Re: book-predicate

[David Kastrup]

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 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.

-- 
David Kastrup