std::span fails to construct on top on a array<T, 1>

[parcollet]

Description

std::span fails to construct from an array<T, 1>

Steps to Reproduce

   auto v= nda::vector<long>{1,2,3};
   auto s  std::span<long>{v.begin(), v.end()};

The issue is that the iterator of array<T, 1> should be a contiguous_iterator, not just a random_access_iterator

Expected behavior:

It should construct the span

Actual behavior:

Does not compile.

Versions

unstable (OS X).

[parcollet]

• Working on a patch, but some discussions necessary