Re: scheme night-mare...

[Arno Waschk]

On Sun, 11 Jul 2010 20:08:10 +0200, Neil Puttock <address@hidden>  
wrote:

> On 11 July 2010 15:52, Arno Waschk <address@hidden> wrote:
>
> > How do i use this in a c line?
>
> Look up the procedure:
>
> SCM proc = ly_lily_module_constant ("map-alist-keys");
>
> Call the procedure, using scm_call_2:
>
> SCM result = scm_call_2 (proc, arg1, arg2);
>
> > > Your question isn't really about converting from scheme to c++, it's
> > > really
> > > about getting all of the keys and/or properties from an alist.  That's  
> > > not
> > > built into scheme.
> >
> > No, it is about easily accessing information buried into some scheme
> > structures by some little c code.
> > As long this is not possible, this information is next to encrypted for  
> > me.
>
> Why do you need to do this in C/C++ though?
>
> If you're running a .ly file, this information's easily available via
> ly:grob-alist-chain:
>
> \relative c' {
>   \override Staff.KeySignature #'after-line-breaking =
>   #(lambda (grob)
>      (for-each (lambda (lst title)
>                  (display (format #f "~a:\n" title))
>                  (for-each (lambda (entry)
>                              (display (format #f " ~a\n" (car entry))))
>                            lst)
>                   (newline))
>       (ly:grob-alist-chain grob '()) '("mutable" "immutable")))
>   \key a \major
>   a1
> }
>
> Cheers,
> Neil

Thanks for your explanations!
My main reason for all this is not to do something on the .ly file level  
(at least not for now) but for learning what is going on on the c++ level,  
including searching for hints onto my theory that lilypond's processing  
times grow far more quadratically than i would believe to be necessary (or  
to prove myself wrong, who knows??

Anyway, i came to a point where it seems very helpful to provide an easy  
option to print somehow the actual content of e. g. a grob at a certain  
point in the c++ code, or easily do some other voodoo to it, which i do  
not know yet...
Where dealing with types including the letters S C M proves to be pure  
horror. Or maybe it is my not-knowledge of those languages? I am musician  
after all...
So i am looking for something fool-proof leading to something easily  
printable (vulgo: string or the like) and not something hidden within a  
scheme type labyrinth which i need to translate into a scheme type to call  
it to have a scheme type result which maybe can or cannot converted into  
something which might be a scheme type which can be translated into  
something c++ might be able to convert,.... you got the point....?


But thank you a lot for your help!

Cheers, Arno


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