Sorter traits
#include <cpp-sort/sorter_traits.h>
The variable templates is_sorter<typename Sorter, typename Iterable>
and is_comparison_sorter<typename Sorter, typename Iterable, typename Compare>
respectively equal true
if the type Sorter
satisfies the Sorter
or ComparisonSorter
concept and equal false
otherwise.
In our case, a Sorter
is a type that can be called with an Iterable&
while a ComparisonSorter
is a that can be called with an Iterable&
and a Compare
. These traits mainly exist for SFINAE purpose and concept checking.
template<typename Sorter, typename Iterable>
constexpr bool is_sorter = /* implementation-defined */;
template<typename Sorter, typename Iterable, typename Compare>
constexpr bool is_comparison_sorter = /* implementation-defined */;
There are also variants of these variable templates which take a potential sorter type and an iterator type. They exist to check whether the sorter can be called with a pair of iterators.
template<typename Sorter, typename Iterator>
constexpr bool is_sorter_iterator = /* implementation-defined */;
template<typename Sorter, typename Iterator, typename Compare>
constexpr bool is_comparison_sorter_iterator = /* implementation-defined */;
The class template sorter_traits<Sorter>
contains information about sorters and sorter adapters such as the kind of iterators accepted by a sorter and whether it implements or not a stable sorting algorithm.
template<typename Sorter>
struct sorter_traits {};
This class template can be specialized for every sorter object and contains the following fields:
using iterator_category = /* depends on the sorter */;
static constexpr bool is_stable = /* depends on the context */;
The non-specialized version of sorter_traits
is defined but empty for SFINAE-friendliness.
template<typename Sorter>
using iterator_category = typename sorter_traits<Sorter>::iterator_category;
Some tools need to know which category of iterators a sorting algorithm can work with. Therefore, a well-defined sorter shall provide one of the standard library iterator tags in order to document that.
When a sorter is adapted so that it may be used with several categories of iterators, the resulting sorter's iterator category will correspond to the most permissive among the original sorters. For example, if an hybrid_sorter
merges sorting algorithms with std::forward_iterator_tag
and std::random_access_iterator_tag
, the resulting sorter's category will be std::forward_iterator_tag
since it is guaranteed to work with any iterable type which has at least forward iterators.
template<typename Sorter>
constexpr bool is_stable = sorter_traits<Sorter>::is_stable;
This variable template contains a boolean value which tells whether a sorting algorithm is stable or not. This information may be useful in some contexts.
When a sorter adapter is used, the stability of the resulting sorter is true
if and only if its stability can be guaranteed and false
otherwise, even when the adapted sorter may be stable (for example, self_sort_adapter
is always false
since you can't guarantee the stability of any sort
method).
template<typename Sorter, typename Category>
struct rebind_iterator_category;
This class allows to get a sorter similar to the one passed but with a stricter iterator category. For example, it can generate a sorter whose iterator category is std::bidirectional_iterator_tag
from another sorter whose iterator category is std::forward_iterator_tag
. It is mostly ueful to make several sorters with the same iterator category work for different iterator categories in an hybrid_adapter
. Let's say we have two sorters, foo_sorter
and bar_sorter
; both have the iterator category std::forward_iterator_tag
, but foo_sorter
is the best to sort forward iterators while bar_sorter
benefits from some optimizations for bidirectional and random-access iterators. It is possible to use the best of both with the following sorter:
using sorter = cppsort::hybrid_adapter<
foo_sorter,
cppsort::rebind_iterator_category<
bar_sorter,
std::bidirectional_iterator_tag
>
>;
The sorter above will pick foo_sorter
for forward iterators, but it will pick bar_sorter
for bidirectional and random-access iterators. A compile-time error will occur if one tries to rebind to an iterator category that is not derived from the sorter's original iterator category.
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