Re: simple scheme function #{ $note #}

[Aaron Hill]

On 2018-05-11 08:46, David Kastrup wrote:
> Aaron Hill <address@hidden> writes:
>
> > On 2018-05-11 06:53, Gianmaria Lari wrote:
> > > Sorry to bother with a simple question. Why this does not work?
> > >
> > > \version "2.19.81"
> > > pit = #(define-music-function
> > >         (p) (ly:pitch?)
> > >         #{ $p #}
> > >         )
> > > { \pit c' }
> >
> > The result is "error: music function cannot return c'".  It appears
> > that a simple pitch by itself is not enough to qualify as music.
>
> It's desirable to be able to enter pitches as #{ c' #} and similar.  
> Add
> a duration to get a music expression.

But can you return an incomplete music expression?  It seems like that 
is the underlying issue why the original code does not work.

> > If you change the function to "#{ { $p } #}", it compiles.
>
> Yes, but the duration is not really well-defined here (happens to end 
> up
> as the default duration of the current parser).

True, I was not advocating that this is a useful construct, merely 
showing that it results in a minimally valid expression.

-- Aaron Hill