Simple maps/sets: parameterize the comparator?

Mark S. Miller erights at
Tue Dec 27 10:20:49 PST 2011

Hi Axel, yes, I would like to extend their constructor in this way.
However, I'm not sure how to spec it -- help appreciated. The problem is
that the comparator needs to provide both an equivalence operation and a
corresponding hash operation. When these agree, all is well. What should we
specify happens when passing in a misbehaving comparator? The dilemma is
1) detecting misbehavior is expensive,
2) having a deterministic collection misbehavior in the face of comparator
misbehavior seems hard, and
3) we'd like to avoid yet more under-specification. The similar
under-specification of Array.prototype.sort is already bad enough.

On Tue, Dec 27, 2011 at 7:22 AM, Axel Rauschmayer <axel at> wrote:

> Currently, using is hard-coded. But one could allow a
> comparator function being handed in (with being the default).
> --
> Dr. Axel Rauschmayer
> axel at
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