% Naive Prober: Like Tit for Tat, but sometimes, after the
% opponent has cooperated, it defects (e.g. at random, in
% one of ten rounds in average).
naive_prober([d|_],d,_,_).
% but only for for 90% if coorporated
naive_prober([c|_],Choice,_,_):-random(Number), (Number < 0.1 -> Choice=d; Choice=c).
% Fallback to coorporate if history is empty.
naive_prober([],c,_,_).