On 14 January 2016 at 11:54, Agustín K-ballo Bergé <kaballo86@hotmail.com> wrote:
On 1/14/2016 2:45 PM, Gottlob Frege wrote:
On Wed, Jan 13, 2016 at 1:56 PM, Nevin Liber <nevin@cplusplusguy.com> wrote:
On 13 January 2016 at 12:25, Lee Clagett <forum@leeclagett.com> 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);
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. -- Nevin ":-)" Liber <mailto:nevin@eviloverlord.com> +1-847-691-1404