🚀 go-pugleaf

From article <1992Aug11.131542.18608@dcs.qmw.ac.uk>, by mmh@cs.qmw.ac.uk (Matthew Huntbach):

[deleted]
> You need to represent your known distances as facts with a separate
> predicate:
> 
> dist(a,b,4).
> dist(b,c,5). etc.
> 
> Now have:
> 
> distance(X,Y,D) :- dist(X,Y,D).
> distance(X,Y,D) :- dist(Y,X,D).
> distance(X,Y,D) :- dist(X,Z,D1),distance(Z,Y,D2),D is D1+D2.

I'm tempted (off the top of my head) to take this a stage further, and
have _three_ nested procedures:

	outer one implements transitivity

		middle one implements symmetry

			innermost one has canonical data 

Somehow it seems eleganter :) to implement these aspects separately.
If only because there are various ways to implement transitivity.
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