Question

I have a std::set<std::string> and I want to know the exact position of the element in the set after the insertion.

I tried with std::distance but without any luck:

#include <iostream>
#include <string>
#include <set>
#include <iterator>

using namespace std;

int main (int argc, char const *argv[])
{

    string array[] = { "zero", "one", "one", "zero", "two", "three", "zero" };
    set<string> numbers;
    for(size_t i = 0; i < 7; ++i)
    {
        int dist = distance(numbers.begin(), numbers.insert(array[i]).first);
        cout << array[i] << "\t" << dist << endl;
    }
    return 0;
}

outputs:

zero    0
one     0
one     0
zero    1
two     1
three   1
zero    3

Instead, I was expecting this:

zero    0
one     1
one     1
zero    0
two     2
three   3
zero    0

Any ideas?

Answer 1

They’re being sorted lexicographically (basically alphabetically). The default comparison for std::set<T> is std::less<T>, which in turn calls operator<.