% Prolog ärgern:


ackermann(M, _, _) :-
   M < 0,
   throw(error(domain_error(not_less_than_zero,M),ackermann/3)).
ackermann(M0,N0,A0) :-
   M0 > 0,
   M1 is M0 - 1,
   N0 > 0,
   !,
   N1 is N0 - 1,
   ackermann(M0,N1,A1),
   ackermann(M1,A1,A0).
ackermann(M0,0,A) :-
   M0 > 0,
   !,
   M1 is M0 - 1,
   ackermann(M1,1,A).
ackermann(0,N,A) :-
   A is N + 1.
ackermann(1,N,A) :-
   A is N + 2.
ackermann(2,N,A) :-
   A is 2*N + 3.
ackermann(3,N,A) :-
   A is 2^(N+3)-3.




run(R) :-
   length(_,S),
   (  R = length(S)
   ;  R = ack(M,N,A),
      between(4,S,M),
      N is S-M,
      (  false, A = call
      ;  catch(ackermann(M,N,A),error(resource_error(_),_),false)
      )
    ).