如何在Prolog中跟踪值？

I am new to Prolog and am having some difficulties coming from OOP. I need to recursively run through some characters, but remember what I have gone through. In OOP I would just create an array or arraylist to keep track of anything I have used. However, I can't seem to find a similar way to do this in Prolog. How would I check to see what I've used already.I am new to Prolog and am having some difficult