%
%  Talk Program for Tokio
% 	Tue Jul  5 01:18:04 JST 1988 

talk(A,B) :- 
	#key(A,In1),#crt(A,Out1),
	#key(B,In2),#crt(A,Out2),
	Buffer1 = [],   Buffer2 = [],
	merge_dequeue(In1,In2,Out1,Buffer1),
	merge_dequeue(In2,In1,Out2,Buffer2).

key(Who,Input) :-  write(Who),write(':in:'), read(Input).
crt(Who,Output) :- write(Who),write(':out:'),write(Output),nl.  

merge_dequeue(In1,In2,Out,Buffer) :-
	merge(In1,In2,Buffer),
	@ dequeue(Out,Buffer),
	@ @ merge_dequeue(In1,In2,Out,Buffer).

merge(In1,In2,Buffer) :- In1 = none, In2 = none,!, 
	@Buffer = Buffer.
merge(In1,In2,Buffer) :- In1 = none, !,
	ap(Buffer,[In2],@Buffer).
merge(In1,In2,Buffer) :- In2 = none, !,
	ap(Buffer,[In1],@Buffer).
merge(In1,In2,Buffer) :- 			% non deterministic choice
	ap(Buffer,[In2],@Buffer).
merge(In1,In2,Buffer) :- 
	ap(Buffer,[In1],@Buffer).

dequeue(Out, Buffer) :- Buffer = [],!.
dequeue(Out, Buffer) :- Buffer = [Out|@Buffer].

ap(Nil,X,X1) :- Nil = [], X = X1.
ap(HX,Z,HY)  :- HX = [H|X], HY = [H|Y],
	ap(X,Y,Z).