Program:
// Lex file: for.l
alpha [A-Za-z]
digit [0-9]
%%
[\t \n]
for return FOR;
{digit}+ return NUM;
{alpha}({alpha}|{digit})* return ID;
"<=" return LE;
">=" return GE;
"==" return EQ;
"!=" return NE;
"||" return OR;
"&&" return AND;
. return yytext[0];
%%
// Yacc file: for.y
%{
#include <stdio.h>
#include <stdlib.h>
%}
%token ID NUM FOR LE GE EQ NE OR AND
%right "="
%left OR AND
%left '>' '<' LE GE EQ NE
%left '+' '-'
%left '*' '/'
%right UMINUS
%left '!'
%%
S : ST {printf("Input accepted\n"); exit(0);}
ST : FOR '(' E ';' E2 ';' E ')' DEF
;
DEF : '{' BODY '}'
| E';'
| ST
|
;
BODY : BODY BODY
| E ';'
| ST
|
;
E : ID '=' E
| E '+' E
| E '-' E
| E '*' E
| E '/' E
| E '<' E
| E '>' E
| E LE E
| E GE E
| E EQ E
| E NE E
| E OR E
| E AND E
| E '+' '+'
| E '-' '-'
| ID
| NUM
;
E2 : E'<'E
| E'>'E
| E LE E
| E GE E
| E EQ E
| E NE E
| E OR E
| E AND E
;
%%
#include "lex.yy.c"
main() {
printf("Enter the expression:\n");
yyparse();
}
Output:
nn@linuxmint ~ $ lex for.l
nn@linuxmint ~ $ yacc for.y
conflicts: 25 shift/reduce, 4 reduce/reduce
nn@linuxmint ~ $ gcc y.tab.c -ll -ly
nn@linuxmint ~ $ ./a.out
Enter the expression:
for(i=0;i<n;i++)
i=i+1;
Input accepted
nn@linuxmint ~ $