Program to recognize nested IF control statements and display the levels of nesting . | Compiler Design Lab Programs | Yacc Programs

Yacc Part :

%token IF RELOP S NUMBER ID

%{

 int count=0;

%}

%%

stmt : if_stmt { printf(“No of nested if statements=%d\n”,count); exit(0);}

 ;

if_stmt : IF ‘(‘ cond ‘)’ if_stmt {count++;}

 | S;

 ;

cond : x RELOP x

 ;

x : ID

 | NUMBER

 ;

%%

int yyerror(char *msg)

{

 printf(“Invalid Expression\n”);

 exit(0);

}

main ()

{

 printf(“Enter the statement”);

 yyparse();

} 

Lex Part :

%{

 #include “y.tab.h”

%}

%%

“if” { return IF; }

[sS][0-9]* {return S;}

“<”|”>”|”==”|”!=”|”<=”|”>=” { return RELOP; }

[0-9]+ { return NUMBER; }

[a-zA-Z][a-zA-Z0-9_]* { return ID; }

\n { ; }

. { return yytext[0]; }

%%