[R6RS] Backward compatibility

[Marc Feeley]

One issue that we should address now is backward compatibility.  In
the process of designing R6RS, should we consider changes that would
not be backward compatible?  That is, should we consider changes that
would cause some R5RS programs to not work anymore in an R6RS
compliant system?

My position is that R6RS need not be backward compatible.  There are a
few things that I consider "broken" in R5RS and fixing these things
will break backward compatibility.  Of course we should limit the
extent of these backward incompatibilities so that in practice there
are few R5RS programs that don't work, and only small changes are
required to get them to work in an R6RS system.

Having said that, I think that if any "cleanup" of the Scheme language
is to be done, we should do it sooner than later.  So I think we
should not be too shy in the language changes that we propose.

Marc