Re: still: beaming

[Erik Sandberg]

On Tuesday 23 March 2004 11.23, Joerg Anders wrote:
> Hi!
>
> I learned a lot about beaming from "scm/auto-beam.scm"
>
> But I'm not quite sure about the "begin" function.
>
> What exactly means:
>
> (begin 1 16 3 8) . ,(ly:make-moment 1 8)
>
> If I comprehend all right: In a 3/8 measure if there
> is a 16th note starting at 1st, 2nd or 3rd beat (means 8th in
> this case), this 16th note is the starting point of a beam.
>
> Thus
>
>         |\   |\   |\   |\   |\
>         | \  |\\  |\\  |\\  |\\
>         |
>         |    | \  | \  | \  | \
>
>         /    /    /    /    /
>
> Should be beamed:
>         |\   |----|----|----|
>         | \  |----|----|----|
>
>         /    /    /    /    /
>
> But LilyPond computes:
>         |----|----|----|----|
>         |
>         |    |----|----|----|
>
>         /    /    /    /    /
>
> A bug or a misunderstanding ?
> Or is it a conflict with another rule ? Perhaps:
>
> (end * * 3 8) . ,(ly:make-moment 3 8)
>
> But this rule has wildcards? Or has "end" higher
> priority than "begin" ?

My understanding is that 'begin' describes where a beam can begin, 'end' 
describes a place where it can end.

And beams are started as soon as they can be started, and ended as soon as 
they can be ended. So, it does not help that a new beam can be started at 2/8 
if it cannot be ended at 1/8. You'll have to add a rule like
(end 1 8 3 8) . (ly:make-moment 1 8)
though this probably will give some undesired results as well

erik.