std::ranges:: replace, std::ranges:: replace_if

From cppreference.net

定义于头文件 `<algorithm>`
调用签名
	(1)
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 = { } ) ;			(C++20 起) (C++26 前)
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 replace ( I first, S last, const T1 & old_value, const T2 & new_value, Proj proj = { } ) ;			(C++26 起)
		(2)
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 = { } ) ;				(C++20 起) (C++26 前)
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 > replace ( R && r, const T1 & old_value, const T2 & new_value, Proj proj = { } ) ;				(C++26 起)
			(3)
template < std:: input_iterator I, std:: sentinel_for < I > S, class T, <span

将范围 [ first , last ) 中满足特定条件的所有元素替换为 new_value 。

1) 将所有等于 old_value 的元素替换，使用 std:: invoke ( proj, * i ) == old_value 进行比较。

3) 替换所有使谓词 pred 求值为 true 的元素，其中求值表达式为 std:: invoke ( pred, std:: invoke ( proj, * i ) ) 。

2,4) 与 (1,3) 相同，但使用 r 作为范围，如同以 ranges:: begin ( r ) 作为 first ，并以 ranges:: end ( r ) 作为 last 。

本页面描述的函数式实体是 算法函数对象 （非正式称为 niebloids ），即：

在调用其中任何函数时，都不能显式指定模板参数列表。
它们对实参依赖查找均不可见。
当通过常规非限定查找将其中任何函数作为函数调用运算符左侧的名称找到时，将禁止进行实参依赖查找。

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 <span class

示例

运行此代码

#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)

参见

ranges::replace_copy ranges::replace_copy_if (C++20) (C++20)	复制范围，将满足特定条件的元素替换为另一个值 (算法函数对象)
replace replace_if	将所有满足特定条件的值替换为另一个值 (函数模板)

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External libraries

first, last	-	定义待处理元素范围的迭代器-哨位对
r	-	待处理的元素范围
old_value	-	待替换的元素值
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

cppreference.net

Namespaces

Variants

std::ranges:: replace, std::ranges:: replace_if

目录

参数

返回值

复杂度

注释

可能的实现

示例

参见