std::ranges::all_of, std::ranges::any_of, std::ranges::none_of
来自 cppreference.cn
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 Proj = std::identity, |
(1) | (since C++20) |
template< ranges::input_range R, class Proj = std::identity, std::indirect_unary_predicate< |
(2) | (since C++20) |
template< std::input_iterator I, std::sentinel_for<I> S, class Proj = std::identity, |
(3) | (since C++20) |
template< ranges::input_range R, class Proj = std::identity, std::indirect_unary_predicate< |
(4) | (since C++20) |
template< std::input_iterator I, std::sentinel_for<I> S, class Proj = std::identity, |
(5) | (since C++20) |
template< ranges::input_range R, class Proj = std::identity, std::indirect_unary_predicate< |
(6) | (since C++20) |
1) 检查一元谓词 pred 对于范围
[
first,
last)
中的至少一个元素(在使用投影 proj 投影后)是否返回 false。3) 检查一元谓词 pred 对于范围
[
first,
last)
中的至少一个元素(在使用投影 proj 投影后)是否返回 true。5) 检查一元谓词 pred 对于范围
[
first,
last)
中的所有元素(在使用投影 proj 投影后)是否都不返回 true。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),即
目录 |
[编辑] 参数
first, last | - | 定义要检查的元素范围的迭代器-哨兵对 |
r | - | 要检查的元素的范围 |
pred | - | 要应用于投影元素的谓词 |
proj | - | 要应用于元素的投影 |
[编辑] 返回值
1,2) 如果对于范围中的每个迭代器 i,std::invoke(pred, std::invoke(proj, *i)) != false,则返回 true,否则返回 false。如果范围为空,则返回 true。
3,4) 如果对于范围中的至少一个迭代器 i,std::invoke(pred, std::invoke(proj, *i)) != false,则返回 true,否则返回 false。如果范围为空,则返回 false。
5,6) 如果对于范围中的每个迭代器 i,std::invoke(pred, std::invoke(proj, *i)) == false,则返回 true,否则返回 false。如果范围为空,则返回 true。
有 true 元素 | 是 | 否 | ||
---|---|---|---|---|
有 false 元素 | 是 | 否 | 是 | 否[1] |
all_of
|
false | true | false | true |
any_of
|
true | true | false | false |
none_of
|
false | false | true | true |
- ↑ 在这种情况下,范围为空。
[编辑] 复杂度
最多 last - first 次谓词和投影的应用。
[编辑] 可能的实现
all_of (1,2) |
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struct all_of_fn { template<std::input_iterator I, std::sentinel_for<I> S, class Proj = std::identity, std::indirect_unary_predicate<std::projected<I, Proj>> Pred> constexpr bool operator()(I first, S last, Pred pred, Proj proj = {}) const { return ranges::find_if_not(first, last, std::ref(pred), std::ref(proj)) == last; } template<ranges::input_range R, class Proj = std::identity, std::indirect_unary_predicate< std::projected<ranges::iterator_t<R>,Proj>> Pred> constexpr bool operator()(R&& r, Pred pred, Proj proj = {}) const { return operator()(ranges::begin(r), ranges::end(r), std::ref(pred), std::ref(proj)); } }; inline constexpr all_of_fn all_of; |
any_of (3,4) |
struct any_of_fn { template<std::input_iterator I, std::sentinel_for<I> S, class Proj = std::identity, std::indirect_unary_predicate<std::projected<I, Proj>> Pred> constexpr bool operator()(I first, S last, Pred pred, Proj proj = {}) const { return ranges::find_if(first, last, std::ref(pred), std::ref(proj)) != last; } template<ranges::input_range R, class Proj = std::identity, std::indirect_unary_predicate< std::projected<ranges::iterator_t<R>,Proj>> Pred> constexpr bool operator()(R&& r, Pred pred, Proj proj = {}) const { return operator()(ranges::begin(r), ranges::end(r), std::ref(pred), std::ref(proj)); } }; inline constexpr any_of_fn any_of; |
none_of (5,6) |
struct none_of_fn { template<std::input_iterator I, std::sentinel_for<I> S, class Proj = std::identity, std::indirect_unary_predicate<std::projected<I, Proj>> Pred> constexpr bool operator()(I first, S last, Pred pred, Proj proj = {}) const { return ranges::find_if(first, last, std::ref(pred), std::ref(proj)) == last; } template<ranges::input_range R, class Proj = std::identity, std::indirect_unary_predicate< std::projected<ranges::iterator_t<R>,Proj>> Pred> constexpr bool operator()(R&& r, Pred pred, Proj proj = {}) const { return operator()(ranges::begin(r), ranges::end(r), std::ref(pred), std::ref(proj)); } }; inline constexpr none_of_fn none_of; |
[编辑] 示例
运行此代码
#include <algorithm> #include <functional> #include <iostream> #include <iterator> #include <numeric> #include <vector> namespace ranges = std::ranges; constexpr bool some_of(auto&& r, auto&& pred) // some but not all { return not (ranges::all_of(r, pred) or ranges::none_of(r, pred)); } constexpr auto w = {1, 2, 3}; static_assert(!some_of(w, [](int x) { return x < 1; })); static_assert( some_of(w, [](int x) { return x < 2; })); static_assert(!some_of(w, [](int x) { return x < 4; })); int main() { std::vector<int> v(10, 2); std::partial_sum(v.cbegin(), v.cend(), v.begin()); std::cout << "Among the numbers: "; ranges::copy(v, std::ostream_iterator<int>(std::cout, " ")); std::cout << '\n'; if (ranges::all_of(v.cbegin(), v.cend(), [](int i) { return i % 2 == 0; })) std::cout << "All numbers are even\n"; if (ranges::none_of(v, std::bind(std::modulus<int>(), std::placeholders::_1, 2))) std::cout << "None of them are odd\n"; auto DivisibleBy = [](int d) { return [d](int m) { return m % d == 0; }; }; if (ranges::any_of(v, DivisibleBy(7))) std::cout << "At least one number is divisible by 7\n"; }
输出
Among the numbers: 2 4 6 8 10 12 14 16 18 20 All numbers are even None of them are odd At least one number is divisible by 7
[编辑] 参见
(C++11)(C++11)(C++11) |
检查谓词对于范围中的所有、任何或没有元素是否为 true (函数模板) |