type markup = Ital | Bold | Font of string type elt = Words of string list | Markup of markup * elt type doc = elt list let d = [ Markup (Bold, Markup (Font "Arial", Words ["Chapter";"One"])); Words ["It"; "was"; "a"; "dark"; "&"; "stormy"; "night."; "A"]; Markup (Ital, Words["shot"]); Markup (Font "Arial", Words ["rang"; "out."] ) ];; let rec chfonts (elts:doc) : doc = failwith "unimplemented";;