Re: [boost] [gsoc16] Can I quickly check if the below really is the best approach?

Subject: Re: [boost] [gsoc16] Can I quickly check if the below really is the best approach?
From: Agustín K-ballo Bergé (kaballo86_at_[hidden])
Date: 2016-01-14 12:54:40

On 1/14/2016 2:45 PM, Gottlob Frege wrote:
> On Wed, Jan 13, 2016 at 1:56 PM, Nevin Liber <nevin_at_[hidden]> wrote:
>> On 13 January 2016 at 12:25, Lee Clagett <forum_at_[hidden]> wrote:
>>
>>> The macro `STRING_VIEW` seems unnecessary because the `string_view`
>>> constructor taking a single NULL-terminated string is also
>>> `constexpr`.
>>>
>>
>> While the templated constructor for basic_string_view is constexpr, this
>> constructor for string_view cannot be used in a constexpr context because
>> char_traits<char>::length isn't constexpr. :-(  See LWG 2232
>> <http://cplusplus.github.io/LWG/lwg-active.html#2232>.
>>
>> I've been told it works this way by design...
>>
>> So yes, we do need the macro.
>
> Can it be a constexpr function that returns an initializer list?

No, because initializer lists are backed by arrays of automatic storage, 
so the returned `initializer_list` would immediately dangle.

> Or
> something, anything,... I hate macros :-(

Yes, templates, as usual:

     template <typename CharT, std::size_t N>
     constexpr std::experimental::basic_string_view<CharT>
     make_string_view(CharT const (&str)[N]) noexcept {
       return {str, N - 1};
     }

     constexpr string_view sv = make_string_view("hello");
     static_assert(sv.size() == 5);

Regards,
-- 
Agustín K-ballo Bergé.-
http://talesofcpp.fusionfenix.com