nb_setarg/3 to use destructive assignest

agg_all_1(min(X,W), Goal, min(X,W)) :-
  State = state(_,W),
  (  call(Goal),
      arg(1, State, M0),
      (   var(M0) -> true; (X<M0)),
     nb_setarg(1, State, X),
     nb_setarg(2, State, W),
     fail
  ;
     arg(1, State, X),
     arg(2, State, W)
  ).