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Hi,
This is what I need to do:
Given a type, u, and a collection of types, ts, find a type t such that:
* t is a member of ts
* t can be unified with u
* There is no type v in ts, which unifies with u and is more general
than t.
(In other words, find the most specific type in ts that is still equal
to or a generalisation of u.)
For example:
ts = list int, int, list 'a, 'a
For u = list int, the result would be list int. For u = list string,
the result would be list 'a, and for u = string the result would be 'a.
Note that I already have a function which can compute if type a is a
specialisation of type b.
I think that in theory, I could do a brute force approach:
* Grab all types in ts that are generalisations of u.
* Order the results according to how specific they are.
* Arbitrarily choose one of the most specific.
But there must be a smarter way! Eg, I think that I should be able to
start with the type u, and incrementally generalise it until I find a
match. It is tricky to find a method of generalisation that will cover
the entire search space, and find the most specific type first.
I am sure there must be papers on this, but I am having trouble coming
up with the right search terms - references appreciated! :)
Thanks in advance,
Jim
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Jim Farrand