Constraints in Prolog III
Logic programming with constraints

Here we look at the following constraint domains available in Prolog III: lists, rationals and Booleans.

The other area, that of trees, is covered in [1] . It should be noted, however, that the equational vision very early on led to the question: what is the solution, in terms of trees, of the equation X = f(1, X)? Prolog II already provided the answer: a rational infinite tree. This type of tree, which allows finite graphs to be represented as objects in their own right (first-class citizens), is still very much under wraps. But we're betting it won't stay that way.