On Wed, 2005-01-26 at 04:49, skaller wrote:
> On Wed, 2005-01-26 at 04:24, skaller wrote:
> 
> > 
> > However, when we're trying to order all the match
> > candidates, it would be nicer to get one of the
> > above four results in one unification step.
> 
> Argg .. sorry for answering my own post,
> but now it is obvious how to do it.
> 
> 1) Set the result to Equal
> 
> 2) if you have an equation 
> 
> 	'a = T 
> or
> 	T = 'a
> 
> where T is not a type variable, and then:
> 
> if the current result is Equal reset it
> to 'less' or 'greater' depending which side
> of the original pair of terms 'a is on,
> 
> otherwise return Incomparable

Argg .. bug .. this should read: 

otherwise if the result is not 'less' or
'greater' consistent with which side of
the original pair 'a is on, return
incomparable (otherwise continue)

> 
> 3) if you get a mismatch, return Incomparable
> 
> 4) Otherwise you have an equation between
> two type variables, which doesn't change
> the current result
> 
> Provided you haven't returned incomparable,
> you continue unifying in the usual way,
> returning the result when the MGU is found.
-- 
John Skaller, mailto:skaller@users.sf.net
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