I have a Haskell program that computes music compositions. A composition consists of sounds that happen at locations. A location is data type Loc. At each location is a list of chords. A chord is data type Chord. Each chord contains some chord-specific data and a list of notes. A note is data type Note.

So we have

data Note = Note ...

data Chord = Chord ChordSpecificData [Note]

type Composition = Map Loc [Chord]

I would like to write a few different functions that operate over all the notes.

The following function breaks out all the notes, tupling them with the associated Locs and Chords:

compositionToList :: Composition -> [(Loc,Chord,Note)]

The following function transforms Notes, keeping only the Just results. If a Chord gets all its notes eliminated, that Chord is removed. If a Loc has all its Chords removed, that Loc is removed from the Map.

mapNotesMaybe :: (Loc -> Chord -> Note -> Maybe Note) -> Composition

-> Composition

Any advice for concise code appreciated.

Dennis

What's a concise way of doing this?

Another useful function would be used for mapping

Dennis