%%
%{
  public int lineno;
  public Object attribute;
  public byte lex() throws ParseError {
     try {
	 attribute = null;
	 byte t = yylex();
	 lineno = yyline+1;
	 return t;
     } catch (java.io.IOException exn) {
	 throw new ParseError("I/O error: " + exn.getMessage(),yyline+1);
     }
  }
%}

%class Lexer
%type byte
%line
%yylexthrow{
  ParseError
%yylexthrow}
%eofval{
  return Token.EOF;
%eofval}

digit=[0-9]
letter=[A-Za-z]
%%
var { return Token.VAR; }
set { return Token.SET; }
ifzero { return Token.IFZERO; }
then { return Token.THEN; }
else { return Token.ELSE; }
{letter}+ { attribute = yytext(); return Token.ID; }
{digit}+ { attribute = Integer.valueOf(yytext()); return Token.NUM; }
"=" { return Token.EQ; }
"{" { return Token.LBRA; }
"}" { return Token.RBRA; }
"(" { return Token.LPAR; }
")" { return Token.RPAR; }
"+" { return Token.PLUS; }
"-" { return Token.MINUS; }
";" { return Token.SEMI; }
[\n \t] {}
. { throw new ParseError("Invalid character \'"  + yytext() + "\'", yyline+1); }