Re: Automated processing of multiple books

[Simon Albrecht]

On 04.11.2015 20:36, David Kastrup wrote:
> Simon Albrecht <address@hidden> writes:
>
> > On 04.11.2015 19:24, David Kastrup wrote:
> > > Simon Albrecht <address@hidden> writes:
> > >
> > > > This compiles fine inasmuch as the output is just as intended, but it
> > > > does sport a:
> > > >
> > > > <0>"/home/simon/lilypond/tests/wrap-multiple-books.ly:17:1: error: bad
> > > > expression type
> > > >
> > > > \printParts one.two"
> > > >
> > > > Is this worth a bug report about this error appearing too easily?
> > > No.  You use map instead of for-each,
> > How would I use for-each here? I’m not familiar with that.
> for-each has exactly the same arguments as map but does not return a
> value.
>
> > > you use define-scheme-function instead of define-void-function.
> > Ah, I see. I wouldn’t have thought that a function which basically
> > runs print-book-with-default would classify as a void function.
> What do you consider "void" then?

Basically, my notion of a ‘void function’ comes from the LilyPond 
documentation, and I’d phrase it as ‘a function which is not executed 
for its output (or return value), but for side-effects’, such as 
variable definitions &c.
And I thought print-book-with-default was executed in order to output a 
‘book’. Is it closer to the truth to say that it only passes the 
information on, instead of ‘returning’ or ‘outputting’ it? I’m not quite 
into any subtleties of programming…

Yours, Simon