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more srfi-12 rationale?

This page is part of the web mail archives of SRFI 12 from before July 7th, 2015. The new archives for SRFI 12 contain all messages, not just those from before July 7th, 2015.

I have some questions with srfi-12, mainly dealing with conditions.

* Why do we need a new condition type, disjoint from other Scheme values,
with 5 new operations, some of which are quite non-trivial?  Why can't
we just use standard lists (perhaps association lists)?  It seems rather
non-Schemey (non-orthoginal) to me, to add a new data-stype, with new
operations, that is *similar* to existing data types, but which is
designed for one very specific applications (exceptions and handlers).

* What is the purpose of composite conditions?

I'm sure the authors, who have lots of experience as Scheme implementors,
have good reasons for this design.  I just don't see it in the srfi.

I also think the word "condition" is a bit of a mis-nomer.  I see
nothing conditional about them.

I will also for the record note that I think it is very desirable
that the exception system be implementable on Scheme systems that
do not support full continuations.  From my first reading, it
looks like the proposal *does* satisfy this goal.
	--Per Bothner
bothner@xxxxxxxxxxx  per@xxxxxxxxxxx   http://www.bothner.com/~per/