Re: Scheme for rhythmic transposition

[Phil Holmes]

----- Original Message ----- 
From: "David Kastrup" <address@hidden>
To: <address@hidden>
Sent: Friday, November 18, 2011 9:14 PM
Subject: Re: Scheme for rhythmic transposition


> James <address@hidden> writes:
>
> > hello,
> >
> > On 18 November 2011 19:38, Adam Good <address@hidden> wrote:
> > > Hi All,
> > > A few years ago I believe a Lilypond user offered some Scheme code to
> > > give transposed rhythms, for example to transpose every rhythmic value
> > > to print half of its entered duration. It was awesome and nifty and
> > > would be very useful to me at this moment :)
> > >
> > > I've searched high and low in the archives and online! Embarrassed to
> > > say I can't find it. Nor am I slick enough to code something like this
> > > on my own.
> > >
> > > If anyone has any leads please let me know.
> >
> >
> > http://lsr.dsi.unimi.it/LSR/Item?id=305
>
> Can we retire this snippet?  It unnecessarily calls ly:music-deep-copy
> and it would be much simpler to use the readily available function
> \shiftDurations for this.
>
> --
> David Kastrup


\shiftDurations seems to be remaining poorly documented.  I'd be happy to 
update the LSR with that function rather than the way it is now, but it 
seems to me that durations can only be made shorter, not longer?  If I use:

   \shiftDurations 1 0 { \music }

all is OK.  However, with

   \shiftDurations -1 0 { \music }

I get:

ShiftDur.ly:11:20: error: wrong type for argument 1.  Expecting integer, 
found #<Prob: Music C++: Music((digit . 1) (origin . #<location 
ShiftDur.ly:11:21>))((display-methods #<procedure #f (event parser)>) (name 
. FingeringEvent) (types general-music fingering-event event)) >

   \shiftDurations
                   -1 0 { \music }

Is this the correct usage, and does this mean that \shiftDurations does only 
shorted music?

--
Phil Holmes