ranges::to #307
ranges::to #307
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... a zero-instantiation version of `std::conditional_t`.
include/stl2/detail/to.hpp
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| _Cont __c(static_cast<_Args&&>(__args)...); | ||
| auto const __size = size(__r); | ||
| using __capacity = decltype(__c.capacity()); | ||
| // if (__can_represent<__capacity>(__size)) ? |
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Yes, this is a potential means of dealing with "What happens if the container's capacity type cannot represent the range's size?" (which is what the comment should really say).
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This is now tagged FIXME, and needs to be fixed before merging.
include/stl2/detail/to.hpp
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| template<class _IRange, class _Cont> | ||
| requires __class_convertible<_Cont, _IRange> | ||
| constexpr auto operator|(_IRange&& __r, __class_closure<_Cont>(&)() noexcept) { |
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I don't think to<std::vector<int>> has the right associated namespaces in order to find this overload in all cases. In range-v3, I needed to have a defaulted function argument (of non-template class type) on to and put the operator| within that type's associated namespace.
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Thanks for the reminder, and more importantly the twitter link. I'd intended to dig the thread out to refresh my memory on which parts of the problem are in the spec and which are compiler bugs. (Notably the workaround doesn't work with MSVC.)
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Huh. I'm certain I got it to work with MSVC on Godbolt. 🤔
include/stl2/detail/to.hpp
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| template<template<class...> class _ContT, class _IRange> | ||
| requires __template_convertible<_ContT, _IRange> | ||
| constexpr auto operator|(_IRange&& __r, __template_closure<_ContT>(&)() noexcept) { |
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Same feedback here. I have it on good authority[*] that this doesn't work in general.
[*]: https://twitter.com/ericniebler/status/1085600729656549377
Per P1206 and Kona LEWG discussion.