22.19 Being involved with: Question

Exercise: Being involved with

In defining the 'jealous/2' predicate, we assumed that we had a predicate called 'involved_with(X,Y)' which told us whether X was involved with Y. We now need to formalize what 'being involved with' means.

The important thing is that if X is involved with Y, then it is also true that Y is involved with X. That is, the relation is "commutative" (as the mathematicians would say).

Assume that you have a predicate 'involved/2' which tells us whether X and Y are involved. The significant part about this predicate is that it does not list relationships twice. That is, it only tells us that X and Y are involved, not that Y and X are involved.

Write a predicate 'involved_with(X,Y)' which codifies the fact that X is involved with Y either if involved(X,Y) is true, or if involved(Y,X) is true.


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