Unifies OldAction with the current action on unknown procedures,
i.e. the current value of the
unknown Prolog flag, sets the
current action to NewAction, and prints a message about the
[error,fail,trace,warning], must be nonvar
This is merely a front-end to the
unknown Prolog flag, which see.
| ?- unknown(Action, Action).
just returns Action without changing it.
Procedures that are known to be dynamic just fail when there are no clauses for them.
Undefined Predicates, ref-ere, ref-lps-flg.