Issue #768: Chord repetition shortcut

Issue #768: Chord repetition shortcut

In the lexer, add a chord repetition state, holding the repetition
symbol (like note names, but for chord repetition), the repetition
function used to copy the previous chord, and a slot to save the
previous chord.  Use the repetition symbol to detect a chord
repetition when lexing.

In the parser, when a note chord is found, save it (it becomes
previous chord).  When a chord repetition token is found, make a chord
using the repetition function and the previous chord.

The repetition symbol and function are initialized in
ly/chord-repetition-init.ly. The repetition symbol defaults to `q' (as
quote or qord -- as suggested by Werner). The function copies the
pitches, but not articulations.

[nicolas.sceaux, 2009-11-11 19:12:55]

Hi,

Here is a patch adding the chord repetition functionality that has been
discussed a few times.

I've defined arbitrary defaults: see ly/chord-repetition-init.ly

For some reason, ly-syntax-constructor.scm was not uploaded

--- a/scm/ly-syntax-constructors.scm
+++ b/scm/ly-syntax-constructors.scm
@@ -131,6 +131,11 @@
 	      'duration duration
 	      'origin location))
 
+(define-ly-syntax (repetition-chord parser location previous-chord
repetition-function duration articulations)
+  (let ((new-chord (repetition-function previous-chord duration
articulations)))
+    (set! (ly:music-property new-chord 'origin) location)
+    new-chord))
+
 (define-ly-syntax-simple (context-specification type id mus ops create-new)
   (let* ((type-sym (if (symbol? type) type (string->symbol type)))
 	 (csm (context-spec-music mus type-sym id)))

[Carl, 2009-11-12 21:40:37]

Nicolas,

It looks great!  Thanks.

I have just a couple of suggestions for changes to the documentation,  and a
question about the init file.

Thanks,

Carl

http://codereview.appspot.com/154056/diff/1/2
File Documentation/notation/simultaneous.itely (right):

http://codereview.appspot.com/154056/diff/1/2#newcode91
Documentation/notation/simultaneous.itely:91: Like in the case of regular
chords, the chord repetition symbol can be
"As" instead of "Like"

http://codereview.appspot.com/154056/diff/1/2#newcode97
Documentation/notation/simultaneous.itely:97: 
Should there be a statement here that only the notes are duplicated?

http://codereview.appspot.com/154056/diff/1/10
File ly/chord-repetition-init.ly (right):

http://codereview.appspot.com/154056/diff/1/10#newcode1
ly/chord-repetition-init.ly:1: \version "2.13.8"
Just a question.  Why do this in a .ly file instead of in a .scm file?

[nicolas.sceaux, 2009-11-13 17:43:17]

On 2009/11/12 21:40:37, Carl wrote:

> http://codereview.appspot.com/154056/diff/1/10#newcode1
> ly/chord-repetition-init.ly:1: \version "2.13.8"
> Just a question.  Why do this in a .ly file instead of in a .scm file?

This initializes the parser object, and thus shall be placed in a .ly file,
where this object is accessible.
It is similar to language files, defining note names: this file in particular
defines the shortcut name.

I'm correcting the documentation as you suggest. Thanks for your review.

[nicolas.sceaux, 2009-11-14 10:30:37]

On 2009/11/12 21:40:37, Carl wrote:
> Nicolas,
> 
> It looks great!  Thanks.
> 
> I have just a couple of suggestions for changes to the documentation

I've addressed your remarks concerning documentation in a new patch

  <http://codereview.appspot.com/154056>