%-*-mode:outline;outline-regexp:"[0-9a-z.]+"-*-
. #false(q_is_not_empty).
  using assumption #false(q_is_not_empty) :- q(X1).
   {X1=nil}
1. q(nil).
    using assumption q(X1) :- tree_3n_plus_2(X1), list_even(X1).
     {X1=nil}
1.1. tree_3n_plus_2(nil) by assumption.
1.2. list_even(nil) by assumption.
