Helpers
	digit = ['0' .. '9'];
	alpha = ['a'..'z'] | ['A'..'Z'];
	tab = 9;
	cr = 10;
	lf = 13;
Tokens
	if = 'if';
	id = ['a'..'z'](['a'..'z'] | (digit))*;
	number = digit+;
	real = ((digit)+ '.' (digit)*) | ((digit)* '.' (digit)+);
	whitespace = (' ' | tab | cr | lf )+;
	comments = ('--' (alpha)*(cr | lf));
Ignored Tokens
	whitespace,
	comments;