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Re: music function patch

From: Han-Wen Nienhuys
Subject: Re: music function patch
Date: Mon, 18 Sep 2006 16:06:35 +0200
User-agent: Thunderbird (X11/20060913)

Erik Sandberg wrote:
On Monday 18 September 2006 12:46, Han-Wen Nienhuys wrote:
Erik Sandberg wrote:

The attached patch cleans up music functions:
- functions can have any arity, and parameters can be mixed in any way.
- implementation: A music function generates a sequence of tokens, so
e.g. a (markup? music? scm?) function generates tokens MUSIC_FUNCTION
EXPECT_SCM EXPECT_MUSIC EXPECT_MARKUP. After that it's easy to write a
grammar to parse the argument list.
- there is still a restriction on 'event functions': A function can only
be applied to a post-event or chord-element if the function has exactly
one music parameter, and if that parameter is last. If this rule is
violated, there will be confusing parser errors ("unexpected
EXPECT_MUSIC") due my implementation, but I also added an error message
which describes the problem in English.
IIRC, this patch is still pending. Can you have a look at integrating this?

BTW, would it be interesting to generalise music functions so they can return non-musics as well? It would be easy to add an extra token RETURNS_MUSIC, so lexer produces e.g.
for an identifier containing a (scm music) => music function, and
for an identifier containing a function with no parameters, returning a duration.

Yes, that would be cool.


Han-Wen Nienhuys - address@hidden -

LilyPond Software Design
 -- Code for Music Notation

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