Select Code to Download

eq(X, X).

inc(X, succ(X)).   % you don't have to understand this.

  foo :-
    inc(X, Y),         % Implicit RELATION.
...
    inc(X, Y),         % Same implicit relation.
    Y = succ(zero),    % Implicitly match X against zero.
    something(X, Y).   % same as something(zero, succ(zero)).