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

On 1/14/2016 2:59 PM, Nevin Liber wrote:

On 14 January 2016 at 11:54, Agustín K-ballo Bergé wrote:

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On 1/14/2016 2:45 PM, Gottlob Frege wrote:

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On Wed, Jan 13, 2016 at 1:56 PM, Nevin Liber wrote:

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On 13 January 2016 at 12:25, Lee Clagett wrote:

The macro `STRING_VIEW` seems unnecessary because the `string_view`

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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

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

Yes, templates, as usual:

template 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);

That does not do the same thing if the literal has embedded '\0' characters or if you pass it an array that isn't a '\0'-terminated string.

"The same thing" than what? It does the exact some thing the macro in this context would do: #define STRING_VIEW(str) { str, sizeof(str)-1 } Regards, -- Agustín K-ballo Bergé.- http://talesofcpp.fusionfenix.com