private Expr Unary()
{
Expr expr = null;
if (Match(TokenType.Bang, TokenType.Minus))
{
Token oper = Previous();
Expr right = Unary();
expr = new Expr.Unary(oper, right);
}
else
{
expr = Call();
}
return(expr);
}
public object Visit(Expr.Unary expr)
{
object ret = null;
object right = Evaluate(expr.right);
switch (expr.oper.type)
{
case TokenType.Minus:
CheckNumberOperand(expr.oper, right);
ret = -(double)right;
break;
case TokenType.Bang:
ret = !IsTruthy(right);
break;
default:
// do nothing
break;
}
return(ret);
}
public string Visit(Expr.Unary unary)
{
return(Parentherize(unary.oper.lexeme, unary.right));
}
public object Visit(Expr.Unary expr)
{
Resolve(expr.right);
return(null);
}