nonvar(X) succeeds if X is not an uninstantiated variable.
Examples
?- nonvar(abc).
yes
?- nonvar(1).
yes
?- nonvar(a(b,c)).
yes
?- nonvar([a,b,c]).
yes
?- X=1, nonvar(X).
X = 1
yes
?- nonvar(X).
no
?- X=Y, nonvar(X).
no
?- nonvar(_).
nononvar(X) - checks that a term is not an uninstantiated variable.nonvar(X) succeeds if X is not an uninstantiated variable.
?- nonvar(abc).
yes
?- nonvar(1).
yes
?- nonvar(a(b,c)).
yes
?- nonvar([a,b,c]).
yes
?- X=1, nonvar(X).
X = 1
yes
?- nonvar(X).
no
?- X=Y, nonvar(X).
no
?- nonvar(_).
no