std::ranges::replace, std::ranges::replace_if
| 定义于头文件 <algorithm> |
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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, class Proj = std::identity > |
(自 C++20 起) (直到 C++26) |
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| template< std::input_iterator I, std::sentinel_for<I> S, class Proj = std::identity, |
(自 C++26 起) | |
| (2) | ||
| template< ranges::input_range R, class T1, class T2, class Proj = std::identity > |
(自 C++20 起) (直到 C++26) |
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| template< ranges::input_range R, class Proj = std::identity, |
(自 C++26 起) | |
| (3) | ||
template< std::input_iterator I, std::sentinel_for<I> S, class T, class Proj = std::identity, |
(自 C++20 起) (直到 C++26) |
|
| template< std::input_iterator I, std::sentinel_for<I> S, class Proj = std::identity, |
(自 C++26 起) | |
| (4) | ||
| template< ranges::input_range R, class T, class Proj = std::identity, std::indirect_unary_predicate< |
(自 C++20 起) (直到 C++26) |
|
| template< ranges::input_range R, class Proj = std::identity, class T = std::projected_value_t<ranges::iterator_t<R>, Proj>, |
(自 C++26 起) | |
将范围 [first, last) 中所有满足特定标准的元素替换为 new_value。
在此页面上描述的类似函数的实体是算法函数对象 (非正式地称为 niebloids)，也就是
目录 |
[编辑] 参数
| first, last | - | 定义要处理的元素范围的迭代器-哨兵对 |
| r | - | 要处理的元素范围 |
| old_value | - | 要替换的元素的值 |
| new_value | - | 用作替换的值 |
| pred | - | 应用于投影元素的谓词 |
| proj | - | 应用于元素的投影 |
[编辑] 返回值
一个等于 last 的迭代器。
[编辑] 复杂度
精确地 ranges::distance(first, last) 次应用对应的谓词 comp 和任何投影 proj。
[编辑] 注解
由于算法通过引用获取 old_value 和 new_value，如果其中任何一个是范围 [first, last) 中元素的引用，则可能具有意外的行为。
| 特性测试 宏 | 值 | Std | 特性 |
|---|---|---|---|
__cpp_lib_algorithm_default_value_type |
202403 |
(C++26) | 算法的列表初始化 (1-4) |
[编辑] 可能的实现
| replace (1,2) |
|---|
struct replace_fn { template<std::input_iterator I, std::sentinel_for<I> S, class Proj = std::identity, class T1 = std::projected_value_t<I, Proj>, class T2 = T1> requires std::indirectly_writable<I, const T2&> && std::indirect_binary_predicate <ranges::equal_to, std::projected<I, Proj>, const T1*> constexpr I operator()(I first, S last, const T1& old_value, const T2& new_value, Proj proj = {}) const { for (; first != last; ++first) if (old_value == std::invoke(proj, *first)) *first = new_value; return first; } template<ranges::input_range R, class Proj = std::identity class T1 = std::projected_value_t<ranges::iterator_t<R>, Proj>, class T2 = T1> requires std::indirectly_writable<ranges::iterator_t<R>, const T2&> && std::indirect_binary_predicate<ranges::equal_to, std::projected<ranges::iterator_t<R>, Proj>, const T1*> constexpr ranges::borrowed_iterator_t<R> operator()(R&& r, const T1& old_value, const T2& new_value, Proj proj = {}) const { return (*this)(ranges::begin(r), ranges::end(r), old_value, new_value, std::move(proj)); } }; inline constexpr replace_fn replace{}; |
| replace_if (3,4) |
struct replace_if_fn { template<std::input_iterator I, std::sentinel_for<I> S, class Proj = std::identity, class T = std::projected_value_t<I, Proj>, std::indirect_unary_predicate<std::projected<I, Proj>> Pred> requires std::indirectly_writable<I, const T&> constexpr I operator()(I first, S last, Pred pred, const T& new_value, Proj proj = {}) const { for (; first != last; ++first) if (!!std::invoke(pred, std::invoke(proj, *first))) *first = new_value; return std::move(first); } template<ranges::input_range R, class Proj = std::identity, class T = std::projected_value_t<ranges::iterator_t<R>, Proj> std::indirect_unary_predicate <std::projected<ranges::iterator_t<R>, Proj>> Pred> requires std::indirectly_writable<ranges::iterator_t<R>, const T&> constexpr ranges::borrowed_iterator_t<R> operator()(R&& r, Pred pred, const T& new_value, Proj proj = {}) const { return (*this)(ranges::begin(r), ranges::end(r), std::move(pred), new_value, std::move(proj)); } }; inline constexpr replace_if_fn replace_if{}; |
[编辑] 示例
#include <algorithm> #include <array> #include <complex> #include <iostream> void println(const auto& v) { for (const auto& e : v) std::cout << e << ' '; std::cout << '\n'; } int main() { namespace ranges = std::ranges; std::array p{1, 6, 1, 6, 1, 6}; println(p); ranges::replace(p, 6, 9); println(p); std::array q{1, 2, 3, 6, 7, 8, 4, 5}; println(q); ranges::replace_if(q, [](int x) { return 5 < x; }, 5); println(q); std::array<std::complex<double>, 2> nums{{{1, 3}, {1, 3}}}; println(nums); #ifdef __cpp_lib_algorithm_default_value_type ranges::replace(nums, {1, 3}, {4, 2}); #else ranges::replace(nums, std::complex<double>{1, 3}, std::complex<double>{4, 2}); #endif println(nums); }
输出
1 6 1 6 1 6 1 9 1 9 1 9 1 2 3 6 7 8 4 5 1 2 3 5 5 5 4 5 (1,3) (1,3) (4,2) (4,2)
[编辑] 参见
| (C++20)(C++20) |
复制一个范围，将满足特定标准的元素替换为另一个值 (算法函数对象) |
| 将所有满足特定标准的值替换为另一个值 (函数模板) |
