[plt-scheme] Re: call/cc vs let/cc at top level - A BUG?

From: Robby Findler (robby.findler at gmail.com)
Date: Mon Jan 1 15:13:14 EST 2007

On 1/1/07, Kyle Smith <airfoil at bellsouth.net> wrote:
> I also think I have an idea as to why, when the code is placed inside
> anything, including a let clause, that it just repeats the first value over
> and over.  After trying the code on several implementations of Scheme, I
> believe it has something to do with whether there are prompts delimiting the
> REPL at top-level.  This would explain why MIT Scheme, which doesn't have
> prompts implemented repeats the first value even at top-level, and why Petite-
> Chez shows similar behavior to DrScheme.  It would also explain why, in the
> first post, I showed that the behavior was consistently correct no matter
> where the code was located if you implemented it with DrScheme's prompt
> primitives instead of call/cc.  That is with call-with-composable-continuation
> used to capture the continuation instead of call/cc.

The interaction between top-level begins and call/cc is something that
is indirectly specified in the R5RS and it seems that most Schemes (mz
& dr included) violate it. Jacob Matthews and I wrote a paper (still a
draft) that, in part, explains that. If you (or anyone else) is
interested, contact me and I'll send you a copy.

> Many thanks Robby, and a happy new year!

Happy New Year!


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