var(Term) succeeds if Term is currently
uninstantiated (which therefore has not been bound to anything, except
possibly another uninstantiated variable).
nonvar(Term) succeeds if Term is currently instantiated
(opposite of var/1).
atom(Term) succeeds if Term is currently instantiated
to an atom.
integer(Term) succeeds if Term is currently
instantiated to an integer.
float(Term) succeeds if Term is currently instantiated
to a floating point number.
number(Term) succeeds if Term is currently instantiated
to an integer or a floating point number.
atomic(Term) succeeds if Term is currently instantiated
to an atom, an integer or a floating point number.
compound(Term) succeeds if Term is currently
instantiated to a compound term, i.e. a term of arity > 0 (a list or a
structure).
callable(Term) succeeds if Term is currently
instantiated to a callable term, i.e. an atom or a compound term.
list(Term) succeeds if Term is currently instantiated
to a list, i.e. the atom [] (empty list) or a term with principal
functor '.'/2 and with second argument (the tail) a list.
partial_list(Term) succeeds if Term is currently
instantiated to a partial list, i.e. a variable or a term whose the main
functor is '.'/2 and the second argument (the tail) is a partial
list.
list_or_partial_list(Term) succeeds if Term is
currently instantiated to a list or a partial list.
Errors
None.
Portability
var/1, nonvar/1, atom/1, integer/1,
float/1, number/1, atomic/1, compound/1
and callable/1 are ISO predicates.
list/1, partial_list/1 and
list_or_partial_list/1 are GNU Prolog predicates.
Copyright (C) 1999,2000 Daniel Diaz
Verbatim copying and distribution of this entire article is permitted in any
medium, provided this notice is preserved.
