This clause succeeds if it's argument is not a variable or a variable with a value.
see also: atom/1 atomic/1 compound/1 float/1 instance/1 integer/1 number/1 var/1
| Examples | |
| nonvar("hello"). | succeeds |
| nonvar(-10.1) | succeeds |
| nonvar(X). | fails |
| X=10, nonvar(X). | succeeds |