var/1
Module: builtins
var/1 — the variable is unbound
nonvar/1 — the variable is instantiated
FORMS
var(Term)
nonvar(Term)
DESCRIPTION
var/1 succeeds if Term is an unbound variable, and fails otherwise.
nonvar/1 succeeds when Term is a constant or structured term.
EXAMPLES
?- var(constant).
no.
?- nonvar(constant).
yes.
?- X=Y, Y=Z, Z=doughnut, var(X).
no.