fact: Definition cat (a b : showM) : showM := fun _ i m => monoid_plus m (a _ i m) (b _ i m).
imports: Coq.Strings.String Coq.Program.Wf Coq.PArith.BinPos Coq.ZArith.ZArith ExtLib.Structures.Monoid ExtLib.Structures.Reducible ExtLib.Programming.Injection ExtLib.Data.Char ExtLib.Data.String ExtLib.Data.Fun ExtLib.Core.RelDec