c++stliteratorcontainersreverse-iterator

calculate std::distance between two std::reverse_iterators

I have a code snippet like this:

int* array = new int[size];
std::reverse_iterator<int*> it2 = ... // arbitrary in array

How can i compute the distance between last and it2? I tried this, but it gives back zero:

std::distance(std::reverse_iterator<int*>(array + size), it2);
Solution

  • Your approach to computing the distance looks correct to me. Certainly, this prints 10 when using gcc or clang:

    #include <algorithm>
#include <iostream>
#include <iterator>

int main()
{
    const int size = 20;
    int* array = new int[size];
    std::cout << "distance="
              << std::distance(std::reverse_iterator<int*>(array + 20),
                               std::reverse_iterator<int*>(array + 10))
              << '\n';
    delete[] array;
}