[mercury-users] partial instantiation?

[Ralph Becket]

Paul Bone, Wednesday, 14 April 2010:
> I also suspect that you think that Mercury supports logic variables, it does
> not.  Cosider:
> 
>     X = Y,
>     Y = 3
> 
> In prolog this will bind X to 3.  In Mercury this is not valid.

Well, the compiler will reorder this particular code so that it works.

What you can't do is something like this:

:- pred aliases(T::out, T::out) is det.

aliases(X, Y) :-
	X = Y.

Unification (=) requires that at least one of the arguments be
instantiated.

-- Ralph
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