std::ranges::ends_with
From cppreference.com
| Defined in header <algorithm>
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| Call signature |
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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
ends_with( I1 first1, S1 last1, I2 first2, S2 last2, Pred pred = {},
Proj1 proj1 = {}, Proj2 proj2 = {} );
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(1) | (since C++23) |
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
ends_with( R1&& r1, R2&& r2, Pred pred = {},
Proj1 proj1 = {}, Proj2 proj2 = {} );
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(2) | (since C++23) |
Checks whether the second range matches the suffix of the first range.
1) Let
N1 and N2 be ranges::distance(first1, last1) and ranges::distance(first2, last2) respectively. If N1 < N2, returns false. Otherwise, returns true if only if every element in the range [first2, last2) is equal to the corresponding element in [first1 + N1 - N2, last1). Comparison is done by applying the binary predicate pred to elements in two ranges projected by proj1 and proj2 respectively.2) Same as (1), but uses
r1 and r2 as the source ranges, as if using ranges::begin(r1) as first1, ranges:begin(r2) as first2, ranges::end(r1) as last1, and ranges::end(r2) as last2.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.
Parameters
| first1, last1 | - | the range of elements to examine |
| r1 | - | the range of elements to examine |
| first2, last2 | - | the range of elements to be used as the suffix |
| r2 | - | the range of elements to be used as the suffix |
| pred | - | the binary predicate that compares the projected elements |
| proj1 | - | the projection to apply to the elements of the range to examine |
| proj2 | - | the projection to apply to the elements of the range to be used as the suffix |
Return value
true if the second range matches the suffix of the first range, false otherwise.
Complexity
Generally linear: at most min(N1, N2) applications of the predicate and both projections. The predicate and both projections are not applied if N1 < N2.
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, the time complexity is constant.
Possible implementation
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 {};
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Notes
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_ranges_starts_ends_with |
202106L |
(C++23) | std::ranges::starts_with, std::ranges::ends_with
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Example
Run this code
#include <algorithm>
#include <array>
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() {}
See also
(C++23) |
checks whether a range starts with another range (algorithm function object) |
(C++20) |
checks if the string ends with the given suffix (public member function of std::basic_string<CharT,Traits,Allocator>)
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(C++20) |
checks if the string view ends with the given suffix (public member function of std::basic_string_view<CharT,Traits>)
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