Modify ly:duration->string

Hi,
consider the following:
#(pretty-print (ly:duration->string (ly:make-duration -3)))
returning:
"log = -3"

Is it possible to let it return "maxima" (similar for "longa", "breve")?
To be more precise, this is a request to modify ly:duration->string (I
have already some clumsy custom code to deal with negative durations).

Cheers,
  Harm