Define markup function extension

Question

I have markup extension to create custom linked markup. The function is, shown below:

(define-markup-command (refer layout props ts) (number?)
   (interpret-markup layout props
                     (markup #:with-url (format #f "~a&t=~a" baseURL ts) "ref")))

This works fine when invoked by a music function inside a score. I was hoping to be able to include linked text inside standard markup — not inside a score.

I had assumed that I could simply do:

\markup \refer 2 4

But that produced error messages.

What am I not understanding?

Answer 1

In your markup function, you declare only one argument, but then you apparently try to call it with two arguments. I assume this is an oversight you made while creating a minimal example.

Other than that, the basic problem is that markup syntax is different from normal syntax. In music, if you write 4, it means the duration of a fourth note, but \markup 4 actually prints the number “4”. In markup mode, numbers are not recognized specially, they are interpreted as strings. Therefore, to pass a number to a markup command, you have to use Scheme explicitly, by prefixing the number with a # character.