Werner LEMBERG <w...@gnu.org> writes: >> If I break down the example I listed before, here are a few >> useful ways of applying it: > > This is much easier to understand, thanks. However: > >> ; this $@ produces elements for a sequential music list via map!. Each >> ; element is constructed from p, a list of pitches making up a chord, >> ; and from d, which is a list first containing a duration followed by >> ; _optional_ articulations, so $@d actually can return several tokens of >> ; _different_ type. > > here I would still like to have an elementary example how mapping > works, something like > > In general, mapping a procedure over lists create a new list, for > example > > (map! + '(1 2 3) '(4 5 6)) => (5 7 9)
You must not! not! not! use map! on constant lists. It may only be used on lists that are freshly consed together for each use. For tutorial use, one would likely use map instead of map! even in my example (and append-reverse rather than reverse!) in order not to have to explain the fine points of destructive list operators. I was not suggesting putting this thing into the Scheme tutorial. It is far too complex. I was merely posting a more advanced Scheme example to the list to give others (who don't really need the tutorial for working with Scheme) a good idea what $@ can be useful for. So that they can come up with better documentation for putting in the tutorial (or elsewhere) than I did. I am really bad at writing nice documentation at the correct level. -- David Kastrup _______________________________________________ lilypond-devel mailing list lilypond-devel@gnu.org https://lists.gnu.org/mailman/listinfo/lilypond-devel
