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

PeteOlcott <>
Tue, 17 Jun 2008 05:30:13 -0700 (PDT)
On Jun 17, 1:00 am, Jerry Coffin <> wrote:

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;



The universe is a figment of its own imagination.

What about the case where the contained class must store its data in
its container?

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