Type Tests

atom(T)

term T is an atom

atomic(T)

term T is an atom, a number or a db_reference

callable(T)

T is an atom or a compound term

compound(T)

T is a compound term (a skeletal predicate specification; see ref-syn-spc)

db_reference(D)

D is a db_reference

float(N)

N is a floating-point number

ground(T)

term T is a nonvar, and all substructures are nonvar

integer(T)

term T is an integer

nonvar(T)

term T is one of atom, db_reference, number, compound (that is, T is instantiated)

number(N)

N is an integer or a float

simple(T)

T is not a compound term; it is either atomic or a var

var(T)

term T is a variable (that is, T is uninstantiated)