Using 'scheme?' as predicate in a markup function.

[Pierre Perol-Schneider]

Hi,

After some fights with 'draw-line thickness in a score containing numbers of arrows I've created this markup function: http://lsr.di.unimi.it/LSR/Item?id=1026

My intention was to stick to the 'arrow-head syntax. So it goes:

#(define-markup-command (foo layout props  axis  direction) (scheme? scheme?)
  (interpret-markup layout props
    (if (and (eq? axis X)(eq? direction 1))
        (markup "foo")
        (markup "no foo"))))

I've never use 'scheme? before. Could this be problematic? If yes, is there any other way?

TIA,

Pierre