Re: [boost] safe-bool CRTP class

Subject: Re: [boost] safe-bool CRTP class
From: Gottlob Frege (gottlobfrege_at_[hidden])
Date: 2011-05-28 12:46:48

On Sat, May 28, 2011 at 9:22 AM, Krzysztof Czainski <1czajnik_at_[hidden]> wrote:
> Thank you all for such large input ;-)
>
> So the way I see it, most of us agree it would be nice to see one official
> safe-bool implementation tool in boost.
>
> The first question is: should it be a CRTP class, or should it be a macro,
> or both perhaps?
>
> I suggest we talk about the name after we answer the first question ;-) And
> later I will try to prepare an implementation with the compiler workarounds
> mentioned in this thread.
>
> CRTP class usage:
> struct X : public convertible_to_bool<X>
> {
>  bool operator!() const { return condition; }
>  // inherit operator unspecified_bool_t implemented in terms of the above
> operator!
> };
>
> Macro usage:
> BOOST_EXPLICIT_BOOL_OPERATOR() const {
>   return ...;
> }
>
> I'm not sure how the macro would be implemented, but we'll get to that once
> we make the choice.
>
> Right now I feel convinced to the macro version.
>
> Regards
> Kris

I suspect that we should offer both versions.

I also think we should look back at the previous reviews and attempts
at safe-bools for Boost.  Although I don't think we should let the
previous failed attempts discourage us.

Tony