std::experimental::ranges::copy, std::experimental::ranges::copy_if

 

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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
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is_partitioned partition_point	partition partition_copy	stable_partition
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is_sorted is_sorted_until	sort stable_sort	partial_sort partial_sort_copy	nth_element
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lower_bound	upper_bound	binary_search	equal_range
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merge inplace_merge	includes	set_difference set_intersection	set_symmetric_difference set_union
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is_heap is_heap_until	make_heap sort_heap	push_heap pop_heap
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max max_element	min min_element	minmax minmax_element
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is_permutation	next_permutation	prev_permutation

 

Defined in header <experimental/ranges/algorithm>
template< InputIterator I, Sentinel<I> S, WeaklyIncrementable O >     requires IndirectlyCopyable<I, O> ranges::tagged_pair<tag::in(I), tag::out(O)>     copy( I first, S last, O result );	(1)	(ranges TS)
template< InputRange R, WeaklyIncrementable O >     requires IndirectlyCopyable<ranges::iterator_t<R>, O> ranges::tagged_pair<tag::in(ranges::safe_iterator_t<R>), tag::out(O)>     copy( R&& r, O result );	(2)	(ranges TS)
template< InputIterator I, Sentinel<I> S, WeaklyIncrementable O,           class Proj = ranges::identity,           IndirectUnaryPredicate<projected<I, Proj>> Pred >     requires IndirectlyCopyable<I, O> ranges::tagged_pair<tag::in(I), tag::out(O)>     copy_if( I first, S last, O result, Pred pred, Proj proj = Proj{} );	(3)	(ranges TS)
template< InputRange R, WeaklyIncrementable O,           class Proj = ranges::identity,           IndirectUnaryPredicate<projected<ranges::iterator_t<R>, Proj>> Pred >     requires IndirectlyCopyable<iterator_t<R>, O> ranges::tagged_pair<tag::in(ranges::safe_iterator_t<R>), tag::out(O)>     copy_if( R&& r, O result, Pred pred, Proj proj = Proj{} );	(4)	(ranges TS)

Copies elements in the source range ([first, last) or r) into the destination range beginning at result, starting from the first element in the source range and proceeding to the last one.

1) Copies all elements in the range [first, last). For each non-negative integer n < (last - first), performs *(result + n) = *(first + n). The behavior is undefined if result is within the range [first, last). In this case, ranges::copy_backward may be used instead.

2) Same as (1), but uses r as the source range, as if by ranges::copy(ranges::begin(r), ranges::end(r), result); except that result may not be copied.

3) Only copies the elements for which the predicate pred returns true when applied to the element's value as projected by the projection proj. The order of the elements that are copied is preserved. The behavior is undefined if the source and the destination ranges overlap.

4) Same as (3), but uses r as the source range, as if by ranges::copy_if(ranges::begin(r), ranges::end(r), result, pred, proj); except that result, pred and proj may not be copied.

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 copy
r	-	the range of elements to copy
result	-	the beginning of the destination range
pred	-	predicate to apply to the projected elements
proj	-	projection to apply to the elements

Return value

A tagged_pair object containing the following two members:

• The first member, with the tag tag::in, is the past-the-end iterator of the source range (that is, an iterator of type I that compares equal to the sentinel last).
• The second member, with the tag tag::out, is the past-the-end iterator of the result range.

Complexity

1) Exactly ranges::distance(first, last) assignments.

2) Exactly ranges::distance(r) assignments.

3) Exactly ranges::distance(first, last) applications of the corresponding projection and predicate.

4) Exactly ranges::distance(r) applications of the corresponding projection and predicate.

Possible implementations

First version
template<InputIterator I, Sentinel<I> S, WeaklyIncrementable O> requires IndirectlyCopyable<I, O>() ranges::tagged_pair<tag::in(I), tag::out(O)> copy(I first, S last, O result) { for (; first != last; ++first, (void)++result) *result = *first; return {first, result}; }
Second version
template<InputRange R, WeaklyIncrementable O> requires IndirectlyCopyable<ranges::iterator_t<R>, O>() ranges::tagged_pair<tag::in(ranges::safe_iterator_t<R>), tag::out(O)> copy(R&& r, O result) { return ranges::copy(ranges::begin(r), ranges::end(r), result); }
Third version
template<InputIterator I, Sentinel<I> S, WeaklyIncrementable O, class Proj = ranges::identity, IndirectUnaryPredicate<projected<I, Proj>> Pred> requires IndirectlyCopyable<I, O>() ranges::tagged_pair<tag::in(I), tag::out(O)> copy_if(I first, S last, O result, Pred pred, Proj proj = Proj{}) { for (; first != last; ++first) if (ranges::invoke(pred, ranges::invoke(proj, *first))) { *result = *first; ++result; } return {first, result}; }
Fourth version
template<InputRange R, WeaklyIncrementable O, class Proj = ranges::identity, IndirectUnaryPredicate<projected<ranges::iterator_t<R>, Proj>> Pred> requires IndirectlyCopyable<ranges::iterator_t<R>, O>() ranges::tagged_pair<tag::in(ranges::safe_iterator_t<R>), tag::out(O)> copy_if(R&& r, O result, Pred pred, Proj proj = Proj{}) { return ranges::copy_if(ranges::begin(r), ranges::end(r), result, pred, proj); }

Example

The following code uses copy to both copy the contents of one vector to another and to display the resulting vector:

Run this code

#include <experimental/ranges/algorithm>
#include <experimental/ranges/iterator>
#include <iostream>
#include <numeric>
#include <vector>
 
int main()
{
    // see https://en.cppreference.com/w/cpp/language/namespace_alias
    namespace ranges = std::experimental::ranges;
 
    std::vector<int> from_vector(10);
    std::iota(from_vector.begin(), from_vector.end(), 0);
 
    std::vector<int> to_vector;
    ranges::copy_if(from_vector.begin(), from_vector.end(),
                    ranges::back_inserter(to_vector),
                    [](const auto i)
                    {
                       return i % 3;
                    });
// or, alternatively,
//  std::vector<int> to_vector(from_vector.size());
//  std::copy(from_vector, to_vector.begin());
 
    std::cout << "to_vector contains: ";
 
    ranges::copy(to_vector, ranges::ostream_iterator<int>(std::cout, " "));
    std::cout << '\n';
}

Output:

to_vector contains: 1 2 4 5 7 8

See also

copycopy_if (C++11)	copies a range of elements to a new location (function template)
copy_backward	copies a range of elements in backwards order (function template)
reverse_copy	creates a copy of a range that is reversed (function template)
copy_n	copies a number of elements to a new location (function template)
fill	assigns a range of elements a certain value (function template)
remove_copyremove_copy_if	copies a range of elements omitting those that satisfy specific criteria (function template)