On 29 Apr 2015 05:12, "Matt Oliveri" <atma...@gmail.com> wrote:
> My understanding from the video is that with this kind of solution,
> you still wouldn't be able to union sets efficiently, because the sets
> may come from people using different Ord instances for the element
> type. Unless the union code and both sets all come from within the
> lexical scope of the same "use" directive; but that restriction seems
> onerous.
If the two orderings define uniqueness differently, say people ordered by
age in one set, and people ordered by name in another, then to union them
is a nonsense.
In some regards all sets need to use the same ordering.
The definition of union should be (using braces for the implicit parameter):
union :: {Ord a} -> Set a -> Set a -> Set a
Keean.
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