flex

%option noyywrap

%x comment_state
%x nested_comment_state
%x multi_comment_state

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

int line_count = 1;
FILE *logout;
FILE *tokenout;
char arr[100];
int comment_line;
%}

AlphaNumeric [a-zA-Z0-9]
digits[0-9]

%%

"//" {	 BEGIN comment_state;}
"/*" {   comment_line = line_count;arr[0]=0;BEGIN multi_comment_state;}
[ \t] {	}
[\n] {line_count++;}
{digits}+ {fprintf(tokenout,"<CONST_INT,%s>\n",yytext);
	   fprintf(logout,"Line no %d: Token <CONST_INT> Lexeme <%s> found .\n",line_count,yytext);}
({digits}*[\.]?{digits}+)|(({digits}*[\.]?{digits}+)([E]?[+|-]?{digits}+)) {fprintf(tokenout,"<CONST_FLOAT,%s>\n",yytext);
			fprintf(logout,"Line no %d: Token <CONST_FLOAT> Lexeme <%s> found .\n",line_count,yytext);}
"if" {fprintf(tokenout,"<IF>\n");
	   fprintf(logout,"Line no %d: Token <IF> Lexeme <%s> found .\n",line_count,yytext);}
"for" {fprintf(tokenout,"<IF>\n");
	   fprintf(logout,"Line no %d: Token <IF> Lexeme <%s> found .\n",line_count,yytext);}
"do" {fprintf(tokenout,"<IF>\n");
	   fprintf(logout,"Line no %d: Token <IF> Lexeme <%s> found .\n",line_count,yytext);}
"int" {fprintf(tokenout,"<IF>\n");
	   fprintf(logout,"Line no %d: Token <IF> Lexeme <%s> found .\n",line_count,yytext);}
"float" {fprintf(tokenout,"<IF>\n");
	   fprintf(logout,"Line no %d: Token <IF> Lexeme <%s> found .\n",line_count,yytext);}
"void" {fprintf(tokenout,"<IF>\n");
	   fprintf(logout,"Line no %d: Token <IF> Lexeme <%s> found .\n",line_count,yytext);}
"switch" {fprintf(tokenout,"<IF>\n");
	   fprintf(logout,"Line no %d: Token <IF> Lexeme <%s> found .\n",line_count,yytext);}
"default" {fprintf(tokenout,"<IF>\n");
	   fprintf(logout,"Line no %d: Token <IF> Lexeme <%s> found .\n",line_count,yytext);}
"else" {fprintf(tokenout,"<IF>\n");
	   fprintf(logout,"Line no %d: Token <IF> Lexeme <%s> found .\n",line_count,yytext);}
"while" {fprintf(tokenout,"<IF>\n");
	   fprintf(logout,"Line no %d: Token <IF> Lexeme <%s> found .\n",line_count,yytext);}
"break" {fprintf(tokenout,"<IF>\n");
	   fprintf(logout,"Line no %d: Token <IF> Lexeme <%s> found .\n",line_count,yytext);}
"char" {fprintf(tokenout,"<IF>\n");
	   fprintf(logout,"Line no %d: Token <IF> Lexeme <%s> found .\n",line_count,yytext);}
"double" {fprintf(tokenout,"<IF>\n");
	   fprintf(logout,"Line no %d: Token <IF> Lexeme <%s> found .\n",line_count,yytext);}
"return" {fprintf(tokenout,"<IF>\n");
	   fprintf(logout,"Line no %d: Token <IF> Lexeme <%s> found .\n",line_count,yytext);}
"case" {fprintf(tokenout,"<IF>\n");
	   fprintf(logout,"Line no %d: Token <IF> Lexeme <%s> found .\n",line_count,yytext);}
"continue" {fprintf(tokenout,"<IF>\n");
	   fprintf(logout,"Line no %d: Token <IF> Lexeme <%s> found .\n",line_count,yytext);}
. {}
<comment_state>[^\n\\]+ {fprintf(logout,"Line no %d: Token <Comment> Lexeme <%s> found .\n",line_count,yytext);}
<comment_state>[\n] {line_count++; BEGIN INITIAL;}
<comment_state>[\\] {BEGIN nested_comment_state;}
<nested_comment_state>[\n] {line_count++;BEGIN comment_state;}
<nested_comment_state>. {fprintf(logout,"Line no %d: Token <Comment> Lexeme <%s> found .\n",line_count,yytext);BEGIN comment_state;}
<multi_comment_state>[^*\n]+ { strcat(arr,yytext);}
<multi_comment_state>[\n] {line_count++;strcat(arr,yytext);}
<multi_comment_state>. {strcat(arr,yytext);}
<multi_comment_state>"*/" {fprintf(logout,"Line no %d: Token <Comment> Lexeme <%s> found .\n",comment_line,arr);arr[0]=0;BEGIN INITIAL;}

%%
int main(int argc,char *argv[]){

/*
{digits}+
	{
		fprintf(tokenout,"<CONST_INT,%s>",yytext);
		fprintf(logout,"Line no %d: Token <CONST_INT> Lexeme <%s> found .\n",line_count,yytext);
	}*/

	if(argc!=2){
		printf("Please provide input file name and try again\n");
		return 0;
	}

	FILE *fin=fopen(argv[1],"r");
	if(fin==NULL){
		printf("Cannot open specified file\n");
		return 0;
	}

	logout = fopen("1405003_log.txt","w");
	tokenout = fopen("1405003_token.txt","w");
	yyin= fin;
	yylex();
	fclose(yyin);
	fclose(logout);
	fclose(tokenout);
	return 0;
}