A flex and bison program for C like variable declaration...

This time we are trying to implement the C like variable declaration in flex-bison:-

Grammar:
S->S F | epsilon
F->E '\n'
E->K V
K->KEY
V->COMMALST | ID ';'
COMMALST->ID ',' CLST
CLST->ID ',' CLST | ID ';'

Here is the flex specification file: saved as identi.l


%{
//to identify the keyword and identifier
#include<stdlib.h>
#include"identi.tab.h"
%}
%%
"int" |
"char" |
"float" |
"long" |
"double" |
"signed" {return KEY;}
[A-Za-z_]+[0-9A-Za-z_]* {return ID;}
[,;\n] {return *yytext;}
. ;
%%

Here is the bison specification file: saved as identi.y

%{
#include<stdio.h>
void yyerror(char*,...);
int yywrap(void);
%}
%token KEY ID;
%%
S:S F
 |
 ;
F:E '\n'
 ;
E:K V {printf("\nValid Declaration\n");}
 ;
K:KEY
 ;
V:COMMALST
 |ID ';'
 ;
COMMALST:ID ',' CLST
 ;
CLST:ID ',' CLST
 |ID ';'
 ;
%%
int main(void)
{
 yyparse();
 return 0;
}
int yywrap(void)
{
 return 1;
}
void yyerror(char* msg, ...)
{
 printf("\nError Occurred\n");
}

Now all you have to do is run the following commands:

flex identi.l

bison -d identi.y

gcc -o identi lex.yy.c identi.tab.c

Now you have to run the program on your linux OS as:

./identi

INPUT EXAMPLES:

int a;

float ad3,t4,e3;