Re: New Lisp ?

[address@hidden (Rob Warnock)]

David Rush  <kumo@bellsouth.net> wrote:
+---------------
| Please note: I am talking about a matter of degree here. My biggest
| beef with exception-based systems is that they end up getting used far
| too generally (for unusual code paths rather than actual failure
| handling).
+---------------

At least as I read it, Kent Pitman's 1990 survey paper on exceptions
<URL:http://world.std.com/~pitman/Papers/Exceptional-Situations-1990.html>
suggests that there's nothing wrong with using exceptions for "unusual
code paths":

	It is important to recognize that this distinction between normal
	and exceptional situations is in some sense contrived. Making this
	distinction does not change the way programs behave; it simply
	changes the way we reason about programs--hopefully for the better.
	...
	In some cases, there may be efficiency reasons for considering
	some cases to be exceptional.

In particular, allowing some [presumably infrequent] non-error code
paths to be considered "exceptional" [and using inconspicuous flow
control primitives to access them, such as CATCH/THROW] can, in turn,
allow the "normal" code paths to be considerably simplified without
compromising program correctness.


-Rob

-----
Rob Warnock, 30-3-510		<rpw3@sgi.com>
SGI Network Engineering		<http://www.meer.net/~rpw3/>
1600 Amphitheatre Pkwy.		Phone: 650-933-1673
Mountain View, CA  94043	PP-ASEL-IA

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