Re: scheme problem in lilypond

[Michael Vanier]

> Cc: address@hidden
> Content-Type: text/plain; charset=us-ascii
> Date: Fri, 19 Jan 2001 13:18:02 +0100
> From: Mats Bengtsson <address@hidden>
> 
> > Hi,
> > 
> > I was wondering why this fails in a lilypond file:
> > 
> > (define speed 60)
> > 
> > ...
> > 
> > \midi { 
> >     \tempo 4 = #speed 
> > }
> > 
> > 
> > I get this:
> > 
> > foo.ly:95:0: error: parse error, expecting `DIGIT' or `NUMBER_IDENTIFIER' 
> > or `UNSIGNED' or `REAL':
> > 
> > 
> > I can define and substitute strings with no problem, so why not numbers?
> > Is there a workaround?
> 
> In the current Lilypond grammar (as defined by lily/parser.yy), 
> the argument to the \tempo command bust be an unsigned integer
> and cannot be specified by a Scheme value. The same holds for, 
> for example, note durations. I agree that this may seem inconsistent
> with the use of strings in the grammar. Why do you want to 
> specify it in Scheme? If you wish, you could define a Lilypond 
> identifier and use as the argument, though:
> 
> speed = 60;
> 
> \midi { 
>     \tempo 4 = \speed
> }
> 
>      /Mats
> 
> 
> 

I'm using scheme definitions to specify a metronome marking like this:

    #(define note 
       '(rows (music "noteheads-2" ((kern . -0.1) "flags-stem"))))
    #(define speed 60)
    #(define speed-string `(string-append " = " ,(number->string 60)))

    % Later, at the beginning of the notes:

    c4^#`(rows ,note ,speed-string)

    % Later still, for midi:

        \midi {
            \tempo 4 = 60
    }

So even if I define \speed as you say, I still have the problem of getting
it into the metronome marking, which amounts to a way to convert scheme
variables into lilypond variables.  Is there a function/macro that does
this?

Slightly off-topic, I'm glad to see lilypond becoming more and more
scheme-ified.  Ultimately I think I would like it if most declarations
could be made in scheme e.g.

    #(key c major)  % instead of "\key c \major;"
        #(midi (tempo 4 60))

etc., although I like the current note syntax the way it is.  Defining a
clean syntax for music notation is clearly non-trivial.

Cheers,

Mike