[plt-scheme] Help with #0 and #0# notation in the REPL

From: Paul Schlie (schlie at comcast.net)
Date: Tue Jan 29 19:44:16 EST 2008

"It only ever worked for quoted cyclic data (and that's what's gone now)."

(sarcasm on) by what logic was this determined? personally I've used cyclic
data to describe many things, inclusive of syntax, semantic, and state
transition information, and can see no obvious benefit to having to
construct such information programmatically, not to mention that once it
was so constructed, it can't be easily written to a file, and then
correspondingly easily restored via read with out such a capability); of
course with immutable lists, programmatic construction, isn't the easiest
either, so might as well eliminate any vestiges of enabling lists as the
basis of a flexible variable data structure. As after all, scheme wasn't
ever known to be a powerful friendly flexible programming language (sarcasms

which is why although I've dabbled with 399, I've had to stick with 372 for
my purposes.

> Robby Findler wrote:
>> On Jan 29, 2008 5:22 AM, Jens Axel Soegaard <jensaxel at soegaard.net> wrote:
>> Robby Findler wrote:
>>  >> Why was this change made?
>>  >
>>  > It simplifies the compiler and tools that operate on program source if
>>  > there are no cycles in what they have to process (it isn't a normal
>>  > thing to think about that a program's AST is cyclic!) and so we
>>  > decided to experiment with leaving it out.
>> Besides syntactically recursive programs doesn't give you more
>> expressive power. What I am talking about?
>> <http://pagesperso-systeme.lip6.fr/Christian.Queinnec/Papers/synrec.ps.gz>
>> [Yes, slightly off-topic but close enough ;-) ]
> FWIW, mzscheme never worked for such programs. It would fail to
> terminate while compiling them. It only ever worked for quoted cyclic
> data (and that's what's gone now).
> Robby

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