Re: book-predicate

[Jan-Peter Voigt]

On 02.03.2012 10:30, David Kastrup wrote:
> Jan-Peter Voigt<address@hidden>  writes:
>
> > Hello David, hello lists,
> >
> > now, when we have a book-predicate, we are dealing with books in
> > scheme. And then we might want to set a header after creating a book.
> > There is a function ly:score-set-header!, which I copied and adapted
> > for the Book-class.
> > This patch compiled and works with the following snippet.
> >
> > --snip--
> > \version "2.15.32"
> >
> > bk = \book {
> >    \score {
> >      \relative c' {
> >        c4 e g b
> >      }
> >    }
> > }
> >
> > #(let ((bh (eval-string "(define-module (a b))")))
> >       (eval '(define title "Hallo") bh)
> >       (ly:book-set-header! bk bh))
> "eval-string" is not exactly what I call "in Scheme".
>
> > \book { \bk }
> > --snip--
> >
> > Is this helpful for lily-devel?
> > And is there another (better) way of creating a module (for header
> > generation) on the fly in scheme?
> make-module would be obvious.
But if you try a (eval '(define title "Titel") (make-module)) it fails 
with "Unbound variable: define"?
> But you could write the above just as
>
> bk = \book {
>    \score {
>      \relative c' {
>        c4 e g b
>      }
>    }
> }
>
> #(define bk #{ \book { \bk \header { title = "Hallo" } } #})
>
> \book { \bk }
>
> It is a bit of cheating since it works on a copy of the book, but not
> all that much.
Yes, that would work, but if I have a function (set-book-headers! book 
head-a-list) I want to modify the header of the actual book.
I am working on my methods to create books with common style but without 
too much copy&paste.

Thanks for your answer and have nice weekend!
Cheers,
Jan-Peter