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<flat_map>: Minor cleanups of iterator operations in flat_map members _Erase_if() etc. #5996

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Merged
Stephan T. Lavavej (StephanTLavavej) merged 4 commits into from
Jan 8, 2026
Merged

<flat_map>: Minor cleanups of iterator operations in flat_map members _Erase_if() etc. #5996

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edc5d78
Simplify iterator operations in _Flat_map_base::_Erase_if and similar.
vmichal Jan 6, 2026
201af88
Small cleanup in _Flat_map_base::_Insert_range
vmichal Jan 7, 2026
94761b6
Rename _Flat_map_base::_Sort_and_erase_dupes_... for consistency with…
vmichal Jan 7, 2026
a8344f2
West const.
StephanTLavavej Jan 8, 2026
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55 changes: 21 additions & 34 deletions stl/inc/flat_map
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Original file line number Diff line number Diff line change
Expand Up @@ -352,7 +352,7 @@ public:
key_container_type _Key_cont, mapped_container_type _Mapped_cont, const key_compare& _Comp = key_compare())
: _Data{.keys = _STD move(_Key_cont), .values = _STD move(_Mapped_cont)}, _Key_compare(_Comp) {
_STL_ASSERT(_Data.keys.size() == _Data.values.size(), "key_cont.size() != mapped_cont.size()");
_Sort_and_erase_dupes_if_not_multi();
_Make_invariants_fulfilled();
}

template <_Usable_allocator_for<key_container_type, mapped_container_type> _Allocator>
Expand All @@ -367,7 +367,7 @@ public:
.values = _STD make_obj_using_allocator<mapped_container_type>(_Alloc, _Mapped_cont)},
_Key_compare(_Comp) {
_STL_ASSERT(_Data.keys.size() == _Data.values.size(), "key_cont.size() != mapped_cont.size()");
_Sort_and_erase_dupes_if_not_multi();
_Make_invariants_fulfilled();
}

_Flat_map_base(_Sorted_t, key_container_type _Key_cont, mapped_container_type _Mapped_cont,
Expand Down Expand Up @@ -1024,16 +1024,13 @@ private:

template <class _Predicate>
_NODISCARD size_type _Erase_if(_Predicate _Pred) {
auto _View = _View_to_mutate();
auto _Mut_first = _View.begin();
const auto _Mut_last = _View.end();
const auto _Old_size = size();

_Clear_guard _Guard{this};

_STD _Seek_wrapped(_Mut_first, _RANGES remove_if(_View, _Pred).begin());
_Data.keys.erase(_Mut_first._Key_it, _Mut_last._Key_it);
_Data.values.erase(_Mut_first._Mapped_it, _Mut_last._Mapped_it);
const auto _New_last = _RANGES remove_if(_View_to_mutate(), _Pred).begin();
const auto _Old_size = size();

_Data.keys.erase(_New_last._Key_it, _Data.keys.end());
_Data.values.erase(_New_last._Mapped_it, _Data.values.end());

_Guard._Target = nullptr;
return _Old_size - size();
Expand Down Expand Up @@ -1067,42 +1064,34 @@ private:
return _Is_sorted_and_unique(_Cont.begin(), _Cont.end());
}

void _Sort_and_erase_dupes_if_not_multi() {
_Clear_guard _Guard{this};
void _Make_invariants_fulfilled() {
if (empty()) { // FIXME maybe consider if (begin() == end()) for consistency with flat_set
return;
}

// O(N) if already sorted.
const auto _Begin_unsorted =
_STD is_sorted_until(_STD cbegin(_Data.keys), _STD cend(_Data.keys), _Pass_key_comp());
const difference_type _Num_sorted = _Begin_unsorted - _STD cbegin(_Data.keys);
const auto _Num_sorted = _RANGES is_sorted_until(_Data.keys, _Pass_key_comp()) - _Data.keys.begin();

auto _View = _View_to_mutate();
const auto _Begin = _STD begin(_View);
const auto _Begin_unsorted_values = _Begin + _Num_sorted;
const auto _End = _STD end(_View);
const auto _Begin_unsorted_values = _STD begin(_View) + _Num_sorted;

_RANGES sort(_Begin_unsorted_values, _End, value_compare{_Key_compare});
_RANGES inplace_merge(_Begin, _Begin_unsorted_values, _End, value_compare{_Key_compare});
_RANGES sort(_Begin_unsorted_values, _STD end(_View), value_compare{_Key_compare});
_RANGES inplace_merge(_View, _Begin_unsorted_values, value_compare{_Key_compare});

_Erase_dupes_if_not_multi();

_STL_INTERNAL_CHECK(_Is_sorted_and_unique());

_Guard._Target = nullptr;
}

void _Erase_dupes_if_not_multi() {
if constexpr (_IsUnique) {
auto _Sorted_view = _View_to_mutate();
const auto _Subrange = _RANGES unique(_Sorted_view, [this](const_reference _Left, const_reference _Right) {
const auto _New_last = _RANGES unique(_Sorted_view, [this](const_reference _Left, const_reference _Right) {
return this->_Key_equal(_Left.first, _Right.first);
});
const auto _Remaining_count = _Subrange.begin() - _Sorted_view.begin();
_Data.keys.erase(
_Data.keys.begin() + static_cast<_RANGES range_difference_t<_KeyContainer>>(_Remaining_count),
_Data.keys.end());
_Data.values.erase(
_Data.values.begin() + static_cast<_RANGES range_difference_t<_MappedContainer>>(_Remaining_count),
_Data.values.end());
}).begin();

_Data.keys.erase(_New_last._Key_it, _Data.keys.end());
_Data.values.erase(_New_last._Mapped_it, _Data.values.end());
}
}

Expand Down Expand Up @@ -1131,9 +1120,7 @@ private:
// Sort the newly inserted elements
auto _Sorted_view = _View_to_mutate();
if constexpr (_NeedSorting) {
auto _Sorted_new_elements = _Sorted_view;
_Sorted_new_elements.advance(_Old_distance);
_RANGES sort(_Sorted_new_elements, value_compare{_Key_compare});
_RANGES sort(_STD begin(_Sorted_view) + _Old_distance, _STD end(_Sorted_view), value_compare{_Key_compare});
} else {
_STL_ASSERT(_Is_sorted_and_unique(
_Data.keys.begin() + static_cast<key_container_type::difference_type>(_Old_distance),
Expand Down