I'm continuing to work on this music layout problem, and I'm trying another angle. A page of music is made of many individual symbols and graphical items like lines and arcs. I decided to call a drawable symbol/item a Grapheme. so type MusicPage = [Grapheme] The program also maintains the more fundamental description of music in conceptual form---that is, notes, chords, time signatures, tempo indications, etc. I decided to call bits of information about music Datemes. type MusicScore = [Dateme] A function to lay out a musical page would have this signature: layoutPage :: [Dateme] -> [Grapheme] Now let's think about the structure of a page of music for a moment. It's made of *systems*, which are groups of notes read from left to right. A page consists of a number of systems stacked vertically (like a page of text has lines of text stacked vertically). The layout algorithm will fit as many systems as it can into a page. When it runs out of space, it will stop (even if there are Dateme left). A layout algorithm in imperative pseudocode would look something like: - initialize the list remainingDateme to the input list of Dateme - loop - looking at the list of remainingDateme, make a system - try to fit the system to the page - if the system doesn't fit, break out of the loop - add the system to the page - drop the used Dateme from remainingDateme - if remainingDateme is empty, break out of the loop - go to top of loop I tried to write this in Haskell, and it seem awkward. It would be something like: -- layout page, produce list of Grapheme and also list of -- unused Dateme layoutPage :: PageDimensions -> [Dateme] -> ( [Grapheme], [Dateme] ) layoutPage dim dateme = layoutPage' dim [] dateme layoutPage' :: PageDimensions -> [Grapheme] -> [Dateme] -> ( [Grapheme], [Dateme] ) layoutPage' dim graphemeSoFar [] = ( graphemeSoFar, [] ) layoutPage' dim graphemeSoFar remainingDateme = let ( newGrapheme, remainingDateme', dim' ) = layoutSystem dim remainingDateme in if null newGrapheme then ( graphemeSoFar, remainingDateme ) else layoutPage' dim' (graphemeSoFar ++ newGrapheme) remainingDateme' We assume this is defined elsewhere: -- layoutSystem takes as input the current page dimensions (think of -- the "current page dimensions" as the room *remaining* on the page), -- and a list of Dateme, and returns the triple: -- ( [Grapheme] for the new system, or null list if no additional system -- can fit on the page, -- remaining [Dateme] that are not consumed, -- new page dimensions ) layoutSystem :: PageDimensions -> [Dateme] -> ( [Grapheme], [Dateme], PageDimensions )