Re: Using Scheme inside Lilypond

[Aaron Hill]

On 2021-09-04 11:39 am, Richard Shann wrote:
> Can someone educate me as to why this works:
>
> \markup \path #0.4 #'((moveto 0 0) (lineto -30 50) (lineto -20 80) 
> (closepath))
>
> but this does not:
>
> \markup \path #0.4 #'((moveto 0 0) (lineto -30 (* 2 25)) (lineto -20
> 80) (closepath))
>
> The difference being I replace 50 with (* 2 25)
>
> (I'm trying to write code that will draw a box round A4 or letter paper
> with just a change of some scaling factors - I can work around it but
> it's distressing not to understand what is going on).
>
> Richard Shann

You are quoting so there is no interpretation of arithmetic expressions. 
 You should quasiquote:

%%%%
\markup \path #0.4
 #`((moveto 0 0) (lineto -30 ,(* 2 25))
    (lineto -20 80) (closepath))
%%%%

-- Aaron Hill