[Lilypond-auto] Issue 3799 in lilypond: Avoid macro at top-level in ly/satb.ly

[lilypond]

Status: Accepted
Owner: tdanielsmusic
CC: address@hidden,  address@hidden
Labels: Type-Defect

New issue 3799 by tdanielsmusic: Avoid macro at top-level in ly/satb.ly
http://code.google.com/p/lilypond/issues/detail?id=3799


[Description paraphrased from discussion between
Devon Schudy and David Kastrop here:
https://codereview.appspot.com/41990043/ ]

The use of a macro at top level in ly/satb.ly to determine
whether a variable is defined or not is not good practice.
Furthermore, this technique will not work in Guile 2.0.

David suggested instead

"How about
define-variables =
#(define-void-function (parser location syms) (symbol-list?)
    (for-each
       (lambda (sym)
         (if (null? (ly:parser-lookup parser sym))
             (ly:parser-define parser sym *unspecified*)))))

"If you write \name for a variable with value *unspecified*, it simply
disappears in the lexer."

Trevor




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