
Henning Thielemann schrieb:
Ivan Lazar Miljenovic schrieb:
On 3 September 2010 04:57, Arie Peterson
wrote: On Thu, 2 Sep 2010 19:30:17 +0200, Daniel Fischer
wrote: Why would one consider using Ord for Map an abuse? A kludge, for performance reasons, but an abuse? Because it forces one to declare Ord instances for types which have no natural ordering. It is useful to *not* have such instances, in order to catch programming errors. What precisely do you mean by natural ordering?
E.g. I wanted to have a Set of Gaussian (complex) integers, but I did not want to define an Ord instance for them, because writing a < (b :: Gaussian) is a bug with high probability.
I like to answer in advance to the objections that might come. :-) You might object, that it is seldom, that someone intentionally writes (a