CODEWITHSUNDEEP
syntaxbisonflex-lexeryacclex
koulini k satya
koulini k satya

Reputation: 25

Unable to find cause of 'syntax error' in Bison code

I'm trying to connect simple flex and bison code that would just recognize a character for now. Yet I'm facing this error. I've read through a lot of answers to figure out what is wrong but am lost. Any help would be highly appreciated as I'm just starting out to explore this and could not find a lot of resources for it.

This is my .l file

%{
#include <stdlib.h>
#include <stdio.h>
#include "MiniJSC.tab.h"
void yyerror (char *s);
int yylex();
%}

%%


[0-9]+                                                              { yylval.num = atoi(yytext); return T_INT_VAL; }

%%
int yywrap (void) {return 1;}

my .y file

%{
void yyerror (char *s);
int yylex();
#include <stdio.h>     /* C declarations used in actions */
#include <stdlib.h>
%}

%union {int num; char id;}         /* Yacc definitions */
%start line
%token print
%token T_INT_VAL
%type <num> line
%type <num> term 
%type <num> T_INT_VAL

%%

/* descriptions of expected inputs     corresponding actions (in C) */

line    : print term ';'            {printf("Printing %d\n", $2);}
        ;
        
term    : T_INT_VAL                 {$$ = $1;}
        ;

%%                     /* C code */
void yyerror (char *s) {
fprintf (stderr, "%s\n", s);
}

int main (void) {

    return yyparse ( );
}

The compilation and output:

$ bison MiniJSC.y -d
$ lex MiniJSC.l
$ gcc lex.yy.c MiniJSC.tab.c
$ ./a.out
10
syntax error
$

Upvotes: 0

Views: 36

Answers (1)

sepp2k
sepp2k

Reputation: 370425

line    : print term ';'

According to this, a valid line contains a print token followed by a term. Since a term must be a T_INT_VAL token, that means a valid line is a print token followed by a T_INT_VAL token.

Your input consists only of a T_INT_VAL token, so it is not a valid line and that's why you get a syntax error.

Also note that your lexer never produces a print token, so even if you entered print 10 as the input, it'd be an error since the lexer isn't going to recognize print as a token. So you should add a pattern for that as well.

You should also rename print to match your naming convention for tokens (i.e. ALL_CAPS).

Upvotes: 1

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