% Tit for Tat:
% Begins with cooperation and then plays what its opponent played in the last
% move (if the opponent defects in some round, Tit for Tat will defect in the
% following one; to cooperation it responds with cooperation).

% Syntax: tit4tat(+history, -choice, +state_in, -state_out)

% Use opponents last decision
tit4tat([Last|_],Last,_,_).
% Fallback to coorporate if history is empty.
tit4tat([],c,_,_).