument -replace "(\D+)(\d*)",‘$2’
$operation = $argument.Substring(0, $argument.Length – $argCountList.Length)
foreach($type in [Decimal],[Math])
{
if ($definition = $type::$operation)
{
if (-not $argCountList)
{
$argCountList = $definition.OverloadDefinitions |
Foreach-Object { ($_ -split ", ").Count } |
Sort-Object -Unique
}
foreach ($argCount in $argCountList)
{
try
{
$methodArguments = $stack.ToArray()[($argCount–1)..0]
$result = $type::$operation.Invoke($methodArguments)
$null = 1..$argCount | Foreach-Object { $stack.Pop() }
$stack.Push($result)
continue ARGUMENT_LOOP
}
catch
{
## If error, try with the next number of arguments
}
}
}
}
}
if ($DisplayState -and $stack.Count)
{
Out-State $stack
if ($stack.Count)
{
Write-Host "`nResult = $($stack.Peek())"
}
}
else
{
$stack
}
}
}
Process
{
Invoke-Expression -Command "New-RpnEvaluation $Expression"
}
End
{
}
}
Invoke-Rpn -Expression "3 4 2 * 1 5 - 2 3 ^ ^ / +" -DisplayState
</syntaxhighlight>
{{Out}}
<pre>
3.000
3.000 4.000
3.000 4.000 2.000
3.000 8.000
3.000 8.000 1.000
3.000 8.000 1.000 5.000
3.000 8.000 -4.000
3.000 8.000 -4.000 2.000
3.000 8.000 -4.000 2.000 3.000
3.000 8.000 -4.000 8.000
3.000 8.000 65536.000
3.000 0.000
3.000
Result = 3.0001220703125
</pre>
=={{header|Prolog}}==
Works with SWI-Prolog.
<syntaxhighlight lang="prolog">rpn(L) :-
writeln('Token Action Stack'),
parse(L, [],[X] ,[]),
format('~nThe final output value is ~w~n', [X]).
% skip spaces
parse([X|L], St) -->
{char_type(X, white)},
parse(L, St).
% detect operators
parse([Op|L], [Y, X | St]) -->
{ is_op(Op, X, Y, V),
writef(' %s', [[Op]]),
with_output_to(atom(Str2), writef('Apply %s on top of stack', [[Op]])),
writef(' %35l', [Str2]),
writef('%w\n', [[V | St]])},
parse(L, [V | St]).
% detect number
parse([N|L], St) -->
{char_type(N, digit)},
parse_number(L, [N], St).
% string is finished
parse([], St) --> St.
% compute numbers
parse_number([N|L], NC, St) -->
{char_type(N, digit)},
parse_number(L, [N|NC], St).
parse_number(S, NC, St) -->
{ reverse(NC, RNC),
number_chars(V, RNC),
writef('%5r', [V]),
with_output_to(atom(Str2), writef('Push num %w on top of stack', [V])),
writef(' %35l', [Str2]),
writef('%w\n', [[V | St]])},
parse(S, [V|St]).
% defining operations
is_op(42, X, Y, V) :- V is X*Y.
is_op(43, X, Y, V) :- V is X+Y.
is_op(45, X, Y, V) :- V is X-Y.
is_op(47, X, Y, V) :- V is X/Y.
is_op(94, X, Y, V) :- V is X**Y.</syntaxhighlight>
{{out}}
<pre>5 ?- rpn("3 4 2 * 1 5 - 2 3 ^ ^ / +").
Token Action Stack
3 'Push num 3 on top of stack' [3]
4 'Push num 4 on top of stack' [4,3]
2 'Push num 2 on top of stack' [2,4,3]
* 'Apply * on top of stack' [8,3]
1 'Push num 1 on top of stack' [1,8,3]
5 'Push num 5 on top of stack' [5,1,8,3]
- 'Apply - on top of stack' [-4,8,3]
2 'Push num 2 on top of stack' [2,-4,8,3]
3 'Push num 3 on top of stack' [3,2,-4,8,3]
^ 'Apply ^ on top of stack' [8,-4,8,3]
^ 'Apply ^ on top of stack' [65536,8,3]
/ 'Apply / on top of stack' [0.0001220703125,3]
+ 'Apply + on top of stack' [3.0001220703125]
The final output value is 3.0001220703125
true .</pre>
=={{header|Python}}==
=== Version 1 ===
<syntaxhighlight lang="python">def op_pow(stack):
b = stack.pop(); a = stack.pop()
stack.append( a ** b )
def op_mul(stack):
b = stack.pop(
stack.append( a * b )
def op_div(stack):
b = stack.pop(
stack.append( a / b )
def op_add(stack):
b = stack.pop(
stack.append( a + b )
def op_sub(stack):
b = stack.pop(
stack.append( a - b )
def op_num(stack, num):
Line 69 ⟶ 5,337:
print( 'For RPN expression: %r\n' % rpn )
rp = rpn_calc(get_input(rpn))
maxcolwidths = [max(len(
row = rp[0]
print( ' '.join('{cell:^{width}}'.format(width=width, cell=cell) for (width, cell) in zip(maxcolwidths, row)))
Line 75 ⟶ 5,343:
print( ' '.join('{cell:<{width}}'.format(width=width, cell=cell) for (width, cell) in zip(maxcolwidths, row)))
print('\n The final output value is: %r' % rp[-1][2])</
{{out}}
<pre>For RPN expression: '3 4 2 * 1 5 - 2 3 ^ ^ / +'
Line 97 ⟶ 5,365:
The final output value is: '3.0001220703125'</pre>
==
<syntaxhighlight lang="python">a=[]
b={'+': lambda x,y: y+x, '-': lambda x,y: y-x, '*': lambda x,y: y*x,'/': lambda x,y:y/x,'^': lambda x,y:y**x}
for c in '3 4 2 * 1 5 - 2 3 ^ ^ / +'.split():
if c in b: a.append(b[c](a.pop(),a.pop()))
else: a.append(float(c))
print c, a</syntaxhighlight>
{{out}}
<pre>3 [3.0]
4 [3.0, 4.0]
2 [3.0, 4.0, 2.0]
* [3.0, 8.0]
1 [3.0, 8.0, 1.0]
5 [3.0, 8.0, 1.0, 5.0]
- [3.0, 8.0, -4.0]
2 [3.0, 8.0, -4.0, 2.0]
3 [3.0, 8.0, -4.0, 2.0, 3.0]
^ [3.0, 8.0, -4.0, 8.0]
^ [3.0, 8.0, 65536.0]
/ [3.0, 0.0001220703125]
+ [3.0001220703125]</pre>
=={{header|Quackery}}==
On an historical note, the first step in developing the language Quackery, as is the case with many stack based/reverse Polish/concatenative languages, was coding an RP calculator much like this one. With the minor difference that the exponentiation operator in Quackery is <code>**</code> rather than <code>^</code> (which is bitwise xor) the test string <code>"3 4 2 * 1 5 - 2 3 ^ ^ / +"</code> ''is'' Quackery code, and could be compiled and evaluated (in the Quackery vernacular, "built and done") by passing it to the Quackery word <code>quackery</code>, which is defined in Quackery as
<code>[ build do ] is quackery ( $ --> [ )</code>, which neatly sums up the language.
Here we interpret rather than compile the code, using a <code>switch</code> statement (not actually defined in Quackery, so the code to define it is included), and using the provided ancillary stack <code>temp</code> to make the stack activity explicit.
(If the gentle gatekeepers will permit a moment of shameless self-promotion… If you are interested in stack processors or concatenative languages, you may wish to consider that Quackery was designed with the intent of being an entry level language suitable for educational and hobbyist use, accessible at the code level by virtue of being coded in (mostly) non-idiomatic Python (24k source) and Quackery (another 24k of course) with the Python code emphasising a straightforward approach and the use of simple algorithms for the sake of legibility in preference to efficiency.)
<syntaxhighlight lang="quackery">
[ stack ] is switch.arg ( --> [ )
[ switch.arg put ] is switch ( x --> )
[ switch.arg release ] is otherwise ( --> )
[ switch.arg share
!= iff ]else[ done
otherwise
]'[ do ]done[ ] is case ( x --> )
[ say "Applying: "
swap echo$ sp
temp take
temp take
swap rot do
temp put ] is apply ( $ x --> )
[ say "Pushing: " dup echo$ sp
$->n drop temp put ] is isnumber ( $ --> )
[ temp copy echo cr ] is display ( --> )
[ nest$ witheach
[ dup switch
[ $ '+' case [ ' + apply ]
$ '-' case [ ' - apply ]
$ '*' case [ ' * apply ]
$ '/' case [ ' / apply ]
$ '^' case [ ' ** apply ]
otherwise [ isnumber ] ]
display ]
temp take ] is rpncalc ( $ --> n )
$ "3 4 2 * 1 5 - 2 3 ^ ^ / +" rpncalc
say "Result: " echo</syntaxhighlight>
{{out}}
<pre>Pushing: 3 [ stack 3 ]
Pushing: 4 [ stack 3 4 ]
Pushing: 2 [ stack 3 4 2 ]
Applying: * [ stack 3 8 ]
Pushing: 1 [ stack 3 8 1 ]
Pushing: 5 [ stack 3 8 1 5 ]
Applying: - [ stack 3 8 -4 ]
Pushing: 2 [ stack 3 8 -4 2 ]
Pushing: 3 [ stack 3 8 -4 2 3 ]
Applying: ^ [ stack 3 8 -4 8 ]
Applying: ^ [ stack 3 8 65536 ]
Applying: / [ stack 3 0 ]
Applying: + [ stack 3 ]
Result: 3</pre>
=={{header|Racket}}==
<syntaxhighlight lang="racket">
#lang racket
(define (calculate-RPN expr)
(for/fold ([stack '()]) ([token expr])
(printf "~a\t -> ~a~N" token stack)
(match* (token stack)
[((? number? n) s) (cons n s)]
[('+ (list x y s ___)) (cons (+ x y) s)]
[('- (list x y s ___)) (cons (- y x) s)]
[('* (list x y s ___)) (cons (* x y) s)]
[('/ (list x y s ___)) (cons (/ y x) s)]
[('^ (list x y s ___)) (cons (expt y x) s)]
[(x s) (error "calculate-RPN: Cannot calculate the expression:"
(reverse (cons x s)))])))
</syntaxhighlight>
Test case
<pre>
-> (calculate-RPN '(3.0 4 2 * 1 5 - 2 3 ^ ^ / +))
3.0 -> ()
4 -> (3.0)
2 -> (4 3.0)
* -> (2 4 3.0)
1 -> (8 3.0)
5 -> (1 8 3.0)
- -> (5 1 8 3.0)
2 -> (-4 8 3.0)
3 -> (2 -4 8 3.0)
^ -> (3 2 -4 8 3.0)
^ -> (8 -4 8 3.0)
/ -> (65536 8 3.0)
+ -> (1/8192 3.0)
3.0001220703125
</pre>
Reading from a string:
<syntaxhighlight lang="racket">
(calculate-RPN (in-port read (open-input-string "3.0 4 2 * 1 5 - 2 3 ^ ^ / +")))
</syntaxhighlight>
=={{header|Raku}}==
(formerly Perl 6)
{{works with|rakudo|2015-09-25}}
<syntaxhighlight lang="raku" line>my $proggie = '3 4 2 * 1 5 - 2 3 ^ ^ / +';
class RPN is Array {
method binop(&op) { self.push: self.pop R[&op] self.pop }
method run($p) {
for $p.words {
say "$_ ({self})";
when /\d/ { self.push: $_ }
when '+' { self.binop: &[+] }
when '-' { self.binop: &[-] }
when '*' { self.binop: &[*] }
when '/' { self.binop: &[/] }
when '^' { self.binop: &[**] }
default { die "$_ is bogus" }
}
say self;
}
}
RPN.new.run($proggie);</syntaxhighlight>
{{out}}
<pre>3 ()
4 (3)
2 (3 4)
* (3 4 2)
1 (3 8)
5 (3 8 1)
- (3 8 1 5)
2 (3 8 -4)
3 (3 8 -4 2)
^ (3 8 -4 2 3)
^ (3 8 -4 8)
/ (3 8 65536)
+ (3 0.0001220703125)
3.0001220703125</pre>
=={{header|REXX}}==
===version 1===
<syntaxhighlight lang="rexx">/* REXX ***************************************************************
* 09.11.2012 Walter Pachl translates from PL/I
**********************************************************************/
fid='rpl.txt'
ex=linein(fid)
Say 'Input:' ex
/* ex=' 3 4 2 * 1 5 - 2 3 ^ ^ / +' */
Numeric Digits 15
expr=''
st.=0
Say 'Stack contents:'
do While ex<>''
Parse Var ex ch +1 ex
expr=expr||ch;
if ch<>' ' then do
select
When pos(ch,'0123456789')>0 Then Do
Call stack ch
Iterate
End
when ch='+' Then do; operand=getstack(); st.sti = st.sti + operand; end;
when ch='-' Then do; operand=getstack(); st.sti = st.sti - operand; end;
when ch='*' Then do; operand=getstack(); st.sti = st.sti * operand; end;
when ch='/' Then do; operand=getstack(); st.sti = st.sti / operand; end;
when ch='^' Then do; operand=getstack(); st.sti = st.sti ** operand; end;
end;
call show_stack
end
end
Say 'The reverse polish expression = 'expr
Say 'The evaluated expression = 'st.1
Exit
stack: Procedure Expose st.
/* put the argument on top of the stack */
z=st.0+1
st.z=arg(1)
st.0=z
Return
getstack: Procedure Expose st. sti
/* remove and return the stack's top element */
z=st.0
stk=st.z
st.0=st.0-1
sti=st.0
Return stk
show_stack: procedure Expose st.
/* show the stack's contents */
ol=''
do i=1 To st.0
ol=ol format(st.i,5,10)
End
Say ol
Return</syntaxhighlight>
{{out}}
<pre>
Input: 3 4 2 * 1 5 - 2 3 ^ ^ / +
Stack contents:
3.0000000000 8.0000000000
3.0000000000 8.0000000000 -4.0000000000
3.0000000000 8.0000000000 -4.0000000000 8.0000000000
3.0000000000 8.0000000000 65536.0000000000
3.0000000000 0.0001220703
3.0001220703
The reverse polish expression = 3 4 2 * 1 5 - 2 3 ^ ^ / +
The evaluated expression = 3.0001220703125
</pre>
===version 2===
This REXX version handles tokens (not characters) so that the RPN could be (for instance):
:::: <big><big> 3.0 .4e1 2e0 * +1. 5 - 2 3 ** ** / + </big></big>
which is the essentially the same as the default used by the REXX program.
<syntaxhighlight lang="rexx">/*REXX program evaluates a ═════ Reverse Polish notation (RPN) ═════ expression. */
parse arg x /*obtain optional arguments from the CL*/
if x='' then x= "3 4 2 * 1 5 - 2 3 ^ ^ / +" /*Not specified? Then use the default.*/
tokens=words(x) /*save the number of tokens " ". */
showSteps=1 /*set to 0 if working steps not wanted.*/
ox=x /*save the original value of X. */
do i=1 for tokens; @.i=word(x,i) /*assign the input tokens to an array. */
end /*i*/
x=space(x) /*remove any superfluous blanks in X. */
L=max(20, length(x)) /*use 20 for the minimum display width.*/
numeric digits L /*ensure enough decimal digits for ans.*/
say center('operand', L, "─") center('stack', L+L, "─") /*display title*/
$= /*nullify the stack (completely empty).*/
do k=1 for tokens; ?=@.k; ??=? /*process each token from the @. list.*/
#=words($) /*stack the count (the number entries).*/
if datatype(?,'N') then do; $=$ ?; call show "add to───►stack"; iterate; end
if ?=='^' then ??= "**" /*REXXify ^ ───► ** (make legal).*/
interpret 'y='word($,#-1) ?? word($,#) /*compute via the famous REXX INTERPRET*/
if datatype(y,'N') then y=y/1 /*normalize the number with ÷ by unity.*/
$=subword($, 1, #-2) y /*rebuild the stack with the answer. */
call show ? /*display steps (tracing into), maybe.*/
end /*k*/
say /*display a blank line, better perusing*/
say ' RPN input:' ox; say " answer──►"$ /*display original input; display ans.*/
parse source upper . y . /*invoked via C.L. or via a REXX pgm?*/
if y=='COMMAND' | \datatype($,"W") then exit /*stick a fork in it, we're all done. */
else exit $ /*return the answer ───► the invoker.*/
/*──────────────────────────────────────────────────────────────────────────────────────*/
show: if showSteps then say center(arg(1), L) left(space($), L); return</syntaxhighlight>
'''output''' when using the default input:
<pre>
─────────operand───────── ──────────────────────stack───────────────────────
add to───►stack 3
add to───►stack 3 4
add to───►stack 3 4 2
* 3 8
add to───►stack 3 8 1
add to───►stack 3 8 1 5
- 3 8 -4
add to───►stack 3 8 -4 2
add to───►stack 3 8 -4 2 3
^ 3 8 -4 8
^ 3 8 65536
/ 3 0.0001220703125
+ 3.0001220703125
answer───► 3.0001220703125
</pre>
===version 3 (error checking)===
This REXX version is the same as above, but also checks for various errors and allows more operators:
::* checks for illegal operator
::* checks for illegal number
::* checks for illegal bit (logical) values
::* checks for malformed RPN expression
::* checks for division by zero
::* allows alternative exponentiation symbol <big>**</big>
::* allows logical operations <big>& </big> <big>&&</big> <big>|</big>
::* allows alternative division symbol <big>÷</big>
::* allows integer division <big>%</big>
::* allows remainder division <big>//</big>
::* allows concatenation <big>||</big>
<syntaxhighlight lang="rexx">/*REXX program evaluates a ═════ Reverse Polish notation (RPN) ═════ expression. */
parse arg x /*obtain optional arguments from the CL*/
if x='' then x= "3 4 2 * 1 5 - 2 3 ^ ^ / +" /*Not specified? Then use the default.*/
tokens=words(x) /*save the number of tokens " ". */
showSteps=1 /*set to 0 if working steps not wanted.*/
ox=x /*save the original value of X. */
do i=1 for tokens; @.i=word(x,i) /*assign the input tokens to an array. */
end /*i*/
x=space(x) /*remove any superfluous blanks in X. */
L=max(20, length(x)) /*use 20 for the minimum display width.*/
numeric digits L /*ensure enough decimal digits for ans.*/
say center('operand', L, "─") center('stack', L+L, "─") /*display title*/
Dop= '/ // % ÷'; Bop='& | &&' /*division operators; binary operands.*/
Aop= '- + * ^ **' Dop Bop; Lop=Aop "||" /*arithmetic operators; legal operands.*/
$= /*nullify the stack (completely empty).*/
do k=1 for tokens; ?=@.k; ??=? /*process each token from the @. list.*/
#=words($); b=word($, max(1, #) ) /*the stack count; the last entry. */
a=word($, max(1, #-1) ) /*stack's "first" operand. */
division =wordpos(?, Dop)\==0 /*flag: doing a some kind of division.*/
arith =wordpos(?, Aop)\==0 /*flag: doing arithmetic. */
bitOp =wordpos(?, Bop)\==0 /*flag: doing some kind of binary oper*/
if datatype(?, 'N') then do; $=$ ?; call show "add to───►stack"; iterate; end
if wordpos(?, Lop)==0 then do; $=e 'illegal operator:' ?; leave; end
if w<2 then do; $=e 'illegal RPN expression.'; leave; end
if ?=='^' then ??= "**" /*REXXify ^ ──► ** (make it legal). */
if ?=='÷' then ??= "/" /*REXXify ÷ ──► / (make it legal). */
if division & b=0 then do; $=e 'division by zero.' ; leave; end
if bitOp & \isBit(a) then do; $=e "token isn't logical: " a; leave; end
if bitOp & \isBit(b) then do; $=e "token isn't logical: " b; leave; end
interpret 'y=' a ?? b /*compute with two stack operands*/
if datatype(y, 'W') then y=y/1 /*normalize the number with ÷ by unity.*/
_=subword($, 1, #-2); $=_ y /*rebuild the stack with the answer. */
call show ? /*display (possibly) a working step. */
end /*k*/
say /*display a blank line, better perusing*/
if word($,1)==e then $= /*handle the special case of errors. */
say ' RPN input:' ox; say " answer───►"$ /*display original input; display ans.*/
parse source upper . y . /*invoked via C.L. or via a REXX pgm?*/
if y=='COMMAND' | \datatype($,"W") then exit /*stick a fork in it, we're all done. */
else exit $ /*return the answer ───► the invoker.*/
/*──────────────────────────────────────────────────────────────────────────────────────*/
isBit: return arg(1)==0 | arg(1)==1 /*returns 1 if arg1 is a binary bit*/
show: if showSteps then say center(arg(1), L) left(space($), L); return</syntaxhighlight>
'''output''' is identical to the 2<sup>nd</sup> REXX version.
<br><br>
=={{header|RPL}}==
'''Straightforward '''
"3 4 2 * 1 5 - 2 3 ^ ^ / +" STR→
{{out}}
<pre>
1: 3.00012207031
</pre>
'''Step-by-step'''
<code>LEXER</code> is defined at [[Parsing/Shunting-yard algorithm#RPL|Parsing/Shunting-yard algorithm]]
{{works with|Halcyon Calc|4.2.7}}
≪ <span style="color:blue">LEXER</span> "" { } 0 → postfix token steps depth
≪ 1 postfix SIZE '''FOR''' j
postfix j GET 'token' STO
'''IF''' token TYPE '''THEN'''
"≪" token + "≫" + STR→ EVAL
depth 1 - ‘depth’ STO
'''ELSE'''
token
depth 1 + ‘depth’ STO
'''END'''
depth DUPN depth →LIST
steps "Token " token →STR + " → " + ROT →STR +
+ ‘steps’ STO
'''NEXT''' steps
≫ ≫ '<span style="color:blue">CALC</span>' STO
"3 4 2 * 1 5 - 2 3 ^ ^ / +" <span style="color:blue">CALC</span>
{{out}}
<pre>
2: 3.00012207031
1: { "Token 3 → { 3 }"
"Token 4 → { 3 4 }"
"Token 2 → { 3 4 2 }"
"Token * → { 3 8 }"
"Token 1 → { 3 8 1 }"
"Token 5 → { 3 8 1 5 }"
"Token - → { 3 8 -4 }"
"Token 2 → { 3 8 -4 2 }"
"Token 3 → { 3 8 -4 2 3 }"
"Token ^ → { 3 8 -4 8 }"
"Token ^ → { 3 8 65536 }"
"Token / → { 3 1.220703125E-04 }"
"Token + → { 3.00012207031 }" }
</pre>
Additional spaces and CR characters have been added to the above output to enhance readability.
=={{header|Ruby}}==
See [[Parsing/RPN/Ruby]]
<syntaxhighlight lang="ruby">rpn = RPNExpression("3 4 2 * 1 5 - 2 3 ^ ^ / +")
value = rpn.eval</syntaxhighlight>
{{out}}
<pre>for RPN expression: 3 4 2 * 1 5 - 2 3 ^ ^ / +
Term Action Stack
Line 148 ⟶ 5,788:
/ DIV [3, 0.0001220703125]
+ ADD [3.0001220703125]
=={{header|Rust}}==
<syntaxhighlight lang="rust">fn rpn(text: &str) -> f64 {
let tokens = text.split_whitespace();
let mut stack: Vec<f64> = vec![];
println!("input operation stack");
for token in tokens {
print!("{:^5} ", token);
match token.parse() {
Ok(num) => {
stack.push(num);
println!("push {:?}", stack);
}
Err(_) => {
match token {
"+" => {
let b = stack.pop().expect("missing first operand");
let a = stack.pop().expect("missing second operand");
stack.push(a + b);
}
"-" => {
let b = stack.pop().expect("missing first operand");
let a = stack.pop().expect("missing second operand");
stack.push(a - b);
}
"*" => {
let b = stack.pop().expect("missing first operand");
let a = stack.pop().expect("missing second operand");
stack.push(a * b);
}
"/" => {
let b = stack.pop().expect("missing first operand");
let a = stack.pop().expect("missing second operand");
stack.push(a / b);
}
"^" => {
let b = stack.pop().expect("missing first operand");
let a = stack.pop().expect("missing second operand");
stack.push(a.powf(b));
}
_ => panic!("unknown operator {}", token),
}
println!("calculate {:?}", stack);
}
}
}
stack.pop().unwrap_or(0.0)
}
fn main() {
let text = "3 4 2 * 1 5 - 2 3 ^ ^ / +";
println!("\nresult: {}", rpn(text));
}</syntaxhighlight>
{{out}}
<pre>input operation stack
3 push [3.0]
4 push [3.0, 4.0]
2 push [3.0, 4.0, 2.0]
* calculate [3.0, 8.0]
1 push [3.0, 8.0, 1.0]
5 push [3.0, 8.0, 1.0, 5.0]
- calculate [3.0, 8.0, -4.0]
2 push [3.0, 8.0, -4.0, 2.0]
3 push [3.0, 8.0, -4.0, 2.0, 3.0]
^ calculate [3.0, 8.0, -4.0, 8.0]
^ calculate [3.0, 8.0, 65536.0]
/ calculate [3.0, 0.0001220703125]
+ calculate [3.0001220703125]
result: 3.0001220703125
</pre>
=={{header|Scala}}==
<syntaxhighlight lang="scala">object RPN {
val PRINT_STACK_CONTENTS: Boolean = true
def main(args: Array[String]): Unit = {
val result = evaluate("3 4 2 * 1 5 - 2 3 ^ ^ / +".split(" ").toList)
println("Answer: " + result)
}
def evaluate(tokens: List[String]): Double = {
import scala.collection.mutable.Stack
val stack: Stack[Double] = new Stack[Double]
for (token <- tokens) {
if (isOperator(token)) token match {
case "+" => stack.push(stack.pop + stack.pop)
case "-" => val x = stack.pop; stack.push(stack.pop - x)
case "*" => stack.push(stack.pop * stack.pop)
case "/" => val x = stack.pop; stack.push(stack.pop / x)
case "^" => val x = stack.pop; stack.push(math.pow(stack.pop, x))
case _ => throw new RuntimeException( s""""$token" is not an operator""")
}
else stack.push(token.toDouble)
if (PRINT_STACK_CONTENTS) {
print("Input: " + token)
print(" Stack: ")
for (element <- stack.seq.reverse) print(element + " ");
println("")
}
}
stack.pop
}
def isOperator(token: String): Boolean = {
token match {
case "+" => true; case "-" => true; case "*" => true; case "/" => true; case "^" => true
case _ => false
}
}
}</syntaxhighlight>
{{out}}
<pre>
Input: 3 Stack: 3.0
Input: 4 Stack: 3.0 4.0
Input: 2 Stack: 3.0 4.0 2.0
Input: * Stack: 3.0 8.0
Input: 1 Stack: 3.0 8.0 1.0
Input: 5 Stack: 3.0 8.0 1.0 5.0
Input: - Stack: 3.0 8.0 -4.0
Input: 2 Stack: 3.0 8.0 -4.0 2.0
Input: 3 Stack: 3.0 8.0 -4.0 2.0 3.0
Input: ^ Stack: 3.0 8.0 -4.0 8.0
Input: ^ Stack: 3.0 8.0 65536.0
Input: / Stack: 3.0 1.220703125E-4
Input: + Stack: 3.0001220703125
Answer: 3.0001220703125</pre>
=={{header|Sidef}}==
{{trans|Raku}}
<syntaxhighlight lang="ruby">var proggie = '3 4 2 * 1 5 - 2 3 ^ ^ / +'
class RPN(arr=[]) {
method binop(op) {
var x = arr.pop
var y = arr.pop
arr << y.(op)(x)
}
method run(p) {
p.each_word { |w|
say "#{w} (#{arr})"
given (w) {
when (/\d/) {
arr << Num(w)
}
when (<+ - * />) {
self.binop(w)
}
when ('^') {
self.binop('**')
}
default {
die "#{w} is bogus"
}
}
}
say arr[0]
}
}
RPN.new.run(proggie)</syntaxhighlight>
{{out}}
<pre>
3 ()
4 (3)
2 (3 4)
* (3 4 2)
1 (3 8)
5 (3 8 1)
- (3 8 1 5)
2 (3 8 -4)
3 (3 8 -4 2)
^ (3 8 -4 2 3)
^ (3 8 -4 8)
/ (3 8 65536)
+ (3 0.0001220703125)
3.0001220703125
</pre>
=={{header|Swift}}==
{{trans|Go}}
<syntaxhighlight lang="swift">let opa = [
"^": (prec: 4, rAssoc: true),
"*": (prec: 3, rAssoc: false),
"/": (prec: 3, rAssoc: false),
"+": (prec: 2, rAssoc: false),
"-": (prec: 2, rAssoc: false),
]
func rpn(tokens: [String]) -> [String] {
var rpn : [String] = []
var stack : [String] = [] // holds operators and left parenthesis
for tok in tokens {
switch tok {
case "(":
stack += [tok] // push "(" to stack
case ")":
while !stack.isEmpty {
let op = stack.removeLast() // pop item from stack
if op == "(" {
break // discard "("
} else {
rpn += [op] // add operator to result
}
}
default:
if let o1 = opa[tok] { // token is an operator?
for op in stack.reverse() {
if let o2 = opa[op] {
if !(o1.prec > o2.prec || (o1.prec == o2.prec && o1.rAssoc)) {
// top item is an operator that needs to come off
rpn += [stack.removeLast()] // pop and add it to the result
continue
}
}
break
}
stack += [tok] // push operator (the new one) to stack
} else { // token is not an operator
rpn += [tok] // add operand to result
}
}
}
return rpn + stack.reverse()
}
func parseInfix(e: String) -> String {
let tokens = e.characters.split{ $0 == " " }.map(String.init)
return rpn(tokens).joinWithSeparator(" ")
}
var input : String
input = "3 + 4 * 2 / ( 1 - 5 ) ^ 2 ^ 3"
"infix: \(input)"
"postfix: \(parseInfix(input))"</syntaxhighlight>
{{out}}
<pre>"postfix: 3 4 2 * 1 5 - 2 3 ^ ^ / +"</pre>
=={{header|Tcl}}==
<syntaxhighlight lang="tcl"># Helper
proc pop stk {
upvar 1 $stk s
set val [lindex $s end]
set s [lreplace $s end end]
return $val
}
proc evaluate rpn {
set stack {}
foreach token $rpn {
set act "apply"
switch $token {
"^" {
# Non-commutative operation
set a [pop stack]
lappend stack [expr {[pop stack] ** $a}]
}
"/" {
# Non-commutative, special float handling
set a [pop stack]
set b [expr {[pop stack] / double($a)}]
if {$b == round($b)} {set b [expr {round($b)}]}
lappend stack $b
}
"*" {
# Commutative operation
lappend stack [expr {[pop stack] * [pop stack]}]
}
"-" {
# Non-commutative operation
set a [pop stack]
lappend stack [expr {[pop stack] - $a}]
}
"+" {
# Commutative operation
lappend stack [expr {[pop stack] + [pop stack]}]
}
default {
set act "push"
lappend stack $token
}
}
puts "$token\t$act\t$stack"
}
return [lindex $stack end]
}
puts [evaluate {3 4 2 * 1 5 - 2 3 ^ ^ / +}]</syntaxhighlight>
{{out}}
<pre>
3 push 3
4 push 3 4
2 push 3 4 2
* apply 3 8
1 push 3 8 1
5 push 3 8 1 5
- apply 3 8 -4
2 push 3 8 -4 2
3 push 3 8 -4 2 3
^ apply 3 8 -4 8
^ apply 3 8 65536
/ apply 3 0.0001220703125
+ apply 3.0001220703125
3.0001220703125
</pre>
=={{header|UNIX Shell}}==
Please note that the asterisk <code>*</code> within the argument string needs to be escaped or quoted, otherwise the shell will interpret and expand it.
Technically, this implementation uses a string to represent a stack and lines to delimit each item of the stack, not spaces as you might expect. However, the input is parsed pretty much as a space-separated argument string, but only with the asterisk quoted.
<syntaxhighlight lang="bash">#!/bin/sh
exp() {
R=1
local i=1
while [ $i -le $2 ]; do
R=$(($R * $1))
i=$(($i + 1))
done
}
rpn() {
local O1 O2 stack
while [ $# -ge 1 ]; do
grep -iE '^-?[0-9]+$' <<< "$1" > /dev/null 2>&1
if [ "$?" -eq 0 ]; then
stack=`sed -e '$a'"$1" -e '/^$/d' <<< "$stack"`
else
grep -iE '^[-\+\*\/\%\^]$' <<< "$1" > /dev/null 2>&1
if [ "$?" -eq 0 ]; then
O2=`sed -n '$p' <<< "$stack"`
stack=`sed '$d' <<< "$stack"`
O1=`sed -n '$p' <<< "$stack"`
case "$1" in
'+')
stack=`sed -e '$a'"$(($O1 + $O2))" -e '/^$/d' -e '$d' \
<<< "$stack"`;;
'-')
stack=`sed -e '$a'"$(($O1 - $O2))" -e '/^$/d' -e '$d' \
<<< "$stack"`;;
'*')
stack=`sed -e '$a'"$(($O1 * $O2))" -e '/^$/d' -e '$d' \
<<< "$stack"`;;
'/')
stack=`sed -e '$a'"$(($O1 / $O2))" -e '/^$/d' -e '$d' \
<<< "$stack"`;;
'%')
stack=`sed -e '$a'"$(($O1 % $O2))" -e '/^$/d' -e '$d' \
<<< "$stack"`;;
'^')
exp $O1 $O2
stack=`sed -e '$a'"$(($R))" -e '/^$/d' -e '$d' <<< \
"$stack"`;;
esac
else
echo "Unknown RPN token \`\`$1''"
fi
fi
echo "$1" ":" $stack
shift
done
sed -n '1p' <<< "$stack"
if [ "`wc -l <<< "$stack"`" -gt 1 ]; then
echo "Malformed input expression" > /dev/stderr
return 1
else
return 0
fi
}
rpn 3 4 2 '*' 1 5 '-' 2 3 '^' '^' '/' '+'</syntaxhighlight>
===Output===
<syntaxhighlight lang="text">3 : 3
4 : 3 4
2 : 3 4 2
* : 3 8
1 : 3 8 1
5 : 3 8 1 5
- : 3 8 -4
2 : 3 8 -4 2
3 : 3 8 -4 2 3
^ : 3 8 -4 8
^ : 3 8 65536
/ : 3 0
+ : 3
3</syntaxhighlight>
=={{header|V (Vlang)}}==
{{trans|C}}
Updated to V (Vlang) version 0.2.2
<syntaxhighlight lang="go">import math
const (
supported_operations = ['+', '-', '*', '/', '^']
max_depth = 256
)
struct Stack {
mut:
data []f32 = [f32(0)].repeat(max_depth)
depth int
}
fn (mut stack Stack) push(value f32) {
if stack.depth >= max_depth {
println('Stack Overflow!!')
return
}
stack.data[stack.depth] = value
stack.depth++
}
fn (mut stack Stack) pop() ?f32 {
if stack.depth > 0 {
stack.depth--
result := stack.data[stack.depth]
return result
}
return error('Stack Underflow!!')
}
fn (stack Stack) peek() ?f32 {
if stack.depth > 0 {
result := stack.data[0]
return result
}
return error('Out of Bounds...')
}
fn (mut stack Stack) rpn(input string) ?f32 {
println('Input: $input')
tokens := input.split(' ')
mut a := f32(0)
mut b := f32(0)
println('Token Stack')
for token in tokens {
if token.str.is_digit() {
stack.push(token.f32())
} else if token in supported_operations {
b = stack.pop() or { f32(0) }
a = stack.pop() or { f32(0) }
match token {
'+' {
stack.push(a + b)
}
'-' {
stack.push(a - b)
}
'*' {
stack.push(a * b)
}
'/' {
stack.push(a / b)
}
'^' {
stack.push(f32(math.pow(a, b)))
}
else {
println('Oofffff')
}
}
}
print('${token:5s} ')
for i := 0; i < stack.depth; i++ {
if i == stack.depth - 1 {
println('${stack.data[i]:0.6f} |>')
} else {
print('${stack.data[i]:0.6f}, ')
}
}
}
return stack.peek()
}
fn main() {
mut calc := Stack{}
result := calc.rpn('3 4 2 * 1 5 - 2 3 ^ ^ / +') or { return }
println('\nResult: $result')
}
</syntaxhighlight>
{{out}}
<pre>Input: 3 4 2 * 1 5 - 2 3 ^ ^ / +
Token Stack
3 3.000000 |>
4 3.000000, 4.000000 |>
2 3.000000, 4.000000, 2.000000 |>
* 3.000000, 8.000000 |>
1 3.000000, 8.000000, 1.000000 |>
5 3.000000, 8.000000, 1.000000, 5.000000 |>
- 3.000000, 8.000000, -4.000000 |>
2 3.000000, 8.000000, -4.000000, 2.000000 |>
3 3.000000, 8.000000, -4.000000, 2.000000, 3.000000 |>
^ 3.000000, 8.000000, -4.000000, 8.000000 |>
^ 3.000000, 8.000000, 65536.000000 |>
/ 3.000000, 0.000122 |>
+ 3.000122 |>
Result: 3.000122</pre>
=={{header|Wren}}==
{{trans|Kotlin}}
{{libheader|Wren-seq}}
<syntaxhighlight lang="wren">import "./seq" for Stack
var rpnCalculate = Fn.new { |expr|
if (expr == "") Fiber.abort("Expression cannot be empty.")
System.print("For expression = %(expr)\n")
System.print("Token Action Stack")
var tokens = expr.split(" ").where { |t| t != "" }
var stack = Stack.new()
for (token in tokens) {
var d = Num.fromString(token)
if (d) {
stack.push(d)
System.print(" %(d) Push num onto top of stack %(stack)")
} else if ((token.count > 1) || !"+-*/^".contains(token)) {
Fiber.abort("%(token) is not a valid token.")
} else if (stack.count < 2) {
Fiber.abort("Stack contains too few operands.")
} else {
var d1 = stack.pop()
var d2 = stack.pop()
stack.push(token == "+" ? d2 + d1 :
token == "-" ? d2 - d1 :
token == "*" ? d2 * d1 :
token == "/" ? d2 / d1 : d2.pow(d1))
System.print(" %(token) Apply op to top of stack %(stack)")
}
}
System.print("\nThe final value is %(stack.pop())")
}
var expr = "3 4 2 * 1 5 - 2 3 ^ ^ / +"
rpnCalculate.call(expr)</syntaxhighlight>
{{out}}
<pre>
For expression = 3 4 2 * 1 5 - 2 3 ^ ^ / +
Token Action Stack
3 Push num onto top of stack [3]
4 Push num onto top of stack [3, 4]
2 Push num onto top of stack [3, 4, 2]
* Apply op to top of stack [3, 8]
1 Push num onto top of stack [3, 8, 1]
5 Push num onto top of stack [3, 8, 1, 5]
- Apply op to top of stack [3, 8, -4]
2 Push num onto top of stack [3, 8, -4, 2]
3 Push num onto top of stack [3, 8, -4, 2, 3]
^ Apply op to top of stack [3, 8, -4, 8]
^ Apply op to top of stack [3, 8, 65536]
/ Apply op to top of stack [3, 0.0001220703125]
+ Apply op to top of stack [3.0001220703125]
The final value is 3.0001220703125
</pre>
=={{header|XPL0}}==
<syntaxhighlight lang "XPL0">real Stack(10);
int SP;
proc Push(X);
real X;
[Stack(SP):= X; SP:= SP+1];
func real Pop;
[SP:= SP-1; return Stack(SP)];
char Str; real Top; int Token, I;
[Str:= "3 4 2 * 1 5 - 2 3 ^^ ^^ / + ";
SP:= 0;
Format(6, 8);
loop [repeat Token:= Str(0); Str:= Str+1;
until Token # ^ ; \skip space characters
case Token of
^+: [Top:= Pop; Push(Pop+Top)];
^-: [Top:= Pop; Push(Pop-Top)];
^*: [Top:= Pop; Push(Pop*Top)];
^/: [Top:= Pop; Push(Pop/Top)];
^^: [Top:= Pop; Push(Pow(Pop, Top))];
$A0: quit \space with MSB set
other [Push(float(Token-^0))]; \single digit number
ChOut(0, Token);
for I:= 0 to SP-1 do \show stack
RlOut(0, Stack(I));
CrLf(0);
];
]</syntaxhighlight>
{{out}}
<pre>
3 3.00000000
4 3.00000000 4.00000000
2 3.00000000 4.00000000 2.00000000
* 3.00000000 8.00000000
1 3.00000000 8.00000000 1.00000000
5 3.00000000 8.00000000 1.00000000 5.00000000
- 3.00000000 8.00000000 -4.00000000
2 3.00000000 8.00000000 -4.00000000 2.00000000
3 3.00000000 8.00000000 -4.00000000 2.00000000 3.00000000
^ 3.00000000 8.00000000 -4.00000000 8.00000000
^ 3.00000000 8.00000000 65536.00000000
/ 3.00000000 0.00012207
+ 3.00012207
</pre>
=={{header|zkl}}==
<syntaxhighlight lang="zkl">var ops=D("^",True, "*",'*, "/",'/, "+",'+, "-",'-);
fcn parseRPN(e){
println("\npostfix: ", e);
stack:=L();
foreach tok in (e.split()){
op:=ops.find(tok);
if(op){
y := stack.pop(); x := stack.pop();
if(True==op) x=x.pow(y);
else x=op(x,y);
stack.append(x);
}
else stack.append(tok.toFloat());
println(tok," --> ",stack);
}
println("result: ", stack[0])
}</syntaxhighlight>
<syntaxhighlight lang="zkl">tests:=T("3 4 2 * 1 5 - 2 3 ^ ^ / +");
foreach t in (tests) { parseRPN(t) }</syntaxhighlight>
{{out}}
<pre>
postfix: 3 4 2 * 1 5 - 2 3 ^ ^ / +
3 --> L(3)
4 --> L(3,4)
2 --> L(3,4,2)
* --> L(3,8)
1 --> L(3,8,1)
5 --> L(3,8,1,5)
- --> L(3,8,-4)
2 --> L(3,8,-4,2)
3 --> L(3,8,-4,2,3)
^ --> L(3,8,-4,8)
^ --> L(3,8,65536)
/ --> L(3,0.00012207)
+ --> L(3.00012)
result: 3.00012
</pre>
| |||