set using alternative hash function?

[Diez B. Roggisch]

Austin Bingham wrote:

> That's definitely a workable solution, but it still rubs me the wrong
> way. The uniqueness criteria of a set seems, to me, like a property of
> the set, whereas the python model forces it onto each set element.

This is a POV, but to to me, the set just deals with a very minimal
protocol - hash-value & equality. Whatever you feed it, it has to cope with
that. It strikes *me* as odd to ask for something else. 

The ideal solution would be to have several hash/eq-methods on your object,
and somehow make the surroundings decide which to use. But there is no
OO-pragma for that.

> Another issue I have with the HashWrapper approach is its space
> requirements. Logically, what I'm asking to do is switch out a single
> function reference (i.e. to point at get_name() rather than hash()),
> but in practice I'm forced to instantiate a new object for each of my
> set members. On a large set, this could be disastrous.
> 
> Don't get me wrong...your solution is a good one, but it's just not
> what I am looking for.

It is the only one you have, short of implementing set your own. And then
the terms of implementation would be that you pass a hash- and eq-function
& create wrapper-objects internally.

Diez