Set.intersection

Christian Maeder wrote:

When trying to use 'Set.intersection s $ singleton e' I just noticed that intersection is not left-biased (see below)!

Set.intersection is neither left- nor right-biased but biased towards the smaller set. I think that needs to be changed (and that may require a function splitLookup). At least the documentation should be adjusted as long as the properties for such pseudo-sets do not correspond to those of maps. Christian