Inductive PrefixFree : list SplitPath -> Prop :=
| FreeNil : PrefixFree []
| FreeCons : forall (p : SplitPath) (l : list SplitPath),
               PrefixFree l ->
               (forall (p' : SplitPath), In p' l ->
                                        (forall p1 p2, p' ++ p1 = p ++ p2-> False)) ->
                                        PrefixFree (p :: l).Inductive PrefixFree : list SplitPath -> Prop :=
| FreeNil : PrefixFree []
| FreeCons : forall (p : SplitPath) (l : list SplitPath),
               PrefixFree l ->
               (forall (p' : SplitPath), In p' l ->
                                        (forall p1 p2, p' ++ p1 = p ++ p2-> False)) ->
                                        PrefixFree (p :: l).Inductive PrefixFree : list SplitPath -> Prop :=
| FreeNil : PrefixFree []
| FreeCons : forall (p : SplitPath) (l : list SplitPath),
               PrefixFree l ->
               (forall (p' : SplitPath), In p' l ->
                                        (forall p1 p2, p' ++ p1 = p ++ p2-> False)) ->
                                        PrefixFree (p :: l).

Lemma prefixFreeEmpty : forall l, PrefixFree ([] :: l) -> l = [].