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std::includes(3) C++ Standard Libary std::includes(3) NAME std::includes - std::includes Synopsis Defined in header <algorithm> template< class InputIt1, class InputIt2 > bool includes( InputIt1 first1, InputIt1 last1, (1) (const- expr since C++20) InputIt2 first2, InputIt2 last2 ); template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2 > bool includes( ExecutionPolicy&& policy, (2) (since C++17) ForwardIt1 first1, ForwardIt1 last1, ForwardIt2 first2, ForwardIt2 last2 ); template< class InputIt1, class InputIt2, class Compare > bool includes( InputIt1 first1, InputIt1 last1, (3) (const- expr since C++20) InputIt2 first2, InputIt2 last2, Compare comp ); template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2, class Compare > bool includes( ExecutionPolicy&& policy, (4) (since C++17) ForwardIt1 first1, ForwardIt1 last1, ForwardIt2 first2, ForwardIt2 last2, Compare comp ); Returns true if the sorted range [first2, last2) is a subsequence of the sorted range [first1, last1) (a subsequence need not be contiguous). 1) If [first1, last1) or [first2, last2) is not sorted with respect to operator< (until C++20) std::less{} (since C++20), the behavior is undefined. 3) If [first1, last1) or [first2, last2) is not sorted with respect to comp, the behavior is undefined. 2,4) Same as (1,3), but executed according to policy. These overloads participate in overload resolution only if 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) Parameters first1, last1 - the sorted range of elements to examine first2, last2 - the sorted range of elements to search for policy - the execution policy to use. See execution policy for details. comparison function object (i.e. an object that sat- isfies the requirements of Compare) which returns true if the first argument is less than (i.e. is ordered before) the second. The signature of the comparison function should be equivalent to the following: bool cmp(const Type1& a, const Type2& b); comp - 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 re- gardless 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 ob- ject of type InputIt can be dereferenced and then implicitly con- verted to both of them. Type requirements - InputIt1, InputIt2 must meet the requirements of LegacyInputItera- tor. - ForwardIt1, ForwardIt2 must meet the requirements of LegacyFor- wardIterator. - Compare must meet the requirements of Compare. Return value true if [first2, last2) is a subsequence of [first1, last1); other- wise false. An empty sequence is a subsequence of any sequence, so true is re- turned if [first2, last2) is empty. Complexity Given \(\scriptsize N_1\)N 1 as std::distance(first1, last1) and \(\scriptsize N_2\)N 2 as std::distance(first2, last2): 1,2) At most \(\scriptsize 2 \cdot (N_1+N_2)-1\)2(N 1+N 2)-1 comparisons using operator< (until C++20) std::less{} (since C++20). 3,4) At most \(\scriptsize 2 \cdot (N_1+N_2)-1\)2(N 1+N 2)-1 applications of the comparison function comp. Exceptions The overloads with a template parameter named ExecutionPolicy report errors as follows: * If execution of a function invoked as part of the algorithm throws an exception and ExecutionPolicy is one of the standard policies, std::termi- nate is called. For any other ExecutionPolicy, the behavior is implementation- defined. * If the algorithm fails to allocate memory, std::bad_alloc is thrown. Possible implementation 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; } Example // Run this code #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) Defect reports The following behavior-changing defect reports were applied retroac- tively to previously published C++ standards. DR Applied to Behavior as published Correct behavior LWG 1205 C++98 the return value was unclear if re- turns true in this [first2, last2) is empty case See also set_difference computes the difference between two sets (function template) search searches for a range of elements (function template) ranges::includes returns true if one sequence is a subsequence of another (C++20) (niebloid) http://cppreference.com 2024.06.10 std::includes(3)
NAME | Synopsis | Parameters | Type requirements | Return value | Complexity | Exceptions | Possible implementation | Example | Output: | See also
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