std::ranges::all_of, std::ranges::any_of, std::ranges::none_of
在标头 <algorithm> 定义
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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) | (C++20 起) |
template< ranges::input_range R, class Proj = std::identity, std::indirect_unary_predicate< |
(2) | (C++20 起) |
template< std::input_iterator I, std::sentinel_for<I> S, class Proj = std::identity, |
(3) | (C++20 起) |
template< ranges::input_range R, class Proj = std::identity, std::indirect_unary_predicate< |
(4) | (C++20 起) |
template< std::input_iterator I, std::sentinel_for<I> S, class Proj = std::identity, |
(5) | (C++20 起) |
template< ranges::input_range R, class Proj = std::identity, std::indirect_unary_predicate< |
(6) | (C++20 起) |
[
first,
last)
中的所有元素(以投影 proj 投影后)返回 true。[
first,
last)
中至少一个元素(以投影 proj 投影后)返回 true。[
first,
last)
中任何元素(以投影 proj 投影后)返回 true。此页面上描述的函数式实体是 niebloid,即:
实践中,可以作为函数对象,或者用某些特殊编译器扩展实现它们。
参数
first, last | - | 要检验的元素范围 |
r | - | 要检验的元素范围 |
pred | - | 应用到投影后元素的谓词 |
proj | - | 应用到元素的投影 |
返回值
i
成立则为 true,否则为 false。若范围为空则返回 true。i
成立则为 true,否则为 false。若范围为空则返回 false。i
成立则为 true,否则为 false。若范围为空则返回 true。参见下文的注解。
复杂度
至多应用 last - first
次谓词和投影。
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; |
注解
Template:all any none of truth table
示例
#include <algorithm> #include <functional> #include <iostream> #include <iterator> #include <numeric> #include <vector> namespace ranges = std::ranges; constexpr bool some_of(auto&& r, auto&& pred) // 一些但非全部 { 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 << "这些数中: "; 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 << "全部都是偶数\n"; if (ranges::none_of(v, std::bind(std::modulus<int>(), std::placeholders::_1, 2))) std::cout << "没有奇数\n"; auto DivisibleBy = [](int d) { return [d](int m) { return m % d == 0; }; }; if (ranges::any_of(v, DivisibleBy(7))) std::cout << "至少一个数可被 7 整除\n"; }
输出:
这些数中: 2 4 6 8 10 12 14 16 18 20 全部都是偶数 没有奇数 至少一个数可被 7 整除
参阅
(C++11)(C++11)(C++11) |
检查谓词是否对范围中所有、任一或无元素为 true (函数模板) |