Re: Extended mensuration signs in markup via Scheme

[Graham King]

On Tue, 2013-09-10 at 04:39 +0200, David Kastrup wrote:
> Inside of markups, you can't use functions defined with
> define-scheme-function (their argument parsing is just not compatible
> with markup mode).  Check out define-markup-command instead.
>
> As a note aside: case can't be used with strings as (eqv? "x" "x") => #f

David, many thanks.  A few hours reading and programming later, and I'm nearly there.

#(define-markup-command (mensSign layout props text) (markup?)
  "Create the markup for an extended list of mensuration signs"
  (interpret-markup layout props
    (if (string=? text "C")
      (markup (#:musicglyph "timesig.mensural44"))
%......
)))

mensuration = #(define-music-function (P L mensuralTimesig .....)
                  (string? .....)
    #{ \mark \markup {
            \concat {
                \mensSign mensuralTimesig  
                " ("
%................

cantusMusic = \relative c' {
    %.....
    \mensuration #"C"  %....

This code is compiling successfully, but with two instances of "programming error: Object is not a markup."
However, if I edit the mensuration function and replace
>     \mensSign mensuralTimesig
with
>     \mensSign "C"
the errors disappear and everything works beautifully.  Utterly baffling!  I'd be grateful for any hints from you or any other guru.