% From the book
% PROLOG PROGRAMMING IN DEPTH
% by Michael A. Covington, Donald Nute, and Andre Vellino
% (Prentice Hall, 1997).
% Copyright 1997 Prentice-Hall, Inc.
% For educational use only

% File FORALL.PL
% Predicate for_all (Chapter 6)

% for_all(GoalA,GoalB)
%  Succeeds if all solutions for GoalA also satisfy GoalB,
%  and there is at least one solution for both goals.

for_all(GoalA,GoalB) :-
   \+ (call(GoalA), \+ call(GoalB)),      % 1
   call(GoalA),                           % 2
   !.                                     % 3


% Test knowledge base

dog(fido).
dog(rover).
dog(X) :- bulldog(X).

bulldog(bucephalus).

animal(X) :- dog(X).
animal(felix).