[mercury-users] DCG expansion and logical connectives

[Ralph Becket]

> As for the first error, I presume the following expansion:
> 
> 	all [X] p(X) => q(X)				<=>
> 		all [X] not (p(X), not q(X))		<=>
> 		not some [X] not(p(X), not q(X))

Got that one wrong: obviously it should be

	all [X] p(X) => q(X)				<=>
 		all [X] not (p(X), not q(X))		<=>
 		not some [X] not not (p(X), not q(X)) <=>
		not some [X] p(X), not q(X)

which still makes the overlapping scope warning a mystery to me.

Ralph
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