fact: Definition mapWriterT (f: m (pprod A W) -> n (pprod B W')) : writerT Monoid_W m A -> writerT Monoid_W' n B := mkWriterT Monoid_W' ∘ f ∘ runWriterT.
imports: ExtLib.Structures.Monads ExtLib.Structures.Monoid ExtLib.Data.PPair ExtLib.Data.Monads.IdentityMonad Coq.Program.Basics