/*
 * Copyright (c) 2012 Benjamin Franzke <benjaminfranzke@googlemail.com>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

pay(c,d,1).
pay(d,d,2).
pay(c,c,3).
pay(d,c,4).

step(A, B, PAY_A, PAY_B) :-
	pay(A, B, PAY_A),
	pay(B, A, PAY_B).

% Use opponents last decision
tit4tat_select(H,[H|_]).
% Fallback to coorporate at beginning
tit4tat_select(c,[]).

tit4tat(A, Hist, PayA, PayB) :-
	tit4tat_select(Old, Hist),
	step(A, Old, PayA, PayB).

loop(end, _).
loop(End, Hist):- End\=end,
	write('Type c,d or end to end: '), read(Choice),

	tit4tat(Choice, Hist, PAY_A, PAY_B),

	write('A Pay: '),write(PAY_A),nl,
	write('B Pay: '),write(PAY_B),nl,

	loop(Choice, [Choice|Hist]). 
	
start:-loop(noend, []).