Nicolas Sceaux <nicolas.sce...@gmail.com> writes: > Le 9 févr. 2010 à 21:32, David Kastrup a écrit : > >> If you really must, you should probably use make-procedure-with-setter >> in order to be able to use >> >> (define (engraver-method engraver 'initialize) ... > > According to: > > > <http://www.gnu.org/software/guile/manual/html_node/Adding-or-Setting-Alist-Entries.html> > > "The only safe way to update an association list variable when adding or > replacing an entry like this is to set! the variable to the returned value" > > You cannot just assoc-set! an associative list. So a procedure with setter > does not help in that case (unless I've misunderstood something).
Well, there are several ways to address this problem. But the most obvious one is that a Scheme engraver may contain an association list, and currently may be specified as one in a list of engravers, but should itself be a recognizable data structure, even if it just means that its associations start with a known car, like '(engraver (initialize . ... or '((type . engraver) (... One reason is that it has to be identifiable by ly:translator?. But personally, I'd make it a separate data structure internally containing either the association list, or a number of fields that are initialized from such an association list. _If_ we want to support the current syntactic entry of anonymous engravers. Which I don't necessarily consider a good idea. It might be preferable for an anonymous form to look like (make-engraver #:initialize (lambda () ...) #:finalize ...) since that saves the programmer the bother of messing with quoting. -- David Kastrup _______________________________________________ lilypond-devel mailing list lilypond-devel@gnu.org http://lists.gnu.org/mailman/listinfo/lilypond-devel
