On 4/14/11 1:47 AM, "Graham Percival" <gra...@percival-music.ca> wrote:
> How do you get values from a context property? I'm trying to access
> the left-bound text. I know I can do it like this:
> (cdr (car (cdr (car (cdr (car (car (ly:context-property context
> 'TextSpanner)))))))))))
> but that's kind-of ugly.
Yes, it is. At the very least, you should use things like (caar x) which is
equal to (car (car x)).
>
> This code:
>
> #(define (format-textspan engraver event)
> (let* ((context (ly:translator-context engraver))
> (moment (ly:context-current-moment context)))
> (display "\n")
> (display
> (ly:context-property context 'TextSpanner)
> )
> ))
>
>
> produces the following (with linebreaks and indents added). I'm
> really confused about the multiple "bound-details", the multiple
> "left/right" inside each bound-details, etc. How can I make sure I
> get the bound-details that I want, without using plain old (car ...) ?
>
The correct bound-details is the first one (overrides are prepended; the old
values are not removed).
The proper way to do it is something like
(let* ((spanner-props (ly:context-property context 'TextSpanner))
(details (assoc-get 'bound-details spanner-props '()))
(left-props (assoc-get 'left details left-props '()))
(left-text (assoc-get 'text left-props '())))
(display left-text))
We try never to use the structure to get things; we always try to use the
associated keys.
HTH,
Carl
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