std::ranges::ends_with - cppreference.com (original) (raw)

Checks whether the second range matches the suffix of the first range.

1. Let N1 be ranges::distance(first1, last1) and N2 be ranges::distance(first2, last2):

• If N1 < N2 is true, returns false.
• Otherwise, returns ranges::equal(std::move(first1) + (N1 - N2), last1,
  std::move(first2), last2, pred, proj1, proj2).

The function-like entities described on this page are algorithm function objects (informally known as niebloids), that is:

• Explicit template argument lists cannot be specified when calling any of them.
• None of them are visible to argument-dependent lookup.
• When any of them are found by normal unqualified lookup as the name to the left of the function-call operator, argument-dependent lookup is inhibited.

Contents

• 1 Parameters
• 2 Return value
• 3 Complexity
• 4 Possible implementation
• 5 Notes
• 6 Example
• 7 Defect reports
• 8 See also

[edit] Parameters

[edit] Return value

true if the second range matches the suffix of the first range, false otherwise.

[edit] Complexity

Generally linear: at most \(\scriptsize \min(N1,N2) \)min(N1,N2) applications of the predicate and both projections. The predicate and both projections are not applied if N1 < N2 is true.

If both N1 and N2 can be calculated in constant time (i.e. both iterator-sentinel type pairs model sized_sentinel_for, or both range types model sized_range) and N1 < N2 is true, the time complexity is constant.

[edit] Possible implementation

struct ends_with_fn { template<std::input_iterator I1, std::sentinel_for S1, std::input_iterator I2, std::sentinel_for S2, class Pred = ranges::equal_to, class Proj1 = std::identity, class Proj2 = std::identity> requires (std::forward_iterator || std::sized_sentinel_for<S1, I1>) && (std::forward_iterator || 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), last1, std::move(first2), last2, pred, proj1, 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 || ranges::sized_range) && (ranges::forward_range || ranges::sized_range) && std::indirectly_comparable<ranges::iterator_t, ranges::iterator_t, Pred, Proj1, Proj2> constexpr bool operator()(R1&& r1, R2&& r2, Pred pred = {}, Proj1 proj1 = {}, Proj2 proj2 = {}) const { const auto n1 = ranges::distance(r1); const auto n2 = ranges::distance(r2); if (n1 < n2) return false; return ranges::equal(views::drop(ranges::ref_view(r1), n1 - static_cast<decltype(n1)>(n2)), r2, pred, proj1, proj2); } };   inline constexpr ends_with_fn ends_with{};

[edit] Notes

[edit] Example

#include #include   static_assert ( ! std::ranges::ends_with("for", "cast") && std::ranges::ends_with("dynamic_cast", "cast") && ! std::ranges::ends_with("as_const", "cast") && std::ranges::ends_with("bit_cast", "cast") && ! std::ranges::ends_with("to_underlying", "cast") && std::ranges::ends_with(std::array{1, 2, 3, 4}, std::array{3, 4}) && ! std::ranges::ends_with(std::array{1, 2, 3, 4}, std::array{4, 5}) );   int main() {}

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

1. ↑ Its result might be of an integer-class type, in this case ranges::drop_view cannot be constructed.

[edit] See also

| | checks whether a range starts with another range(algorithm function object)[edit] | | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | | checks if the string ends with the given suffix (public member function of std::basic_string<CharT,Traits,Allocator>) [edit] | | | checks if the string view ends with the given suffix (public member function of std::basic_string_view<CharT,Traits>) [edit] |