%%

%class Lexer 
%type Token
%function next_token
%char
%line
%eofval{
   return new Token (sym.EOF, null);
%eofval}
%yylexthrow{
   Exception
%yylexthrow}

WHITESPACE = [\ \t\r\n]+
INTEGER_LITERAL = [0-9]+
IDENTIFIER = [a-zA-Z][a-zA-Z0-9]*
FLOAT_LITERAL = [0-9]*"."[0-9]+
%%
<YYINITIAL> ";" 	{return new Token (sym.SEMICOLON,   yychar,yychar+1,yytext(),yyline);}
<YYINITIAL> "="         {return new Token (sym.EQ,          yychar,yychar+1,yytext(),yyline);}
<YYINITIAL> "{"	        {return new Token (sym.LBRACE,      yychar,yychar+1,yytext(),yyline);}
<YYINITIAL> "}"		{return new Token (sym.RBRACE,      yychar,yychar+1,yytext(),yyline);}
<YYINITIAL> "if"	{return new Token (sym.IF,          yychar,yychar+2,yytext(),yyline);}
<YYINITIAL> "("    	{return new Token (sym.LPAREN,      yychar,yychar+1,yytext(),yyline);}
<YYINITIAL> ")"		{return new Token (sym.RPAREN,      yychar,yychar+1,yytext(),yyline);}
<YYINITIAL> "while"     {return new Token (sym.WHILE,       yychar,yychar+5,yytext(),yyline);}
<YYINITIAL> "=="	{return new Token (sym.EQEQ,	    yychar,yychar+2,yytext(),yyline);}
<YYINITIAL>{INTEGER_LITERAL} {return new Token (sym.INTEGER_LITERAL,yychar,yychar+yytext().length(),new Integer(yytext()),yyline);}
<YYINITIAL>{IDENTIFIER}      {return new Token (sym.IDENTIFIER,yychar,yychar+yytext().length(),yytext(),yyline);}
<YYINITIAL>{FLOAT_LITERAL}   {return new Token (sym.FLOAT_LITERAL,yychar,yychar+yytext().length(),new Float(yytext()),yyline);}
<YYINITIAL>{WHITESPACE}   { }
. { throw new Exception ("Lexical: unmatched input at line " + (yyline+1));
  }