S6 CSE COMPILER LAB : PARSER FOR 'FOR' LOOP

/*  PARSER FOR 'FOR' LOOP  */

Yacc program

%{

#include<stdio.h>

#include<stdlib.h>

%}

%token num alpha LT GT EQ LE GE NE AND OR NL FOR INC DEC

%left '+''-'

%left '*''/'

%right '^'

%right '='

%nonassoc UMINUS

%nonassoc FOR

%left LT GT EQ LE GE NE

%left AND OR

%%

S:ST NL  {printf("ACCEPTED\n");exit(0);}

ST:FOR'('INIT';'COND';'UNARY')''{'ST'}'

     |E';'ST

     |E';'

COND:C LO C

            |C

LO:AND

      |OR

C:E RELOP E

INIT:alpha'='num

UNARY:alpha INC

              |alpha DEC

E:alpha'='E

  |E'+'E

  |E'-'E

  |E'*'E

  |E'/'E

  |E'^'E

  |'-'E %prec UMINUS

  |alpha INC

  |alpha DEC

  |num DEC

  |num INC

 |alpha

 |num

RELOP:LT

             |GT

             |EQ

             |GE

             |LE

             |NE

             ;

%%

#include "lex.yy.c"

#include "stdio.h"

 int main()

 {

  yyparse();

  yylex();

  return 0;

 }

 yyerror(char *s)

 {

  printf("\nERROR");

 }

Lex program

%{

#include "y.tab.h"

%}

%%

"for"      {return FOR;}

"&&"      {return AND;}

"||"      {return OR;}

"<"       {return LT;}

">"       {return GT;}

"<="      {return LE;}

">="      {return GE;}

"!="      {return NE;}

"=="      {return EQ;}

"++"      {return INC;}

"--"      {return DEC;}

[a-z]+    {return alpha;}

[0-9]+    {return num;}

[ \t]     ;

[\n]      {return NL;}

.         {return yytext[0];}

%%

OUTPUT

for(i=0;i<10;i++){a=b+c;}

ACCEPTED

for(i=0;j=2;i++){i++;}

ERROR

for(i=0;i<10;i++){j++;}

ACCEPT ED