Problem 11
Problem Statement: Design a LEX code to check whether the given number is even or odd.
Source Code:
%{
#include<stdio.h>
#include<stdlib.h>
%}
%%
[0-9]+ {int num=atoi(yytext);
if(num%2==0)
printf("%s is even\n", yytext);
else
printf("%s is odd\n", yytext);}
[A-Za-z0-9]+ {printf("%s is not a valid number\n", yytext);}
.|\n ;
%%
int main(){
printf("Eenter the string:");
yylex();
return 0;
}
int yywrap(){
return 1;
}
Name: Tanishq Bisht University Roll: 2219803 Section: A2
Output
Name: Tanishq Bisht University Roll: 2219803 Section: A2
Problem 12
Problem Statement: Design a LEX Code to count number of vowels and consonants in a given
pattern.
Source Code:
%{
#include <stdio.h>
int v=0,c=0;
%}
%%
[aeiouAEIOU] {v++;}
[a-zA-Z] {c++;}
.|\n;
%%
int yywrap(){
return 1;
}
int main(){
printf("Enter a string: ");
yylex();
printf("Total number of vowels are:%d\n",v);
printf("Total number of consonants are:%d\n",c);
return 0;
}
Name: Tanishq Bisht University Roll: 2219803 Section: A2
Output
Name: Tanishq Bisht University Roll: 2219803 Section: A2
Problem 13
Problem Statement: Design a LEX Code to check for a valid E-mail Id.
Source Code:
%{
#include <stdio.h>
%}
%%
[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,} { printf("Valid Email: %s\n",
yytext); }
.|\n {}
%%
int main() {
printf("Enter the E-mail: ");
yylex();
return 0;
}
int yywrap() {
return 1;
}
Name: Tanishq Bisht University Roll: 2219803 Section: A2
Output
Name: Tanishq Bisht University Roll: 2219803 Section: A2
Problem 14
Problem Statement: Design a DFA in LEX Code which accepts all possible set of string
containing even number of ‘a’ and even number of ‘b’ over input alphabet Σ = {a, b}.
Source Code:
%{
#include<stdio.h>
%}
%s A DEAD
%%
<INITIAL>a BEGIN A;
<INITIAL>b BEGIN INITIAL;
<INITIAL>\n printf("Accepted\n"); BEGIN INITIAL;
<INITIAL>[^ab\n] BEGIN DEAD;
<A>a BEGIN INITIAL;
<A>b BEGIN A;
<A>\n printf("Not Accepted\n"); BEGIN INITIAL;
<A>[^ab\n] BEGIN DEAD;
<DEAD>\n printf("Invalid Input\n"); BEGIN INITIAL;
<DEAD>[^\n] BEGIN DEAD;
%%
int yywrap(){
return 1;
}
int main(){
printf("Enter the input: ");
yylex();
return 0;
}
Name: Tanishq Bisht University Roll: 2219803 Section: A2
Output
Name: Tanishq Bisht University Roll: 2219803 Section: A2
Problem 15
Problem Statement: Design a DFA in LEX Code to Identify and print Integer, Float Constants
and Identifier.
Source Code:
%{
#include<stdio.h>
%}
%s INT A FLOAT IDENTIFIER DEAD
%%
<INITIAL>[0-9] BEGIN INT;
<INITIAL>[a-zA-Z_] BEGIN IDENTIFIER;
<INITIAL>[^a-zA-Z0-9_\n] BEGIN DEAD;
<INITIAL>\n BEGIN INITIAL;
<INT>[0-9] BEGIN INT;
<INT>[.] BEGIN A;
<INT>[^0-9.\n] BEGIN DEAD;
<INT>\n printf("Integer\n"); BEGIN INITIAL;
<A>[0-9] BEGIN FLOAT;
<A>[^0-9\n] BEGIN DEAD;
<A>\n printf("Invalid Input\n"); BEGIN INITIAL;
<FLOAT>[0-9] BEGIN FLOAT;
<FLOAT>[^0-9\n] BEGIN DEAD;
<FLOAT>\n printf("Float\n"); BEGIN INITIAL;
<IDENTIFIER>[a-zA-Z0-9_] BEGIN IDENTIFIER;
<IDENTIFIER>[^a-zA-Z0-9_\n] BEGIN DEAD;
<IDENTIFIER>\n printf("Identifier\n"); BEGIN INITIAL;
<DEAD>[^\n] BEGIN DEAD;
<DEAD>\n printf("INVALID\n"); BEGIN INITIAL;
%%
int yywrap(){
return 1;
}
int main() {
printf("Enter a input: ");
yylex();
return 0; }
Name: Tanishq Bisht University Roll: 2219803 Section: A2
Output
Name: Tanishq Bisht University Roll: 2219803 Section: A2
Problem 16
Problem Statement: Design a DFA in LEX Code over Σ = {a, b} which contains set of all possible
strings where every string starts with a and ends with b.
Source Code:
%{
#include<stdio.h>
%}
%s A B DEAD
%%
<INITIAL>a BEGIN A;
<INITIAL>[^a\n] BEGIN DEAD;
<INITIAL>\n printf("Not Accepted\n"); BEGIN INITIAL;
<A>a BEGIN A;
<A>b BEGIN B;
<A>[^ab\n] BEGIN DEAD;
<A>\n printf("Not Accepted\n"); BEGIN INITIAL;
<B>b BEGIN B;
<B>a BEGIN A;
<B>[^ab\n] BEGIN DEAD;
<B>\n printf("ACCEPTED\n"); BEGIN INITIAL;
<DEAD>[^\n] BEGIN DEAD;
<DEAD>\n printf("Invalid Input\n"); BEGIN INITIAL;
%%
int yywrap() {
return 1;
}
int main() {
printf("Enter a string:\n");
yylex();
return 0;
}
Name: Tanishq Bisht University Roll: 2219803 Section: A2
Output
Name: Tanishq Bisht University Roll: 2219803 Section: A2
Problem 17
Problem Statement: Design YACC / LEX code to recognize valid arithmetic expression with
operators +,-,* and /.
YACC PART:
%{
#include <stdio.h>
int valid = 1;
int yylex();
int yyerror(const char *s);
%}
%token num id op
%%
start : id '=' s ';';
s: id x
| num x
| '-' num x
Arnav Rana G2 13
| '(' s ')' x
;
x : op s
| '-' s
|
;
%%
int yyerror(const char *s)
{
valid = 0;
printf("\nInvalid expression: %s\n", s);
Name: Tanishq Bisht University Roll: 2219803 Section: A2
return 0;
}
int main()
{
printf("\nEnter the expression:\n");
yyparse();
if (valid)
{
printf("\nValid expression!\n");
}
return 0;
}
LEX Code:
%{
#include "exp.tab.h"
%}
%%
[0-9]+ { yylval = atoi(yytext); return num; }
[a-zA-Z_][a-zA-Z0-9_]* { return id; }
[-+*/] { return op; }
"=" { return '='; }
";" { return ';'; }
"(" { return '('; }
")" { return ')'; }
[ \t\n]+ ; // Ignore whitespace
. { return yytext[0]; }
%%
Name: Tanishq Bisht University Roll: 2219803 Section: A2
Output
Name: Tanishq Bisht University Roll: 2219803 Section: A2
Problem 18
Problem Statement: Design YACC / LEX code to evaluate arithmetic expression involving
operators +, -, * and / without operator precedence grammar and with operator precedence
grammar.
YACC PART:
%{
#include <stdio.h>
#include <stdlib.h>
int yylex(void);
void yyerror(const char *s);
%}
%token NUMBER
%left '+' '-'
%left '*' '/'
%left UMINUS
%%
input:
/* empty */
| input line
;
line:
'\n'
| expr '\n' { printf("= %d\n", $1); }
;
expr:
expr '+' expr { $$ = $1 + $3; }
| expr '-' expr { $$ = $1 - $3; }
| expr '*' expr { $$ = $1 * $3; }
| expr '/' expr {
if ($3 == 0) {
yyerror("Division by zero");
$$ = 0;
} else {
Name: Tanishq Bisht University Roll: 2219803 Section: A2
$$ = $1 / $3;
}
}
| '-' expr %prec UMINUS { $$ = -$2; }
| '(' expr ')' { $$ = $2; }
| NUMBER { $$ = $1; }
;
%%
int main() {
printf("Simple Desk Calculator (Ctrl+D to exit):\n");
yyparse();
return 0;
}
void yyerror(const char *s) {
fprintf(stderr, "Error: %s\n", s);
}
LEX Code:
%{
#include "y.tab.h"
#include <stdlib.h>
%}
%%
[0-9]+ { yylval = strdup(yytext); return NUMBER; }
[ \t]+ ;
\n { return '\n'; }
. { return yytext[0]; }
%%
Name: Tanishq Bisht University Roll: 2219803 Section: A2
Output
Name: Tanishq Bisht University Roll: 2219803 Section: A2
Problem 19
Problem Statement: Design YACC / LEX code that translates INFIX Expression to POSTFIX
Expression.
YACC PART:
%{
#include <stdio.h>
#include <stdlib.h>
int yylex(void);
void yyerror(const char *s);
%}
%token NUMBER
%left '+' '-'
%left '*' '/'
%left UMINUS
%%
input:
/* empty */
| input line
;
line:
'\n'
| expr '\n' { printf("= %d\n", $1); }
;
expr:
expr '+' expr { $$ = $1 + $3; }
| expr '-' expr { $$ = $1 - $3; }
| expr '*' expr { $$ = $1 * $3; }
| expr '/' expr {
if ($3 == 0) {
yyerror("Division by zero");
$$ = 0;
} else {
Name: Tanishq Bisht University Roll: 2219803 Section: A2
$$ = $1 / $3;
}
}
| '-' expr %prec UMINUS { $$ = -$2; }
| '(' expr ')' { $$ = $2; }
| NUMBER { $$ = $1; }
;
%%
int main() {
printf("Simple Desk Calculator (Ctrl+D to exit):\n");
yyparse();
return 0;
}
void yyerror(const char *s) {
fprintf(stderr, "Error: %s\n", s);
}
LEX Code:
%{
#include "y.tab.h"
#include <stdlib.h>
%}
%%
[0-9]+ { yylval = strdup(yytext); return NUMBER; }
[ \t]+ ;
\n { return '\n'; }
. { return yytext[0]; }
%%
Name: Tanishq Bisht University Roll: 2219803 Section: A2
Output
Name: Tanishq Bisht University Roll: 2219803 Section: A2
Problem 20
Problem Statement: Design a Desk Calculator using YACC / LEX code.
YACC PART:
%{
#include <stdio.h>
#include <stdlib.h>
int yylex(void);
void yyerror(const char *s);
%}
%token NUMBER
%left '+' '-'
%left '*' '/'
%left UMINUS
%%
input:
/* empty */
| input line
;
line:
'\n'
| expr '\n' { printf("= %d\n", $1); }
;
expr:
expr '+' expr { $$ = $1 + $3; }
| expr '-' expr { $$ = $1 - $3; }
| expr '*' expr { $$ = $1 * $3; }
| expr '/' expr {
if ($3 == 0) {
yyerror("Division by zero");
$$ = 0;
} else {
$$ = $1 / $3;
Name: Tanishq Bisht University Roll: 2219803 Section: A2
}
}
| '-' expr %prec UMINUS { $$ = -$2; }
| '(' expr ')' { $$ = $2; }
| NUMBER { $$ = $1; }
;
%%
int main() {
printf("Simple Desk Calculator (Ctrl+D to exit):\n");
yyparse();
return 0;
}
void yyerror(const char *s) {
fprintf(stderr, "Error: %s\n", s);
}
LEX Code:
%{
#include <stdio.h>
%}
%%
(abb)+[b]* { printf("Valid: %s\n", yytext); }
[a-b]+ { printf("Invalid: %s\n", yytext); }
.|\n ;
%%
int main() {
printf("Enter strings over {a, b} (Ctrl+D to end):\n");
yylex();
return 0;
}
Name: Tanishq Bisht University Roll: 2219803 Section: A2
Output
Name: Tanishq Bisht University Roll: 2219803 Section: A2
