std::ranges::replace_copy, std::ranges::replace_copy_if, std::ranges::replace_copy_result, std::ranges::replace_copy_if_result
| 在标头 <algorithm> 定义
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| 调用签名 |
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| (1) | ||
template< std::input_iterator I, std::sentinel_for<I> S, class T1, class T2, std::output_iterator<const T2&> O, class Proj = std::identity > |
(C++20 起) (C++26 前) |
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template< std::input_iterator I, std::sentinel_for<I> S, class O, class Proj = std::identity, |
(C++26 起) | |
| (2) | ||
| template< ranges::input_range R, class T1, class T2, std::output_iterator<const T2&> O, class Proj = std::identity > |
(C++20 起) (C++26 前) |
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| template< ranges::input_range R, class O, class Proj = std::identity, |
(C++26 起) | |
| (3) | ||
template< std::input_iterator I, std::sentinel_for<I> S, class T, std::output_iterator<const T&> O, |
(C++20 起) (C++26 前) |
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| template< std::input_iterator I, std::sentinel_for<I> S, class O, class T = std::iter_value_t<O> |
(C++26 起) | |
| (4) | ||
| template< ranges::input_range R, class T, std::output_iterator<const T&> O, |
(C++20 起) (C++26 前) |
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| template< ranges::input_range R, class O, class T = std::iter_value_t<O> |
(C++26 起) | |
| 辅助类型 |
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| template< class I, class O > using replace_copy_result = ranges::in_out_result<I, O>; |
(5) | (C++20 起) |
| template< class I, class O > using replace_copy_if_result = ranges::in_out_result<I, O>; |
(6) | (C++20 起) |
从源范围 [first, last) 复制元素到始于 result 的目标范围，以 new_value 替换所欲满足特定标准的元素。若源范围与目标范围重叠则行为未定义。
此页面上描述的函数式实体是 niebloid，即：
实践中，可以作为函数对象，或者用某些特殊编译器扩展实现它们。
参数
| first, last | - | 要复制的元素范围 |
| r | - | 要复制的元素范围 |
| result | - | 目标范围的起始 |
| old_value | - | 要替换的元素的值 |
| new_value | - | 用作替换品的值 |
| pred | - | 应用到投影后元素的谓词 |
| proj | - | 应用到元素的投影 |
返回值
{last, result + N}，其中
复杂度
准确应用 N 次对应的谓词 comp 与投影 proj。
可能的实现
| replace_copy (1,2) |
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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 {}; |
注解
| 功能特性测试宏 | 值 | 标准 | 功能特性 |
|---|---|---|---|
__cpp_lib_algorithm_default_value_type |
202403 | (C++26) | 算法中的列表初始化 (1-4) |
示例
#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 被推导 {2.2, 4.8}); // T2 被推导 #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}); // 可以这样做，因为 T 是被推导的。 #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); }
输出：
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)
参阅
| (C++20)(C++20) |
将所有满足特定判别标准的值替换为另一个值 (niebloid) |
| 复制一个范围，并将满足特定判别标准的元素替换为另一个值 (函数模板) |