std::ranges::replace_copy, std::ranges::replace_copy_if, std::ranges::replace_copy_result, std::ranges::replace_copy_if_result - cppreference.com
| Defined in header |
||
| Call signature |
||
| (1) | ||
|
(since C++20) (until C++26) |
|
|
(since C++26) | |
| (2) | ||
|
|
(since C++20) (until C++26) |
|
|
|
(since C++26) | |
| (3) | ||
|
(since C++20) (until C++26) |
|
|
|
(since C++26) | |
| (4) | ||
|
|
(since C++20) (until C++26) |
|
|
|
(since C++26) | |
| Helper types |
||
|
|
(5) | (since C++20) |
|
|
(6) | (since C++20) |
Copies the elements from the source range [first, last) to the destination range beginning at result, replacing all elements satisfying specific criteria with new_value. The behavior is undefined if the source and destination ranges overlap.
1) Replaces all elements that are equal to old_value, using std::invoke(proj, *(first + (i - result))) == old_value to compare.
3) Replaces all elements for which the predicate pred evaluates to true, where the evaluating expression is std::invoke(pred, std::invoke(proj, *(first + (i - result)))).
2,4) Same as (1,3), but uses 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 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.
Parameters
| first, last | - | the iterator-sentinel pair defining the range of elements to copy |
| r | - | the range of elements to copy |
| result | - | the beginning of the destination range |
| old_value | - | the value of elements to replace |
| new_value | - | the value to use as a replacement |
| pred | - | predicate to apply to the projected elements |
| proj | - | projection to apply to the elements. |
Return value
{last, result + N}, where
1,3) N = ranges::distance(first, last);
2,4) N = ranges::distance(r).
Complexity
Exactly N applications of the corresponding predicate comp and any projection proj.
Possible implementation
| replace_copy (1,2) |
|---|
struct replace_copy_fn { template<std::input_iterator I, std::sentinel_for<I> S, class O, class Proj = std::identity, class T1 = std::projected_value_t<I, Proj>, class T2 = std::iter_value_t<O>> requires std::indirectly_copyable<I, O> && std::indirect_binary_predicate <ranges::equal_to, std::projected<I, Proj>, const T1*> && std::output_iterator<O, const T2&> constexpr ranges::replace_copy_result<I, O> operator()(I first, S last, O result, const T1& old_value, const T2& new_value, Proj proj = {}) const { for (; first != last; ++first, ++result) *result = (std::invoke(proj, *first) == old_value) ? new_value : *first; return {std::move(first), std::move(result)}; } template<ranges::input_range R, class O, class Proj = std::identity, class T1 = std::projected_value_t<ranges::iterator_t<R>, Proj>, class T2 = std::iter_value_t<O>> requires std::indirectly_copyable<ranges::iterator_t<R>, O> && std::indirect_binary_predicate <ranges::equal_to, std::projected<ranges::iterator_t<R>, Proj>, const T1*> constexpr ranges::replace_copy_result<ranges::borrowed_iterator_t<R>, O> operator()(R&& r, O result, const T1& old_value, const T2& new_value, Proj proj = {}) const { return (*this)(ranges::begin(r), ranges::end(r), std::move(result), old_value, new_value, std::move(proj)); } }; inline constexpr replace_copy_fn replace_copy {}; |
| replace_copy_if (3,4) |
struct replace_copy_if_fn { template<std::input_iterator I, std::sentinel_for<I> S, class O, class T = std::iter_value_t<O> class Proj = std::identity, std::indirect_unary_predicate<std::projected<I, Proj>> Pred> requires std::indirectly_copyable<I, O> && std::output_iterator<O, const T&> constexpr ranges::replace_copy_if_result<I, O> operator()(I first, S last, O result, Pred pred, const T& new_value, Proj proj = {}) const { for (; first != last; ++first, ++result) *result = std::invoke(pred, std::invoke(proj, *first)) ? new_value : *first; return {std::move(first), std::move(result)}; } template<ranges::input_range R, class O, class T = std::iter_value_t<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> && std::output_iterator<O, const T&> constexpr ranges::replace_copy_if_result<ranges::borrowed_iterator_t<R>, O> operator()(R&& r, O result, Pred pred, const T& new_value, Proj proj = {}) const { return (*this)(ranges::begin(r), ranges::end(r), std::move(result), std::move(pred), new_value, std::move(proj)); } }; inline constexpr replace_copy_if_fn replace_copy_if {}; |
Notes
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_algorithm_default_value_type |
202403 |
(C++26) | list-initialization for algorithms (1-4) |
Example
#include <algorithm> #include <array> #include <complex> #include <iostream> #include <vector> void println(const auto rem, const auto& v) { for (std::cout << rem << ": "; const auto& e : v) std::cout << e << ' '; std::cout << '\n'; } int main() { std::vector<int> o; std::array p{1, 6, 1, 6, 1, 6}; o.resize(p.size()); println("p", p); std::ranges::replace_copy(p, o.begin(), 6, 9); println("o", o); std::array q{1, 2, 3, 6, 7, 8, 4, 5}; o.resize(q.size()); println("q", q); std::ranges::replace_copy_if(q, o.begin(), [](int x) { return 5 < x; }, 5); println("o", o); std::vector<std::complex<short>> r{{1, 3}, {2, 2}, {4, 8}}; std::vector<std::complex<float>> s(r.size()); println("r", r); #ifdef __cpp_lib_algorithm_default_value_type std::ranges::replace_copy(r, s.begin(), {1, 3}, // T1 gets deduced {2.2, 4.8}); // T2 gets deduced #else std::ranges::replace_copy(r, s.begin(), std::complex<short>{1, 3}, std::complex<float>{2.2, 4.8}); #endif println("s", s); std::vector<std::complex<double>> b{{1, 3}, {2, 2}, {4, 8}}, d(b.size()); println("b", b); #ifdef __cpp_lib_algorithm_default_value_type std::ranges::replace_copy_if(b, d.begin(), [](std::complex<double> z){ return std::abs(z) < 5; }, {4, 2}); // Possible, since the T is deduced. #else std::ranges::replace_copy_if(b, d.begin(), [](std::complex<double> z){ return std::abs(z) < 5; }, std::complex<double>{4, 2}); #endif println("d", d); }
Output:
p: 1 6 1 6 1 6 o: 1 9 1 9 1 9 q: 1 2 3 6 7 8 4 5 o: 1 2 3 5 5 5 4 5 r: (1,3) (2,2) (4,8) s: (2.2,4.8) (2,2) (4,8) b: (1,3) (2,2) (4,8) d: (4,2) (4,2) (4,8)