% From The Art of Eyepl, Chapter 6.
next(X, Y) :- add(X, 1, Y).
area_rectangle(W, H, Area) :- mul(W, H, Area).

hypotenuse(A, B, C) :-
  mul(A, A, A2),
  mul(B, B, B2),
  add(A2, B2, C2),
  sqrt(C2, C).