lexical.flex

import java.util.*;
%%
%class lexical
%standalone
%unicode
%line
%column
LineTerminator = \r|\n|\r\n
Numbers = [0-9]+
Keywords = "if"|"then"|"else"|"endif"|"while"|"do"|"endwhile"|"print"|"newline"|"read"
Identifier = [A-Za-z0-9_]+
Operator = "="|"+"|"-"|"*"|"/"
Comment = (\/\/)[A-Za-z0-9_ ]* | (\/\*)[A-Za-z0-9_ ]*(\*\/)
String = (\")[A-Za-z0-9_ ]*(\")
Separator = "("|")"|";"
Whitespace = \s+
%{
	List<String> keywords = new ArrayList();
	List<String> identifiers = new ArrayList();
%}

%%
{Numbers}  {System.out.printf("integer : %s \n", yytext());}

{Keywords} {System.out.printf("keyword : %s \n", yytext());
	    keywords.add(yytext());
           }
		   
{Identifier} {
				if(!identifiers.contains(yytext())) {
					System.out.printf("new identifier : %s \n", yytext());
					if(!keywords.contains(yytext())){
						identifiers.add(yytext());
					}
				} else {
					System.out.printf("identifier : %s already in symbol table \n", yytext());
				}
	     }
			 
{Operator}  {System.out.printf("operator : %s \n", yytext());}

{String}    {System.out.printf("string : %s \n", yytext());}

{Comment}   {System.out.printf("comments : %s \n", yytext());}

{Separator} {System.out.printf("separator : %s \n", yytext());}

{LineTerminator} {}

{Whitespace} {}

.	     {
	      System.out.printf("Error \n");
	      System.exit(0);
	     }