is a list or symbol.
is any backward chaining goal.
The backward chaining inference engine is started to look for any set of bindings which satisfy
. Using those bindings,
is instantiated and returned.
Two values are returned. The second value indicates with
that a proof was found, or with
that no proof exists. In the former case, the first value is the instantiated version of
, in the latter case, the first value is
(any '(?x is in (1 2 3)) '(member ?x (1 2 3)))
(1 is in (1 2 3))
(any '(?truck is a truck) '(truck ?truck))
(#<TRUCK TRUCK5> IS A TRUCK)
KnowledgeWorks and Prolog User Guide - 4 Apr 2005