Re: [boost] request: BOOST_NO_SFINAE_EXPR macro

Subject: Re: [boost] request: BOOST_NO_SFINAE_EXPR macro
From: Simonson, Lucanus J (lucanus.j.simonson_at_[hidden])
Date: 2009-07-31 11:52:26

Beman Dawes wrote:
> On Thu, Jul 30, 2009 at 10:20 AM, Mathias
> Gaunard<mathias.gaunard_at_[hidden]> wrote:
>> It would be very nice if Boost.Config provided the
>> BOOST_NO_SFINAE_EXPR macro, that would be defined if the compiler
>> does not support SFINAE applied to expressions.
>> http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2634.html 
>> 
>> GCC supports this feature since 4.4 both for C++03 and C++0x for
>> example. 
> 
> Yes, such a macro is needed

So we could do this instead of use mpl and?

template <typename T1, typename T2>
enable_if_c<is_a_A<T1>::value && is_a_B<T2>::value>::type foo();

> Also, it turns out that the ability to provide a default template
> parameter for function templates markedly clarifies code using
> enable_if. (I learned this Howard Hinnant, but I think he may have
> gotten the idea from Peter Dimov.)
 
This sounds interesting.  Can you explain how?

Thanks,
Luke