| creates a compound term or determines functor and arity.
functor(+CompoundTerm, -Functor, -Arity)
functor(-CompoundTerm, +Functor, +Arity)
If CompoundTerm is a compound term then Functor is the functor
and Arity is the arity of that CompoundTerm.
If CompoundTerm is an atomic term (an atom or a number) then Functor
is that atomic term and Arity is 0.
If CompoundTerm is a variable then Functor must
be an atomic term and Arity must be an integer between 0 and
max_arity (127). If is not an atom, the arity must be 0.
Arguments
CompoundTerm compound term or atomic term
Functor atomic term
Arity integer or integer-expression (between 0 and 127)
Examples
| functor(f(a,b,c),F,A). |
Succeeds with substitution F <- f, A <- 3. |
| functor(X,functor,3). |
Succeeds with substitution X <- functor(_1, _2, _3). |
| functor(f(X),f,2). |
Fails. |
Standard
This predicate is part of the ISO-Prolog Standard.
See also
arg/3,
copy_term/2,
'=..'/2.
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