From: Per Bothner <xxxxxx@bothner.com>
   Date: 15 Oct 1999 18:52:25 -0700

   I know I'm out of the official "Scheme experts" loop.  Still, as the
   author of a frequently-praised Scheme implementation, I thought I knew
   something about Scheme.  Thus I am rather surprised that no one else
   agrees with me that the whole "conditions" concept requires some
   justification.

Exceptions and conditions have been discussed at length on the
Scheme Author's mailing list.  You can read all about it in the
archives at:

  http://www.swiss.ai.mit.edu/projects/scheme/rrrs-archive.html

The relevent messages are from 1995 and 1996 and have `exception
system' in the subject.

The quick answer is that exception systems are used to communicate
between programs.  Within a single a program you can use whatever
method you want for catching exceptions and whatever values you want
as conditions.  If two or more programs are involved they need to
agree on both the exception-raising mechanism and on the kind of
values that are passed to the handler.

(Note to Shriram: schemers.org's link to the archives is incorrect.)
(Note to the authors of SRFI-12: Hello?  Is anyone home?)

                                        -Richard Kelsey