proposition: Lemma refine_pick_val A a (P : A -> Prop) : P a -> @refine A ({x | P x })%comp (ret a).
proof: Proof. t_refine. Qed.
imports: Coq.Strings.String Coq.Sets.Ensembles Coq.Bool.Bool Fiat.Common Fiat.Common.BoolFacts Fiat.Common.LogicFacts Fiat.Computation.Core Fiat.Computation.Monad Fiat.Computation.SetoidMorphisms Fiat.Computation.Refinements.Tactics