std::experimental::ranges::copy, std::experimental::ranges::copy_if - cppreference.com (original) (raw)

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.

Contents

• 1 Parameters
• 2 Return value
• 3 Complexity
• 4 Possible implementations
• 5 Example
• 6 See also

[edit] Parameters

[edit] 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.

[edit] Complexity

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

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

[edit] Possible implementations

[edit] Example

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

#include <experimental/ranges/algorithm> #include <experimental/ranges/iterator> #include #include #include   int main() { // see https://en.cppreference.com/w/cpp/language/namespace_alias namespace ranges = std::experimental::ranges;   std::vector from_vector(10); std::iota(from_vector.begin(), from_vector.end(), 0);   std::vector 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 to_vector(from_vector.size()); // std::copy(from_vector, to_vector.begin());   std::cout << "to_vector contains: ";   ranges::copy(to_vector, ranges::ostream_iterator(std::cout, " ")); std::cout << '\n'; }

Output:

to_vector contains: 1 2 4 5 7 8

[edit] See also