(Prolog) assume

% If the user enters a number from 1 to an including 3
% the right clauses are called.
% then the input '2' would results in calling both action(2) and action(X)
%
%
%
% Note that you can remove 'nondeterm' from the action's predicate,
% but I left it in, so you do can comment out the cuts
PREDICATES
	assumeEqual(integer, integer)
	assumeEqual(integer, integer, string)
	assumeUnequal(integer, integer)
	assumeUnequal(integer, integer, string)
	nondeterm action(integer)
	
CLAUSES
	assumeEqual(X,Y) :- 
	  X=Y, 
	  !.
	  
	assumeEqual(X,Y) :- 
	  X<>Y, 
	  !, 
	  write("Condition X=Y for X=",X, " and Y=",Y," failed!"), 
	  exit(1).
	assumeEqual(X,Y,_) :- 
	  X=Y, 
	  !.
	 
	  
	assumeEqual(X,Y,DebugMessage) :- 
	  X<>Y,
	  !, 
	  write("Condition X=Y for X=",X, " and Y=",Y," failed!"), 
	  nl,
	  write("Debug message: ", DebugMessage),
	  exit(1).
	assumeUnequal(X,Y) :- 
	  X<>Y, 
	  !.
	assumeUnequal(X,Y) :- 
	  X=Y, 
	  !, 
	  write("Condition X<>Y for X=",X, " and Y=",Y," failed!"), 
	  exit(1).
	assumeUnequal(X,Y,_) :- 
	  X<>Y, 
	  !.
	  
	assumeUnequal(X,Y,DebugMessage) :- 
	  X=Y, 
	  !, 
	  write("Condition X<>Y for X=",X, " and Y=",Y," failed!"), 
	  nl,
	  write("Debug message: ", DebugMessage),
	  exit(1).
	  
	action(1) :- 
%	!, % Cut removed on purpose
	nl,
	write("You typed one").
	
	action(2) :- 
%	!, % Cut removed on purpose
	nl,
	write("You typed two").
	action(3) :- 
%	!, % Cut removed on purpose
	nl,
	write("You typed three").
	action(X) :- 
	assumeUnequal(X,1,"action(X)"),
	assumeUnequal(X,2,"action(X)"),
	assumeUnequal(X,3,"action(X)"),
	!,
	nl,
	write("You typed an unknown number").
	
GOAL
	write("Type a number from 1 to 3: "),
	readInt(Num),
	action(Num),
	nl.

Code links

• !, Cut
• CLAUSES
• Cut, !
• GOAL
• nl
• PREDICATES
•  ?readInt
• write