# 27 Algorithms library [algorithms]

## 27.8 Sorting and related operations [alg.sorting]

### 27.8.7 Set operations on sorted structures [alg.set.operations]

#### 27.8.7.2includes[includes]

```template<class InputIterator1, class InputIterator2> constexpr bool includes(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2> bool includes(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2); template<class InputIterator1, class InputIterator2, class Compare> constexpr bool includes(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, Compare comp); template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2, class Compare> bool includes(ExecutionPolicy&& exec, ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2, Compare comp); template<input_iterator I1, sentinel_for<I1> S1, input_iterator I2, sentinel_for<I2> S2, class Proj1 = identity, class Proj2 = identity, indirect_strict_weak_order<projected<I1, Proj1>, projected<I2, Proj2>> Comp = ranges::less> constexpr bool ranges::includes(I1 first1, S1 last1, I2 first2, S2 last2, Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {}); template<input_range R1, input_range R2, class Proj1 = identity, class Proj2 = identity, indirect_strict_weak_order<projected<iterator_t<R1>, Proj1>, projected<iterator_t<R2>, Proj2>> Comp = ranges::less> constexpr bool ranges::includes(R1&& r1, R2&& r2, Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {}); ```
Let comp be less{}, proj1 be identity{}, and proj2 be identity{}, for the overloads with no parameters by those names.
Preconditions: The ranges [first1, last1) and [first2, last2) are sorted with respect to comp and proj1 or proj2, respectively.
Returns: true if and only if [first2, last2) is a subsequence of [first1, last1).
[Note 1:
A sequence S is a subsequence of another sequence T if S can be obtained from T by removing some, all, or none of T's elements and keeping the remaining elements in the same order.
â€” end note]
Complexity: At most 2 * ((last1 - first1) + (last2 - first2)) - 1 comparisons and applications of each projection.