std::includes
(on partitioned ranges)
<algorithm>
bool includes( InputIt1 first1, InputIt1 last1,
class ForwardIt1, class ForwardIt2 >
bool includes( ExecutionPolicy&& policy,
ForwardIt1 first1, ForwardIt1 last1,
bool includes( InputIt1 first1, InputIt1 last1,
class ForwardIt1, class ForwardIt2, class Compare >
bool includes( ExecutionPolicy&& policy,
ForwardIt1 first1, ForwardIt1 last1,
Returns true if the sorted range [
first2,
last2)
is a subsequence of the sorted range [
first1,
last1)
(a subsequence need not be contiguous).
[
first1,
last1)
or [
first2,
last2)
is not sorted with respect to operator<(until C++20)std::less {}(since C++20), the behavior is undefined.[
first1,
last1)
or [
first2,
last2)
is not sorted with respect to comp, the behavior is undefined.std::is_execution_policy_v <std::decay_t <ExecutionPolicy>> is true.
(until C++20)std::is_execution_policy_v <std::remove_cvref_t <ExecutionPolicy>> is true.
(since C++20)The signature of the comparison function should be equivalent to the following:
bool cmp(const Type1& a, const Type2& b);
While the signature does not need to have const&, the function must not modify the objects passed to it and must be able to accept all values of type (possibly const) Type1
and Type2
regardless of value category (thus, Type1&
is not allowed, nor is Type1
unless for Type1
a move is equivalent to a copy(since C++11)).
The types Type1 and Type2 must be such that an object of type InputIt can be dereferenced and then implicitly converted to both of them.
InputIt1, InputIt2
must meet the requirements of LegacyInputIterator.
ForwardIt1, ForwardIt2
must meet the requirements of LegacyForwardIterator.
Compare
must meet the requirements of Compare.
true if [
first2,
last2)
is a subsequence of [
first1,
last1)
; otherwise false.
An empty sequence is a subsequence of any sequence, so true is returned if [
first2,
last2)
is empty.
Given \(\scriptsize N_1\)N1 as std::distance (first1, last1) and \(\scriptsize N_2\)N2 as std::distance (first2, last2):
The overloads with a template parameter named ExecutionPolicy
report errors as follows:
ExecutionPolicy
is one of the standard policies, std::terminate is called. For any other ExecutionPolicy
, the behavior is implementation-defined.
include (1) |
---|
template<class InputIt1, class InputIt2> bool includes(InputIt1 first1, InputIt1 last1, InputIt2 first2, InputIt2 last2) { for (; first2 != last2; ++first1) { if (first1 == last1 || *first2 < *first1) return false; if (!(*first1 < *first2)) ++first2; } return true; } |
include (3) |
template<class InputIt1, class InputIt2, class Compare> bool includes(InputIt1 first1, InputIt1 last1, InputIt2 first2, InputIt2 last2, Compare comp) { for (; first2 != last2; ++first1) { if (first1 == last1 || comp(*first2, *first1)) return false; if (!comp(*first1, *first2)) ++first2; } return true; } |
#include <algorithm> #include <cctype> #include <iostream> template<class Os, class Co> Os& operator<<(Os& os, const Co& v) { for (const auto& i : v) os << i << ' '; 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); }; std::cout << v1 << "\nincludes:\n" << std::boolalpha << v2 << ": " << std::includes(v1.begin(), v1.end(), v2.begin(), v2.end()) << '\n' << v3 << ": " << std::includes(v1.begin(), v1.end(), v3.begin(), v3.end()) << '\n' << v4 << ": " << std::includes(v1.begin(), v1.end(), v4.begin(), v4.end()) << '\n' << v5 << ": " << std::includes(v1.begin(), v1.end(), v5.begin(), v5.end()) << '\n' << v6 << ": " << std::includes(v1.begin(), v1.end(), v6.begin(), v6.end()) << '\n' << v7 << ": " << std::includes(v1.begin(), v1.end(), v7.begin(), v7.end(), 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)
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR | Applied to | Behavior as published | Correct behavior |
---|---|---|---|
LWG 1205 | C++98 | the return value was unclear if [ first2, last2) is empty
|
returns true in this case |