I may have missed this in the documentation, but I don't think felix
currently supports keyword/default arguments. I currently know of two
ways of implementing this. First is ocaml's labels, which I believe exist in
a separate namespace than standard arguments. Second is python's
implementation to pull everything into a dictionary.
Both of these have their own advantages and disadvantages, though
personally I would prefer python's technique as you can grab all the
arguments with a good "*args, **kwds", but I don't know how to make
that typesafe, so ocaml's may be the way to go, unless you have other
ideas.