Defined in header <algorithm> | ||
|---|---|---|
| Call signature | ||
template< std::input_iterator I, std::sentinel_for<I> S, std::weakly_incrementable O >
requires std::indirectly_copyable<I, O>
constexpr copy_result<I, O>
copy( I first, S last, O result );
| (1) | (since C++20) |
template< ranges::input_range R, std::weakly_incrementable O >
requires std::indirectly_copyable<ranges::iterator_t<R>, O>
constexpr copy_result<ranges::borrowed_iterator_t<R>, O>
copy( R&& r, O result );
| (2) | (since C++20) |
template< std::input_iterator I, std::sentinel_for<I> S, std::weakly_incrementable O,
class Proj = std::identity,
std::indirect_unary_predicate<std::projected<I, Proj>> Pred >
requires std::indirectly_copyable<I, O>
constexpr copy_if_result<I, O>
copy_if( I first, S last, O result, Pred pred, Proj proj = {} );
| (3) | (since C++20) |
template< ranges::input_range R, std::weakly_incrementable O,
class Proj = std::identity,
std::indirect_unary_predicate<
std::projected<ranges::iterator_t<R>, Proj>> Pred >
requires std::indirectly_copyable<ranges::iterator_t<R>, O>
constexpr copy_if_result<ranges::borrowed_iterator_t<R>, O>
copy_if( R&& r, O result, Pred pred, Proj proj = {} );
| (4) | (since C++20) |
| Helper types | ||
template< class I, class O > using copy_result = ranges::in_out_result<I, O>; | (5) | (since C++20) |
template< class I, class O > using copy_if_result = ranges::in_out_result<I, O>; | (6) | (since C++20) |
Copies the elements in the range, defined by [first, last), to another range beginning at result.
[first, last) starting from first and proceeding to last - 1. The behavior is undefined if result is within the range [first, last). In this case, ranges::copy_backward may be used instead.pred returns true. The relative order of the elements that are copied is preserved. The behavior is undefined if the source and the destination ranges overlap.r as the source range, as if using ranges::begin(r) as first and ranges::end(r) as last.The function-like entities described on this page are niebloids, that is:
In practice, they may be implemented as function objects, or with special compiler extensions.
| first, last | - | the range of elements to copy |
| r | - | the range of elements to copy |
| result | - | the beginning of the destination range. |
| pred | - | predicate to apply to the projected elements |
| proj | - | projection to apply to the elements |
A ranges::in_out_result containing an input iterator equal to last and an output iterator past the last element copied.
last - first assignments.last - first applications of the predicate and projection, between 0 and last - first assignments (assignment for every element for which predicate returns true, dependent on predicate and input data).In practice, implementations of ranges::copy avoid multiple assignments and use bulk copy functions such as std::memmove if the value type is TriviallyCopyable and the iterator types satisfy contiguous_iterator.
When copying overlapping ranges, ranges::copy is appropriate when copying to the left (beginning of the destination range is outside the source range) while ranges::copy_backward is appropriate when copying to the right (end of the destination range is outside the source range).
| copy |
|---|
struct copy_fn
{
template<std::input_iterator I, std::sentinel_for<I> S, std::weakly_incrementable O>
requires std::indirectly_copyable<I, O>
constexpr ranges::copy_result<I, O> operator()(I first, S last, O result) const
{
for (; first != last; ++first, (void)++result)
*result = *first;
return {std::move(first), std::move(result)};
}
template<ranges::input_range R, std::weakly_incrementable O>
requires std::indirectly_copyable<ranges::iterator_t<R>, O>
constexpr ranges::copy_result<ranges::borrowed_iterator_t<R>, O>
operator()(R&& r, O result) const
{
return (*this)(ranges::begin(r), ranges::end(r), std::move(result));
}
};
inline constexpr copy_fn copy; |
| copy_if |
struct copy_if_fn
{
template<std::input_iterator I, std::sentinel_for<I> S, std::weakly_incrementable O,
class Proj = std::identity,
std::indirect_unary_predicate<std::projected<I, Proj>> Pred>
requires std::indirectly_copyable<I, O>
constexpr ranges::copy_if_result<I, O>
operator()(I first, S last, O result, Pred pred, Proj proj = {}) const
{
for (; first != last; ++first)
if (std::invoke(pred, std::invoke(proj, *first)))
{
*result = *first;
++result;
}
return {std::move(first), std::move(result)};
}
template<ranges::input_range R, std::weakly_incrementable O,
class Proj = std::identity,
std::indirect_unary_predicate<
std::projected<ranges::iterator_t<R>, Proj>> Pred>
requires std::indirectly_copyable<ranges::iterator_t<R>, O>
constexpr ranges::copy_if_result<ranges::borrowed_iterator_t<R>, O>
operator()(R&& r, O result, Pred pred, Proj proj = {}) const
{
return (*this)(ranges::begin(r), ranges::end(r),
std::move(result),
std::ref(pred), std::ref(proj));
}
};
inline constexpr copy_if_fn copy_if; |
The following code uses ranges::copy to both copy the contents of one std::vector to another and to display the resulting std::vector:
#include <algorithm>
#include <iostream>
#include <iterator>
#include <numeric>
#include <vector>
int main()
{
std::vector<int> source(10);
std::iota(source.begin(), source.end(), 0);
std::vector<int> destination;
std::ranges::copy(source.begin(), source.end(),
std::back_inserter(destination));
// or, alternatively,
// std::vector<int> destination(source.size());
// std::ranges::copy(source.begin(), source.end(), destination.begin());
// either way is equivalent to
// std::vector<int> destination = source;
std::cout << "destination contains: ";
std::ranges::copy(destination, std::ostream_iterator<int>(std::cout, " "));
std::cout << '\n';
std::cout << "odd numbers in destination are: ";
std::ranges::copy_if(destination, std::ostream_iterator<int>(std::cout, " "),
[](int x) { return (x % 2) == 1; });
std::cout << '\n';
}Output:
destination contains: 0 1 2 3 4 5 6 7 8 9 odd numbers in destination are: 1 3 5 7 9
|
(C++20) | copies a range of elements in backwards order (niebloid) |
|
(C++20) | creates a copy of a range that is reversed (niebloid) |
|
(C++20) | copies a number of elements to a new location (niebloid) |
|
(C++20) | assigns a range of elements a certain value (niebloid) |
|
(C++20)(C++20) | copies a range of elements omitting those that satisfy specific criteria (niebloid) |
|
(C++11) | copies a range of elements to a new location (function template) |
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