std::ranges::move_backward, std::ranges::move_backward_result
Defined in header <algorithm> |
||
---|---|---|
Call signature | ||
template< std::bidirectional_iterator I1, std::sentinel_for<I1> S1, std::bidirectional_iterator I2 > requires std::indirectly_movable<I1, I2> constexpr move_backward_result<I1, I2> move_backward( I1 first, S1 last, I2 result ); |
(1) | (since C++20) |
template< ranges::bidirectional_range R, std::bidirectional_iterator I > requires std::indirectly_movable<ranges::iterator_t<R>, I> constexpr move_backward_result<ranges::borrowed_iterator_t<R>, I> move_backward( R&& r, I result ); |
(2) | (since C++20) |
Helper types | ||
template< class I, class O > using move_backward_result = ranges::in_out_result<I, O>; |
(3) | (since C++20) |
[first, last)
, to another range
[result - N, result)
, where
N = ranges::distance(first, last)
. The elements are moved in reverse order (the last element is moved first), but their relative order is preserved. The behavior is undefined if
result
is within
(first, last]
. In such a case,
ranges::move
may be used instead.
r
as the source range, as if using
ranges::begin(r)
as
first
, and
ranges::end(r)
as
last
.
The elements in the moved-from range will still contain valid values of the appropriate type, but not necessarily the same values as before the move, as if using *(result - n) = ranges::iter_move(last - n)
for each integer n
, where 0 ≤ n < N
.
The function-like entities described on this page are niebloids, that is:
- Explicit template argument lists may not be specified when calling any of them.
- None of them is visible to argument-dependent lookup.
- When one of them is found by normal unqualified lookup for the name to the left of the function-call operator, it inhibits argument-dependent lookup.
In practice, they may be implemented as function objects, or with special compiler extensions.
Parameters
first | - | the beginning of the range of elements to move |
last | - | the end of the range of elements to move |
r | - | the range of the elements to move |
result | - | the end of the destination range |
Return value
{last, result - N}
.
Complexity
N
move assignments.
ranges::distance(r)
move assignments.
Notes
When moving overlapping ranges, ranges::move
is appropriate when moving to the left (beginning of the destination range is outside the source range) while ranges::move_backward
is appropriate when moving to the right (end of the destination range is outside the source range).
Possible implementation
struct move_backward_fn { template<std::bidirectional_iterator I1, std::sentinel_for<I1> S1, std::bidirectional_iterator I2> requires std::indirectly_movable<I1, I2> constexpr ranges::move_backward_result<I1, I2> operator()( I1 first, S1 last, I2 result ) const { auto i {last}; for (; i != first; *--result = ranges::iter_move(--i)); return {std::move(last), std::move(result)}; } template<ranges::bidirectional_range R, std::bidirectional_iterator I> requires std::indirectly_movable<ranges::iterator_t<R>, I> constexpr ranges::move_backward_result<ranges::borrowed_iterator_t<R>, I> operator()( R&& r, I result ) const { return (*this)(ranges::begin(r), ranges::end(r), std::move(result)); } }; inline constexpr move_backward_fn move_backward{}; |
Example
#include <algorithm> #include <iostream> #include <string> #include <string_view> #include <vector> using Vec = std::vector<std::string>; void print(std::string_view rem, Vec const& vec) { std::cout << rem << "[" << vec.size() << "]: "; for (const std::string& s : vec) std::cout << (s.size() ? s : std::string{"·"}) << ' '; std::cout << '\n'; } int main() { Vec a{"▁", "▂", "▃", "▄", "▅", "▆", "▇", "█"}; Vec b(a.size()); print("Before move:\n" "a", a); print("b", b); std::ranges::move_backward(a, b.end()); print("\n" "Move a >> b:\n" "a", a); print("b", b); std::ranges::move_backward(b.begin(), b.end(), a.end()); print("\n" "Move b >> a:\n" "a", a); print("b", b); std::ranges::move_backward(a.begin(), a.begin()+3, a.end()); print("\n" "Overlapping move a[0, 3) >> a[5, 8):\n" "a", a); }
Possible output:
Before move: a[8]: ▁ ▂ ▃ ▄ ▅ ▆ ▇ █ b[8]: · · · · · · · · Move a >> b: a[8]: · · · · · · · · b[8]: ▁ ▂ ▃ ▄ ▅ ▆ ▇ █ Move b >> a: a[8]: ▁ ▂ ▃ ▄ ▅ ▆ ▇ █ b[8]: · · · · · · · · Overlapping move a[0, 3) >> a[5, 8): a[8]: · · · ▄ ▅ ▁ ▂ ▃
See also
(C++20)
|
moves a range of elements to a new location (niebloid) |
(C++20)(C++20)
|
copies a range of elements to a new location (niebloid) |
(C++20)
|
copies a range of elements in backwards order (niebloid) |
(C++11)
|
moves a range of elements to a new location (function template) |
(C++11)
|
obtains an rvalue reference (function template) |
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