The 2 objects are found equal if they unify. Note that for some goals, we won't be able to conclude either equality or inequality. Less and greater , correspondingly. The functionality is pretty much self-explanatory. One argument, the predicate to be declared complete.
Predicate completion is a non-monotonic logic technique.
When you declare the relation foo to be complete, you state that if a tuple of arguments cannot be proved to be in foo, then this tuple is not in foo . Use with caution, only if you really know what you are doing, otherwise the system can become unsound. This is more of a macro than a real predicate. The goal is successful if every member of the set produces a solution. This is because of the wy parser works, and will change in later versions.