A continuable error is signaled. Invoking the
continue restart causes the existing inferencing state to be returned.
The existing inferencing state is destroyed and a new one is returned.
The existing inferencing state is returned.
If set-current-p is non-nil, then *inferencing-state* is set to new inferencing state.
KnowledgeWorks and Prolog User Guide (Macintosh version) - 24 Mar 2017