Question

Like the question says, I’m wondering about the reason for that. Because I get an error when I try to get the distance between const and non-const iterators.

vector<int> v;
auto it=v.begin();
auto cit=v.cbegin();
distance(it,cit);


no matching function for call to ‘distance(__gnu_cxx::__normal_iterator<int*, std::vector<int> >&, __gnu_cxx::__normal_iterator<const int*, std::vector<int> >&)

From my limited understanding of iterators, I see no reason why it shouldn’t work.

Answer 1

You have a mutable iterator and a constant iterator in the call to std::distance, so template argument deduction is failing. You can fix this by specifying the template argument explicitly.

std::vector<int> v;
auto i1 = v.begin();
auto i2 = v.cbegin();

auto dist = std::distance<std::vector<int>::const_iterator>( i1, i2 );