 [semidet]cmp_versions(?Cmp, 
+V1, +V2)
[semidet]cmp_versions(?Cmp, 
+V1, +V2)<, =<, =, >= 
or >. If
Cmp is unbound we check whether < or > 
hold or else bind Cmp to
=.
When comparing for equality (=), the versions are 
considered equal if they compare equal up to the detail level of the 
least specified. E.g,’9.1.2’is considered equal to’9.1’.