std::ranges::includes
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Constrained algorithms
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std::ranges
(C++23)
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Defined in header
<algorithm>
Call signature
template< std::input_iterator I1, std::sentinel_for <I1> S1,
(1)
(since C++20)
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,
template< ranges::input_range R1, ranges::input_range R2,
(2)
(since C++20)
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
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.
[edit] 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
[edit] Return value
true if [first2, last2) is a subsequence of [first1, last1); otherwise false.
[edit] 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).
[edit] 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 {};
[edit] 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[edit] See also
(C++23)(C++23)
(algorithm function object)[edit]