prod([],[],Result) :-
    attach_attribute(_1,float(-0.0)),
    _1=Result,
    true.
prod([X|Xs],[Y|Ys],Result) :-
    solve_mult(_1,X,Y),
    solve_generic_3(eq,-0.0,_1,-1,Rest,-1,Result,1),
    user:prod(Xs,Ys,Rest).