Re: Tuplets and cross-staff beams

[Malte Meyn]

Am 11.09.2017 um 14:22 schrieb Samuel Cederlund:
> Hello all,
> I have a piece of code that causes lilypond to say Drawing systems...lilypond: 
> ../flower/include/drul-array.hh:35: T& Drul_array<T>::at(Direction) [with T = 
> double]: Assertion `d == 1 || d == -1' failed.
> the code is as follows:
>    \tuplet 3/2 4 {
>      <b b'>8 { \change Staff = "upper" } cess'''8[ b] ass e ess d
>      { \change Staff = "lower" }
>      cess b ass e ess }
>
> in the left hand of of the piano staff. The right hand has the same notes but 
> one octave higher. Appreciate any help,greetings
> Samuel

This looks like LilyPond isn’t able to decide whether a certain grob 
(for example, a beam or a slur) has to be placed up or down, but I 
cannot say more because I cannot reproduce this error.

Please give a complete, compilable, but small/minimal example of your 
code that contains a \version statement so we know which LilyPond 
version you are using. At least the definition of the staves "upper" and 
"lower" and a \language statement are missing to reproduce this error.