30 Sep
2008
30 Sep
'08
3:55 p.m.
Johannes Waldmann
The StopList class [...]
BTW, that is a horrible name for what is simply a *set* (look at the methods you wrote: empty, insert, member).
I originally called the typeclass Set, but it isn't, so I changed it. It omits some Set functionality. One couldn't write an implementation of union or intersect with it, because there's no way to enumerate its elements. In any case, it's moot, because we're ditching StopLists. :-)
The design problem here is that you don't want to use Data.Set because currently it is an implementation, not an interface.
If by that you mean that it would be nice if Set was a typeclass, and there was a [] implementation as well as the current OrdSet implementation, I tend to agree. C'est la vie.