On Sunday 07 January 2007 04:55, [EMAIL PROTECTED] wrote:
> > > > . . . Note also that the tupletSequence
> > > > function would be implemented entirely in Scheme . . .
>
> I'm not very fluent in Scheme, so this is a naive question.
>
> I presume that ratios like 3:2 (or 2/3) could be made into some kind of
> object type (possibly a "moment"). So I could imagine that it would be
> possible to write a Scheme function definition to cover a syntax like
>
> \tupletSequence m:n #'( {...} {...} ... )
>
> where the first argument is a moment and the second is a list of literal
> music expressions. (And I suppose I'm too optimistic about that syntax;
> probably those {...} would have to be sprinkled with # or $ or other
> spices.) But there are some questions:
>
> 1) I don't see how this could accommodate the case where one of the music
> expressions *were* a variable reference (\var) or *contained* a variable
> reference.
Music functions are not macros; the arguments are evaluated before the
function is called. So \var always means to dereference a variable.
(I'm working on a system for 'music macros', which should make it possible to
delay the dereferencing of variables, this will mainly be useful to clean up
\relative)
> 2) Because the syntax \tupletSequence m:n { {...} {...} }
> is "nicer", it would be good if it could be written that way, but then the
> second argument would not be a standard Scheme entity, so I don't see how
> Scheme could handle it at all.
There is a distinction between Scheme functions and Music functions. Music
functions are invoked as \function arg1 arg2, while Scheme functions are
invoked in Scheme expressions, as #(function arg1 arg2). tupletSequence would
be a music function.
There are three types of arguments to music functions: Music, Markup and
Scheme. This suggestion would add another argument type 'fraction'. The
parser takes care of identifying argument types. Music arguments are notated
as music, so you can use {{c}{d}} syntax out-of-the-box. E.g., partcombine is
a music function.
In Scheme functions, you can use the #{ #} syntax to easily create music
expressions as arguments.
> Can tupletSequence really be defined in pure Scheme, as long as the parser
> is modified to recognize the object m:n or n/m (so that there would exist
> a type-verification-name for the object m:n for use in defining Scheme
> functions)?
yes, the only thing we need is a new parameter type.
BTW, one of the biggest problems (IMHO) in the lilypond language is that we
can't extend the parser to accept durations as parameters to music functions:
\foo c 4. is ambiguous; it's unclear whether the 4. is the c's duration, or
if it's a separate argument.
--
Erik
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