Defining < for STL sort algorithm - operator overload, functor or standalone function?

Question

I have a stl::list containing Widget class objects. They need to be sorted according to two members in the Widget class.

For the sorting to work, a less-than compara

Answer 1

They should all be the same in terms of performance, but there are other differences between them:

• The first two save you having to explicitly specify the comparator, and can be used easily with other operations, possibly poorly defined ones that don't allow explicit specification of a comparator.

• Only the functor allows additional data for the comparison. For example, if you were comparing ints, you could create a comparison that compares their distance from a third point, P, which would be a member of the functor instance.

• Functors are generally less easy to read (to those not familiar with C++).

Note, you don't need to inherit binary_operator for it to work, although it does give you some nice typedefs.