When to Overload the Comma Operator?

c++ function operator-overloading
user541686 picture user541686 · Apr 9, 2011 · Viewed 25.1k times · Source

I see questions on SO every so often about overloading the comma operator in C++ (mainly unrelated to the overloading itself, but things like the notion of sequence points), and it makes me wonder:

When should you overload the comma? What are some examples of its practical uses?

I just can't think of any examples off the top of my head where I've seen or needed to something like

foo, bar;

in real-world code, so I'm curious as to when (if ever) this is actually used.

Answer

Petter picture Petter · Aug 8, 2013

I have used the comma operator in order to index maps with multiple indices.

enum Place {new_york, washington, ...};

pair<Place, Place> operator , (Place p1, Place p2)
{
    return make_pair(p1, p2);
}


map< pair<Place, Place>, double> distance;

distance[new_york, washington] = 100;

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