🚀 go-pugleaf

In article <199@qt.cs.utexas.edu> bradley@cs.utexas.edu (Bradley L. Richards) writes:
>I'm working on a meta-programming project and have run across something I just
>can't figure a way to do.  I want to locate a clause via unification with its
>head, and then be able to retrieve the clause *without binding any variables*.

I hope RO'K will provide a more definitive answer, but until
the post makes it to Oz this will have to do.

A general technique (note ``logic programming'' degenerates to
a matter of ``technique'') is to use double negation to
verify whether something can be proved. For example:

verify(X) :- not(not(X)).

?- verify(X=1).

produces

X=_

The extension to unification of clause headds with goals is
straightforward.

-Kym Horsell