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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 >
requires std::indirectly_writable<I, const T2&> && std::indirect_binary_predicate<
ranges::equal_to, std::projected<I,
Proj>, const
T1*>
constexpr I
replace( I first, S last, const T1& old_value,
const T2& new_value,
Proj proj = {} );
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(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&> &&
std::indirect_binary_predicate<ranges::equal_to,
std::projected<ranges::iterator_t<R>, Proj>, const T1*>
constexpr ranges::borrowed_iterator_t<R>
replace( R&& r,
const T1& old_value,
const T2& new_value,
Proj proj = {} );
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(2) |
(C++20 起) |
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
replace_if( I first, S last, Pred pred, const T& new_value, Proj
proj = {} );
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(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 >
requires std::indirectly_writable<ranges::iterator_t<R>, const T&>
constexpr ranges::borrowed_iterator_t<R>
replace_if( R&& r,
Pred pred, const T&
new_value, Proj proj = {} );
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(4) |
(C++20 起) |
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以 new_value 替换范围中 [first, last) 所有满足特定判别标准的元素。
1) 替换所有等于
old_value 的元素。用
std::invoke(proj, *i) ==
old_value 比较。
2,4) 同 (1,3) ，但以
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，或者某些特殊编译器扩展实现。
参数
| first, last
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-
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要处理的元素范围
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| r
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-
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要处理的元素范围
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| old_value
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-
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要替换的元素的值
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| new_value
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-
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要用作替换品的值
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| pred
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-
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应用到投影后元素的谓词
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| proj
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-
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应用到谓词的投影
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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{};
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| 版本二
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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{};
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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
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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) |
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将所有满足特定判别标准的值替换为另一个值
(函数模板) |