It's hard to improve on a 20 line Awk program for generating text but I thought it would be fun to investigate a Haskell solution.

Why can't I cons an element onto an existing list?

Michael

Prelude Data.List Data.Map> insertWith (:) ("Moby", "Dick") "will" (fromList [(("Joe", "Blow"),["is"]), (("Moby", "Dick"),["may"])])

<interactive>:1:11:

    Occurs check: cannot construct the infinite type: a = [a]

      Expected type: a

      Inferred type: [a]

    In the first argument of `insertWith', namely `(:)'

    In the expression:

        insertWith

          (:)

          ("Moby", "Dick")

          "will"

          (fromList [(("Joe", "Blow"), ["is"]), (("Moby", "Dick"), ["may"])])

Prelude Data.List Data.Map>