Practice of LEX / YACC in compiler writing.

 //Write a program to print “Compiler” when input is “Hi” else print “Wrong Input”

%{

#include <stdio.h>

%}

%%

^Hi$ { printf("Compiler\n"); }

.|\n { printf("Wrong Input\n"); }

%%

int main() {

 yylex(); // Start lexical analysis

 return 0;

}

int yywrap(){

 return 0;

}

//Write a program to check whether a number is even or odd.

%{

#include <stdio.h>

%}

%%

[0-9]+ {

 if (atoi(yytext) % 2 == 0)

 printf("Even\n");

 else

 printf("Odd\n");}

.* { printf("Wrong Input\n"); }

%%

int main() {

 yylex(); // Start lexical analysis

 return 0;}

int yywrap(){

 return 0;

}

//Write a program to find greatest of two numbers.

%{

#include <stdio.h>

int a, b, c = 0;

%}

%%

[0-9]+ {

 if (c == 0)

 a = atoi(yytext);

 else

 b = atoi(yytext);

}

\n {

 if (a > b)

 printf("%d is greater\n", a);

 else if (a < b)

 printf("%d is greater\n", b);

 else

 printf("Both are equal\n");

 c = 0;

}

. {

 c = 1;

}

%%

int main() {

 printf("Enter two space-separated integers: \n");

 yylex();

 return 0;

}

int yywrap() {

 return 0;

}