Re: book-predicate / mail delay

[Jan-Peter Voigt]

Hello David,

thank you for answering!
Now I know about (make-module) and (module-define! ...) - these are the 
two I was missing, while reading the guile 1.8 docs ...

So these are the set-book/score-headers! functions:
--snip--
(define-public (set-book-headers! book header)
  (let ((bookhead (ly:book-header book)))
       ; if book has no header, create one ... needs "ly:book-set-header!"
       ;(if (not bookhead) (let ((mod (make-module))) (set! bookhead 
mod) (ly:book-set-header! book bookhead)))
       (for-each (lambda (p)
                         (if (pair? p)
                             (let ((key (car p))
                                   (val (cdr p)))
                                  (module-define! bookhead key val)))) 
header)
))
(define-public (set-score-headers! score header)
  (let ((scorehead (ly:score-header score)))
       ; if score has no header, create one
       (if (list? scorehead)(let ((mod (make-module))) (set! scorehead 
mod) (ly:score-set-header! score scorehead)))
       (for-each (lambda (p)
                         (if (pair? p)
                             (let ((key (car p))
                                   (val (cdr p)))
                                  (module-define! scorehead key val)))) 
header)
))
--snip--

Another thing to mention: Thank you David, for answering so quickly ...

@GNU admins or who else is in charge:
The e-mail took quite a time to reach me, there is a lack of about 6 
hours in the received-headers. This is not a problem for me, but this 
might lead to twice-sent-posts or confusion, "why is nobody answering?"
--snip--

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--snip--

Cheers, Jan-Peter

On 04.03.2012 11:14, David Kastrup wrote:
> Jan-Peter Voigt<address@hidden>  writes:
>
> > sorry for this kind-a-basic-scheme-question(s) ... ;-)
> > How do I inject variables into an empty module?
> >
> > ...
> >
> > So AFAICS there are at least 3 different ways to create a module to
> > use in a header:
> > 1: (eval-string "(define-module (a b))")
> What's with the eval-string nonsense?  Why don't you just use
> (define-module (a b)) instead?
because: "define-module can only be used at the top level"
> > 2: (ly:book-header #{ \book { \header { } } #})
> > 3: (make-module)
> >
> > The first two are some kind of cheating, but create modules, where I
> > can inject my vars using
> > (eval `(define ,key (quote ,val)) bookhead)
> >
> > I would prefer the 3rd one, if I knew, how to inject the vars inside
> > the empty module.
> (module-define! module key val)
>
> Not all that hard.
yes, that is right!
> > In my first post, regarding this stuff, I used eval-string, because I
> > assume it produces less overhead than creating a book in inline
> > lily-code.
> Sure, but why eval-string?  Why not write what you want instead?
see above, I just didn't find "make-module" and "module-define!" in the 
docs.