From: "Stephan Kämper" <Stephan.Kaemper@...>
Date: 2005-01-24T20:15:52+09:00
Subject: Re: Is overloading of the "! operator" possible or not

Neulinger Robert (SMS T CARS SW External) wrote:
> Hello,
> 
> I'm tying to overload the "! operator", which should be possible due

Do you mean "overload" or "override"?
You _override_ a method if you change the behaviour of the method in an 
ancestor (or singleton object).

To _overload_ a method means to check the classes/types of the arguments 
and to use that information to decide which method body to execute.
Overloading just doesn't cut the mustard in Ruby; IIRC this has been 
discussed here before.

> to the explanation in the book "Programming ruby" -> The Ruby
> Language ->Operator Expressions,
> but it's not working.
> 
> On the other hand in the FAQ the ! operator is marked as non-overloadable.
> ---------------
 > http://www.rubycentral.com/faq/rubyfaq-7.html
> See section 7.2...
> However, the following are built-in control structures, not methods, which
> cannot be overridden.
> 
> What is the truth and/or how does it work?
> 
> Thanks for help in advance Robert

That should be "override", not "overload" in the FAQ.
As I understand the table in the pickaxe (2nd ed. PDF instance, p. 324):

tick-mark     ! ~ + -       Not,complement, unary plus and minus
                             (method names for the last two are +@ and
                              -@)

indicates that all these operations may be overridden. Which indeed work 
for '~', '+' and '-', but not for '!'.

At least this is how I understand what Matz posted and what the FAQ 
states. (The operator group in the pickaxe should probably be split up.)

Furthermore I'll go and suggest another 'Q' for the FAQ: A discussion 
about the difference of overriding and overloading in Ruby.

Happy rubying

Stephan