Re: Minor variations on a re-used section

[Aaron Hill]

On 2019-06-22 1:46 pm, Evan Driscoll wrote:
> Originally I was going to say that would work well in many cases if I 
> have
> a music variable, but I don't know how to use them in the context of
> \repeat unfold, which I very much prefer when applicable(*).
>
> But I realized that I could write something that helps here. Any 
> thoughts
> on the following? Am I missing something that means I don't have to do 
> this?
>     \version "2.19.80"
>
>     fancy_repeat_unfold =
>       #(define-music-function
>         (parser location rep_spec notes)
>         (integer? ly:music?)
>         #{
>           \removeWithTag #'last_rep  $notes
>           \removeWithTag #'(first_rep last_rep)
>               \repeat unfold #(- rep_spec 2) $notes
>           \removeWithTag #'first_rep $notes
>         #})
>
>     \relative c' {
>       \fancy_repeat_unfold 3 {
>         c1
>         d-\tag #'first_rep \ff
>         e-\tag #'last_rep \p
>         f
>       }
>     }

I would opt for a design like this which is more flexible w.r.t. the 
naming and number of tags to be used:

%%%%
\version "2.19.82"

#(define (multipleWithTagHelper proc)
  (define (symbol-list-list? x)
    (and (list? x) (every symbol-list? x)))
  (define-music-function (tags music) (symbol-list-list? ly:music?)
    #{ $@(map (lambda (x) #{ $proc $x $music #}) tags) #} ))

multipleKeepWithTag = #(multipleWithTagHelper keepWithTag)
multipleRemoveWithTag = #(multipleWithTagHelper removeWithTag)

{
  \multipleKeepWithTag #'((a) (a b) (b))
  { \tag #'a a'4 \tag #'b b'4 c''4 }
  \multipleRemoveWithTag #'((a) (a b) (b))
  { \tag #'a a'4 \tag #'b b'4 c''4 }
}
%%%%


-- Aaron Hill