Generating a (#:column ...) list in Scheme

[Urs Liska]

Hi,

I have this construct in a function that creates a combined time signature:

   (grob-interpret-markup grob
     (markup #:override '(baseline-skip . 0) #:number
       (#:line ((#:column (numOne denOne))
                (#:column (numTwo denTwo))))))

It creates two columns from the four given arguments, but I want to be 
able to create an arbitrary number of columns.

I see that #:line gets a list of (#:column ()) entries.
But I'm lost with the #: part. What does that mean? And how can I 
generate such a list with an arbitrary number of columns?

Input is a list of lists, such as #'((3 8) (4 8)).
I assume that I'll have to "map" this input list, but I don't know how 
these individual sublists can be processed. Of course I have to do a 
number->string conversion for each element, but I could also massage the 
original input to be in the right state already.

Any help appreciated.
Urs