std::ranges::unique_copy, std::ranges::unique_copy_result
std::ranges
<algorithm>
class Proj = std::identity,
std::indirect_equivalence_relation <std::projected <I, Proj>>
C = ranges::equal_to >
requires std::indirectly_copyable <I, O> && (std::forward_iterator <I> ||
(std::input_iterator <O> && std::same_as <std::iter_value_t <I>,
std::iter_value_t <O>>) || std::indirectly_copyable_storable <I, O>)
constexpr unique_copy_result<I, O>
class Proj = std::identity,
std::indirect_equivalence_relation <std::projected <ranges::iterator_t <R>,
Proj>> C = ranges::equal_to >
requires std::indirectly_copyable <ranges::iterator_t <R>, O> &&
(std::forward_iterator <ranges::iterator_t <R>> ||
(std::input_iterator <O> && std::same_as <ranges::range_value_t <R>,
std::iter_value_t <O>>) ||
std::indirectly_copyable_storable <ranges::iterator_t <R>, O>)
constexpr unique_copy_result<ranges::borrowed_iterator_t <R>, O>
using unique_copy_result = ranges::in_out_result <I, O>;
[
first,
last)
, to the destination range beginning at result in such a way that there are no consecutive equal elements. Only the first element of each group of equal elements is copied.[
first,
last)
and [
result,
result + N)
must not overlap. N = ranges::distance (first, last).i
is an iterator in the range [
first + 1,
last)
.The function-like entities described on this page are algorithm function objects (informally known as niebloids), that is:
- Explicit template argument lists cannot be specified when calling any of them.
- None of them are visible to argument-dependent lookup.
- When any of them are found by normal unqualified lookup as the name to the left of the function-call operator, argument-dependent lookup is inhibited.
[edit] Parameters
[edit] Return value
{last, result + N}
[edit] Complexity
Exactly N - 1 applications of the corresponding predicate comp and no more than twice as many applications of any projection proj.
[edit] Possible implementation
See also the implementations in libstdc++ and MSVC STL (and third-party libraries: cmcstl2, NanoRange, and range-v3).
struct unique_copy_fn { template<std::input_iterator I, std::sentinel_for <I> S, std::weakly_incrementable O, class Proj = std::identity, std::indirect_equivalence_relation <std::projected <I, Proj>> C = ranges::equal_to > requires std::indirectly_copyable <I, O> && (std::forward_iterator <I> || (std::input_iterator <O> && std::same_as <std::iter_value_t <I>, std::iter_value_t <O>>) || std::indirectly_copyable_storable <I, O>) constexpr ranges::unique_copy_result<I, O> operator()(I first, S last, O result, C comp = {}, Proj proj = {}) const { if (!(first == last)) { std::iter_value_t <I> value = *first; *result = value; ++result; while (!(++first == last)) { auto&& value2 = *first; if (!std::invoke (comp, std::invoke (proj, value2), std::invoke (proj, value))) { value = std::forward <decltype(value2)>(value2); *result = value; ++result; } } } return {std::move(first), std::move(result)}; } template<ranges::input_range R, std::weakly_incrementable O, class Proj = std::identity, std::indirect_equivalence_relation <std::projected <ranges::iterator_t <R>, Proj>> C = ranges::equal_to > requires std::indirectly_copyable <ranges::iterator_t <R>, O> && (std::forward_iterator <ranges::iterator_t <R>> || (std::input_iterator <O> && std::same_as <ranges::range_value_t <R>, std::iter_value_t <O>>) || std::indirectly_copyable_storable <ranges::iterator_t <R>, O>) constexpr ranges::unique_copy_result<ranges::borrowed_iterator_t <R>, O> operator()(R&& r, O result, C comp = {}, Proj proj = {}) const { return (*this)(ranges::begin (r), ranges::end (r), std::move(result), std::move(comp), std::move(proj)); } }; inline constexpr unique_copy_fn unique_copy {};
[edit] Example
#include <algorithm> #include <cmath> #include <iostream> #include <iterator> #include <list> #include <string> #include <type_traits> void print(const auto& rem, const auto& v) { using V = std::remove_cvref_t <decltype(v)>; constexpr bool sep{std::is_same_v <typename V::value_type, int>}; std::cout << rem << std::showpos ; for (const auto& e : v) std::cout << e << (sep ? " " : ""); std::cout << '\n'; } int main() { std::string s1{"The string with many spaces!"}; print("s1: ", s1); std::string s2; std::ranges::unique_copy( s1.begin(), s1.end(), std::back_inserter (s2), [](char c1, char c2) { return c1 == ' ' && c2 == ' '; } ); print("s2: ", s2); const auto v1 = {-1, +1, +2, -2, -3, +3, -3}; print("v1: ", v1); std::list <int> v2; std::ranges::unique_copy( v1, std::back_inserter (v2), {}, // default comparator std::ranges::equal_to [](int x) { return std::abs(x); } // projection ); print("v2: ", v2); }
Output:
s1: The string with many spaces! s2: The string with many spaces! v1: -1 +1 +2 -2 -3 +3 -3 v2: -1 +2 -3
[edit] See also
(algorithm function object)[edit]
(function template) [edit]