callable/1 exist but don’t know how it relates to the criteria as noted by Jan W. in this post.
callable/1 is often seen as a guard, e.g.
predicate_xyz(_:Head) :-
callable(Head),
!
...
example in syspred.pl
and with a conditional ->/2 e.g.
( callable(Head)
-> ...
; ...
).
example in autoload.pl
callable/1 is also used as part of the type checking from library(error), e.g. has_type(callable,X)
NB Do not call has_type/2 but use the other wrapper predicates as demonstrated in the following.
must_be(callable,Predicate)
must_be/2 throws instantiation_error if Term is insufficiently instantiated and type_error(Type, Term) if Term is not of Type.
example in sandbox.pl
must_be(list(callable), List)
example in thread.pl
has_type/2
has_type(callable,Predicate)
fails silently