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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| template< std::input_iterator I, std::sentinel_for<I> S, class T1, class T2, class Proj = std::identity > |
(1) | (C++20 起) |
| template< ranges::input_range R, class T1, class T2, class Proj = std::identity > requires std::indirectly_writable<ranges::iterator_t<R>, const T2&> && |
(2) | (C++20 起) |
| template< std::input_iterator I, std::sentinel_for<I> S, class T, class Proj = std::identity, std::indirect_unary_predicate< |
(3) | (C++20 起) |
| template< ranges::input_range R, class T, class Proj = std::identity, std::indirect_unary_predicate<std::projected<ranges::iterator_t<R>, Proj>> Pred > |
(4) | (C++20 起) |
以 new_value 替换范围中 [first, last) 所有满足特定判别标准的元素。
r 为范围，如同以 ranges::begin(r) 为 first 并以 ranges::end(r) 为 last 。此页面上描述的仿函数实体是 niebloid ，即：
实际上，它们能以函数对象，或以某些特殊编译器扩展实现。
参数
| first, last | - | 要处理的元素范围 |
| r | - | 要处理的元素范围 |
| old_value | - | 要替换的元素的值 |
| new_value | - | 要用作替换品的值 |
| pred | - | 应用到投影后元素的谓词 |
| proj | - | 应用到谓词的投影 |
返回值
等于 last 的迭代器。
复杂度
准确应用 ranges::distance(first, last) 次对应的谓词 comp 与任何投影 proj 。
注解
由于算法按引用接收 old_value 与 new_value ，它可能在任一参数为到范围 [first, last) 中元素的引用时有非期待的行为。
可能的实现
| 版本一 |
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struct replace_fn { template <std::input_iterator I, std::sentinel_for<I> S, class T1, class T2, class Proj = std::identity> 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 T1, class T2, class Proj = std::identity> 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{}; |
| 版本二 |
struct replace_if_fn { template <std::input_iterator I, std::sentinel_for<I> S, class T, class Proj = std::identity, 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 T, class Proj = std::identity, 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{}; |
示例
#include <algorithm> #include <array> #include <iostream> int main() { auto print = [](const auto& v) { for (const auto& e : v) { std::cout << e << ' '; } std::cout << '\n'; }; std::array p{1, 6, 1, 6, 1, 6}; print(p); std::ranges::replace(p, 6, 9); print(p); std::array q{1, 2, 3, 6, 7, 8, 4, 5}; print(q); std::ranges::replace_if(q, [](int x){ return 5 < x; }, 5); print(q); }
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
参阅
| (C++20)(C++20) |
复制一个范围内的元素，并将满足特定判别标准的元素替换为另一个值 (niebloid) |
| 将所有满足特定判别标准的值替换为另一个值 (函数模板) |