Copy a range of elements
12345678910111213141516171819 | #include <vector>
#include <algorithm>
#include <iterator>
std::vector<int> target2(5);
std::vector<int> target3;
template <typename RangeOfInts>
void foo(RangeOfInts source)
{
std::vector<int> target1{std::begin(source),
std::end(source)};
std::copy(std::begin(source), std::end(source),
std::begin(target2));
std::copy(std::begin(source), std::end(source),
std::back_inserter(target3));
} |
This pattern is licensed under the CC0 Public Domain Dedication.
Intent
Copy elements from a range to another range or container.
Description
We start with a source range object on line 9 and, for the purposes
of this example, we assume its elements are of type int.
On lines 11–12, we copy the elements from the source range into a
container, target1, simply by passing the begin and end iterators
of the range to the std::vector<T>’s constructor. We use
std::begin and std::end
to obtain these iterators.
To copy the elements of source into a range or container which
already has the appropriate number of elements allocated,
represented by target2 on line 5, we use std::copy
on lines 14–15. The first two iterator arguments denote the source
range, and the third iterator argument denotes the start of the
target range. For this to work, the elements must already exist in
the target range.
To demonstrate how we can copy into a container that does not
yet contain any elements, we have an empty std::vector<int>
called target3 on line 6. For the third argument of
std::copy (lines 17–18), we call std::back_inserter
to get an iterator that automatically calls push_back on target3
for each element that is copied.
