Rules lhs_not and lhs_exist are analogous, and both of them are derivations of lhs_unary.
But lhs_unary also has the alternative lhs_not_binding, which permits us to write one of
these two forms:
not $label : Fact( )
not $label : ( Fact1() || Fact2() || ... )
Is this binding, which is restricted to the scope of 'not', useful in any way?
Possibly within the 1st form, in an inline eval. But I don't see how it can
be used in the second case.
Why is the same binding not possible with 'exists'?
(This is not meant to say that I'd like to have binding for 'exists', too.)
-W