Compiler/AST interpreter
< Compiler
AST interpreter
You are encouraged to solve this task according to the task description, using any language you may know.
An AST interpreter interprets an Abstract Syntax Tree (AST) produced by a Syntax Analyzer.
Task[|_}}%20*%2F%20 edit]
Take the AST output from the Syntax analyzer task, and interpret it as appropriate. Refer to the Syntax analyzer task for details of the AST.
- Loading the AST from the syntax analyzer is as simple as (pseudo code)
<lang python>def load_ast()
line = readline() # Each line has at least one token line_list = tokenize the line, respecting double quotes
text = line_list[0] # first token is always the node type
if text == ";" # a terminal node
return NULL
node_type = text # could convert to internal form if desired
# A line with two tokens is a leaf node
# Leaf nodes are: Identifier, Integer, String
# The 2nd token is the value
if len(line_list) > 1
return make_leaf(node_type, line_list[1])
left = load_ast() right = load_ast() return make_node(node_type, left, right)</lang>
- The interpreter algorithm is relatively simple
<lang python>interp(x)
if x == NULL return NULL
elif x.node_type == Integer return x.value converted to an integer
elif x.node_type == Ident return the current value of variable x.value
elif x.node_type == String return x.value
elif x.node_type == Assign
globals[x.left.value] = interp(x.right)
return NULL
elif x.node_type is a binary operator return interp(x.left) operator interp(x.right)
elif x.node_type is a unary operator, return return operator interp(x.left)
elif x.node_type == If
if (interp(x.left)) then interp(x.right.left)
else interp(x.right.right)
return NULL
elif x.node_type == While
while (interp(x.left)) do interp(x.right)
return NULL
elif x.node_type == Prtc
print interp(x.left) as a character, no newline
return NULL
elif x.node_type == Prti
print interp(x.left) as an integer, no newline
return NULL
elif x.node_type == Prts
print interp(x.left) as a string, respecting newlines ("\n")
return NULL
elif x.node_type == Sequence
interp(x.left)
interp(x.right)
return NULL
else
error("unknown node type")</lang>
Notes:
Because of the simple nature of our tiny language, Semantic analysis is not needed.
Your interpreter should use C like division semantics, for both division and modulus. For division of positive operands, only the non-fractional portion of the result should be returned. In other words, the result should be truncated towards 0.
This means, for instance, that 3 / 2 should result in 1.
For division when one of the operands is negative, the result should be truncated towards 0.
This means, for instance, that 3 / -2 should result in -1.
- Test program
| prime.t | parse | interp |
|---|---|
|
<lang c>/* Simple prime number generator */ count = 1; n = 1; limit = 100; while (n < limit) { k=3;
p=1;
n=n+2;
while ((k*k<=n) && (p)) {
p=n/k*k!=n;
k=k+2;
}
if (p) {
print(n, " is prime\n");
count = count + 1;
}
} print("Total primes found: ", count, "\n"); </lang> |
3 is prime 5 is prime 7 is prime 11 is prime 13 is prime 17 is prime 19 is prime 23 is prime 29 is prime 31 is prime 37 is prime 41 is prime 43 is prime 47 is prime 53 is prime 59 is prime 61 is prime 67 is prime 71 is prime 73 is prime 79 is prime 83 is prime 89 is prime 97 is prime 101 is prime Total primes found: 26 |
- Additional examples
Your solution should pass all the test cases above and the additional tests found Here.
Reference
The C and Python versions can be considered reference implementations.
- Related Tasks
ALGOL W
<lang algolw>begin % AST interpreter %
% parse tree nodes %
record node( integer type
; reference(node) left, right
; integer iValue % nString/nIndentifier number or nInteger value %
);
integer nIdentifier, nString, nInteger, nSequence, nIf, nPrtc, nPrts
, nPrti, nWhile, nAssign, nNegate, nNot, nMultiply
, nDivide, nMod, nAdd, nSubtract, nLess, nLessEqual
, nGreater, nGreaterEqual, nEqual, nNotEqual, nAnd, nOr
;
string(14) array ndName ( 1 :: 25 );
integer MAX_NODE_TYPE;
% string literals and identifiers - uses a linked list - a hash table might be better... %
string(1) array text ( 0 :: 4095 );
integer textNext, TEXT_MAX;
record textElement ( integer start, length; reference(textElement) next );
reference(textElement) idList, stList;
% memory - identifiers hold indexes to locations here %
integer array data ( 1 :: 4096 );
% returns a new node with left and right branches %
reference(node) procedure opNode ( integer value opType; reference(node) value opLeft, opRight ) ; begin
node( opType, opLeft, opRight, 0 )
end opNode ;
% returns a new operand node %
reference(node) procedure operandNode ( integer value opType, opValue ) ; begin
node( opType, null, null, opValue )
end operandNode ;
% reports an error and stops %
procedure rtError( string(80) value message ); begin
integer errorPos;
write( s_w := 0, "**** Runtime error " );
errorPos := 0;
while errorPos < 80 and message( errorPos // 1 ) not = "." do begin
writeon( s_w := 0, message( errorPos // 1 ) );
errorPos := errorPos + 1
end while_not_at_end_of_message ;
writeon( s_w := 0, "." );
assert( false )
end rtError ;
% reads a node from standard input %
reference(node) procedure readNode ; begin
reference(node) resultNode;
% parses a string from line and stores it in a string in the text array %
% - if it is not already present in the specified textElement list. %
% returns the position of the string in the text array %
integer procedure readString ( reference(textElement) value result txList; string(1) value terminator ) ; begin
string(256) str;
integer sLen, sPos, ePos;
logical found;
reference(textElement) txPos, txLastPos;
% get the text of the string %
str := " ";
sLen := 0;
str( sLen // 1 ) := line( lPos // 1 );
sLen := sLen + 1;
lPos := lPos + 1;
while lPos <= 255 and line( lPos // 1 ) not = terminator do begin
str( sLen // 1 ) := line( lPos // 1 );
sLen := sLen + 1;
lPos := lPos + 1
end while_more_string ;
if lPos > 255 then rtError( "Unterminated String in node file." );
% attempt to find the text in the list of strings/identifiers %
txLastPos := txPos := txList;
found := false;
ePos := 0;
while not found and txPos not = null do begin
ePos := ePos + 1;
found := ( length(txPos) = sLen );
sPos := 0;
while found and sPos < sLen do begin
found := str( sPos // 1 ) = text( start(txPos) + sPos );
sPos := sPos + 1
end while_not_found ;
txLastPos := txPos;
if not found then txPos := next(txPos)
end while_string_not_found ;
if not found then begin
% the string/identifier is not in the list - add it %
ePos := ePos + 1;
if txList = null then txList := textElement( textNext, sLen, null )
else next(txLastPos) := textElement( textNext, sLen, null );
if textNext + sLen > TEXT_MAX then rtError( "Text space exhausted." )
else begin
for cPos := 0 until sLen - 1 do begin
text( textNext ) := str( cPos // 1 );
textNext := textNext + 1
end for_cPos
end
end if_not_found ;
ePos
end readString ;
% gets an integer from the line - no checks for valid digits %
integer procedure readInteger ; begin
integer n;
n := 0;
while line( lPos // 1 ) not = " " do begin
n := ( n * 10 ) + ( decode( line( lPos // 1 ) ) - decode( "0" ) );
lPos := lPos + 1
end while_not_end_of_integer ;
n
end readInteger ;
string(256) line;
string(16) name;
integer lPos, tPos, ndType;
tPos := lPos := 0;
readcard( line );
% get the node type name %
while line( lPos // 1 ) = " " do lPos := lPos + 1;
name := "";
while lPos < 256 and line( lPos // 1 ) not = " " do begin
name( tPos // 1 ) := line( lPos // 1 );
lPos := lPos + 1;
tPos := tPos + 1
end while_more_name ;
% determine the node type %
ndType := 1;
resultNode := null;
if name not = ";" then begin
% not a null node %
while ndType <= MAX_NODE_TYPE and name not = ndName( ndType ) do ndType := ndType + 1;
if ndType > MAX_NODE_TYPE then rtError( "Malformed node." );
% handle the additional parameter for identifier/string/integer, or sub-nodes for operator nodes %
if ndType = nInteger or ndType = nIdentifier or ndType = nString then begin
while line( lPos // 1 ) = " " do lPos := lPos + 1;
if ndType = nInteger then resultNode := operandNode( ndType, readInteger )
else if ndType = nIdentifier then resultNode := operandNode( ndType, readString( idList, " " ) )
else % ndType = nString % resultNode := operandNode( ndType, readString( stList, """" ) )
end
else begin
% operator node %
reference(node) leftNode;
leftNode := readNode;
resultNode := opNode( ndType, leftNode, readNode )
end
end if_non_null_node ;
resultNode
end readNode ;
% interprets the specified node and returns the value %
integer procedure eval ( reference(node) value n ) ; begin
integer v;
% prints a string from text, escape sequences are interpreted %
procedure writeOnText( reference(textElement) value txHead; integer value txNumber ) ;
begin
reference(textElement) txPos;
integer count;
txPos := txHead;
count := 1;
while count < txNumber and txPos not = null do begin
txPos := next(txPos);
count := count + 1
end while_text_element_not_found ;
if txPos = null then rtError( "INTERNAL ERROR: text not found." )
else begin
% found the text - output it, handling escape sequences %
integer cPos;
cPos := 1; % start from 1 to skip over the leading " %
while cPos < length(txPos) do begin
string(1) ch;
ch := text( start(txPos) + cPos );
if ch not = "\" then writeon( s_w := 0, ch )
else begin
% escaped character %
cPos := cPos + 1;
if cPos > length(txPos) then rtError( "String terminates with ""\""." )
else begin
ch := text( start(txPos) + cPos );
if ch = "n" then % newline % write()
else writeon( s_w := 0, ch )
end
end;
cPos := cPos + 1
end while_not_end_of_string
end
end writeOnText ;
% returns 1 if val is true, 0 otherwise %
integer procedure booleanResult ( logical value val ) ; begin
if val then 1 else 0
end booleanResult ;
v := 0;
if n = null then v := 0
else if type(n) = nIdentifier then v := data( iValue(n) )
else if type(n) = nString then v := iValue(n)
else if type(n) = nInteger then v := iValue(n)
else if type(n) = nSequence then begin
% sequence - evaluate and discard the left branch and return the right branch %
v := eval( left(n) );
v := eval( right(n) )
end
else if type(n) = nIf then % if-else % begin
if eval( left(n) ) not = 0 then v := eval( left(right(n)) )
else v := eval( right(right(n)) );
v := 0
end
else if type(n) = nPrtc then % print character % writeon( s_w := 0, code( eval( left(n) ) ) )
else if type(n) = nPrts then % print string % writeOnText( stList, eval( left(n) ) )
else if type(n) = nPrti then % print integer % writeon( s_w := 0, i_w := 1, eval( left(n) ) )
else if type(n) = nWhile then % while-loop % begin
while eval( left(n) ) not = 0 do v := eval( right(n) );
v := 0
end
else if type(n) = nAssign then % assignment % data( iValue(left(n)) ) := eval( right(n) )
else if type(n) = nNegate then % unary - % v := - eval( left(n) )
else if type(n) = nNot then % unary not % v := booleanResult( eval( left(n) ) = 0 )
else if type(n) = nMultiply then % multiply % v := eval( left(n) ) * eval( right(n) )
else if type(n) = nDivide then % division % begin
integer lv, rv;
lv := eval( left(n) );
rv := eval( right(n) );
if rv = 0 then rtError( "Division by 0." )
else v := lv div rv
end
else if type(n) = nMod then % modulo % begin
integer lv, rv;
lv := eval( left(n) );
rv := eval( right(n) );
if rv = 0 then rtError( "Right operand of % is 0." )
else v := lv rem rv
end
else if type(n) = nAdd then % addition % v := eval( left(n) ) + eval( right(n) )
else if type(n) = nSubtract then % subtraction % v := eval( left(n) ) - eval( right(n) )
else if type(n) = nLess then % less-than % v := booleanResult( eval( left(n) ) < eval( right(n) ) )
else if type(n) = nLessEqual then % less or equal % v := booleanResult( eval( left(n) ) <= eval( right(n) ) )
else if type(n) = nGreater then % greater-than % v := booleanResult( eval( left(n) ) > eval( right(n) ) )
else if type(n) = nGreaterEqual then % greater or eq % v := booleanResult( eval( left(n) ) >= eval( right(n) ) )
else if type(n) = nEqual then % test equal % v := booleanResult( eval( left(n) ) = eval( right(n) ) )
else if type(n) = nNotEqual then % not-equal % v := booleanResult( eval( left(n) ) not = eval( right(n) ) )
else if type(n) = nAnd then % boolean "and" % begin
v := eval( left(n) );
if v not = 0 then v := eval( right(n) )
end
else if type(n) = nOr then % boolean "or" % begin
v := eval( left(n) );
if v = 0 then v := eval( right(n) );
end
else % unknown node % begin
rtError( "Unknown node type in eval." )
end;
v
end eval ;
nIdentifier := 1; ndName( nIdentifier ) := "Identifier"; nString := 2; ndName( nString ) := "String"; nInteger := 3; ndName( nInteger ) := "Integer"; nSequence := 4; ndName( nSequence ) := "Sequence"; nIf := 5; ndName( nIf ) := "If"; nPrtc := 6; ndName( nPrtc ) := "Prtc"; nPrts := 7; ndName( nPrts ) := "Prts"; nPrti := 8; ndName( nPrti ) := "Prti"; nWhile := 9; ndName( nWhile ) := "While"; nAssign := 10; ndName( nAssign ) := "Assign"; nNegate := 11; ndName( nNegate ) := "Negate"; nNot := 12; ndName( nNot ) := "Not"; nMultiply := 13; ndName( nMultiply ) := "Multiply"; nDivide := 14; ndName( nDivide ) := "Divide"; nMod := 15; ndName( nMod ) := "Mod"; nAdd := 16; ndName( nAdd ) := "Add"; nSubtract := 17; ndName( nSubtract ) := "Subtract"; nLess := 18; ndName( nLess ) := "Less"; nLessEqual := 19; ndName( nLessEqual ) := "LessEqual" ; nGreater := 20; ndName( nGreater ) := "Greater"; nGreaterEqual := 21; ndName( nGreaterEqual ) := "GreaterEqual"; nEqual := 22; ndName( nEqual ) := "Equal"; nNotEqual := 23; ndName( nNotEqual ) := "NotEqual"; nAnd := 24; ndName( nAnd ) := "And"; nOr := 25; ndName( nOr ) := "Or"; MAX_NODE_TYPE := 25; TEXT_MAX := 4095; textNext := 0; stList := idList := null;
% parse the output from the syntax analyser and intetrpret parse tree % eval( readNode )
end.</lang>
- Output:
3 is prime 5 is prime 7 is prime 11 is prime ... 83 is prime 89 is prime 97 is prime 101 is prime Total primes found: 26
C
Tested with gcc 4.81 and later, compiles warning free with -Wall -Wextra <lang C>#include <stdlib.h>
- include <stdio.h>
- include <string.h>
- include <stdarg.h>
- include <ctype.h>
- define da_dim(name, type) type *name = NULL; \
int _qy_ ## name ## _p = 0; \
int _qy_ ## name ## _max = 0
- define da_rewind(name) _qy_ ## name ## _p = 0
- define da_redim(name) do {if (_qy_ ## name ## _p >= _qy_ ## name ## _max) \
name = realloc(name, (_qy_ ## name ## _max += 32) * sizeof(name[0]));} while (0)
- define da_append(name, x) do {da_redim(name); name[_qy_ ## name ## _p++] = x;} while (0)
- define da_len(name) _qy_ ## name ## _p
- define da_add(name) do {da_redim(name); _qy_ ## name ## _p++;} while (0)
typedef enum {
nd_Ident, nd_String, nd_Integer, nd_Sequence, nd_If, nd_Prtc, nd_Prts, nd_Prti, nd_While, nd_Assign, nd_Negate, nd_Not, nd_Mul, nd_Div, nd_Mod, nd_Add, nd_Sub, nd_Lss, nd_Leq, nd_Gtr, nd_Geq, nd_Eql, nd_Neq, nd_And, nd_Or
} NodeType;
typedef struct Tree Tree; struct Tree {
NodeType node_type; Tree *left; Tree *right; int value;
};
// dependency: Ordered by NodeType, must remain in same order as NodeType enum
struct {
char *enum_text; NodeType node_type;
} atr[] = {
{"Identifier" , nd_Ident, }, {"String" , nd_String, },
{"Integer" , nd_Integer,}, {"Sequence" , nd_Sequence,},
{"If" , nd_If, }, {"Prtc" , nd_Prtc, },
{"Prts" , nd_Prts, }, {"Prti" , nd_Prti, },
{"While" , nd_While, }, {"Assign" , nd_Assign, },
{"Negate" , nd_Negate, }, {"Not" , nd_Not, },
{"Multiply" , nd_Mul, }, {"Divide" , nd_Div, },
{"Mod" , nd_Mod, }, {"Add" , nd_Add, },
{"Subtract" , nd_Sub, }, {"Less" , nd_Lss, },
{"LessEqual" , nd_Leq, }, {"Greater" , nd_Gtr, },
{"GreaterEqual", nd_Geq, }, {"Equal" , nd_Eql, },
{"NotEqual" , nd_Neq, }, {"And" , nd_And, },
{"Or" , nd_Or, },
};
FILE *source_fp; da_dim(string_pool, const char *); da_dim(global_names, const char *); da_dim(global_values, int);
void error(const char *fmt, ... ) {
va_list ap; char buf[1000];
va_start(ap, fmt);
vsprintf(buf, fmt, ap);
printf("error: %s\n", buf);
exit(1);
}
Tree *make_node(NodeType node_type, Tree *left, Tree *right) {
Tree *t = calloc(sizeof(Tree), 1); t->node_type = node_type; t->left = left; t->right = right; return t;
}
Tree *make_leaf(NodeType node_type, int value) {
Tree *t = calloc(sizeof(Tree), 1); t->node_type = node_type; t->value = value; return t;
}
int interp(Tree *x) { /* interpret the parse tree */
if (!x) return 0;
switch(x->node_type) {
case nd_Integer: return x->value;
case nd_Ident: return global_values[x->value];
case nd_String: return x->value;
case nd_Assign: return global_values[x->left->value] = interp(x->right);
case nd_Add: return interp(x->left) + interp(x->right);
case nd_Sub: return interp(x->left) - interp(x->right);
case nd_Mul: return interp(x->left) * interp(x->right);
case nd_Div: return interp(x->left) / interp(x->right);
case nd_Mod: return interp(x->left) % interp(x->right);
case nd_Lss: return interp(x->left) < interp(x->right);
case nd_Gtr: return interp(x->left) > interp(x->right);
case nd_Leq: return interp(x->left) <= interp(x->right);
case nd_Eql: return interp(x->left) == interp(x->right);
case nd_Neq: return interp(x->left) != interp(x->right);
case nd_And: return interp(x->left) && interp(x->right);
case nd_Or: return interp(x->left) || interp(x->right);
case nd_Negate: return -interp(x->left);
case nd_Not: return !interp(x->left);
case nd_If: if (interp(x->left))
interp(x->right->left);
else
interp(x->right->right);
return 0;
case nd_While: while (interp(x->left))
interp(x->right);
return 0;
case nd_Prtc: printf("%c", interp(x->left));
return 0;
case nd_Prti: printf("%d", interp(x->left));
return 0;
case nd_Prts: printf("%s", string_pool[interp(x->left)]);
return 0;
case nd_Sequence: interp(x->left);
interp(x->right);
return 0;
default: error("interp: unknown tree type %d\n", x->node_type);
}
return 0;
}
void init_in(const char fn[]) {
if (fn[0] == '\0')
source_fp = stdin;
else {
source_fp = fopen(fn, "r");
if (source_fp == NULL)
error("Can't open %s\n", fn);
}
}
NodeType get_enum_value(const char name[]) {
for (size_t i = 0; i < sizeof(atr) / sizeof(atr[0]); i++) {
if (strcmp(atr[i].enum_text, name) == 0) {
return atr[i].node_type;
}
}
error("Unknown token %s\n", name);
return -1;
}
char *read_line(int *len) {
static char *text = NULL; static int textmax = 0;
for (*len = 0; ; (*len)++) {
int ch = fgetc(source_fp);
if (ch == EOF || ch == '\n') {
if (*len == 0)
return NULL;
break;
}
if (*len + 1 >= textmax) {
textmax = (textmax == 0 ? 128 : textmax * 2);
text = realloc(text, textmax);
}
text[*len] = ch;
}
text[*len] = '\0';
return text;
}
char *rtrim(char *text, int *len) { // remove trailing spaces
for (; *len > 0 && isspace(text[*len - 1]); --(*len))
;
text[*len] = '\0'; return text;
}
int fetch_string_offset(char *st) {
int len = strlen(st); st[len - 1] = '\0'; ++st; char *p, *q; p = q = st;
while ((*p++ = *q++) != '\0') {
if (q[-1] == '\\') {
if (q[0] == 'n') {
p[-1] = '\n';
++q;
} else if (q[0] == '\\') {
++q;
}
}
}
for (int i = 0; i < da_len(string_pool); ++i) {
if (strcmp(st, string_pool[i]) == 0) {
return i;
}
}
da_add(string_pool);
int n = da_len(string_pool) - 1;
string_pool[n] = strdup(st);
return da_len(string_pool) - 1;
}
int fetch_var_offset(const char *name) {
for (int i = 0; i < da_len(global_names); ++i) {
if (strcmp(name, global_names[i]) == 0)
return i;
}
da_add(global_names);
int n = da_len(global_names) - 1;
global_names[n] = strdup(name);
da_append(global_values, 0);
return n;
}
Tree *load_ast() {
int len; char *yytext = read_line(&len); yytext = rtrim(yytext, &len);
// get first token char *tok = strtok(yytext, " ");
if (tok[0] == ';') {
return NULL;
}
NodeType node_type = get_enum_value(tok);
// if there is extra data, get it
char *p = tok + strlen(tok);
if (p != &yytext[len]) {
int n;
for (++p; isspace(*p); ++p)
;
switch (node_type) {
case nd_Ident: n = fetch_var_offset(p); break;
case nd_Integer: n = strtol(p, NULL, 0); break;
case nd_String: n = fetch_string_offset(p); break;
default: error("Unknown node type: %s\n", p);
}
return make_leaf(node_type, n);
}
Tree *left = load_ast(); Tree *right = load_ast(); return make_node(node_type, left, right);
}
int main(int argc, char *argv[]) {
init_in(argc > 1 ? argv[1] : "");
Tree *x = load_ast(); interp(x);
return 0;
}</lang>
- Output — prime numbers output from AST interpreter:
lex prime.t | parse | interp 3 is prime 5 is prime 7 is prime 11 is prime 13 is prime 17 is prime 19 is prime 23 is prime 29 is prime 31 is prime 37 is prime 41 is prime 43 is prime 47 is prime 53 is prime 59 is prime 61 is prime 67 is prime 71 is prime 73 is prime 79 is prime 83 is prime 89 is prime 97 is prime 101 is prime Total primes found: 26
COBOL
Code by Steve Williams. Tested with GnuCOBOL 2.2.
<lang cobol> >>SOURCE FORMAT IS FREE identification division.
- > this code is dedicated to the public domain
- > (GnuCOBOL) 2.3-dev.0
program-id. astinterpreter. environment division. configuration section. repository. function all intrinsic. data division. working-storage section. 01 program-name pic x(32) value spaces global. 01 input-name pic x(32) value spaces global. 01 input-status pic xx global.
01 ast-record global.
03 ast-type pic x(14).
03 ast-value pic x(48).
03 filler redefines ast-value.
05 asl-left pic 999.
05 asl-right pic 999.
01 error-record pic x(64) value spaces global.
01 loadstack global.
03 l pic 99 value 0.
03 l-lim pic 99 value 64.
03 load-entry occurs 64.
05 l-node pic x(14).
05 l-left pic 999.
05 l-right pic 999.
05 l-link pic 999.
01 abstract-syntax-tree global.
03 t pic 999 value 0.
03 t1 pic 999.
03 n1 pic 999.
03 t-lim pic 999 value 998.
03 filler occurs 998.
05 leaf.
07 leaf-type pic x(14).
07 leaf-value pic x(48).
05 node redefines leaf.
07 node-type pic x(14).
07 node-left pic 999.
07 node-right pic 999.
01 interpreterstack global.
03 stack1 pic 99 value 2.
03 stack2 pic 99 value 1.
03 stack-lim pic 99 value 32.
03 stack-entry occurs 32.
05 stack-source pic 99.
05 stack usage binary-int.
01 variables global.
03 v pic 99.
03 v-max pic 99 value 0.
03 v-lim pic 99 value 16.
03 filler occurs 16.
05 variable-value binary-int.
05 variable-name pic x(48).
01 strings global.
03 s pic 99.
03 s-max pic 99 value 0.
03 s-lim pic 99 value 16.
03 filler occurs 16 value spaces.
05 string-value pic x(48).
01 string-fields global.
03 string-length pic 99. 03 string1 pic 99. 03 length1 pic 99. 03 count1 pic 99.
01 display-fields global.
03 display-number pic -(9)9.
03 display-pending pic x value 'n'.
03 character-value.
05 character-number usage binary-char.
procedure division chaining program-name. start-astinterpreter.
call 'loadast'
if program-name <> spaces
call 'readinput' *> close the input-file
end-if
>>d perform print-ast
call 'runast' using t
if display-pending = 'y'
display space
end-if
stop run
.
print-ast.
call 'printast' using t
display 'ast:' upon syserr
display 't=' t
perform varying t1 from 1 by 1 until t1 > t
if leaf-type(t1) = 'Identifier' or 'Integer' or 'String'
display t1 space trim(leaf-type(t1)) space trim(leaf-value(t1)) upon syserr
else
display t1 space node-left(t1) space node-right(t1) space trim(node-type(t1))
upon syserr
end-if
end-perform
.
identification division. program-id. runast common recursive. data division. working-storage section. 01 word-length constant as length of binary-int. linkage section. 01 n pic 999. procedure division using n. start-runast.
if n = 0
exit program
end-if
evaluate node-type(n)
when 'Integer'
perform push-stack
move numval(leaf-value(n)) to stack(stack1)
when 'Identifier'
perform get-variable-index
perform push-stack
move v to stack-source(stack1)
move variable-value(v) to stack(stack1)
when 'String'
perform get-string-index
perform push-stack
move s to stack-source(stack1)
when 'Assign'
call 'runast' using node-left(n)
call 'runast' using node-right(n)
move stack-source(stack2) to v
move stack(stack1) to variable-value(v)
perform pop-stack
perform pop-stack
when 'If'
call 'runast' using node-left(n)
move node-right(n) to n1
if stack(stack1) <> 0
call 'runast' using node-left(n1)
else
call 'runast' using node-right(n1)
end-if
perform pop-stack
when 'While'
call 'runast' using node-left(n)
perform until stack(stack1) = 0
perform pop-stack
call 'runast' using node-right(n)
call 'runast' using node-left(n)
end-perform
perform pop-stack
when 'Add'
perform get-values
add stack(stack1) to stack(stack2)
perform pop-stack
when 'Subtract'
perform get-values
subtract stack(stack1) from stack(stack2)
perform pop-stack
when 'Multiply'
perform get-values
multiply stack(stack1) by stack(stack2)
perform pop-stack
when 'Divide'
perform get-values
divide stack(stack1) into stack(stack2)
perform pop-stack
when 'Mod'
perform get-values
move mod(stack(stack2),stack(stack1)) to stack(stack2)
perform pop-stack
when 'Less'
perform get-values
if stack(stack2) < stack(stack1)
move 1 to stack(stack2)
else
move 0 to stack(stack2)
end-if
perform pop-stack
when 'Greater'
perform get-values
if stack(stack2) > stack(stack1)
move 1 to stack(stack2)
else
move 0 to stack(stack2)
end-if
perform pop-stack
when 'LessEqual'
perform get-values
if stack(stack2) <= stack(stack1)
move 1 to stack(stack2)
else
move 0 to stack(stack2)
end-if
perform pop-stack
when 'GreaterEqual'
perform get-values
if stack(stack2) >= stack(stack1)
move 1 to stack(stack2)
else
move 0 to stack(stack2)
end-if
perform pop-stack
when 'Equal'
perform get-values
if stack(stack2) = stack(stack1)
move 1 to stack(stack2)
else
move 0 to stack(stack2)
end-if
perform pop-stack
when 'NotEqual'
perform get-values
if stack(stack2) <> stack(stack1)
move 1 to stack(stack2)
else
move 0 to stack(stack2)
end-if
perform pop-stack
when 'And'
perform get-values
call "CBL_AND" using stack(stack1) stack(stack2) by value word-length
perform pop-stack
when 'Or'
perform get-values
call "CBL_OR" using stack(stack1) stack(stack2) by value word-length
perform pop-stack
when 'Not'
call 'runast' using node-left(n)
if stack(stack1) = 0
move 1 to stack(stack1)
else
move 0 to stack(stack1)
end-if
when 'Negate'
call 'runast' using node-left(n)
compute stack(stack1) = - stack(stack1)
when 'Prtc'
call 'runast' using node-left(n)
move stack(stack1) to character-number
display character-value with no advancing
move 'y' to display-pending
perform pop-stack
when 'Prti'
call 'runast' using node-left(n)
move stack(stack1) to display-number
display trim(display-number) with no advancing
move 'y' to display-pending
perform pop-stack
when 'Prts'
call 'runast' using node-left(n)
move stack-source(stack1) to s
move length(trim(string-value(s))) to string-length
move 2 to string1
compute length1 = string-length - 2
perform until string1 >= string-length
move 0 to count1
inspect string-value(s)(string1:length1)
tallying count1 for characters before initial '\' *> ' (workaround Rosetta Code highlighter problem)
evaluate true
when string-value(s)(string1 + count1 + 1:1) = 'n' *> \n
display string-value(s)(string1:count1)
move 'n' to display-pending
compute string1 = string1 + 2 + count1
compute length1 = length1 - 2 - count1
when string-value(s)(string1 + count1 + 1:1) = '\' *> \\ '
display string-value(s)(string1:count1 + 1) with no advancing
move 'y' to display-pending
compute string1 = string1 + 2 + count1
compute length1 = length1 - 2 - count1
when other
display string-value(s)(string1:count1) with no advancing
move 'y' to display-pending
add count1 to string1
subtract count1 from length1
end-evaluate
end-perform
perform pop-stack
when 'Sequence'
call 'runast' using node-left(n)
call 'runast' using node-right(n)
when other
string 'in astinterpreter unknown node type ' node-type(n) into error-record
call 'reporterror'
end-evaluate
exit program
.
push-stack.
if stack1 >= s-lim
string 'in astinterpreter at ' n ' stack overflow' into error-record
call 'reporterror'
end-if
add 1 to stack1 stack2
initialize stack-entry(stack1)
.
pop-stack.
if stack1 < 2
string 'in astinterpreter at ' n ' stack underflow ' into error-record
call 'reporterror'
end-if
subtract 1 from stack1 stack2
.
get-variable-index.
perform varying v from 1 by 1 until v > v-max
or variable-name(v) = leaf-value(n)
continue
end-perform
if v > v-max
if v-max = v-lim
string 'in astinterpreter number of variables exceeds ' v-lim into error-record
call 'reporterror'
end-if
move v to v-max
move leaf-value(n) to variable-name(v)
move 0 to variable-value(v)
end-if
.
get-string-index.
perform varying s from 1 by 1 until s > s-max
or string-value(s) = leaf-value(n)
continue
end-perform
if s > s-max
if s-max = s-lim
string 'in astinterpreter number of strings exceeds ' s-lim into error-record
call 'reporterror'
end-if
move s to s-max
move leaf-value(n) to string-value(s)
end-if
.
get-values.
call 'runast' using node-left(n) call 'runast' using node-right(n) .
end program runast.
identification division. program-id. loadast common recursive. procedure division. start-loadast.
if l >= l-lim
string 'in astinterpreter loadast l exceeds ' l-lim into error-record
call 'reporterror'
end-if
add 1 to l
call 'readinput'
evaluate true
when ast-record = ';'
when input-status = '10'
move 0 to return-code
when ast-type = 'Identifier'
when ast-type = 'Integer'
when ast-type = 'String'
call 'makeleaf' using ast-type ast-value
move t to return-code
when ast-type = 'Sequence'
move ast-type to l-node(l)
call 'loadast'
move return-code to l-left(l)
call 'loadast'
move t to l-right(l)
call 'makenode' using l-node(l) l-left(l) l-right(l)
move t to return-code
when other
move ast-type to l-node(l)
call 'loadast'
move return-code to l-left(l)
call 'loadast'
move return-code to l-right(l)
call 'makenode' using l-node(l) l-left(l) l-right(l)
move t to return-code
end-evaluate
subtract 1 from l
.
end program loadast.
identification division. program-id. makenode common. data division. linkage section. 01 parm-type any length. 01 parm-l-left pic 999. 01 parm-l-right pic 999. procedure division using parm-type parm-l-left parm-l-right. start-makenode.
if t >= t-lim
string 'in astinterpreter makenode t exceeds ' t-lim into error-record
call 'reporterror'
end-if
add 1 to t
move parm-type to node-type(t)
move parm-l-left to node-left(t)
move parm-l-right to node-right(t)
.
end program makenode.
identification division. program-id. makeleaf common. data division. linkage section. 01 parm-type any length. 01 parm-value pic x(48). procedure division using parm-type parm-value. start-makeleaf.
add 1 to t
if t >= t-lim
string 'in astinterpreter makeleaf t exceeds ' t-lim into error-record
call 'reporterror'
end-if
move parm-type to leaf-type(t)
move parm-value to leaf-value(t)
.
end program makeleaf.
identification division. program-id. printast common recursive. data division. linkage section. 01 n pic 999. procedure division using n. start-printast.
if n = 0
display ';' upon syserr
exit program
end-if
display leaf-type(n) upon syserr
evaluate leaf-type(n)
when 'Identifier'
when 'Integer'
when 'String'
display leaf-type(n) space trim(leaf-value(n)) upon syserr
when other
display node-type(n) upon syserr
call 'printast' using node-left(n)
call 'printast' using node-right(n)
end-evaluate
.
end program printast.
identification division. program-id. readinput common. environment division. input-output section. file-control.
select input-file assign using input-name
status is input-status
organization is line sequential.
data division. file section. fd input-file. 01 input-record pic x(64). procedure division. start-readinput.
if program-name = spaces
move '00' to input-status
accept ast-record on exception move '10' to input-status end-accept
exit program
end-if
if input-name = spaces
string program-name delimited by space '.ast' into input-name
open input input-file
if input-status = '35'
string 'in astinterpreter ' trim(input-name) ' not found' into error-record
call 'reporterror'
end-if
end-if
read input-file into ast-record
evaluate input-status
when '00'
continue
when '10'
close input-file
when other
string 'in astinterpreter ' trim(input-name) ' unexpected input-status: ' input-status
into error-record
call 'reporterror'
end-evaluate
.
end program readinput.
program-id. reporterror common. procedure division. start-reporterror. report-error.
display error-record upon syserr stop run with error status -1 .
end program reporterror. end program astinterpreter.</lang>
- Output — Primes:
prompt$ ./lexer <testcases/Primes | ./parser | ./astinterpreter 3 is prime 5 is prime 7 is prime 11 is prime 13 is prime 17 is prime 19 is prime 23 is prime 29 is prime 31 is prime 37 is prime 41 is prime 43 is prime 47 is prime 53 is prime 59 is prime 61 is prime 67 is prime 71 is prime 73 is prime 79 is prime 83 is prime 89 is prime 97 is prime 101 is prime Total primes found: 26
Forth
Tested with Gforth 0.7.3 <lang Forth>CREATE BUF 0 , \ single-character look-ahead buffer
- PEEK BUF @ 0= IF KEY BUF ! THEN BUF @ ;
- GETC PEEK 0 BUF ! ;
- SPACE? DUP BL = SWAP 9 14 WITHIN OR ;
- >SPACE BEGIN PEEK SPACE? WHILE GETC DROP REPEAT ;
- DIGIT? 48 58 WITHIN ;
- GETINT >SPACE 0
BEGIN PEEK DIGIT? WHILE GETC [CHAR] 0 - SWAP 10 * + REPEAT ;
- GETNAM >SPACE PAD 1+
BEGIN PEEK SPACE? INVERT WHILE GETC OVER C! CHAR+ REPEAT PAD TUCK - 1- PAD C! ;
- GETSTR ( -- c-addr u)
HERE >R 0 >SPACE GETC DROP \ skip leading " BEGIN GETC DUP [CHAR] " <> WHILE C, 1+ REPEAT DROP R> SWAP ;
- \TYPE BEGIN DUP 0> WHILE
OVER C@ [CHAR] \ = IF
1- >R CHAR+ R>
OVER C@ [CHAR] n = IF CR ELSE
OVER C@ [CHAR] \ = IF [CHAR] \ EMIT THEN THEN
ELSE OVER C@ EMIT THEN 1- >R CHAR+ R> REPEAT
DROP DROP ;
- . S>D SWAP OVER DABS <# #S ROT SIGN #> TYPE ;
- CONS ( v l -- l) HERE >R SWAP , , R> ;
- HEAD ( l -- v) @ ;
- TAIL ( l -- l) CELL+ @ ;
CREATE GLOBALS 0 ,
- DECLARE ( c-addr -- a-addr) HERE TUCK
OVER C@ CHAR+ DUP ALLOT CMOVE HERE SWAP 0 , GLOBALS @ CONS GLOBALS ! ;
- LOOKUP ( c-addr -- a-addr) DUP COUNT GLOBALS @ >R
BEGIN R@ 0<>
WHILE R@ HEAD COUNT 2OVER COMPARE 0=
IF 2DROP DROP R> HEAD DUP C@ CHAR+ + EXIT
THEN R> TAIL >R
REPEAT
2DROP RDROP DECLARE ;
DEFER GETAST
- >Identifier GETNAM LOOKUP 0 ;
- >Integer GETINT 0 ;
- >String GETSTR ;
- >; 0 0 ;
- NODE ( xt left right -- addr) HERE >R , , , R> ;
CREATE BUF' 12 ALLOT
- PREPEND ( c-addr c -- c-addr) BUF' 1+ C!
COUNT DUP 1+ BUF' C! BUF' 2 + SWAP CMOVE BUF' ;
- HANDLER ( c-addr -- xt) [CHAR] $ PREPEND FIND
0= IF ." No handler for AST node '" COUNT TYPE ." '" THEN ;
- READER ( c-addr -- xt t | f)
[CHAR] > PREPEND FIND DUP 0= IF NIP THEN ;
- READ ( c-addr -- left right) READER
IF EXECUTE ELSE GETAST GETAST THEN ;
- (GETAST) GETNAM DUP HANDLER SWAP READ NODE ;
' (GETAST) IS GETAST
- INTERP DUP 2@ ROT [ 2 CELLS ]L + @ EXECUTE ;
- $; DROP DROP ;
- $Identifier ( l r -- a-addr) DROP @ ;
- $Integer ( l r -- n) DROP ;
- $String ( l r -- c-addr u) ( noop) ;
- $Prtc ( l r --) DROP INTERP EMIT ;
- $Prti ( l r --) DROP INTERP . ;
- $Prts ( l r --) DROP INTERP \TYPE ;
- $Not ( l r --) DROP INTERP 0= ;
- $Negate ( l r --) DROP INTERP NEGATE ;
- $Sequence ( l r --) SWAP INTERP INTERP ;
- $Assign ( l r --) SWAP CELL+ @ >R INTERP R> ! ;
- $While ( l r --)
>R BEGIN DUP INTERP WHILE R@ INTERP REPEAT RDROP DROP ;
- $If ( l r --) SWAP INTERP 0<> IF CELL+ THEN @ INTERP ;
- $Subtract ( l r -- n) >R INTERP R> INTERP - ;
- $Add >R INTERP R> INTERP + ;
- $Mod >R INTERP R> INTERP MOD ;
- $Multiply >R INTERP R> INTERP * ;
- $Divide >R INTERP S>D R> INTERP SM/REM SWAP DROP ;
- $Less >R INTERP R> INTERP < ;
- $LessEqual >R INTERP R> INTERP <= ;
- $Greater >R INTERP R> INTERP > ;
- $GreaterEqual >R INTERP R> INTERP >= ;
- $Equal >R INTERP R> INTERP = ;
- $NotEqual >R INTERP R> INTERP <> ;
- $And >R INTERP IF R> INTERP 0<> ELSE RDROP 0 THEN ;
- $Or >R INTERP IF RDROP -1 ELSE R> INTERP 0<> THEN ;
GETAST INTERP </lang> Passes all tests.
Julia
<lang julia>struct Anode
node_type::String
left::Union{Nothing, Anode}
right::Union{Nothing, Anode}
value::Union{Nothing, String}
end
make_leaf(t, v) = Anode(t, nothing, nothing, v) make_node(t, l, r) = Anode(t, l, r, nothing)
const OP2 = Dict("Multiply" => "*", "Divide" => "/", "Mod" => "%", "Add" => "+", "Subtract" => "-",
"Less" => "<", "Greater" => ">", "LessEqual" => "<=", "GreaterEqual" => ">=",
"Equal" => "==", "NotEqual" => "!=", "And" => "&&", "Or" => "||")
const OP1 = Dict("Not" => "!", "Minus" => "-")
tobool(i::Bool) = i tobool(i::Int) = (i != 0) tobool(s::String) = eval(Symbol(s)) != 0
const stac = Vector{Any}()
function call2(op, x, y)
if op in ["And", "Or"]
x, y = tobool(x), tobool(y)
end
eval(Meta.parse("push!(stac, $(x) $(OP2[op]) $(y))"))
return Int(floor(pop!(stac)))
end
call1(op, x) = (if op in ["Not"] x = tobool(x) end; eval(Meta.parse("$(OP1[op]) $(x)"))) evalpn(op, x, y = nothing) = (haskey(OP2, op) ? call2(op, x, y) : call1(op, x))
function load_ast(io)
line = strip(readline(io))
line_list = filter(x -> x != nothing, match(r"(?:(\w+)\s+(\d+|\w+|\".*\")|(\w+|;))", line).captures)
text = line_list[1]
if text == ";"
return nothing
end
node_type = text
if length(line_list) > 1
return make_leaf(line_list[1], line_list[2])
end
left = load_ast(io)
right = load_ast(io)
return make_node(line_list[1], left, right)
end
function interp(x)
if x == nothing return nothing
elseif x.node_type == "Integer" return parse(Int, x.value)
elseif x.node_type == "Identifier" return "_" * x.value
elseif x.node_type == "String" return replace(replace(x.value, "\"" => ""), "\\n" => "\n")
elseif x.node_type == "Assign" s = "$(interp(x.left)) = $(interp(x.right))"; eval(Meta.parse(s)); return nothing
elseif x.node_type in keys(OP2) return evalpn(x.node_type, interp(x.left), interp(x.right))
elseif x.node_type in keys(OP1) return evalpn(x.node_type, interp(x.left))
elseif x.node_type == "If" tobool(eval(interp(x.left))) ? interp(x.right.left) : interp(x.right.right); return nothing
elseif x.node_type == "While" while tobool(eval(interp(x.left))) interp(x.right) end; return nothing
elseif x.node_type == "Prtc" print(Char(eval(interp(x.left)))); return nothing
elseif x.node_type == "Prti" s = interp(x.left); print((i = tryparse(Int, s)) == nothing ? eval(Symbol(s)) : i); return nothing
elseif x.node_type == "Prts" print(eval(interp(x.left))); return nothing
elseif x.node_type == "Sequence" interp(x.left); interp(x.right); return nothing
else
throw("unknown node type: $x")
end
end
const testparsed = """ Sequence Sequence Sequence Sequence Sequence
Assign Identifier count Integer 1 Assign Identifier n Integer 1 Assign Identifier limit Integer 100 While Less Identifier n Identifier limit Sequence Sequence Sequence Sequence Sequence
Assign Identifier k Integer 3 Assign Identifier p Integer 1 Assign Identifier n Add Identifier n Integer 2 While And LessEqual Multiply Identifier k Identifier k Identifier n Identifier p Sequence Sequence
Assign Identifier p NotEqual Multiply Divide Identifier n Identifier k Identifier k Identifier n Assign Identifier k Add Identifier k Integer 2 If Identifier p If Sequence Sequence
Sequence Sequence
Prti Identifier n
Prts String \" is prime\\n\"
Assign Identifier count Add Identifier count Integer 1
Sequence Sequence Sequence
Prts String \"Total primes found: \"
Prti Identifier count
Prts String \"\\n\"
- """
const lio = IOBuffer(testparsed)
interp(load_ast(lio))
</lang>
- Output:
3 is prime 5 is prime 7 is prime 11 is prime 13 is prime 17 is prime 19 is prime 23 is prime 29 is prime 31 is prime 37 is prime 41 is prime 43 is prime 47 is prime 53 is prime 59 is prime 61 is prime 67 is prime 71 is prime 73 is prime 79 is prime 83 is prime 89 is prime 97 is prime 101 is prime Total primes found: 26
Perl
Tested with perl v5.26.1
<lang Perl>#!/usr/bin/perl
use strict; # interpreter.pl - execute a flatAST use warnings; # http://www.rosettacode.org/wiki/Compiler/AST_interpreter use integer;
my %variables;
tree()->run;
sub tree
{
my $line = <> // die "incomplete tree\n";
(local $_, my $arg) = $line =~ /^(\w+|;)\s+(.*)/ or die "bad input $line";
/String/ ? bless [$arg =~ tr/""//dr =~ s/\\(.)/$1 eq 'n' ? "\n" : $1/ger], $_ :
/Identifier|Integer/ ? bless [ $arg ], $_ :
/;/ ? bless [], 'Null' :
bless [ tree(), tree() ], $_;
}
sub Add::run { $_[0][0]->run + $_[0][1]->run } sub And::run { $_[0][0]->run && $_[0][1]->run } sub Assign::run { $variables{$_[0][0][0]} = $_[0][1]->run } sub Divide::run { $_[0][0]->run / $_[0][1]->run } sub Equal::run { $_[0][0]->run == $_[0][1]->run ? 1 : 0 } sub Greater::run { $_[0][0]->run > $_[0][1]->run ? 1 : 0 } sub GreaterEqual::run { $_[0][0]->run >= $_[0][1]->run ? 1 : 0 } sub Identifier::run { $variables{$_[0][0]} // 0 } sub If::run { $_[0][0]->run ? $_[0][1][0]->run : $_[0][1][1]->run } sub Integer::run { $_[0][0] } sub Less::run { $_[0][0]->run < $_[0][1]->run ? 1 : 0 } sub LessEqual::run { $_[0][0]->run <= $_[0][1]->run ? 1 : 0 } sub Mod::run { $_[0][0]->run % $_[0][1]->run } sub Multiply::run { $_[0][0]->run * $_[0][1]->run } sub Negate::run { - $_[0][0]->run } sub Not::run { $_[0][0]->run ? 0 : 1 } sub NotEqual::run { $_[0][0]->run != $_[0][1]->run ? 1 : 0 } sub Null::run {} sub Or::run { $_[0][0]->run || $_[0][1]->run } sub Prtc::run { print chr $_[0][0]->run } sub Prti::run { print $_[0][0]->run } sub Prts::run { print $_[0][0][0] } sub Sequence::run { $_->run for $_[0]->@* } sub Subtract::run { $_[0][0]->run - $_[0][1]->run } sub While::run { $_[0][1]->run while $_[0][0]->run }</lang> Passes all tests.
Phix
Reusing parse.e from the Syntax Analyzer task <lang Phix>-- -- demo\rosetta\Compiler\interp.exw -- ================================
include parse.e
sequence vars = {},
vals = {}
function var_idx(sequence inode)
if inode[1]!=tk_Identifier then ?9/0 end if
string ident = inode[2]
integer n = find(ident,vars)
if n=0 then
vars = append(vars,ident)
vals = append(vals,0)
n = length(vars)
end if
return n
end function
function interp(object t)
if t!=NULL then
integer ntype = t[1]
object t2 = t[2],
t3 = iff(length(t)=3?t[3]:0)
switch ntype do
case tk_Sequence: {} = interp(t2) {} = interp(t3)
case tk_assign: vals[var_idx(t2)] = interp(t3)
case tk_Identifier: return vals[var_idx(t)]
case tk_Integer: return t2
case tk_String: return t2
case tk_lt: return interp(t2) < interp(t3)
case tk_add: return interp(t2) + interp(t3)
case tk_sub: return interp(t2) - interp(t3)
case tk_while: while interp(t2) do {} = interp(t3) end while
case tk_Prints: puts(1,interp(t2))
case tk_Printi: printf(1,"%d",interp(t2))
case tk_putc: printf(1,"%c",interp(t2))
case tk_and: return interp(t2) and interp(t3)
case tk_or: return interp(t2) or interp(t3)
case tk_le: return interp(t2) <= interp(t3)
case tk_ge: return interp(t2) >= interp(t3)
case tk_ne: return interp(t2) != interp(t3)
case tk_gt: return interp(t2) > interp(t3)
case tk_mul: return interp(t2) * interp(t3)
case tk_div: return trunc(interp(t2)/interp(t3))
case tk_mod: return remainder(interp(t2),interp(t3))
case tk_if: {} = interp(t3[iff(interp(t2)?2:3)])
case tk_not: return not interp(t2)
case tk_neg: return - interp(t2)
else
error("unknown node type")
end switch
end if
return NULL
end function
procedure main(sequence cl)
open_files(cl)
toks = lex()
object t = parse()
{} = interp(t)
close_files()
end procedure
--main(command_line()) main({0,0,"primes.c"})</lang>
- Output:
3 is prime 5 is prime 7 is prime 11 is prime 13 is prime 17 is prime 19 is prime 23 is prime 29 is prime 31 is prime 37 is prime 41 is prime 43 is prime 47 is prime 53 is prime 59 is prime 61 is prime 67 is prime 71 is prime 73 is prime 79 is prime 83 is prime 89 is prime 97 is prime 101 is prime Total primes found: 26
Python
Tested with Python 2.7 and 3.x <lang Python>from __future__ import print_function import sys, shlex, operator
nd_Ident, nd_String, nd_Integer, nd_Sequence, nd_If, nd_Prtc, nd_Prts, nd_Prti, nd_While, \ nd_Assign, nd_Negate, nd_Not, nd_Mul, nd_Div, nd_Mod, nd_Add, nd_Sub, nd_Lss, nd_Leq, \ nd_Gtr, nd_Geq, nd_Eql, nd_Neq, nd_And, nd_Or = range(25)
all_syms = {
"Identifier" : nd_Ident, "String" : nd_String, "Integer" : nd_Integer, "Sequence" : nd_Sequence, "If" : nd_If, "Prtc" : nd_Prtc, "Prts" : nd_Prts, "Prti" : nd_Prti, "While" : nd_While, "Assign" : nd_Assign, "Negate" : nd_Negate, "Not" : nd_Not, "Multiply" : nd_Mul, "Divide" : nd_Div, "Mod" : nd_Mod, "Add" : nd_Add, "Subtract" : nd_Sub, "Less" : nd_Lss, "LessEqual" : nd_Leq, "Greater" : nd_Gtr, "GreaterEqual": nd_Geq, "Equal" : nd_Eql, "NotEqual" : nd_Neq, "And" : nd_And, "Or" : nd_Or}
input_file = None globals = {}
- show error and exit
def error(msg):
print("%s" % (msg))
exit(1)
class Node:
def __init__(self, node_type, left = None, right = None, value = None):
self.node_type = node_type
self.left = left
self.right = right
self.value = value
def make_node(oper, left, right = None):
return Node(oper, left, right)
def make_leaf(oper, n):
return Node(oper, value = n)
def fetch_var(var_name):
n = globals.get(var_name, None)
if n == None:
globals[var_name] = n = 0
return n
def interp(x):
global globals
if x == None: return None elif x.node_type == nd_Integer: return int(x.value) elif x.node_type == nd_Ident: return fetch_var(x.value) elif x.node_type == nd_String: return x.value
elif x.node_type == nd_Assign:
globals[x.left.value] = interp(x.right)
return None
elif x.node_type == nd_Add: return interp(x.left) + interp(x.right)
elif x.node_type == nd_Sub: return interp(x.left) - interp(x.right)
elif x.node_type == nd_Mul: return interp(x.left) * interp(x.right)
# use C like division semantics
# another way: abs(x) / abs(y) * cmp(x, 0) * cmp(y, 0)
elif x.node_type == nd_Div: return int(float(interp(x.left)) / interp(x.right))
elif x.node_type == nd_Mod: return int(float(interp(x.left)) % interp(x.right))
elif x.node_type == nd_Lss: return interp(x.left) < interp(x.right)
elif x.node_type == nd_Gtr: return interp(x.left) > interp(x.right)
elif x.node_type == nd_Leq: return interp(x.left) <= interp(x.right)
elif x.node_type == nd_Geq: return interp(x.left) >= interp(x.right)
elif x.node_type == nd_Eql: return interp(x.left) == interp(x.right)
elif x.node_type == nd_Neq: return interp(x.left) != interp(x.right)
elif x.node_type == nd_And: return interp(x.left) and interp(x.right)
elif x.node_type == nd_Or: return interp(x.left) or interp(x.right)
elif x.node_type == nd_Negate: return -interp(x.left)
elif x.node_type == nd_Not: return not interp(x.left)
elif x.node_type == nd_If:
if (interp(x.left)):
interp(x.right.left)
else:
interp(x.right.right)
return None
elif x.node_type == nd_While:
while (interp(x.left)):
interp(x.right)
return None
elif x.node_type == nd_Prtc:
print("%c" % (interp(x.left)), end=)
return None
elif x.node_type == nd_Prti:
print("%d" % (interp(x.left)), end=)
return None
elif x.node_type == nd_Prts:
print(interp(x.left), end=)
return None
elif x.node_type == nd_Sequence:
interp(x.left)
interp(x.right)
return None
else:
error("error in code generator - found %d, expecting operator" % (x.node_type))
def str_trans(srce):
dest = ""
i = 0
srce = srce[1:-1]
while i < len(srce):
if srce[i] == '\\' and i + 1 < len(srce):
if srce[i + 1] == 'n':
dest += '\n'
i += 2
elif srce[i + 1] == '\\':
dest += '\\'
i += 2
else:
dest += srce[i]
i += 1
return dest
def load_ast():
line = input_file.readline() line_list = shlex.split(line, False, False)
text = line_list[0]
value = None
if len(line_list) > 1:
value = line_list[1]
if value.isdigit():
value = int(value)
if text == ";":
return None
node_type = all_syms[text]
if value != None:
if node_type == nd_String:
value = str_trans(value)
return make_leaf(node_type, value) left = load_ast() right = load_ast() return make_node(node_type, left, right)
- main driver
input_file = sys.stdin if len(sys.argv) > 1:
try:
input_file = open(sys.argv[1], "r", 4096)
except IOError as e:
error(0, 0, "Can't open %s" % sys.argv[1])
n = load_ast() interp(n)</lang>
- Output — prime numbers output from AST interpreter:
lex prime.t | parse | interp 3 is prime 5 is prime 7 is prime 11 is prime 13 is prime 17 is prime 19 is prime 23 is prime 29 is prime 31 is prime 37 is prime 41 is prime 43 is prime 47 is prime 53 is prime 59 is prime 61 is prime 67 is prime 71 is prime 73 is prime 79 is prime 83 is prime 89 is prime 97 is prime 101 is prime Total primes found: 26
Scheme
<lang scheme> (import (scheme base)
(scheme file)
(scheme process-context)
(scheme write)
(only (srfi 13) string-delete string-index string-trim))
- Mappings from operation symbols to internal procedures.
- We define operations appropriate to virtual machine
- e.g. division must return an int, not a rational
- boolean values are treated as numbers
- 0 is false, other is true
(define *unary-ops*
(list (cons 'Negate (lambda (a) (- a)))
(cons 'Not (lambda (a) (if (zero? a) 1 0)))))
(define *binary-ops*
(let ((number-comp (lambda (op) (lambda (a b) (if (op a b) 1 0)))))
(list (cons 'Add +)
(cons 'Subtract -)
(cons 'Multiply *)
(cons 'Divide (lambda (a b) (truncate (/ a b)))) ; int division
(cons 'Mod modulo)
(cons 'Less (number-comp <))
(cons 'Greater (number-comp >))
(cons 'LessEqual (number-comp <=))
(cons 'GreaterEqual (number-comp >=))
(cons 'Equal (lambda (a b) (if (= a b) 1 0)))
(cons 'NotEqual (lambda (a b) (if (= a b) 0 1)))
(cons 'And (lambda (a b) ; make "and" work on numbers
(if (and (not (zero? a)) (not (zero? b))) 1 0)))
(cons 'Or (lambda (a b) ; make "or" work on numbers
(if (or (not (zero? a)) (not (zero? b))) 1 0))))))
- Read AST from given filename
- - return as an s-expression
(define (read-code filename)
(define (read-expr)
(let ((line (string-trim (read-line))))
(if (string=? line ";")
'()
(let ((space (string-index line #\space)))
(if space
(list (string->symbol (string-trim (substring line 0 space)))
(string-trim (substring line space (string-length line))))
(list (string->symbol line) (read-expr) (read-expr)))))))
;
(with-input-from-file
filename
(lambda ()
(read-expr))))
- interpret AST provided as an s-expression
(define run-program
(let ((env '())) ; env is an association list for variable names
(lambda (expr)
(define (tidy-string str)
(string-delete ; remove any quote marks
#\" ; " (to appease Rosetta code's syntax highlighter)
(list->string
(let loop ((chars (string->list str))) ; replace newlines, obeying \\n
(cond ((< (length chars) 2) ; finished list
chars)
((and (>= (length chars) 3) ; preserve \\n
(char=? #\\ (car chars))
(char=? #\\ (cadr chars))
(char=? #\n (cadr (cdr chars))))
(cons (car chars)
(cons (cadr chars)
(cons (cadr (cdr chars))
(loop (cdr (cdr (cdr chars))))))))
((and (char=? #\\ (car chars)) ; replace \n with newline
(char=? #\n (cadr chars)))
(cons #\newline (loop (cdr (cdr chars)))))
(else ; keep char and look further
(cons (car chars) (loop (cdr chars)))))))))
; define some more meaningful names for fields
(define left cadr)
(define right (lambda (x) (cadr (cdr x))))
;
(if (null? expr)
'()
(case (car expr) ; interpret AST from the head node
((Integer)
(string->number (left expr)))
((Identifier)
(let ((val (assq (string->symbol (left expr)) env)))
(if val
(cdr val)
(error "Variable not in environment"))))
((String)
(left expr))
((Assign)
(set! env (cons (cons (string->symbol (left (left expr)))
(run-program (right expr)))
env)))
((Add Subtract Multiply Divide Mod
Less Greater LessEqual GreaterEqual Equal NotEqual
And Or)
(let ((binop (assq (car expr) *binary-ops*)))
(if binop
((cdr binop) (run-program (left expr))
(run-program (right expr)))
(error "Could not find binary operator"))))
((Negate Not)
(let ((unaryop (assq (car expr) *unary-ops*)))
(if unaryop
((cdr unaryop) (run-program (left expr)))
(error "Could not find unary operator"))))
((If)
(if (not (zero? (run-program (left expr)))) ; 0 means false
(run-program (left (right expr)))
(run-program (right (right expr))))
'())
((While)
(let loop ()
(unless (zero? (run-program (left expr)))
(run-program (right expr))
(loop)))
'())
((Prtc)
(display (integer->char (run-program (left expr))))
'())
((Prti)
(display (run-program (left expr)))
'())
((Prts)
(display (tidy-string (run-program (left expr))))
'())
((Sequence)
(run-program (left expr))
(run-program (right expr))
'())
(else
(error "Unknown node type")))))))
- read AST from file and interpret, from filename passed on command line
(if (= 2 (length (command-line)))
(run-program (read-code (cadr (command-line)))) (display "Error: pass an ast filename\n"))
</lang>
- Output:
Output for primes program from above. Also tested on programs in Compiler/Sample programs.
3 is prime 5 is prime 7 is prime 11 is prime 13 is prime 17 is prime 19 is prime 23 is prime 29 is prime 31 is prime 37 is prime 41 is prime 43 is prime 47 is prime 53 is prime 59 is prime 61 is prime 67 is prime 71 is prime 73 is prime 79 is prime 83 is prime 89 is prime 97 is prime 101 is prime Total primes found: 26
zkl
<lang zkl>const{ var _n=-1; var[proxy]N=fcn{ _n+=1 }; } // enumerator const FETCH=N, STORE=N, PUSH=N, ADD=N, SUB=N, MUL=N, DIV=N, MOD=N,
LT=N, GT=N, LE=N, GE=N, EQ=N, NE=N,
AND=N, OR=N, NEG=N, NOT=N,
JMP=N, JZ=N, PRTC=N, PRTS=N, PRTI=N, HALT=N;
const nd_String=N, nd_Sequence=N, nd_If=N, nd_While=N; var [const]
all_syms=Dictionary(
"Identifier" ,FETCH, "String" ,nd_String,
"Integer" ,PUSH, "Sequence" ,nd_Sequence,
"If" ,nd_If, "Prtc" ,PRTC,
"Prts" ,PRTS, "Prti" ,PRTI,
"While" ,nd_While, "Assign" ,STORE,
"Negate" ,NEG, "Not" ,NOT,
"Multiply" ,MUL, "Divide" ,DIV,
"Mod" ,MOD, "Add" ,ADD,
"Subtract" ,SUB, "Less" ,LT,
"LessEqual" ,LE, "Greater" ,GT,
"GreaterEqual",GE, "Equal" ,EQ,
"NotEqual" ,NE, "And" ,AND,
"Or" ,OR, "halt" ,HALT),
bops=Dictionary(ADD,'+, SUB,'-, MUL,'*, DIV,'/, MOD,'%,
LT,'<, GT,'>, LE,'<=, GE,'>=, NE,'!=, EQ,'==, NE,'!=);
class Node{
fcn init(_node_type, _value, _left=Void, _right=Void){
var type=_node_type, left=_left, right=_right, value=_value;
}
}
fcn runNode(node){
var vars=Dictionary(); // fcn local static var
if(Void==node) return();
switch(node.type){
case(PUSH,nd_String){ return(node.value) }
case(FETCH){ return(vars[node.value]) }
case(STORE){ vars[node.left.value]=runNode(node.right); return(Void); }
case(nd_If){
if(runNode(node.left)) runNode(node.right.left);
else runNode(node.right.right);
}
case(nd_While)
{ while(runNode(node.left)){ runNode(node.right) } return(Void) }
case(nd_Sequence){ runNode(node.left); runNode(node.right); return(Void) }
case(PRTC) { print(runNode(node.left).toAsc()) }
case(PRTI,PRTS) { print(runNode(node.left)) }
case(NEG) { return(-runNode(node.left)) }
case(NOT) { return(not runNode(node.left)) }
case(AND) { return(runNode(node.left) and runNode(node.right)) }
case(OR) { return(runNode(node.left) or runNode(node.right)) }
else{
if(op:=bops.find(node.type)) return(op(runNode(node.left),runNode(node.right))); else throw(Exception.AssertionError( "Unknown node type: %d".fmt(node.type)))
} } Void
}</lang> <lang zkl>fcn load_ast(file){
line:=file.readln().strip(); // one or two tokens
if(line[0]==";") return(Void);
parts,type,value := line.split(),parts[0],parts[1,*].concat(" ");
type=all_syms[type];
if(value){
try{ value=value.toInt() }catch{}
if(type==nd_String) value=value[1,-1].replace("\\n","\n");
return(Node(type,value));
}
left,right := load_ast(file),load_ast(file);
Node(type,Void,left,right)
}</lang> <lang zkl>ast:=load_ast(File(vm.nthArg(0))); runNode(ast);</lang>
- Output:
$ zkl runAST.zkl primeAST.txt 3 is prime 5 is prime 7 is prime 11 is prime ... 89 is prime 97 is prime 101 is prime Total primes found: 26