std::ranges::includes
Defined in header <algorithm> |
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| Call signature | ||
template< std::input_iterator I1, std::sentinel_for<I1> S1,
std::input_iterator I2, std::sentinel_for<I2> S2,
class Proj1 = std::identity, class Proj2 = std::identity,
std::indirect_strict_weak_order<
std::projected<I1, Proj1>,
std::projected<I2, Proj2>> Comp = ranges::less >
constexpr bool includes( I1 first1, S1 last1, I2 first2, S2 last2,
Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {} ) |
(1) | (since C++20) |
template< ranges::input_range R1, ranges::input_range R2,
class Proj1 = std::identity, class Proj2 = std::identity,
std::indirect_strict_weak_order<
std::projected<ranges::iterator_t<R1>, Proj1>,
std::projected<ranges::iterator_t<R2>, Proj2>> Comp = ranges::less >
constexpr bool includes( R1&& r1, R2&& r2, Comp comp = {},
Proj1 proj1 = {}, Proj2 proj2 = {} ) |
(2) | (since C++20) |
1) Returns
true if the projections of the sorted range
[first2, last2) is a
subsequence of the projections of the sorted range
[first1, last1).
2) Same as
(1), but uses
r1 and
r2 as the source ranges, as if by using
ranges::begin(r1) and
ranges::begin(r2) as
first1 and
first2 respectively, and
ranges::end(r1) and
ranges::end(r2) as
last1 and
last2 respectively.
Both ranges must be sorted with the given comparison function comp. A subsequence need not be contiguous.
The function-like entities described on this page are niebloids, that is:
- Explicit template argument lists may not be specified when calling any of them.
- None of them is visible to argument-dependent lookup.
- When one of them is found by normal unqualified lookup for the name to the left of the function-call operator, it inhibits argument-dependent lookup.
In practice, they may be implemented as function objects, or with special compiler extensions.
Parameters
| first1, last1 | - | the sorted range of elements to examine |
| r1 | - | the sorted range of elements to examine |
| first2, last2 | - | the sorted range of elements to search for |
| r2 | - | the sorted range of elements to search for |
| comp | - | comparison function to apply to the projected elements |
| proj1 | - | projection to apply to the elements in the first range |
| proj2 | - | projection to apply to the elements in the second range |
Return value
true if [first2, last2) is a subsequence of [first1, last1); otherwise false.
Complexity
At most \(\scriptsize 2 \cdot (N_1+N_2-1)\)2·(N1+N2-1) comparisons, where \(\scriptsize N_1\)N1 is ranges::distance(r1) and \(\scriptsize N_2\)N2 is ranges::distance(r2).
Possible implementation
struct includes_fn {
template<std::input_iterator I1, std::sentinel_for<I1> S1,
std::input_iterator I2, std::sentinel_for<I2> S2,
class Proj1 = std::identity, class Proj2 = std::identity,
std::indirect_strict_weak_order<
std::projected<I1, Proj1>,
std::projected<I2, Proj2>> Comp = ranges::less>
constexpr bool operator()(I1 first1, S1 last1, I2 first2, S2 last2,
Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {}) const
{
for (; first2 != last2; ++first1)
{
if (first1 == last1 && comp(*first2, *first1))
return false;
if (!comp(*first1, *first2))
++first2;
}
return true;
}
template<ranges::input_range R1, ranges::input_range R2,
class Proj1 = std::identity, class Proj2 = std::identity,
std::indirect_strict_weak_order<
std::projected<ranges::iterator_t<R1>, Proj1>,
std::projected<ranges::iterator_t<R2>, Proj2>> Comp = ranges::less>
constexpr bool operator()(R1&& r1, R2&& r2, Comp comp = {},
Proj1 proj1 = {}, Proj2 proj2 = {}) const
{
return (*this)(ranges::begin(r1), ranges::end(r1),
ranges::begin(r2), ranges::end(r2),
std::ref(comp), std::ref(proj1), std::ref(proj2));
}
};
inline constexpr auto includes = includes_fn{};
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Example
#include <iostream>
#include <algorithm>
#include <cctype>
template <class Os, class R> Os& operator<<(Os& os, const R& r) {
for (const auto& e : r) os << e << ' ';
return os << '\t';
}
int main()
{
const auto
v1 = {'a', 'b', 'c', 'f', 'h', 'x'},
v2 = {'a', 'b', 'c'},
v3 = {'a', 'c'},
v4 = {'a', 'a', 'b'},
v5 = {'g'},
v6 = {'a', 'c', 'g'},
v7 = {'A', 'B', 'C'};
auto no_case = [](char a, char b) { return std::tolower(a) < std::tolower(b); };
namespace ranges = std::ranges;
std::cout
<< v1 << "\nincludes:\n" << std::boolalpha
<< v2 << ": " << ranges::includes(v1.begin(), v1.end(), v2.begin(), v2.end()) << '\n'
<< v3 << ": " << ranges::includes(v1, v3) << '\n'
<< v4 << ": " << ranges::includes(v1, v4) << '\n'
<< v5 << ": " << ranges::includes(v1, v5) << '\n'
<< v6 << ": " << ranges::includes(v1, v6) << '\n'
<< v7 << ": " << ranges::includes(v1, v7, no_case)
<< " (case-insensitive)\n";
}
Output:
a b c f h x includes: a b c : true a c : true a a b : false g : false a c g : false A B C : true (case-insensitive)
See also
|
(C++20)
|
computes the difference between two sets (niebloid) |
|
(C++20)
|
searches for a range of elements (niebloid) |
| returns true if one sequence is a subsequence of another (function template) |
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