std::experimental::ranges::find, std::experimental::ranges::find_if, std::experimental::ranges::find_if_not

 

C++

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Feature test macros (C++20)

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Concepts library (C++20)

Metaprogramming library (C++11)

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Ranges library (C++20)

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Technical specifications

Symbols index

External libraries

 

Technical specifications

Filesystem library (filesystem TS)

Library fundamentals (library fundamentals TS)

Library fundamentals 2 (library fundamentals TS v2)

Library fundamentals 3 (library fundamentals TS v3)

Extensions for parallelism (parallelism TS)

Extensions for parallelism 2 (parallelism TS v2)

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Extensions for concurrency 2 (concurrency TS v2)

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Ranges

Concepts

General utilities

Iterators

Ranges

Algorithms

 

Algorithms library

Non-modifying sequence operations
all_ofany_ofnone_of countcount_if	findfind_iffind_if_not find_end find_first_of	adjacent_find search search_n mismatch	equal for_each lexicographical_compare
Modifying sequence operations
copycopy_if copy_n copy_backward move move_backward	fill fill_n generate generate_n swap_ranges shuffle transform	removeremove_if replacereplace_if reverse rotate unique	remove_copyremove_copy_if 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 partial_sort_copy	nth_element
Binary search operations
lower_bound	upper_bound	binary_search	equal_range
Set operations (on sorted ranges)
merge inplace_merge	includes	set_difference set_intersection	set_symmetric_difference set_union
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
Permutations
is_permutation	next_permutation	prev_permutation

 

Defined in header <experimental/ranges/algorithm>
template< InputIterator I, Sentinel<I> S, class T, class Proj = ranges::identity >     requires IndirectRelation<ranges::equal_to<>, projected<I, Proj>, const T*> I find( I first, S last, const T& value, Proj proj = Proj{} );	(1)	(ranges TS)
template< InputRange R, class T, class Proj = ranges::identity >     requires IndirectRelation<ranges::equal_to<>,                               projected<ranges::iterator_t<R>, Proj>, const T*> ranges::safe_iterator_t<R> find( R&& r, const T& value, Proj proj = Proj{} );	(2)	(ranges TS)
template< InputIterator I, Sentinel<I> S, class Proj = ranges::identity,           IndirectUnaryPredicate<projected<I, Proj>> Pred > I find_if( I first, S last, Pred pred, Proj proj = Proj{} );	(3)	(ranges TS)
template< InputRange R, class Proj = ranges::identity,           IndirectUnaryPredicate<projected<ranges::iterator_t<R>, Proj>> Pred > ranges::safe_iterator_t<R> find_if( R&& r, Pred pred, Proj proj = Proj{} );	(4)	(ranges TS)
template< InputIterator I, Sentinel<I> S, class Proj = ranges::identity,           IndirectUnaryPredicate<projected<I, Proj>> Pred > I find_if_not( I first, S last, Pred pred, Proj proj = Proj{} );	(5)	(ranges TS)
template< InputRange R, class Proj = ranges::identity,           IndirectUnaryPredicate<projected<ranges::iterator_t<R>, Proj>> Pred > ranges::safe_iterator_t<R> find_if_not( R&& r, Pred pred, Proj proj = Proj{} );	(6)	(ranges TS)

Returns the first element in the range [first, last) that satisfies specific criteria:

1) find searches for an element whose projected value is equal to value (i.e., value == ranges::invoke(proj, *i)).

3) find_if searches for an element for whose projected value predicate p returns true (i.e., ranges::invoke(pred, ranges::invoke(proj, *i))) is true).

5) find_if_not searches for an element for whose projected value predicate q returns false (i.e., ranges::invoke(pred, ranges::invoke(proj, *i))) is false).

2,4,6) Same as (1,3,5), but uses r as the source range, as if using ranges::begin(r) as first and ranges::end(r) as last.

Notwithstanding the declarations depicted above, the actual number and order of template parameters for algorithm declarations is unspecified. Thus, if explicit template arguments are used when calling an algorithm, the program is probably non-portable.

Parameters

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

Return value

Iterator to the first element satisfying the condition. If no such element is found, returns an iterator that compares equal to last.

Complexity

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

Possible implementation

First version
template<InputIterator I, Sentinel<I> S, class T, class Proj = ranges::identity> requires IndirectRelation<ranges::equal_to<>, projected<I, Proj>, const T*> I find(I first, S last, const T& value, Proj proj = Proj{}) { for (; first != last; ++first) if (ranges::invoke(proj, *first) == value) break; return first; }
Second version
template<InputIterator I, Sentinel<I> S, class Proj = ranges::identity, IndirectUnaryPredicate<projected<I, Proj>> Pred> I find_if(I first, S last, Pred pred, Proj proj = Proj{}) { for (; first != last; ++first) if (ranges::invoke(pred, ranges::invoke(proj, *first))) break; return first; }
Third version
template<InputIterator I, Sentinel<I> S, class Proj = ranges::identity, IndirectUnaryPredicate<projected<I, Proj>> Pred> I find_if_not(I first, S last, Pred pred, Proj proj = Proj{}) { for (; first != last; ++first) if (!ranges::invoke(pred, ranges::invoke(proj, *first))) break; return first; }

See also

findfind_iffind_if_not (C++11)	finds the first element satisfying specific criteria (function template)
adjacent_find	finds the first two adjacent items that are equal (or satisfy a given predicate) (function template)
find_end	finds the last sequence of elements in a certain range (function template)
find_first_of	searches for any one of a set of elements (function template)
mismatch	finds the first position where two ranges differ (function template)
search	searches for a range of elements (function template)