Using Scheme inside Lilypond

[Richard Shann]

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