Re: Problem compiling: music-functions-init.ly

[Urs Liska]

Am 14.11.18 um 10:06 schrieb David Kastrup:
> Davide Liessi <address@hidden> writes:
>
> > Il giorno mer 14 nov 2018 alle ore 08:25 Keizen Li Qian
> > <address@hidden> ha scritto:
> > > Parsing.../usr/share/lilypond/2.18.2/ly/music-functions-init.ly:564:11:
> > > In procedure ly:music-transpose in expression (ly:music-transpose
> > > (make-music # # ...) tonic):
> > > /usr/share/lilypond/2.18.2/ly/music-functions-init.ly:564:11: Wrong
> > > type (expecting pair): major
> > You probably wrote
> > \key c major
> > instead of
> > \key c \major
> Well spotted.  The embarrassing thing is that we even get there: this
> is something that should rather be caught earlier.  We have
>
> key =
> #(define-music-function (tonic pitch-alist)
>     ((ly:pitch? '()) (list? '()))
> [...]
>
> and the word major qualifies as list? by getting converted to '(major)
> which is a symbol list like needed for some override/tweak
> specifications.
>
> So it very much looks like we should use a more specific predicate than
> list? for the scale type in order to not have that user error pass down
> in this manner.
>
> Suggestions?

major and minor are lists with seven number pairs where the cars are 
0..6 and the cdrs are 0 or -1/2.

I'm not sure how the definition of custom scales works and how much 
freedom the user has to that, but I'd assume that requiring number-pairs 
(probably an unspecified number of pairs) with the cars forming a row of 
natural numbers should be the right thing.

As you mention in the other post there should be a specific predicate 
(why not `pitch-alist?`).

Urs