Goal:
    A : Type  n : nat  l : list A
  ============================
   ((firstn n l, skipn n l) = (firstn n l, skipn n l))


DEBUG:Going to execute:
done
DEBUG LTAC Evaluated term: split_at
DEBUG LTAC Evaluated term: split_at
DEBUG LTAC Evaluated term: split_at_aux_firstn_skipn
DEBUG LTAC Evaluated term: split_at_aux_firstn_skipn
DEBUG LTAC Evaluated term: Prop
DEBUG LTAC Evaluated term: Prop
DEBUG LTAC Evaluated term: Prop
DEBUG LTAC Evaluated term: Prop