[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: 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.

To my:
> * 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).
Shriram Krishnamurthi <shriram@xxxxxxxxxxx> responded:
> All of this is also true of continuations.

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.  I thought one goal for Scheme is maximal expressiveness
while minimizing primitive concepts.  Instead, the only response I get
is something that seems completely beside the point.  Continuations
give you a lot of expressive power using a mechanism that is very
difficult for users to build using other constructs.  I don't see how
that is true for conditions, which from what I can tell give *no*
expressive power or even convenience over using plain association or
property lists.  Clearly, there is some background I'm missing.  I am
aware of the Common Lisp condition system, but have never used it or
really studied it.  Has the collective wisdom of the "Lisp community"
decided that CL conditions is "good"?
	--Per Bothner
bothner@xxxxxxxxxxx  per@xxxxxxxxxxx   http://www.bothner.com/~per/