Re: aligning variables with upbeats

[智樂喬]

Thanks, Pedro, this is some interesting code! There's definitely something for me to learn here.

On Wed, Feb 13, 2019 at 4:13 AM Pedro Pessoa <address@hidden> wrote:

Hello John,
I took this task as a way of learning a bit more about moments and durations
(and also, I wanted to achieve this a while ago). It is certainly not a very
robust or elegant solution, but seems to work for this particular case.

%% \makeRestOfLenght \mus "rest/skip" upbeat %%

\version "2.19.82"
partA = { c'2 b | R1*3 }
partB = { \partial 4 g4 | \bar "||"  c'1 }

#(define (make-dynamic-rest len event)
   "The rest/skip body."
   (make-music
    event ; To choose if it is gonna be Skip or Rest
    'duration
    ; intlog transforms the rational values used in Moments (the
denominator) into log values used in Durations.
    ; 1 (whole)->0
    ; 2 (half)->1
    ; 4 (quarter)->2 ... etc
    (ly:make-duration (ly:intlog2 len))))

#(define (makeRestofLog num den opts)
   "Logging function"
   (display (format "~%>> \\makeRestOfLenght:~%~A ~As of value ~A will be
created:~%" num opts den)))

makeRestOfLenght=
#(define-scheme-function (mus opts upbeat)(ly:music? string? ly:music?)
   "Creates a series of rests/skips of the same length as the given music
minus an upbeat value. Opts are 'rest', 'skip'. Anything else calls 'rest'."
   (let* ((musLen (ly:music-length mus));
           (upBeatLen (ly:music-length upbeat))
           (musMinusUp (ly:moment-sub musLen upBeatLen))
           (den (ly:moment-main-denominator musMinusUp))
           (num (ly:moment-main-numerator musMinusUp))
           (event (cond
                   ((string>= opts "skip")
                    'SkipEvent)
                   ((string>= opts "rest")
                    'RestEvent)
                   (else
                    (set! opts "rest")
                    'RestEvent)
                   ))
           (rests '()))
     (makeRestofLog num den opts) ; Didatic logging.

     ; Iterate over the number of rest needed (given by the numerator).
     ; The value of the rest is given by the denominator.
     (let loop ((i 0))
       (if (< i num)
           (begin
            (set! rests (append rests (list (make-dynamic-rest den event))))
            (loop (+ i 1)))))
     (newline)
     (make-music
      'SequentialMusic
      'elements
      rests)
     ))

\score {
  \new Staff <<
    \new Voice \partA
    \new Voice {
      % \makeRestOfLenght \partA "rest" 4 % To visualize rests.
      \makeRestOfLenght \partA "skip" 4
      \partB
    }
  >>
}





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