Re: [boost] safe-bool CRTP class

Subject: Re: [boost] safe-bool CRTP class
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2011-05-27 13:08:49

Krzysztof Czainski wrote:
> 2011/5/27 Gregory Crosswhite <gcross_at_[hidden]>
> > On 5/27/11 9:28 AM, Stewart, Robert wrote:
> >
> >> template<  class Derived, class Base = empty_t>
> >>>
> >> I like that you're allowing for a base class.
> >>
> >>
> > That was my first reaction too, though the more that I have
> > been thinking about it the more that I am having trouble
> > thinking of an example of exactly why it is that one would
> > ever need or want this functionality.
>
> That's for base class chaining to avoid multiple inheritance,
> just like the operators library has it.
>
> struct X : boolable<X, addable<X> >  {...};

It's also for cases in which one would normally have this:

struct derived : base
{
   ...
};

Then, to provide safe-bool functionality for derived, one would do the following to avoid MI:

struct derived : safe_bool<derived, base>
{
   ...
};

_____
Rob Stewart                           robert.stewart_at_[hidden]
Software Engineer                     using std::disclaimer;
Dev Tools & Components
Susquehanna International Group, LLP  http://www.sig.com

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