%% %% :- check pred powers(A,B,C)
%% %%    : ( list_num(A), num(B), var(C) )
%% %%    => list_num(C).

:- checked calls powers(A,B,C)
   : ( list_num(A), num(B), var(C) ).

:- checked success powers(A,B,C)
   : ( list_num(A), num(B), var(C) )
   => list_num(C).

