Make reshape_view accept -1 as a wildcard dimension

[spectre-ns]

Checklist

• [ x] The title and commit message(s) are descriptive.
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Description

Fix #2417
@JohanMabille @tdegeus this is failing the type check at test_xstrided_view.cpp(709). I was unable to cast the underlying std::array to unsigned using std::make_unsigned as I expected. Any help would be appreciated. I think apart from that it should be identical to the previous implementation as it only implements the check when given signed integers and preserves static lengths using std::array<T,N>

[spectre-ns]

I got everything working without modifying the unit tests. I question the need to compare if the view and expression have the same shape type. The machinery required to do the cast to std::size_t is pretty complicated for what it is. I'd prefer to drop it.

[tdegeus]

I'm probably missing something, but is there not a way to re-use existing machinery?

[spectre-ns]

I'm probably missing something, but is there not a way to re-use existing machinery?

I could have reused xcontainer's implementation but the mechanics seemed looked up in a member function. I suppose I could refactor to have a shared implementation, but it doesn't seem right to have the view depend on xcontainer.

xtensor/include/xtensor/xcontainer.hpp

Line 1118 in 5f49f64

xstrided_container<D>::reshape_impl(S&& shape, std::false_type /* is unsigned */, layout_type layout)

Let me know what you think.

[spectre-ns]

@JohanMabille @tdegeus I think this one should be implemented as requested. I'd like some suggestions on implementation clean up. I'm still learning my metatemplate syntax and idioms.

[tdegeus]

Thanks! Great work. Some minor comments

[spectre-ns]

@JohanMabille I think the PR should be ready to merge! :)

[JohanMabille]

@spectre-ns thanks a lot for your work on this and your patience! I added some minor comments.

[spectre-ns]

@spectre-ns thanks a lot for your work on this and your patience! I added some minor comments.

@JohanMabille I have addressed your comments

[JohanMabille]

Thanks again!