% Select distraction only if opponents both last decision were to distract.
% See: http://en.wikipedia.org/wiki/Tit_for_tat#Tit_for_two_tats

% Syntax: tit42tat(+history, -choice, +state_in, -state_out)

tit42tat([d,d|_],d,_,_):-!.
tit42tat(_,c,_,_).