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Implement LWG-4054 Repeating a repeat_view should repeat the view #4540

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Merged
Stephan T. Lavavej (StephanTLavavej) merged 2 commits into from
Apr 9, 2024
Merged

Implement LWG-4054 Repeating a repeat_view should repeat the view #4540

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64da81b
Implement LWG-4054
frederick-vs-ja Mar 28, 2024
d3d9929
Drop unnecessary `std::`.
StephanTLavavej Mar 30, 2024
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6 changes: 3 additions & 3 deletions stl/inc/ranges
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Original file line number Diff line number Diff line change
Expand Up @@ -1705,10 +1705,10 @@ namespace ranges {
struct _Repeat_fn {
template <class _Ty>
_NODISCARD _STATIC_CALL_OPERATOR constexpr auto operator()(_Ty&& _Value) _CONST_CALL_OPERATOR
noexcept(noexcept(repeat_view(_STD forward<_Ty>(_Value))))
requires requires { repeat_view(_STD forward<_Ty>(_Value)); }
noexcept(noexcept(repeat_view<decay_t<_Ty>>(_STD forward<_Ty>(_Value))))
requires requires { repeat_view<decay_t<_Ty>>(_STD forward<_Ty>(_Value)); }
{
return repeat_view(_STD forward<_Ty>(_Value));
return repeat_view<decay_t<_Ty>>(_STD forward<_Ty>(_Value));
}

template <class _Ty1, class _Ty2>
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9 changes: 7 additions & 2 deletions tests/std/tests/P2474R2_views_repeat/test.cpp
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Expand Up @@ -363,14 +363,19 @@ constexpr bool test() {
return true;
}

// Check LWG-3875
// Check LWG-3875 "std::ranges::repeat_view<T, IntegerClass>::iterator may be ill-formed"
static_assert(CanViewRepeat<string, long long>);
static_assert(CanViewRepeat<string, unsigned long long>);
static_assert(CanViewRepeat<string, _Signed128>);
static_assert(
!CanViewRepeat<string, _Unsigned128>); // _Unsigned128 does not satisfy 'integer-like-with-usable-difference-type'

// Check GH-3392
// Check LWG-4054 "Repeating a repeat_view should repeat the view"
static_assert(is_same_v<decltype(views::repeat(views::repeat(42))), ranges::repeat_view<ranges::repeat_view<int>>>);
static_assert(is_same_v<decltype(views::repeat("Hello world!")), ranges::repeat_view<const char*>>);
static_assert(is_same_v<decltype(views::repeat(test)), ranges::repeat_view<bool (*)()>>);

// Check GH-3392 "<ranges>: views::repeat(...) | views::take(...) is not always a valid range"
static_assert(ranges::range<decltype(views::repeat('3', 100ull) | views::take(3))>);
static_assert(ranges::range<decltype(views::repeat('3', 100ull) | views::drop(3))>);

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