S6 CSE COMPILER LAB : PARSER FOR TYPE CHECKING

                                                     

                                   /*    PARSER FOR TYPE CHECKING   */

Yacc program

%{

#include<stdio.h>

#include<stdlib.h>

#include<string.h>

char *yytext;

%}

%token INT FLOAT CHAR ID SP

%left '+' '-'

%left '*' '/'

%left ','

%right '='

%%

S:DCL ST {printf("CHECKED\n");}

DCL:INT SP IIDS';'

    |FLOAT SP FIDS';'

    |CHAR SP CHIDS';'

    |DCL INT SP IIDS';'

    |DCL FLOAT SP FIDS';'

    |DCL CHAR SP CHIDS';'

   

CHIDS:ID {insert(yytext,1);}

      |CHIDS','ID {insert(yytext,1);}

   

IIDS:ID {insert(yytext,2);}

     |IIDS','ID {insert(yytext,2);}

  

FIDS:ID {insert(yytext,3);}

    |FIDS','ID {insert(yytext,3);}

  

ST:E';'

  |ST E';'

E:E'+'E {if(($$<$1)||($$<$3)){printf("+ error\n");exit(0);}} 

  |E'-'E {if(($$<$1)||($$<$3)){printf("- error\n");exit(0);}} 

  |E'*'E {if(($$<$1)||($$<$3)){printf("* error\n");exit(0);}}

  |E'/'E {if(($$<$1)||($$<$3)){printf("/ error\n");exit(0);}} 

  |IDD'='E {if(($$<$1)||($$<$3)){printf("= error\n");exit(0);}}

  |IDD

IDD:ID {$$=lookup(yytext);};

%%

#include "lex.yy.c"

#include "ctype.h"

struct types

{

char var[10];

int type;

}TC[10];

int top=0,i;int main()

{

yyparse();

}

yyerror(char *s)

{

 printf("%s\n",s);

}

insert(char *sl,int tp)

{

 strcpy(TC[top].var,sl);

 TC[top].type=tp;

 top++;

}

int lookup(char *cc)

{

 int flag=0;

 for(i=0;i<top;i++)

 {

  if(strcmp(cc,TC[i].var)==0)

    return(TC[i].type);

 }

printf("lookup error");

exit(0);

}

Lex program

%{

#include "y.tab.h"

extern int yylval;

%}

%%

"char"   {yylval=1;return CHAR;}

"int"    {yylval=2;return INT;}

"float"  {yylval=3;return FLOAT;}

[a-z]+   {return ID;}

[\t]     ;

" "      {return SP;}

[\n]     {return 0;}

.        {return yytext[0];}

%%

 OUTPUT

int x,y;float z;z=x+y;

CHECKED

int x;float y;x=y;

= error