Re: Request for feedback on SRFI-126

[taylanbayirli@gmail.com (Taylan Ulrich Bayırlı/Kammer)]

Christopher Allan Webber <cwebber@dustycloud.org> writes:

> Taylan Ulrich Bayırlı/Kammer writes:
>
>> I will probably work on a delimited continuations SRFI, heavily inspired
>> by Guile's call-with-prompt, since I find it *immensely* more easy to
>> grok than shift/reset and prompt/control because those mingle together
>> the "stack slice" and the "handler" code whereas call-with-prompt
>> clearly separates them.
>
> This could be interesting!  I wonder how hard it will be to do?  IIRC
> from reading wingolog, delimited continuations need to be planned in at
> a pretty low level, and I wonder how hard it will be for many
> implementations to bring them in who don't have them at present?  Will
> be interesting to see!
>
> Anyway, interesting to hear, good luck!

Thanks for the encouragement!

Yeah, AFAIUI delimited continuations are a very fundamental feature.
They can't really be implemented in call/cc for instance, as some people
used to claim I think.

(And that's why they need to be part of the language, as I see it; if
the language itself doesn't have them, there's no way to have them, and
no way to implement all the things they make possible on a higher
level.)

Of course it might be useful not to entirely turn one's back against
implementations that have a difficulty with that feature (it's pretty
new compared to some other Scheme features AFAIK, and going fairly deep
into the implementation), so it could be left optional, but sanctioned
as the official API for implementations to support, if they support it
in any way at all.  Like SRFI-106 does for sockets.

Taylan