Definition coin_flips (n : nat) : dist (list bool) :=
  constm_list coin_flip n.

(* Specifications: *)
Lemma coin_flips_length (n : nat): plift (fun p => length p = n) (coin_flips n).
Lemma coin_flips_length (n : nat): plift (fun p => length p = n) (coin_flips n).