:- type busy_beaver_states  ---> a ; b ; c ; halt.
:- type busy_beaver_symbols ---> '0' ; '1'.

:- func busy_beaver_config = config(busy_beaver_states, busy_beaver_symbols).
busy_beaver_config = config(a,           % initial state
                            set([halt]), % set of terminating states
                            '0').        % blank symbol

:- pred busy_beaver(busy_beaver_states::in,
                    busy_beaver_symbols::in,
                    busy_beaver_symbols::out,
                    action::out,
                    busy_beaver_states::out) is semidet.
busy_beaver(a, '0', '1', right, b).
busy_beaver(a, '1', '1', left,  c).
busy_beaver(b, '0', '1', left,  a).
busy_beaver(b, '1', '1', right, b).
busy_beaver(c, '0', '1', left,  b).
busy_beaver(c, '1', '1', stay,  halt).

TapeOut = turing(busy_beaver_config, busy_beaver, []).