std::ranges::copy_n, std::ranges::copy_n_result - cppreference.com (original) (raw)
| Defined in header | ||
|---|---|---|
| Call signature | ||
| template< std::input_iterator I, std::weakly_incrementable O > requires std::indirectly_copyable<I, O> constexpr copy_n_result<I, O> copy_n( I first, std::iter_difference_t<I> n, O result ); | (1) | (since C++20) |
| Helper type | ||
| template< class I, class O > using copy_n_result = ranges::in_out_result<I, O>; | (2) | (since C++20) |
- Copies exactly n values from the range beginning at first to the range beginning at result by performing *(result + i) = *(first + i) for each integer in
[0,n). The behavior is undefined if result is within the range[first,first + n)(ranges::copy_backward might be used instead in this case).
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
| first | - | the beginning of the range of elements to copy from |
|---|---|---|
| n | - | number of the elements to copy |
| result | - | the beginning of the destination range |
[edit] Return value
ranges::copy_n_result{first + n, result + n} or more formally, a value of type ranges::in_out_result that contains an input_iterator iterator equals to ranges::next(first, n) and a weakly_incrementable iterator equals to ranges::next(result, n).
[edit] Complexity
Exactly n assignments.
[edit] Notes
In practice, implementations of std::ranges::copy_n may 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. Alternatively, such copy acceleration can be injected during an optimization phase of a compiler.
When copying overlapping ranges, std::ranges::copy_n is appropriate when copying to the left (beginning of the destination range is outside the source range) while std::ranges::copy_backward is appropriate when copying to the right (end of the destination range is outside the source range).
[edit] Possible implementation
[edit] Example
Output:
"ABCD" in[5] = 'F' out[5] = 'f'
[edit] See also
| ranges::copyranges::copy_if(C++20)(C++20) | copies a range of elements to a new location(algorithm function object)[edit] |
|---|---|
| ranges::copy_backward(C++20) | copies a range of elements in backwards order(algorithm function object)[edit] |
| ranges::remove_copyranges::remove_copy_if(C++20)(C++20) | copies a range of elements omitting those that satisfy specific criteria(algorithm function object)[edit] |
| ranges::replace_copyranges::replace_copy_if(C++20)(C++20) | copies a range, replacing elements satisfying specific criteria with another value(algorithm function object)[edit] |
| ranges::reverse_copy(C++20) | creates a copy of a range that is reversed(algorithm function object)[edit] |
| ranges::rotate_copy(C++20) | copies and rotate a range of elements(algorithm function object)[edit] |
| ranges::unique_copy(C++20) | creates a copy of some range of elements that contains no consecutive duplicates(algorithm function object)[edit] |
| ranges::move(C++20) | moves a range of elements to a new location(algorithm function object)[edit] |
| ranges::move_backward(C++20) | moves a range of elements to a new location in backwards order(algorithm function object)[edit] |
| copy_n(C++11) | copies a number of elements to a new location (function template) [edit] |