Carl Sorensen <c_soren...@byu.edu> writes:
> On 12/26/11 12:50 PM, "David Kastrup" <d...@gnu.org> wrote:
>>
>>Actually, what about the following rather minimalistic approach?
>>#(define-macro (make-engraver . translist)
>> (define (make-lambdas translist)
>> `(list
>> ,@(map (lambda (x)
>> (if (pair? (car x))
>> `(cons ',(caar x) (lambda ,(cdar x) ,@(cdr x)))
>> `(cons ',(car x) ,(make-lambdas (cdr x)))))
>> translist)))
>> (make-lambdas translist))
>
> Very nice! The only think that I think ought to be added would be some
> way of storing a global status variable in the engraver, as they are
> frequently used. The status variable should be persistent between calls
> to the engraver, I think.
What's to be added? The following works as expected (including the
expected warnings...).
#(define-macro (make-engraver . translist)
(define (make-lambdas translist)
`(list
,@(map (lambda (x)
(if (pair? (car x))
`(cons ',(caar x) (lambda ,(cdar x) ,@(cdr x)))
`(cons ',(car x) ,(make-lambdas (cdr x)))))
translist)))
(make-lambdas translist))
\header {
texidoc = "Scheme engravers may be instantiated, with
instance-scoped slots, by defining a 1 argument procedure which
shall return the engraver definition as an alist, with the private
slots defined in a closure. The argument procedure argument is the
context where the engraver is instantiated."
}
\version "2.14.0"
\layout {
\context {
\Voice
\consists
#(let ((instance-counter 0))
(lambda (context)
(set! instance-counter (1+ instance-counter))
(let ((instance-id instance-counter)
(private-note-counter 0))
(make-engraver
(listeners
((note-event engraver event)
(set! private-note-counter (1+ private-note-counter))
(let ((text (ly:engraver-make-grob engraver 'TextScript event)))
(ly:grob-set-property! text 'text
(format #f "~a.~a" instance-id
private-note-counter)))))))))
}
}
<<
\relative c'' { c4 d e f }
\\ \relative c' { c4 d e f }
>>
--
David Kastrup
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