std::ranges::includes
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 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 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 iterator-sentinel pair defining the sorted range of elements to examine |
| r1 | - | the sorted range of elements to examine |
| first2, last2 | - | the iterator-sentinel pair defining 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 2·(N1+N2-1) comparisons, where N1 is ranges::distance(r1) and 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
Run this code
#include <algorithm>
#include <cctype>
#include <initializer_list>
#include <iomanip>
#include <iostream>
#include <locale>
#include <string>
template<class T>
std::ostream& operator<<(std::ostream& os, std::initializer_list<T> const& list)
{
for (os << "{ "; auto const& elem : list)
os << elem << ' ';
return os << "} ";
}
struct true_false : std::numpunct<char>
{
std::string do_truename() const { return "? Yes\n"; }
std::string do_falsename() const { return "? No\n"; }
};
int main()
{
std::cout.imbue(std::locale(std::cout.getloc(), new true_false));
auto ignore_case = [](char a, char b) { return std::tolower(a) < std::tolower(b); };
const auto
a = {'a', 'b', 'c'},
b = {'a', 'c'},
c = {'a', 'a', 'b'},
d = {'g'},
e = {'a', 'c', 'g'},
f = {'A', 'B', 'C'},
z = {'a', 'b', 'c', 'f', 'h', 'x'};
std::cout
<< z << "includes\n" << std::boolalpha
<< a << std::ranges::includes(z.begin(), z.end(), a.begin(), a.end())
<< b << std::ranges::includes(z, b)
<< c << std::ranges::includes(z, c)
<< d << std::ranges::includes(z, d)
<< e << std::ranges::includes(z, e)
<< f << std::ranges::includes(z, f, ignore_case);
}
Output:
{ a b c f h x } includes
{ a b c } ? Yes
{ a c } ? Yes
{ a a b } ? No
{ g } ? No
{ a c g } ? No
{ A B C } ? Yes
See also
(C++20) |
computes the difference between two sets (algorithm function object) |
(C++20) |
searches for the first occurrence of a range of elements (algorithm function object) |
(C++23)(C++23) |
checks if the range contains the given element or subrange (algorithm function object) |
returns true if one sequence is a subsequence of another (function template) |