std::ranges:: replace_copy, std::ranges:: replace_copy_if, std::ranges:: replace_copy_result, std::ranges:: replace_copy_if_result

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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, std:: output_iterator < const T2 & > O, class Proj = std:: identity > requires std:: indirectly_copyable < I, O > && std:: indirect_binary_predicate < ranges:: equal_to , std :: projected < I, Proj > , const T1 * > constexpr replace_copy_result < I, O > replace_copy ( I first, S last, O result, 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 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 replace_copy_result < I, O > replace_copy ( I first, S last, O result, const T1 & old_value, const T2 & new_value, Proj proj = { } ) ;			(C++26 起)
		(2)
template < ranges:: input_range R, class T1, class T2, std:: output_iterator < const T2 & > O, class Proj = std:: identity > 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 replace_copy_result < ranges:: borrowed_iterator_t < R > , O > replace_copy ( R && r, O result, const T1 & old_value, const T2 & new_value, Proj proj = { } ) ;				(C++20 起) (C++26 前)
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 * > && std:: output_iterator < O, const T2 & > constexpr replace_copy_result &lt

将源范围 [ first , last ) 中的元素复制到以 result 开始的目标范围，并将所有满足特定条件的元素替换为 new_value 。若源范围与目标范围重叠，则行为未定义。

1) 替换所有等于 old_value 的元素，使用 std:: invoke ( proj, * ( first + ( i - result ) ) ) == old_value 进行比较。

3) 替换所有谓词 pred 评估为 true 的元素，其中评估表达式为 std:: invoke ( pred, std:: invoke ( proj, * ( first + ( i - result ) ) ) ) 。

2,4) 与 (1,3) 相同，但使用 r 作为源范围，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：

在调用其中任何一个时，都不能指定显式模板实参列表。
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一个作为函数调用运算符左侧的名称找到时，会抑制实参依赖查找。

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(

注释

功能测试宏	值	标准	功能
`__cpp_lib_algorithm_default_value_type`	`202403`	(C++26)	算法的列表初始化 ( 1-4 )

示例

运行此代码

#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}); // 可行，因为 T 被推导
    #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

参见

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

Compiler support
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Language
Standard library
Standard library headers
Named requirements
Feature test macros (C++20)
Language support library
Concepts library (C++20)
Diagnostics library
Memory management library
Metaprogramming library (C++11)
General utilities library
Containers library
Iterators library
Ranges library (C++20)
Algorithms library
Strings library
Text processing library
Numerics library
Date and time library
Input/output library
Filesystem library (C++17)
Concurrency support library (C++11)
Execution control library (C++26)
Technical specifications
Symbols index
External libraries

first, last	-	定义待复制元素范围的迭代器-哨位对
r	-	待复制的元素范围
result	-	目标范围的起始位置
old_value	-	待替换元素的值
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

cppreference.net

Namespaces

Variants

std::ranges:: replace_copy, std::ranges:: replace_copy_if, std::ranges:: replace_copy_result, std::ranges:: replace_copy_if_result

目录

参数

返回值

复杂度

可能的实现

注释

示例

参见