Adding two tokens together (integers). Flex/Bison
I have a simple Bison file with some simple grammar. I am taking an unending list of expressions, and my goal is to make a single definition for the expression that adds the values of two tokens together.
At line 20, there is a grammar rule that shows what I am trying to achieve. Unfortunately, it does not work. How can I achieve this functionality?
Bison File
%{
#include <stdio.h>
#include <stdlib.h>
int yylex();
void yyerror(const char* msg);
%}
%token INT
%token PLUS
%token END
%%
expr_list: END
{ exit(0); }
| expr
| expr expr_list
;
expr: INT PLUS INT
{ printf("%dn", ($1 + $3)); }
;
%%
int main(int argc, char** argv) {
yyparse();
return 0;
}
void yyerror(const char* msg) {
fprintf(stderr, "ERROR! %sn", msg);
}
Flex File
%{
#include "adder.tab.h"
%}
%%
(+) return PLUS;
[0-9]+ return INT;
(END) return END;
%%
bison
asked Nov 27 '18 at 3:35
Farid KaradshehFarid Karadsheh
218210
add a comment |
I have a simple Bison file with some simple grammar. I am taking an unending list of expressions, and my goal is to make a single definition for the expression that adds the values of two tokens together.
At line 20, there is a grammar rule that shows what I am trying to achieve. Unfortunately, it does not work. How can I achieve this functionality?
Bison File
%{
#include <stdio.h>
#include <stdlib.h>
int yylex();
void yyerror(const char* msg);
%}
%token INT
%token PLUS
%token END
%%
expr_list: END
{ exit(0); }
| expr
| expr expr_list
;
expr: INT PLUS INT
{ printf("%dn", ($1 + $3)); }
;
%%
int main(int argc, char** argv) {
yyparse();
return 0;
}
void yyerror(const char* msg) {
fprintf(stderr, "ERROR! %sn", msg);
}
Flex File
%{
#include "adder.tab.h"
%}
%%
(+) return PLUS;
[0-9]+ return INT;
(END) return END;
%%
bison
asked Nov 27 '18 at 3:35
Farid KaradshehFarid Karadsheh
218210
please copy the file here instead of in an external link. questions should be self-contained
– phuclv
Nov 27 '18 at 3:37
@phuclv added bison and flex source.
– Farid Karadsheh
Nov 27 '18 at 3:43
Can you clarify "does not work"? In what way does it not work? Do you get an error? An unexpected result? Something else? In either case, what's your input, expected output and actual output or error message?
– sepp2k
Nov 27 '18 at 7:35
@sepp2k Everything gets up and running fine. When I type in "END" the program exits. When I type in10 + 5,0is printed. This is likely due to a poorly defined grammar rule.
– Farid Karadsheh
Nov 27 '18 at 14:31
add a comment |
I have a simple Bison file with some simple grammar. I am taking an unending list of expressions, and my goal is to make a single definition for the expression that adds the values of two tokens together.
At line 20, there is a grammar rule that shows what I am trying to achieve. Unfortunately, it does not work. How can I achieve this functionality?
Bison File
%{
#include <stdio.h>
#include <stdlib.h>
int yylex();
void yyerror(const char* msg);
%}
%token INT
%token PLUS
%token END
%%
expr_list: END
{ exit(0); }
| expr
| expr expr_list
;
expr: INT PLUS INT
{ printf("%dn", ($1 + $3)); }
;
%%
int main(int argc, char** argv) {
yyparse();
return 0;
}
void yyerror(const char* msg) {
fprintf(stderr, "ERROR! %sn", msg);
}
Flex File
%{
#include "adder.tab.h"
%}
%%
(+) return PLUS;
[0-9]+ return INT;
(END) return END;
%%
bison
asked Nov 27 '18 at 3:35
Farid KaradshehFarid Karadsheh
218210
I have a simple Bison file with some simple grammar. I am taking an unending list of expressions, and my goal is to make a single definition for the expression that adds the values of two tokens together.
At line 20, there is a grammar rule that shows what I am trying to achieve. Unfortunately, it does not work. How can I achieve this functionality?
Bison File
%{
#include <stdio.h>
#include <stdlib.h>
int yylex();
void yyerror(const char* msg);
%}
%token INT
%token PLUS
%token END
%%
expr_list: END
{ exit(0); }
| expr
| expr expr_list
;
expr: INT PLUS INT
{ printf("%dn", ($1 + $3)); }
;
%%
int main(int argc, char** argv) {
yyparse();
return 0;
}
void yyerror(const char* msg) {
fprintf(stderr, "ERROR! %sn", msg);
}
Flex File
%{
#include "adder.tab.h"
%}
%%
(+) return PLUS;
[0-9]+ return INT;
(END) return END;
%%
bison
bison
asked Nov 27 '18 at 3:35
Farid KaradshehFarid Karadsheh
218210
asked Nov 27 '18 at 3:35
Farid KaradshehFarid Karadsheh
218210
edited Nov 28 '18 at 5:56
Farid Karadsheh
asked Nov 27 '18 at 3:35
Farid KaradshehFarid Karadsheh
218210
asked Nov 27 '18 at 3:35
Farid KaradshehFarid Karadsheh
218210
asked Nov 27 '18 at 3:35
Farid KaradshehFarid Karadsheh
218210
218210
please copy the file here instead of in an external link. questions should be self-contained
– phuclv
Nov 27 '18 at 3:37
@phuclv added bison and flex source.
– Farid Karadsheh
Nov 27 '18 at 3:43
Can you clarify "does not work"? In what way does it not work? Do you get an error? An unexpected result? Something else? In either case, what's your input, expected output and actual output or error message?
– sepp2k
Nov 27 '18 at 7:35
@sepp2k Everything gets up and running fine. When I type in "END" the program exits. When I type in10 + 5,0is printed. This is likely due to a poorly defined grammar rule.
– Farid Karadsheh
Nov 27 '18 at 14:31
add a comment |
please copy the file here instead of in an external link. questions should be self-contained
– phuclv
Nov 27 '18 at 3:37
@phuclv added bison and flex source.
– Farid Karadsheh
Nov 27 '18 at 3:43
Can you clarify "does not work"? In what way does it not work? Do you get an error? An unexpected result? Something else? In either case, what's your input, expected output and actual output or error message?
– sepp2k
Nov 27 '18 at 7:35
@sepp2k Everything gets up and running fine. When I type in "END" the program exits. When I type in10 + 5,0is printed. This is likely due to a poorly defined grammar rule.
– Farid Karadsheh
Nov 27 '18 at 14:31
please copy the file here instead of in an external link. questions should be self-contained
– phuclv
Nov 27 '18 at 3:37
please copy the file here instead of in an external link. questions should be self-contained
– phuclv
Nov 27 '18 at 3:37
@phuclv added bison and flex source.
– Farid Karadsheh
Nov 27 '18 at 3:43
@phuclv added bison and flex source.
– Farid Karadsheh
Nov 27 '18 at 3:43
Can you clarify "does not work"? In what way does it not work? Do you get an error? An unexpected result? Something else? In either case, what's your input, expected output and actual output or error message?
– sepp2k
Nov 27 '18 at 7:35
Can you clarify "does not work"? In what way does it not work? Do you get an error? An unexpected result? Something else? In either case, what's your input, expected output and actual output or error message?
– sepp2k
Nov 27 '18 at 7:35
@sepp2k Everything gets up and running fine. When I type in "END" the program exits. When I type in
10 + 5, 0 is printed. This is likely due to a poorly defined grammar rule.– Farid Karadsheh
Nov 27 '18 at 14:31
@sepp2k Everything gets up and running fine. When I type in "END" the program exits. When I type in
10 + 5, 0 is printed. This is likely due to a poorly defined grammar rule.– Farid Karadsheh
Nov 27 '18 at 14:31
add a comment |
1 Answer
1
active
oldest
votes
In your parser you have this:
expr: INT PLUS INT
{ printf("%dn", ($1 + $3)); }
This takes the semantic values of the two INT tokens and adds them, which is fine. If this always produces 0, that means there must be something wrong with the tokens' semantic values. So let's look at the corresponding lexer action:
[0-9]+ return INT;
Here you never assign anything to yylval, so $1 and $3 in your parser rule will be unassigned. To assign a meaningful semantic value you can use strtol to convert the string in yytext to an integer:
[0-9]+ yylval = strtol(yytext, NULL, 10); return INT;
For proper error handling for numbers outside of int's range, you should check errno after calling strtol.
answered Nov 27 '18 at 14:45
sepp2ksepp2k
296k38596613
add a comment |
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1 Answer
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active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
In your parser you have this:
expr: INT PLUS INT
{ printf("%dn", ($1 + $3)); }
This takes the semantic values of the two INT tokens and adds them, which is fine. If this always produces 0, that means there must be something wrong with the tokens' semantic values. So let's look at the corresponding lexer action:
[0-9]+ return INT;
Here you never assign anything to yylval, so $1 and $3 in your parser rule will be unassigned. To assign a meaningful semantic value you can use strtol to convert the string in yytext to an integer:
[0-9]+ yylval = strtol(yytext, NULL, 10); return INT;
For proper error handling for numbers outside of int's range, you should check errno after calling strtol.
answered Nov 27 '18 at 14:45
sepp2ksepp2k
296k38596613
add a comment |
In your parser you have this:
expr: INT PLUS INT
{ printf("%dn", ($1 + $3)); }
This takes the semantic values of the two INT tokens and adds them, which is fine. If this always produces 0, that means there must be something wrong with the tokens' semantic values. So let's look at the corresponding lexer action:
[0-9]+ return INT;
Here you never assign anything to yylval, so $1 and $3 in your parser rule will be unassigned. To assign a meaningful semantic value you can use strtol to convert the string in yytext to an integer:
[0-9]+ yylval = strtol(yytext, NULL, 10); return INT;
For proper error handling for numbers outside of int's range, you should check errno after calling strtol.
answered Nov 27 '18 at 14:45
sepp2ksepp2k
296k38596613
add a comment |
In your parser you have this:
expr: INT PLUS INT
{ printf("%dn", ($1 + $3)); }
This takes the semantic values of the two INT tokens and adds them, which is fine. If this always produces 0, that means there must be something wrong with the tokens' semantic values. So let's look at the corresponding lexer action:
[0-9]+ return INT;
Here you never assign anything to yylval, so $1 and $3 in your parser rule will be unassigned. To assign a meaningful semantic value you can use strtol to convert the string in yytext to an integer:
[0-9]+ yylval = strtol(yytext, NULL, 10); return INT;
For proper error handling for numbers outside of int's range, you should check errno after calling strtol.
answered Nov 27 '18 at 14:45
sepp2ksepp2k
296k38596613
In your parser you have this:
expr: INT PLUS INT
{ printf("%dn", ($1 + $3)); }
This takes the semantic values of the two INT tokens and adds them, which is fine. If this always produces 0, that means there must be something wrong with the tokens' semantic values. So let's look at the corresponding lexer action:
[0-9]+ return INT;
Here you never assign anything to yylval, so $1 and $3 in your parser rule will be unassigned. To assign a meaningful semantic value you can use strtol to convert the string in yytext to an integer:
[0-9]+ yylval = strtol(yytext, NULL, 10); return INT;
For proper error handling for numbers outside of int's range, you should check errno after calling strtol.
answered Nov 27 '18 at 14:45
sepp2ksepp2k
296k38596613
edited Nov 27 '18 at 14:53
answered Nov 27 '18 at 14:45
sepp2ksepp2k
296k38596613
answered Nov 27 '18 at 14:45
sepp2ksepp2k
296k38596613
answered Nov 27 '18 at 14:45
sepp2ksepp2k
296k38596613
296k38596613
add a comment |
add a comment |
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please copy the file here instead of in an external link. questions should be self-contained
– phuclv
Nov 27 '18 at 3:37
@phuclv added bison and flex source.
– Farid Karadsheh
Nov 27 '18 at 3:43
Can you clarify "does not work"? In what way does it not work? Do you get an error? An unexpected result? Something else? In either case, what's your input, expected output and actual output or error message?
– sepp2k
Nov 27 '18 at 7:35
@sepp2k Everything gets up and running fine. When I type in "END" the program exits. When I type in
10 + 5,0is printed. This is likely due to a poorly defined grammar rule.– Farid Karadsheh
Nov 27 '18 at 14:31