std::ranges::swap_ranges, std::ranges::swap_ranges_result
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Constrained algorithms
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std::ranges
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Defined in header
<algorithm>
Call signature
template< std::input_iterator I1, std::sentinel_for <I1> S1,
(1)
(since C++20)
std::input_iterator I2, std::sentinel_for <I2> S2 >
requires std::indirectly_swappable <I1, I2>
constexpr swap_ranges_result<I1, I2>
template< ranges::input_range R1, ranges::input_range R2 >
(2)
(since C++20)
requires std::indirectly_swappable <ranges::iterator_t <R1>, ranges::iterator_t <R2>>
constexpr swap_ranges_result<ranges::borrowed_iterator_t <R1>,
ranges::borrowed_iterator_t <R2>>
Helper types
template< class I1, class I2 >
using swap_ranges_result = ranges::in_in_result <I1, I2>;
(3)
(since C++20)
using swap_ranges_result = ranges::in_in_result <I1, I2>;
1) Exchanges elements between first range
[first1, first1 + M) and second range [first2, first2 + M) via ranges::iter_swap (first1 + i, first2 + i), where M = ranges::min (ranges::distance (first1, last1), ranges::distance (first2, last2)). The ranges
[first1, last1) and [first2, last2) must not overlap.2) Same as (1), but uses r1 as the first range and r2 as the second range, as if using ranges::begin (r1) as first1, ranges::end (r1) as last1, ranges::begin (r2) as first2, and ranges::end (r2) as last2.
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.
Contents
[edit] Parameters
first1, last1
-
the iterator-sentinel pair defining the first range of elements to swap
first2, last2
-
the iterator-sentinel pair defining the second range of elements to swap
r1
-
the first range of elements to swap
r2
-
the second range of elements to swap.
[edit] Return value
{first1 + M, first2 + M}.
[edit] Complexity
Exactly M swaps.
[edit] Notes
Implementations (e.g. MSVC STL) may enable vectorization when the iterator type models contiguous_iterator and swapping its value type calls neither non-trivial special member function nor ADL-found swap.
[edit] Possible implementation
struct swap_ranges_fn { template<std::input_iterator I1, std::sentinel_for <I1> S1, std::input_iterator I2, std::sentinel_for <I2> S2> requires std::indirectly_swappable <I1, I2> constexpr ranges::swap_ranges_result<I1, I2> operator()(I1 first1, S1 last1, I2 first2, S2 last2) const { for (; !(first1 == last1 or first2 == last2); ++first1, ++first2) ranges::iter_swap (first1, first2); return {std::move(first1), std::move(first2)}; } template<ranges::input_range R1, ranges::input_range R2> requires std::indirectly_swappable <ranges::iterator_t <R1>, ranges::iterator_t <R2>> constexpr ranges::swap_ranges_result<ranges::borrowed_iterator_t <R1>, ranges::borrowed_iterator_t <R2>> operator()(R1&& r1, R2&& r2) const { return (*this)(ranges::begin (r1), ranges::end (r1), ranges::begin (r2), ranges::end (r2)); } }; inline constexpr swap_ranges_fn swap_ranges {};
[edit] Example
Run this code
#include <algorithm> #include <iostream> #include <list> #include <string_view> #include <vector> auto print(std::string_view name, auto const& seq, std::string_view term = "\n") { std::cout << name << " : "; for (const auto& elem : seq) std::cout << elem << ' '; std::cout << term; } int main() { std::vector <char> p {'A', 'B', 'C', 'D', 'E'}; std::list <char> q {'1', '2', '3', '4', '5', '6'}; print("p", p); print("q", q, "\n\n"); // swap p[0, 2) and q[1, 3): std::ranges::swap_ranges(p.begin(), p.begin() + 4, std::ranges::next (q.begin(), 1), std::ranges::next (q.begin(), 3)); print("p", p); print("q", q, "\n\n"); // swap p[0, 5) and q[0, 5): std::ranges::swap_ranges(p, q); print("p", p); print("q", q); }
Output:
p : A B C D E q : 1 2 3 4 5 6 p : 2 3 C D E q : 1 A B 4 5 6 p : 1 A B 4 5 q : 2 3 C D E 6
[edit] See also
(C++20)
(customization point object)[edit]