Re: [boost] Bounded types (or maybe not 'bounded' anymore? ;-)

From: Robert Kawulak (kawulak_at_[hidden])
Date: 2005-09-26 05:16:26

Hi, 

> > I also 
> believe, that it'd
> > be better to supply operator const value() than operator 
> value() - this
> > conversion is implicit so the const version would be safer.
> 
> Why bother with the "const"?  The usage will already return a 
> r-value, i.e.
> a temporary.  The kinds of mutable operations that can be 
> done on it are
> already restricted.  The only times I've seen mutable 
> operations on such
> values are ones that were deliberately done.  The "const" 
> adds nothing but
> annoyance; the safety-conscious won't need it since they wouldn't try
> mutable code, and the programmers that want to abuse a 
> mutable operation
> would be upset that you locked them out.  It's the same kind 
> of controversy
> about (member) functions returning non-reference objects with "const"
> attached.  (And we seen "cute" tricks in C++ made for our "benefit"
> back-fire later, like std::vector<bool>.)
> 
> -- 
> Daryle Walker

Probably you're right, I wasn't thinking it over very much because in the
current implementation I'm working on the conversion operator returns const
value_type & (because it must also support UDTs, that might be inefficient
to return by value) so there's no question whether const is needed or not,
it must be there.

The reason I was thinking so was "Exceptional C++" item 20 p.9 which says
that postincrement operator should return a const value, from this I deduced
that conversion operator should also. But as I mentioned, I didn't think of
it a lot so I may be wrong ;-).

Best regards,
Robert