Re: [boost] New dependency report

Subject: Re: [boost] New dependency report
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2014-06-07 13:25:29

On Saturday 07 June 2014 18:46:19 Peter Dimov wrote:
> 
> I have another solution, which appears good enough to go into Core. We could
> also enhance mpl::bool_ in the same way. Note that the trait knows nothing
> about bool_, but dispatch still works.
> 
> template< class T > struct is_pointer
> {
>     BOOST_STATIC_CONSTANT( bool, value = false );
> };
> 
> template< class T > struct is_pointer< T* >
> {
>     BOOST_STATIC_CONSTANT( bool, value = true );
> };
> 
> int f( true_ )
> {
>     return 5;
> }
> 
> int f( false_ )
> {
>     return 11;
> }
> 
> int main()
> {
>     BOOST_TEST( f( is_pointer< int* >() ) == 5 );
>     BOOST_TEST( f( is_pointer< int >() ) == 11 );
> 
>     return boost::report_errors();
> }

It's still a partial solution since

 f(is_pointer< int >::type());

is also valid with the current implementation. We can add the conversion 
constructor to mpl::bool_ but that is not a replacement for the current 
mechanism, at least not a backward compatible one.

I think our previous plan with TypeTraits.Core is better. Pulling type traits 
to Core doesn't sound good, it's better to create a separate submodule for it.