-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Am Donnerstag, 14. August 2008 schrieb Carl D. Sorensen: > >> 2 - The implementation I provide is very dirty, as I said. [...] > >> and inside the function I don't know how I can increment the values for > >> the horizontal placement of the boxes in an elegant way. > > > > I think the easiest and most Scheme-like way would be to loop through the > > seven entries of the pedal list using recursive calls of a named let > > clause... In particular: > > > > (let process-pedal ((remaining-pedals initial-pedals) > > (xpos 0)) > > ; print the box for the (car remaining-pedals) > > ; > > ; now call the process-pedal loop with the cdr (unless we are > > finished) ; > > (if (not (empty? (cdr remaining-pedals))) > > (process-pedal (cdr remaining-pedals) (+ xpos width-of-this-pedal)) > > ) > > ) > > This is a nice Scheme-like way to do it. However, the problem is that you > can't just do a recursive call. You have to do a stencil-add for each > pedal. And you can't have a null list as an argument to stencil-add.
Hehe, you are right of course, but that's easily resolved in a Scheme-like fashion: simply collect the list of stencils created so far as a third variable in the let clause. And the whole let clause returns (cons final-x-pos created-stencils), so that one can then draw the horizontal line and combine all stencils for the final markup. > The key here is that you can't just return a stencil (which would be very > easy to do recursively); you need to return an add-stencil function. Or you can simply return a list of stencils, to which you add one stencil after the other. No set! required here, since I do the prepending right in the next call to the let clause. > Another way to do it, while less Scheme-like, is more straightforward. > You initialize the stencil with the first element, then do a set! for > the rest of the elements. Abelson and Sussman would have a heart attack > about doing it, but this seems to be the LilyPond way of doing it. > LilyPond is full of set! assignments. I started off like this, but then I realized how I could do it with recursion and the code got significantly easier... > However, I can see that you (Reinhold) are a better LilyPond programmer > than me, so you may know how to do it better than I do. Looking at your fret diagrams, I sincerely doubt your statement. You are definitely more versed in scheme programming than I am. I have hardly any Scheme experience (learned it only for lilypond), I simply saw some nice scheme constructs in a patch for the part-combiner that Kristof Bastiaensen sent to the list three years ago... That's my whole experience! > If I were starting from scratch, I would have only the terse format for > markups, and the list format for internal LilyPond grob calls. That's what I intended to do, too. But since internally everything is implemented with the list-based definitions, it's trivial to provide a list-based command, too. Given that harp pedals are a lot simpler than fret diagrams, it doesn't add any complexity, it simply saves one loop over the characters of the string. Cheers, Reinhold - -- - ------------------------------------------------------------------ Reinhold Kainhofer, Vienna University of Technology, Austria email: [EMAIL PROTECTED], http://reinhold.kainhofer.com/ * Financial and Actuarial Mathematics, TU Wien, http://www.fam.tuwien.ac.at/ * K Desktop Environment, http://www.kde.org, KOrganizer maintainer * Chorvereinigung "Jung-Wien", http://www.jung-wien.at/ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQFIpKjnTqjEwhXvPN0RAuF1AJ9iMbfLG+pby+vSpOAThkNSo1eFowCcCX1S rt3e7SpkMff3rU3/CMlyc1w= =YtyN -----END PGP SIGNATURE----- _______________________________________________ lilypond-user mailing list lilypond-user@gnu.org http://lists.gnu.org/mailman/listinfo/lilypond-user
