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Reserve the container size across remappings

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This commit is contained in:
Denis Blank 2018-03-09 10:10:56 +01:00
parent de40af0927
commit 22ce1840b9
1 changed files with 23 additions and 3 deletions
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26
include/continuable/detail/traverse.hpp
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@ -441,6 +441,25 @@ template <typename T, typename M>
using container_mapping_tag_of_t =
container_mapping_tag<is_empty_mapped<T, M>::value, can_reuse<T, M>::value>;
/// Deduces to a true type if the given parameter T supports a `reserve` method
template <typename From, typename To, typename = void>
struct is_reservable_from : std::false_type {};
template <typename From, typename To>
struct is_reservable_from<From, To,
traits::void_t<decltype(std::declval<To>().reserve(
std::declval<From>().size()))>> : std::true_type {
};
template <typename Dest, typename Source>
void reserve_if(std::true_type, Dest&& dest, Source&& source) {
// Reserve the mapped size
dest.reserve(source.size());
}
template <typename Dest, typename Source>
void reserve_if(std::false_type, Dest&&, Source&&) noexcept {
// We do nothing here, since the container doesn't support reserving
}
/// We create a new container, which may hold the resulting type
template <typename M, typename T>
auto remap_container(container_mapping_tag<false, false>, M&& mapper,
@ -456,9 +475,10 @@ auto remap_container(container_mapping_tag<false, false>, M&& mapper,
auto remapped = rebind_container<mapped_type_from_t<T, M>>(container);
// We try to reserve the original size from the source
// container to the destination container.
// TODO Re-implement this
// traits::detail::reserve_if_reservable(remapped, container.size());
// container inside the destination container.
reserve_if(
is_reservable_from<std::decay_t<T>, std::decay_t<decltype(remapped)>>{},
remapped, container);
// Perform the actual value remapping from the source to
// the destination.