Type Checking

The following predicates take a term as their argument. They are provided to check the type of that term. The reference pages for these predicates include examples of their use.

atom(+T)   ISO
term T is an atom
atomic(+T)   ISO
term T is an atom or a number
T is an atom or a compound term
compound(+T)   ISO
T is a compound term
db_reference(+X)   since release 4.1
X is a db_reference
float(+N)   ISO
N is a floating-point number
term T is a nonvar, and all substructures are nonvar
integer(+T)   ISO
term T is an integer
X is a mutable term
nonvar(+T)   ISO
term T is one of atom, number, compound (that is, T is instantiated)
number(+N)   ISO
N is an integer or a float
T is not a compound term; it is either atomic or a var
var(+T)   ISO
term T is a variable (that is, T is uninstantiated)

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