Re: A question about a scheme function with two input notes

[Jean Abou Samra]

Le 30/12/2022 à 00:12, Alasdair McAndrew a écrit :
> Hello,
>
> I am typesetting some late Renaissance, early Baroque music for which 
> a double stop (= chord with two notes) on a stringed instrument would 
> be notated with the stem of the top note up and the stem of the lower 
> note down.  So instead of using the standard notation
>
> <a e>4
>
> for a double stop, I am using
>
> << {a4} \\ {e4} >>
>
> This is convenient as most of the music is with single notes, so I 
> just bung in one of these when I need to.
>
> And I thought I'd be clever by writing this into a little Scheme function:
>
> dStop =
> #(define-music-function
>      (topnote bottomnote)
>      (ly:music? ly:music?)
>    #{
>     << {#topnote} \\ {#bottomnote} >>


Try adding spaces here:

<< { #topnote } \\ { #bottomnote } >>

Scheme is very lax about what can happen in identifiers. It mostly 
separates elements by spaces. Therefore, if you write no space between 
'#topnote' and '}', Scheme sees a reference to a variable called 
'topnote}', which is the meaning of the error message

Unbound variable: #{topnote\x7d;}#

Best,

Jean

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