Escape from Zurg

[Joel Reymont]

Here's another Prolog riddle from http://web.engr.oregonstate.edu/ 
~erwig/zurg/.

Please help me translate it!

	Thanks, Joel

P.S.

/* The Zurg Riddle */

time(buzz,5).
time(woody,10).
time(rex,20).
time(hamm,25).

toys([buzz,hamm,rex,woody]).

cost([],0) :- !.
cost([X|L],C) :-
      time(X,S),
      cost(L,D),
      C is max(S,D).

split(L,[X,Y],M) :-
      member(X,L),
      member(Y,L),
      compare(<,X,Y),
      subtract(L,[X,Y],M).

move(st(l,L1),st(r,L2),r(M),D) :-
      split(L1,M,L2),
      cost(M,D).

move(st(r,L1),st(l,L2),l(X),D) :-
      toys(T),
      subtract(T,L1,R),
      member(X,R),
      merge_set([X],L1,L2),
      time(X,D).

trans(st(r,[]),st(r,[]),[],0).
trans(S,U,L,D) :-
      move(S,T,M,X),
      trans(T,U,N,Y),
      append([M],N,L),
      D is X + Y.

cross(M,D) :-
      toys(T),
      trans(st(l,T),st(r,[]),M,D0),
      D0=<D.

solution(M) :- cross(M,60).

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