Conditions involving more than one variable

[jariji]

Is there a way I can put conditions on the relationship between variables?

@rule x y (x < y) x - y --> 0

[Kyle Deeds]

Not sure if this is still helpful, but I think that this is a good use case for the where predicate. It allows you to insert a general boolean function of the arguments. For example, this rule would look like:

@rule x y   x - y --> 0  where (x < y)

However, you will want to be careful about types and making sure that all of the arguments work in your boolean function, e.g. sometimes the arguments will be EClasses.