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Re: Generating music from a list of identifiers


From: Trevor Daniels
Subject: Re: Generating music from a list of identifiers
Date: Wed, 1 Apr 2015 21:27:40 +0100

David Kastrup wrote Wednesday, April 01, 2015 8:36 PM


> "Trevor Daniels" <address@hidden> writes:
>
>> I'm struggling to find how to do the following:
>>
>> I have a list of the identifiers of variables which contain either music or 
>> #f and I'd like to generate the parallel music of all of them which contain 
>> music.  I can do this by listing the identifiers explicitly, like this:
>>
>> AllMusic = <<
>>   #(if DescantMusic DescantMusic)
>>   #(if SopranoMusic SopranoMusic)
>>   ...
>>   #(if PianoLHMusic PianoLHMusic)
>>>>
>>
>> But I'd like to do the same thing without listing each one explicitly, using 
>> a list like this, which is generated algorithmically:
>>
>> #(define AllMusicNames
>>    (list
>>      "DescantMusic"
>>      "SopranoMusic"
>>      ...
>>      "PianoLHMusic"))
> 
> Untested:
> 
> #(simultaneous-music
>  (filter ly:music?
>    (map (lambda (x) (ly:parser-lookup parser x))
>      (map string->symbol AllMusicNames))))

Thanks David.  I must be gaining some small facility
with Scheme now, as I can understand this immediately
and appreciate its elegance!  It was using
simultaneous-music that was escaping me, so thanks to
you (and Jan-Peter) for pointing that out to me.

Trevor

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