CD LAB 25-02-2020

id.l

%{
	#include "y.tab.h"
%}

%%
[0-9] {return DIGIT;}
[a-zA-Z] {return LETTER;}
[_] {return UND;}
\n {return NL;}
. {return yytext[0];}
%%

int yywrap()
{
	return 1;
}

id.y

%{
    #include <stdio.h>
    #include <stdlib.h>
%}

%token NL DIGIT LETTER UND
%%
id: letter_und alphanum NL { printf("Valid\n");exit(0);}
;
letter_und: LETTER | UND
alphanum_: LETTER|UND|DIGIT
;
alphanum: alphanum_ alphanum | alphanum_
;
%%  
int yyerror(char *msg)
{
    printf("Invalid statements\n");
    exit(0);
}

int main()
{
    printf("Enter input: \n");
    yyparse();
    return 0;
}

nested_if.l

%{
	#include "y.tab.h"
%}

%%
"if" {return IF;}
[sS][0-9]* {return S;}
[a-zA-Z][a-zA-Z0-9]* {return ID;}
[0-9]+ {return NUM;}
">"|"<"|">="|"<="|"=="|"!=" {return RELOP;}
\n {return NL;}
. {return yytext[0];}
%%

int yywrap()
{
	return 1;
}

nested_if.y

%{
    #include <stdio.h>
    #include <stdlib.h>
int count;
%}

%token NL S ID NUM IF RELOP 
%%
stmt : ifstmt NL {printf("valid \t"); printf("Number of nested statements is : %d\n",count);exit(0);};
ifstmt : IF'('cond')''{'ifstmt'}' {count++;}
        | S | 
        ;
        
cond : X RELOP X
     ;
X : ID | NUM
  ;
%%  
int yyerror(char *msg)
{
    printf("Invalid statement");
    exit(0);
}

int main()
{
    printf("Enter input: \n");
    yyparse();
    return 0;
}