lexanalyser.l

%{
	#include "parser.tab.h"
	#include<string.h>
	#include <stdio.h>
	#include<stdlib.h>
	
	/*
		This is the code block where we can write header files and other C functions which we need to implement		
	*/

%}
	/*
		Enclosed betweeen %%..%% are the rules  for matching the tokens which we need .
		A rule is written  in the form of a regular expression  followed by the action which is written in curly braces . 
		In this case it returns constants which find their  value from the "parser.tab.h" header file
		( constants like and IF used in rules) .
		Detailed expressions for regualar expressions can be found in the dragon book (Compiler Principles Tools & Techniques).
	*/

%%
"&"				    { 	return and; 	}
"|"				    { 	return or; 	}
"if"				    {	return IF;	}
"else"				    {	return ELSE;	}
"=="			  	    {	return eq;	}
"!="			  	    {	return ne;	}
"<="			            {	return le;	}
">="			  	    {	return ge;	}
"while"                             {   return WHILE;   }
"return"                            {   return RETURN;  }
"def"                               {   return DEF;     }
"exit"			    	    {	return EXIT;	} 		
"print"			 	    {	return print;	} 
"ptable"			    { 	return ptable;	}
"do"                                {   return DO;      }
"#define"	                    {   return HASHDEF; }
","                                 {   return comma;   }
[0-9]+				    {	

					yylval.no=atoi(yytext) ; 
					return num;
	                            }
[a-z]([a-z]|[0-9])*		    {	
					strcpy(yylval.var,yytext); 
					return id;
				    } 
[ \t\n]					;
[- + ; ( ) * / = < > { } % ? : ]    {  return *yytext;  }
.				    {   printf("invalid char.");  }
%%


int yywrap()
{
return 1;
}