// evaluates sub-expression and applies unary operator
public object VisitUnaryExpr(Expr.Unary expr)
{
object right = Evaluate(expr.right);
switch (expr.op.type)
{
case Token.TokenType.Bang:
return(!IsTruthy(right));
case Token.TokenType.Minus:
return(-(double)right);
}
// Unreachable.
return(null);
}
public string VisitUnaryExpr(Expr.Unary expr)
{
return(Parenthesize(expr.op.lexeme, expr.right));
}
public object VisitUnaryExpr(Expr.Unary expr)
{
Resolve(expr.right);
return(null);
}
