(*Join juice from all threads *)
Fixpoint join_list (ls: seq.seq res) r:=
if ls is phi::ls' then exists r', join phi r' r /\ join_list ls' r' else
app_pred emp r.  (*Or is is just [amp r]?*)
Definition join_threads (tp : thread_pool) r:= join_list (getThreadsR tp) r.

Lemma nth_error_enum : forall n m (H : (n <= m)%coq_nat) i, i < n ->
exists Hlt, nth_error (enum_from H) i = Some (@Ordinal m (n - 1 - i)%coq_nat Hlt).