Re: Warning when defining variables on the command line

[Matt Wallis]

On 19/11/2019 15:39, Aaron Hill wrote:
> On 2019-11-19 3:37 am, Matt Wallis wrote:
> > I want to pass the subtitle into lilypond on the command line because
> > it is also required by other programmes (e.g. sox needs the subtitle
> > to create a tag for the mp3 it creates).
> > [ . . . ]
> > But I now get the warning:
> >
> >     Parsing...WARNING: #f: imported module (guile-user) overrides core
> > binding `%module-public-interface'
> >
> > Should I be concerned? Is it safe to ignore? Can I suppress this warning?
>
> With a little more work, you can peek into the guile-user module and 
> grab out what you need without importing the entire module into the 
> current environment:
>
> %%%%
> \version "2.19.83"
>
> #(define (guile-user-lookup sym def)
>    (let ((mod (resolve-module '(guile-user))))
>      (if (module-defined? mod sym) (eval sym mod) def)))
>
> #(format #t "\nHello, ~a!" (guile-user-lookup 'hello "..."))
> %%%%

Very interesting! Thank Aaron.

So, I have added the line (in place of your call to format):

    subtitle = #(guile-user-lookup 'subtitle "...")

in order to get back into the world of lilypond variables, and it all 
works. Without this line I get:

$ lilypond -e '(define subtitle "One Two Three")' SatbScore.ly
GNU LilyPond 2.19.83
Processing `SatbScore.ly'
Parsing...
SatbScore.ly:16:22: error: unknown escaped string: `\subtitle'
\header { subtitle =
                     \subtitle }

A possibly related question ... the lilypond docs use `define-public`, 
and you use `define`. What is the difference?