#include <iostream>
#include <algorithm>
#include <string>

int main() 
{
    std::string s = "foo123bar456wibble";
    auto end = std::unique(s.begin(), s.end(), [](char l, char r){
        return std::isdigit(l) && std::isdigit(r);
    });
    // What does s hold?
    std::cout << std::string(s.begin(), end) << '\n';
}