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functor/3
ISOfunctor(+Term, -Name, -Arity)
functor(-Term, +Name, +Arity)
Succeeds if the principal functor of term Term has name Name and arity Arity.
term
atom
arity
There are two ways of using this predicate:
instantiation_error
Term and either Name or Arity are uninstantiated.
type_error
Name is not atomic, or Arity is not an integer, or Name is not an atom when Arity > 0.
domain_error
Arity is an integer < 0.
representation_error
Term is uninstantiated and Arity > 255.
| ?- functor(foo(a,b), N, A). N = foo, A = 2 | ?- functor(X, foo, 2). X = foo(_A,_B)
| ?- functor(X, 2, 0). X = 2
arg/3
, name/2
, =../2
, ref-lte-act.