Re: for-each?

[David Kastrup]

Jean Abou Samra <jean@abou-samra.fr> writes:

> Le dimanche 02 juillet 2023 à 15:05 -0400, Pierre-Luc Gauthier a écrit :
>
>> How can I go about using for-each in this example for the group function to 
>> accept an arbitrary number of parts ?
>
>
> You can't — for-each is not the right tool for this. for-each is a purely 
> imperative tool: it runs the same operation on each element of a list, and 
> discards the result. What you actually want is called list splicing:
>
>
> ```
> \version "2.25.6"
>
> parts = #(list
>           #{ {c'} #}
>           #{ {d'} #}
>           #{ {e'} #}
>           #{ {f'} #} )
>
> group =
> #(define-music-function
>   (parts) (list?)
>   #{\new StaffGroup << #@parts >>#})
>
> \group \parts
> ```

That has an awkward look.  I'd rather use

```
\version "2.25.6"

parts = {
          {c'}
          {d'}
          {e'}
          {f'}
        }

group =
#(define-music-function
  (parts) (ly:music?)
  #{\new StaffGroup << #@(ly:music-property parts 'elements) >>#})

\group \parts
```

-- 
David Kastrup