[plt-scheme] optional arguments in function contracts

Sorry this sounds cranky;
> I'd advise against anyone using mzlib/contract.

What I mean is; the legacy contract library is useful, but it is
probably worth the small effort to port your contracts. (changing
things like 'union' and 'opt->')

Cheers,

Stephen

--
Stephen De Gabrielle
s.degabrielle at cs.ucl.ac.uk
Telephone +44 (0)20 7679 0693 (x30693)
Mobile                  079 851 890 45
Project: Making Sense of Information (MaSI)
http://www.uclic.ucl.ac.uk/annb/MaSI.html

UCL Interaction Centre
MPEB 8th floor
University College London
Gower Street
London WC1E 6BT