(=..)/2

Availability:built-in

[ISO]?Term =.. ?List

List is a list whose head is the functor of Term and the remaining arguments are the arguments of the term. Either side of the predicate may be a variable, but not both. This predicate is called‘Univ'.

?- foo(hello, X) =.. List.
List = [foo, hello, X]

?- Term =.. [baz, foo(1)].
Term = baz(foo(1))

SWI-Prolog also supports terms with arity 0, as in a() (see section 5). Such terms must be processed using compound_name_arguments/3. This predicate raises a domain error as shown below. See also functor/3.

?- a() =.. L.
ERROR: Domain error: `compound_non_zero_arity' expected, found `a()'