Re: Providing a no-overhead way for a contained class to access its container?

Jerry Coffin <>
Tue, 17 Jun 2008 00:00:11 -0600
In article <5dd80816-49c4-442d-a25c-076b6c260305>, says...

[ ... ]

The only reason that I even need to have the contained class is so
that I can overload the operator<() on it, and thus use std::sort().

You can use std::sort without having an overloaded operator< for the
type. You can create the comparison as either a function or a functor,
and then pass it as the third parameter to std::sort. For example:

#include <vector>
#include <algorithm>
#include <iostream>

class X {
    int y;
    X(int a=0) : y(a) {}
    operator int() const { return y; }

struct less {
    bool operator()(X const &a, X const &b) {
        return (int)a < (int)b;

int main() {
    std::vector<X> x;

    for (int i=0; i<20; i++)

    std::sort(x.begin(), x.end(), less());
    std::copy(x.begin(), x.end(),
        std::ostream_iterator<int>(std::cout, "\n"));
    return 0;


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