std::ranges::ends_with
定义于头文件 <algorithm>
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调用签名 |
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template<std::input_iterator I1, std::sentinel_for<I1> S1, std::input_iterator I2, std::sentinel_for<I2> S2, |
(1) | (C++23 起) |
template<ranges::input_range R1, ranges::input_range R2, class Pred = ranges::equal_to, |
(2) | (C++23 起) |
检查第二范围是否匹配第一范围的后缀。
N1
与 N2
分别为 ranges::distance(first1, last1) 与 ranges::distance(first2, last2) 。若 N1 < N2 则返回 false 。否则,当且仅当 [first2, last2)
范围中的每个元素均等于 [first1 + N1 - N2, last1)
中的对应元素才返回 true 。通过应用二元谓词 pred
到分别由 proj1
与 proj2
投影的两个范围中的元素进行比较。r1
与 r2
为源范围,如同以 ranges::begin(r1) 为 first1
,以 ranges:begin(r2) 为 first2
,以 ranges::end(r1) 为 last1
,并以 ranges::end(r2) 为 last2
。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
first1, last1 | - | 要检验的元素范围 |
r1 | - | 要检验的元素范围 |
first2, last2 | - | 要用作后缀的元素范围 |
r2 | - | 要用作后缀的元素范围 |
pred | - | 比较投影后元素的二元谓词 |
proj1 | - | 应用到要检验的元素范围的投影 |
proj2 | - | 应用到要用作后缀的元素范围的投影 |
返回值
若第二范围匹配第一范围的后缀则为 true ,否则为 false 。
复杂度
线性:至多应用 min(N1, N2)
次谓词和两个投影。若 N1 < N2 则不应用谓词和两个投影。
若 N1
与 N2
均能以常数时间计算(即两个迭代器-哨位类型对均实现 sized_sentinel_for
,或两个范围类型均实现 sized_range
)且 N1 < N2 ,则时间复杂度为常数。
可能的实现
struct ends_with_fn { template<std::input_iterator I1, std::sentinel_for<I1> S1, std::input_iterator I2, std::sentinel_for<I2> S2, class Pred = ranges::equal_to, class Proj1 = std::identity, class Proj2 = std::identity> requires (std::forward_iterator<I1> || std::sized_sentinel_for<S1, I1>) && (std::forward_iterator<I2> || std::sized_sentinel_for<S2, I2>) && std::indirectly_comparable<I1, I2, Pred, Proj1, Proj2> constexpr bool operator()(I1 first1, S1 last1, I2 first2, S2 last2, Pred pred = {}, Proj1 proj1 = {}, Proj2 proj2 = {}) const { const auto n1 = ranges::distance(first1, last1); const auto n2 = ranges::distance(first2, last2); if (n1 < n2) return false; ranges::advance(first1, n1 - n2); return ranges::equal(std::move(first1), std::move(last1), std::move(first2), std::move(last2), std::move(pred), std::move(proj1), std::move(proj2)); } template<ranges::input_range R1, ranges::input_range R2, class Pred = ranges::equal_to, class Proj1 = std::identity, class Proj2 = std::identity> requires (ranges::forward_range<R1> || ranges::sized_range<R1>) && (ranges::forward_range<R2> || ranges::sized_range<R2>) && std::indirectly_comparable<ranges::iterator_t<R1>, ranges::iterator_t<R2>, Pred, Proj1, Proj2> constexpr bool operator()(R1&& r1, R2&& r2, Pred pred = {}, Proj1 proj1 = {}, Proj2 proj2 = {}) const { return (*this)(ranges::begin(r1), ranges::end(r1), ranges::begin(r2), ranges::end(r2), std::move(pred), std::move(proj1), std::move(proj2)); } }; inline constexpr ends_with_fn ends_with{}; |
示例
#include <array> #include <algorithm> #include <iostream> int main() { std::cout << std::boolalpha << std::ranges::ends_with("static_cast", "cast") << '\n' << std::ranges::ends_with("const_cast", "cast") << '\n' << std::ranges::ends_with("reinterpret_cast", "cast") << '\n' << std::ranges::ends_with("dynamic_cast", "cast") << '\n' << std::ranges::ends_with("move", "cast") << '\n' << std::ranges::ends_with("move_if_noexcept", "cast") << '\n' << std::ranges::ends_with("forward", "cast") << '\n' << std::ranges::ends_with("as_const", "cast") << '\n' << std::ranges::ends_with("bit_cast", "cast") << '\n' << std::ranges::ends_with("to_underlying", "cast") << '\n'; << std::ranges::ends_with(std::array{1,2,3,4}, std::array{3,4}) << '\n' << std::ranges::ends_with(std::array{1,2,3,4}, std::array{4,5}) << '\n'; }
输出:
true true true true false false false false true false
参阅
(C++23) |
检查一个范围是否始于另一范围 (niebloid) |
(C++20) |
检查 string 是否终于给定后缀 ( std::basic_string<CharT,Traits,Allocator> 的公开成员函数) |
(C++20) |
检查 string_view 是否终于给定后缀 ( std::basic_string_view<CharT,Traits> 的公开成员函数) |