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P0896R4 changes to insert iterators #589

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merged 6 commits into from
Mar 10, 2020
Merged

P0896R4 changes to insert iterators #589

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P0896R4 changes to insert iterators
CaseyCarter Mar 6, 2020
1db61ea
Review comments
CaseyCarter Mar 6, 2020
223cf23
Revert NFC changes to reduce conflict potential
CaseyCarter Mar 6, 2020
62e0cc6
Skip libc++ tests broken by this change
CaseyCarter Mar 7, 2020
79c979a
Update stl/inc/iterator
CaseyCarter Mar 7, 2020
48ea79b
clang-format
CaseyCarter Mar 8, 2020
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35 changes: 28 additions & 7 deletions stl/inc/iterator
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Original file line number Diff line number Diff line change
Expand Up @@ -25,12 +25,19 @@ class back_insert_iterator { // wrap pushes to back of container as output itera
public:
using iterator_category = output_iterator_tag;
using value_type = void;
using difference_type = void;
using pointer = void;
using reference = void;

using container_type = _Container;

#ifdef __cpp_lib_concepts
using difference_type = ptrdiff_t;

constexpr back_insert_iterator() noexcept = default;
#else // ^^^ __cpp_lib_concepts / !__cpp_lib_concepts vvv
using difference_type = void;
#endif // __cpp_lib_concepts

explicit back_insert_iterator(_Container& _Cont) noexcept /* strengthened */ : container(_STD addressof(_Cont)) {}

back_insert_iterator& operator=(const typename _Container::value_type& _Val) {
Expand All @@ -56,7 +63,7 @@ public:
}

protected:
_Container* container; // pointer to container
_Container* container = nullptr;
};

// FUNCTION TEMPLATE back_inserter
Expand All @@ -72,12 +79,19 @@ class front_insert_iterator { // wrap pushes to front of container as output ite
public:
using iterator_category = output_iterator_tag;
using value_type = void;
using difference_type = void;
using pointer = void;
using reference = void;

using container_type = _Container;

#ifdef __cpp_lib_concepts
using difference_type = ptrdiff_t;

constexpr front_insert_iterator() noexcept = default;
#else // ^^^ __cpp_lib_concepts / !__cpp_lib_concepts vvv
using difference_type = void;
#endif // __cpp_lib_concepts

explicit front_insert_iterator(_Container& _Cont) : container(_STD addressof(_Cont)) {}

front_insert_iterator& operator=(const typename _Container::value_type& _Val) { // push value into container
Expand All @@ -103,7 +117,7 @@ public:
}

protected:
_Container* container; // pointer to container
_Container* container = nullptr;
};

// FUNCTION TEMPLATE front_inserter
Expand All @@ -119,12 +133,19 @@ class insert_iterator { // wrap inserts into container as output iterator
public:
using iterator_category = output_iterator_tag;
using value_type = void;
using difference_type = void;
using pointer = void;
using reference = void;

using container_type = _Container;

#ifdef __cpp_lib_concepts
using difference_type = ptrdiff_t;

insert_iterator() = default;
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out of curiosity: Why isn't this one constexpr (in the standard)

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I have absolutely no idea. (To be honest, I don't understand why we ever put an explicit constexpr on a defaulted default constructor.) These default constructors came from P0896, which crossed with P1032 that added constexpr to all of the members of the insert iterators, and apparently the editors decided to put constexpr on some subset of the default constructors for reasons not apparent to me.

#else // ^^^ __cpp_lib_concepts / !__cpp_lib_concepts vvv
using difference_type = void;
#endif // __cpp_lib_concepts

insert_iterator(_Container& _Cont, typename _Container::iterator _Where)
: container(_STD addressof(_Cont)), iter(_Where) {}

Expand Down Expand Up @@ -155,8 +176,8 @@ public:
}

protected:
_Container* container; // pointer to container
typename _Container::iterator iter; // iterator into container
_Container* container = nullptr;
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typename _Container::iterator iter = {};
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};

// FUNCTION TEMPLATE inserter
Expand Down
25 changes: 25 additions & 0 deletions tests/std/tests/P0896R4_ranges_iterator_machinery/test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5,8 +5,10 @@
#include <compare>
#include <concepts>
#include <iterator>
#include <list>
#include <type_traits>
#include <utility>
#include <vector>

#define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)

Expand Down Expand Up @@ -2770,6 +2772,29 @@ namespace iter_ops {
}
} // namespace iter_ops

namespace insert_iterators {
template <class Container>
constexpr bool test() {
using std::back_insert_iterator, std::front_insert_iterator, std::insert_iterator;
using std::default_initializable, std::is_nothrow_default_constructible_v, std::iter_difference_t,
std::ptrdiff_t, std::same_as;

STATIC_ASSERT(default_initializable<back_insert_iterator<Container>>);
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STATIC_ASSERT(is_nothrow_default_constructible_v<back_insert_iterator<Container>>);
STATIC_ASSERT(default_initializable<front_insert_iterator<Container>>);
STATIC_ASSERT(is_nothrow_default_constructible_v<front_insert_iterator<Container>>);
STATIC_ASSERT(default_initializable<insert_iterator<Container>>);
STATIC_ASSERT(same_as<iter_difference_t<back_insert_iterator<Container>>, ptrdiff_t>);
STATIC_ASSERT(same_as<iter_difference_t<front_insert_iterator<Container>>, ptrdiff_t>);
STATIC_ASSERT(same_as<iter_difference_t<insert_iterator<Container>>, ptrdiff_t>);

return true;
}

STATIC_ASSERT(test<std::list<double>>());
STATIC_ASSERT(test<std::vector<int>>());
} // namespace insert_iterators

int main() {
iterator_cust_swap_test::test();
iter_ops::test();
Expand Down