std::ranges::all_of, std::ranges::any_of, std::ranges::none_of
来自cppreference.com
| 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) | (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) |
1) 检查一元谓词
pred 是否对范围 [first, last) 中的所有元素（以投影 proj 投影后）返回 true 。3) 检查一元谓词
pred 是否对范围 [first, last) 中至少一个元素（以投影 proj 投影后）返回 true 。5) 检查一元谓词
pred 是否不对范围 [first, last) 中任何元素（以投影 proj 投影后）返回 true 。2,4,6) 同 (1,3,5) ，但以
r 为源范围，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，或以某些特殊编译器扩展实现。
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
1-2) 若 std::invoke(pred, std::invoke(proj, *i)) != false 对范围中的每个迭代器
i 成立则为 true ，否则为 false 。若范围为空则返回 true 。3-4) 若 std::invoke(pred, std::invoke(proj, *i)) != false 对范围中的至少一个迭代器
i 成立则为 true ，否则为 false 。若范围为空则返回 false 。5-6) 若 std::invoke(pred, std::invoke(proj, *i)) == false 对范围中的每个迭代器
i 成立则为 true ，否则为 false 。若范围为空则返回 true 。复杂度
至多应用 last - first 次谓词和投影。
可能的实现
| 版本一 |
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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; |
| 版本二 |
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; |
| 版本三 |
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; |
示例
运行此代码
#include <vector> #include <numeric> #include <algorithm> #include <iterator> #include <iostream> #include <functional> namespace ranges = std::ranges; 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
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) |
