[mercury-users] Pred defns

[Thomas Charles CONWAY]

Ralph Becket, you write:
> 
> Before I go on, the point behind my suggested notation is that there
> are times when a *metaphor* for destructive assigment is useful.

Exactly right! I don't expect Richard nor anyone else would disagree
with you here. I think Richard's point, and the point illustrated by
SISAL is that the *right* thing to do is find a metaphore not just for
the destructive assignments, but for the (for want of a better term)
`algorithmic notion' that those assignments are encoding.

It may be that we don't have a good collection of such metaphores yet,
but I really think that the right way forward is to try to find them,
not to throw up our hands and use schemes that merely maintain the
status quo.

We have a collection of metaphores for a number of algorithmic notions
such as map, foldl, aggregate, and solutions, and these are very
useful, but they are insufficient in two ways:
	1) we probably need a richer collection of such tools
	2) we need more kinds of polymorphism to maximize their
	   usefulness (ie polymorphic [ground] modes)

Thomas
-- 
Thomas Conway    || conway at cs.mu.oz.au
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