std::ranges::contains, std::ranges::contains_subrange

 

C++

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Feature test macros (C++20)

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Concepts library (C++20)

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Diagnostics library

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Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Execution support library (C++26)

Technical specifications

Symbols index

External libraries

 

Algorithm library

Constrained algorithms and algorithms on ranges (C++20)
Constrained algorithms, e.g. ranges::copy, ranges::sort, ...
Execution policies (C++17)
is_execution_policy (C++17)   execution::seqexecution::parexecution::par_unseqexecution::unseq (C++17)    (C++17)(C++17)(C++20)	execution::sequenced_policyexecution::parallel_policyexecution::parallel_unsequenced_policyexecution::parallel_unsequenced (C++17)(C++17)(C++17)(C++20)
Non-modifying sequence operations Batch operations for_each for_each_n (C++17) Search operations all_ofany_ofnone_of (C++11)                (C++11)(C++11) countcount_if mismatch equal findfind_iffind_if_not (C++11) find_end find_first_of adjacent_find search search_n Modifying sequence operations Copy operations copycopy_if (C++11) copy_backward copy_n (C++11) move (C++11) move_backward (C++11) Swap operations swap iter_swap swap_ranges Transformation operations replacereplace_if transform replace_copyreplace_copy_if Generation operations fill fill_n generate generate_n Removing operations removeremove_if unique remove_copyremove_copy_if unique_copy Order-changing operations reverse reverse_copy rotate rotate_copy random_shuffleshuffle (until C++17)(C++11) shift_leftshift_right (C++20)(C++20) Sampling operations sample (C++17)	Sorting and related operations Partitioning operations partition partition_copy (C++11)   stable_partition is_partitioned (C++11) partition_point (C++11) Sorting operations sort stable_sort partial_sort partial_sort_copy is_sorted (C++11) is_sorted_until (C++11) nth_element Binary search operations (on partitioned ranges) lower_bound upper_bound equal_range binary_search Set operations (on sorted ranges) includes set_union set_intersection set_difference set_symmetric_difference Merge operations (on sorted ranges) merge inplace_merge Heap operations push_heap pop_heap make_heap sort_heap is_heap (C++11) is_heap_until (C++11) Minimum/maximum operations max min minmax (C++11) clamp (C++17) max_element min_element minmax_element (C++11) Lexicographical comparison operations lexicographical_compare lexicographical_compare_three_way (C++20) Permutation operations next_permutation prev_permutation is_permutation (C++11) C library qsort bsearch
Numeric operations
iota (C++11) inner_product adjacent_difference    accumulate reduce (C++17) transform_reduce (C++17)	partial_sum inclusive_scan (C++17)    exclusive_scan (C++17) transform_inclusive_scan (C++17) transform_exclusive_scan (C++17)
Operations on uninitialized memory
uninitialized_copy uninitialized_move (C++17)    uninitialized_fill uninitialized_copy_n (C++11) uninitialized_move_n (C++17) uninitialized_fill_n	destroy (C++17) destroy_n (C++17) destroy_at (C++17) construct_at (C++20)       uninitialized_default_construct (C++17) uninitialized_value_construct (C++17) uninitialized_default_construct_n (C++17) uninitialized_value_construct_n (C++17)

 

Constrained algorithms

All names in this menu belong to namespace std::ranges

Non-modifying sequence operations

all_ofany_ofnone_of for_each for_each_n    countcount_if adjacent_find mismatch equal lexicographical_compare    containscontains_subrange (C++23)(C++23) findfind_iffind_if_not find_lastfind_last_iffind_last_if_not (C++23)(C++23)(C++23)   find_end find_first_of search search_n starts_with (C++23) ends_with (C++23)

Modifying sequence operations

copycopy_if copy_n copy_backward    move move_backward shift_leftshift_right (C++23)(C++23)   fill fill_n generate generate_n    transform swap_ranges    shuffle sample removeremove_if replacereplace_if reverse rotate remove_copyremove_copy_if    unique replace_copyreplace_copy_if reverse_copy rotate_copy unique_copy

Partitioning operations

is_partitioned    partition_point    partition    partition_copy    stable_partition

Sorting operations

is_sorted is_sorted_until     sort stable_sort         partial_sort       nth_element partial_sort_copy

Binary search operations (on sorted ranges)

lower_bound         upper_bound         binary_search      equal_range

Set operations (on sorted ranges)

merge inplace_merge       set_difference set_intersection    set_union          includes set_symmetric_difference

Heap operations

is_heap is_heap_until       make_heap           sort_heap push_heap pop_heap

Minimum/maximum operations

max max_element         min min_element         minmax minmax_element     clamp

Permutation operations

is_permutation      next_permutation    prev_permutation

Fold operations

fold_left (C++23) fold_left_first (C++23)   fold_right (C++23) fold_right_last (C++23)   fold_left_with_iter (C++23) fold_left_first_with_iter (C++23)

Numeric operations iota (C++23)             Random number generation generate_random (C++26)

Operations on uninitialized storage

construct_at    destroy destroy_n destroy_at uninitialized_copy    uninitialized_move uninitialized_fill uninitialized_copy_n    uninitialized_move_n uninitialized_fill_n uninitialized_default_construct uninitialized_default_construct_n uninitialized_value_construct uninitialized_value_construct_n

Return types

in_fun_result in_in_result in_found_result    in_out_result in_in_out_result    in_out_out_result    min_max_result out_value_result (C++23) in_value_result (C++23)

 

Defined in header <algorithm>
Call signature
template<input_­iterator I, sentinel_­for<I> S, class T, class Proj = identity> requires indirect_­binary_­predicate<ranges::equal_to, projected<I, Proj>, const T*> constexpr bool ranges::contains(I first, S last, const T& value, Proj proj = {});	(1)	(since C++23)
template<input_­range R, class T, class Proj = identity> requires indirect_­binary_­predicate<ranges::equal_to, projected<iterator_t<R>, Proj>, const T*> constexpr bool ranges::contains(R&& r, const T& value, Proj proj = {});	(2)	(since C++23)
template<forward_­iterator I1, sentinel_­for<I1> S1, forward_­iterator I2,          sentinel_­for<I2> S2, class Pred = ranges::equal_to,          class Proj1 = identity, class Proj2 = identity> requires indirectly_­comparable<I1, I2, Pred, Proj1, Proj2> constexpr bool ranges::contains_subrange(I1 first1, S1 last1, I2 first2, S2 last2, Pred pred = {},                             Proj1 proj1 = {}, Proj2 proj2 = {});	(3)	(since C++23)
template<forward_­range R1, forward_­range R2, class Pred = ranges::equal_to,          class Proj1 = identity, class Proj2 = identity> requires indirectly_­comparable<iterator_t<R1>, iterator_t<R2>, Pred, Proj1, Proj2> constexpr bool ranges::contains_subrange(R1&& r1, R2&& r2, Pred pred = {},                             Proj1 proj1 = {}, Proj2 proj2 = {});	(4)	(since C++23)

1) Search-based algorithm that checks whether or not a given range contains a value with iterator-sentinel pairs.

2) Same as (1) but with range objects rather iterator-sentinel pairs.

3) Search-based algorithm that checks whether or not a given range is a subrange of another range with iterator-sentinel pairs.

4) Same as (3) but with range objects rather iterator-sentinel pairs.

Up until C++20, we’ve had to write

std::ranges::find(r, value) != std::ranges::end(r)

to determine if a single value is inside a range, and to check if a range contains a subrange of interest, we use

not std::ranges::search(haystack, needle).empty()

While this is accurate, it isn’t necessarily convenient, and it hardly expresses intent (especially in the latter case). Being able to say std::ranges::contains(r, value) addresses both of these points. Further evidence for the existence of a contains algorithm is that the STL gave C++98 an obscurely-named contains algorithm called binary_search, and any_of is “contains with a predicate”, showing that there’s prior art for this contains to be an algorithm.

Notes

The interfaces supports both iterator-sentinel pairs and range objects. Due to multi-pass iteration, these algorithms requires both ranges to be forward ranges, and the elements' projections need to be comparable when using the predicate.

ranges::contains_subrange provides no access to searchers like Boyer-Moore, but that's no more true than for ranges::search.

Parameters

first, last	-	the range of elements to examine
r	-	the range of the elements to examine
value	-	value to compare the elements to
pred	-	predicate to apply to the projected elements
proj	-	projection to apply to the elements

Return value

(1) and (2):

ranges::find(std::move(first), last, value, proj) != last;

(3) and (4):

first2 == last2 or !ranges::search(first1, last1, first2, last2, pred, proj1, proj2).empty();

Complexity

At most last - first applications of the predicate and projection.

See also

ranges::findranges::find_ifranges::find_if_not (C++20)(C++20)(C++20)	finds the first element satisfying specific criteria (niebloid)
ranges::search (C++20)	searches for the first occurrence of a range of elements (niebloid)