Re: Combining multiple \tags?

[Nicolas Sceaux]

"Panteck" <address@hidden> writes:

> I've got three sets of tags ( letter/a4/bigprint, part/score, and
> original/edit ).  What I want to do is something like \keepWithTag
> #'letter #'part #'edit, but \keepWithTag doesn't take multiple values,
> and \keepWithTag #'value1{ \keepWithTag #'value2 } doesn't work,
> because the inner \keep strips out all the other tags.
>
> Has anyone else ever attempted to do something like this?  Is there a
> better way of doing what I'm after?
>
> Thanks!

I use the following (maybe there's something already available in
LilyPond that I've missed):

#(use-modules (srfi srfi-1))
#(define* (has-some-member? list1 list2 #:key (test eqv?))
   "Return a true value iif there exists an element of list1 that also 
belongs to list2 under test."
   (if (null? list1)
       #f
       (or (member (car list1) list2 test)
           (has-some-member? (cdr list1) list2 #:test test))))

#(define (symbol-or-symbols? x)
   (or (null? x)
       (symbol? x)
       (and (list? x) (every symbol? x))))

keepWithTags =
#(define-music-function (parser location tags music)
                        (symbol-or-symbols? ly:music?)
   (music-filter
    (lambda (m)
      (let ((m.tags (ly:music-property m 'tags)))
        (cond ((symbol? tags)
               (or (null? m.tags) (memq tags m.tags)))
              ((null? tags)
               (null? m.tags))
              ((list? tags)
               (or (null? m.tags) (has-some-member? tags m.tags)))
              (else #t))))
    music))

\keepWithTags #'foo \music
--> same as \keepWithTag #'foo \music

\keepWithTags #'(foo baz) \music
--> keep elements tagged with foo or baz, and elements not tagged

\keepWithTags #'() \music
--> keep elements not tagged.

nicolas