fact: Definition prod_pred {A B : Type} (PA : A -> Prop) (PB : B -> Prop) : A * B -> Prop := fun '(a,b) => PA a /\ PB b.
imports: Coq(RelationClasses) ExtLib(Structures.Functor Structures.Monad Data.Monads.StateMonad Data.Monads.ReaderMonad Data.Monads.OptionMonad Data.Monads.EitherMonad)