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Accept anb
n
LEX PROGRAM
%{
#include "y.tab.h"
%}
%%
{
"\n" {return E; }
a {return A;}
b {return B;}
}
%%
int yywrap()
{
}
YACC PROGRAM
%{
#include<stdio.h>
#include<stdlib.h>
void yyerror(char*);
%}
%token A B E
%%
P:S E { printf("matching"); exit(0); }
;
S:A S B |A B
;
%%
main()
{
printf("enter the string:");
yyparse();
}
void yyerror(char *p)
{
printf("mismatch");
}
Syntax of for loop
LEX PROGRAM
id[a-zA-Z0-9]
op "<"|">"|"<="|"<="|">="|"=="|"!="
i "++"|"--"|"+"|"-"|"*"|"/"
eq "="
ob "("
cb ")"
sem ";"
keyword "for"
%{
#include "y.tab.h"
%}
%%
{id} { return ID; }
{op} { return OP; }
{i} { return I; }
{ob} { return OB; }
{cb} { return CB; }
{sem} { return SEM; }
{keyword} { return F; }
{eq} { return EQ; }
"\n" { return E; }
%%
yywrap()
{
}
YACC PROGRAM
%{
#include<stdio.h>
#include<stdlib.h>
void yyerror(char *);
%}
%token OP I CB OB SEM ID F E EQ
%%
P:S E {printf("matching\n"); exit(0);}
;
S:F OB ID EQ ID SEM ID OP ID SEM ID I CB|
F OB ID EQ ID SEM ID OP ID SEM I ID CB|
F OB SEM ID OP ID SEM ID I CB|
F OB SEM ID OP ID SEM I ID CB
;
%%
main()
{
printf("enter the expression:\n");
yyparse();
}
void yyerror(char *p)
{
printf("mismatch\n");
}
Accept anb
nc
md
m
LEX PROGRAM
%{
#include"y.tab.h"
%}
%%
{
a { return A; }
b { return B; }
c { return C; }
d { return D; }
\n { return E; }
}
%%
int yywrap()
{
}
YACC PROGRAM
%{
#include<stdio.h>
#include<stdlib.h>
void yyerror(char *);
%}
%token A B C D E
%%
P: S E { printf("accept\n"); exit(0); }
;
S: M N|M|N
;
M: A M B|A|B
;
N: C N D|C|D
;
%%
main()
{
printf("enter the expression:");
yyparse();
}
void yyerror(char *p)
{
printf("mismatch");
}
Relational Expression
LEX PROGRAM
letters [a-z A-Z 0-9]
op “<”| “>”| “=”
%{
#include “y.tab.h”
%}
%%
{
{letters}* { return ID; }
{op} { return OP; }
}
%%
int yywrap()
{
}
YACC PROGRAM
%{
#include<stdio.h>
void yyerror( char *);
%}
% token ID OP
%%
S : ID OP ID { printf(“correct”);
;
%%
main()
{
printf(“enter the expression:”);
yyparse();
}
void yyerror( char *p)
{
printf(“mismatch”);
}
Accept anc
md
mb
n
LEX PROGRAM
%{
#include"y.tab.h"
%}
%%
{
a { return A; }
b { return B; }
c { return C; }
d { return D; }
\n { return E; }
}
%%
int yywrap()
{
}
YACC PROGRAM
%{
#include<stdio.h>
#include<stdlib.h>
void yyerror(char *);
%}
%token A B C D E
%%
P: S E { printf("accept\n"); exit(0); }
;
S: A M B| A S B| A B| M
;
M: C M D| C D
;
%%
main()
{
printf("enter the expression:");
yyparse();
}
void yyerror(char *p)
{
printf("mismatch");
}
Integer calculator
LEX PROGRAM
op "+"|"-"|"*"|"/"
%{
#include <stdio.h>
#include "y.tab.h"
%}
%%
{op} { return *yytext; }
[0-9]* { yylval=atoi(yytext); return NUM; }
\n { return N; }
"(" { }
")" { }
%%
int yywrap()
{
}
YACC PROGRAM
%{
#include<stdio.h>
#include<stdlib.h>
void yyerror(char *);
%}
%token NUM N
%left '+' '-'
%left '*' '/'
%left '(' ')'
%%
S:E N { printf("result:%d\n",$1); exit(0); }
;
E:E '+' E { $$=$1+$3; }
|E '-' E { $$=$1-$3; }
|E '*' E { $$=$1*$3; }
|E '/' E { $$=$1/$3; }
|'(' E ')' { $$=$2; }
|NUM { $$=$1; }
;
%%
main()
{
printf("enter the expression:\n");
yyparse();
}
void yyerror(char *p)
{
printf("invalid\n");
}
