In my hand-write vector I needed to implement insert function, so I did it like this:
void insert(size_t index, const T& x) {
std::copy(begin() + index, end() - 1, begin() + index + 1);
new(storage_ + index) T(x); // "storage_" is my vector's inner array
}
And this works absolutely correct on test like this:
myvector<int> v;
for (int i = 0; i < 10; i++)
v.push_back(i + 1);
v.insert(5, 0); // insert(size_t position, const T& element)
This outputs:
1 2 3 4 5 0 6 7 8 9 10
(this means insert worked fine)
But I absolutely don't understand why this code works the way it is because on cplusplus.com (link) I found that std::copy works like this:
template<class InputIterator, class OutputIterator>
OutputIterator copy (InputIterator first, InputIterator last, OutputIterator result)
{
while (first!=last) {
*result = *first;
++result; ++first;
}
return result;
}
But doesn't it mean, that if I call
std::copy(begin() + index, end() - 1, begin() + index + 1);
It will replace 7 with 6 when it executes *result = *first; and
after ++result; ++first; it will replace 8 with 6 and so on.
In myvector iterators are defined like this:
typedef T* iterator;
and my begin/end is:
iterator begin() {
return storage_ + 0;
}
iterator end() {
return storage_ + size_;
}
