How prevalent/practical are continuation-style web apps in the lisp world?
Joost Diepenmaat
based webapps in Lisp, with some suggestions that continuations were
somehow needed and also memory hungry.
I've never build any serious webapp with Lisp, and none using
continuations but I have built quite a few in other languages, and I am
interested in using Lisp in future webapp projects.
I can see the appeal of continuation style in webapps in /certain/ types
of web apps, though I doubt it's useful for the more "static" parts of a
site.
I can also believe having many continuations/closures hanging off
sessions is pretty memory intensive, especially if you want to have a
history for people to go back to.
I may ofcourse be completely misguided.
If anyone here has pointers to comparisons between continuation and
REST / "sessions as plain data" style web development in Lisp (especially
regarding differences in development time, debugging and system
resources) or has any other comments I'd be grateful.
Thanks in advance,
Joost.
Slobodan Blazeski
> The "world delivery" thread below there was some mention of continuation-
> based webapps in Lisp, with some suggestions that continuations were
> somehow needed and also memory hungry.
group about seaside type look at below :
http://groups.google.com/group/weblocks/browse_thread/thread/9d929ccc21a1b286
http://www.nabble.com/Continuations---their-future--tt14246898.html
Also nice folks from Hungary made a success story with an app using
continuations
http://groups.google.com/group/comp.lang.lisp/browse_thread/thread/9c2f0dfc46befcf4/9ef57b4d214a1c6a?lnk=gst&q=+cl-perec#9ef57b4d214a1c6a
, not to mention Paul Graham's ViaWeb ( he even holds patents on
continuation based servers http://lambda-the-ultimate.org/node/1365
if you can believe previous link)
>
> I've never build any serious webapp with Lisp, and none using
> continuations but I have built quite a few in other languages, and I am
> interested in using Lisp in future webapp projects.
you should get some insite
http://tourdelisp.blogspot.com/2007/12/delimited-continuations-with-cl-cont.html
>
> I can see the appeal of continuation style in webapps in /certain/ types
> of web apps, though I doubt it's useful for the more "static" parts of a
> site.
framework that I'm using for my app( and even submitted couple of
patches) has an excellent article about them at
http://www.defmacro.org/ramblings/continuations-web.html
>
> I can also believe having many continuations/closures hanging off
> sessions is pretty memory intensive, especially if you want to have a
> history for people to go back to.
>
> I may ofcourse be completely misguided.
>
> If anyone here has pointers to comparisons between continuation and
> REST / "sessions as plain data" style web development in Lisp (especially
> regarding differences in development time, debugging and system
> resources) or has any other comments I'd be grateful.
at
http://common-lisp.net/project/ucw/rest.html
>
> Thanks in advance,
> Joost.
cheers
Slobodan
Slobodan Blazeski
wrote:
> On Dec 17, 2:28 pm, Joost Diepenmaat <jo...@zeekat.nl> wrote:> The "world delivery" thread below there was some mention of continuation-
> > based webapps in Lisp, with some suggestions that continuations were
> > somehow needed and also memory hungry.
>
> Depends of the continuations, it was already discussed in weblocks
> Also nice folks from Hungary made a success story with an app using
> , not to mention Paul Graham's ViaWeb ( he even holds patents on
> if you can believe previous link)
>
> > I've never build any serious webapp with Lisp, and none using
> > continuations but I have built quite a few in other languages, and I am
> > interested in using Lisp in future webapp projects.
>
> You can look at my tutorial what continuations really are, pretty sure
>
> > I can see the appeal of continuation style in webapps in /certain/ types
> > of web apps, though I doubt it's useful for the more "static" parts of a
> > site.
>
> Slava author of weblockshttp://common-lisp.net/project/cl-weblocks/,
> framework that I'm using for my app( and even submitted couple of
>
> > I can also believe having many continuations/closures hanging off
> > sessions is pretty memory intensive, especially if you want to have a
> > history for people to go back to.
> it depends .
>
> > I may ofcourse be completely misguided.
>
> > If anyone here has pointers to comparisons between continuation and
> > REST / "sessions as plain data" style web development in Lisp (especially
> > regarding differences in development time, debugging and system
> > resources) or has any other comments I'd be grateful.
>
> Marco Baringer author of the Uncommon Web has interesthing discussion
>
>
>
> > Thanks in advance,
> > Joost.
>
> cheers
> Slobodan
I almost forgeth If you have an huge appetite look at
http://groups.google.com/group/comp.lang.lisp/browse_thread/thread/ccc371be797e4bf/6d123d47e314eccf?q=web+continuation+marco+baringer&lnk=ol&
pay attention especially to Marco Baringer posts.
cheers
Slobodan
http://tourdelisp.blogspot.com/
Joost Diepenmaat
[ lots of stuff ]
Slobodan, thanks!
All that will probably take some time to read, but from what I've seen so
far it looks pretty useful.
Cheers,
Joost.
Harold Lee
>
Where do I order my Kenny Tilton poster?
-Harold
Slobodan Blazeski
This is item currently available only to qualified lispers who fully
understand cells.
Please contact Kenny Tilton about next available Cells Certification
Program for details.
the management
P.S:
Yobbos & whiners : STAY AWAY!
Alex Mizrahi
JD> types of web apps, though I doubt it's useful for the more "static"
JD> parts of a site.
my personal opinion is that continuations are good in two cases: if you have
very reach stateful UI (i.e. multipage wizard in some accounting app), or if
you'd like to hack prototype rapidly (continuations allow you to do function
calls instead of URLs/dispatching). in other cases they are as useful as a
fifth wheel.
tim Josling
> my personal opinion is that continuations are good in two cases: if you have
> very reach stateful UI (i.e. multipage wizard in some accounting app), or if
> you'd like to hack prototype rapidly (continuations allow you to do function
> calls instead of URLs/dispatching). in other cases they are as useful as a
> fifth wheel.
There are other cases where it is useful. Traversing multiple structures
in parallel and resuming at arbitrary points, trial and error type
searching of calculation possibilities such as parsing. What continuations
give you is a context for little effort. Without that, you have to convert
the context into a data structure. There is an example in "Paradigms of
AI" by Peter Norvig.
I had a situation last week where continuations would have been quite
useful. A number of "processes" (actually all in one lisp image) formed a
"pipe" where the "processes" have to stop and start based on various events
and feedback moving up and down the pipe. I coded the restarting manually
but it would have been a lot easier if I had call/cc.
This reminds me of the "impedance mismatch" between classes and relational
databases. There is nothing you can't do with relational databases but it
can be very tedious.
Tim Josling
Alex Mizrahi
you
??>> have very reach stateful UI (i.e. multipage wizard in some accounting
??>> app), or if you'd like to hack prototype rapidly (continuations allow
??>> you to do function calls instead of URLs/dispatching). in other cases
??>> they are as useful as a fifth wheel.
tJ> There are other cases where it is useful.
i meant in context of web programming, of course continuations are useful in
other areas :)
tJ> Traversing multiple structures in parallel and resuming at arbitrary
tJ> points, trial and error type searching of calculation possibilities
tJ> such as parsing. What continuations give you is a context for little
tJ> effort. Without that, you have to convert the context into a data
tJ> structure. There is an example in "Paradigms of AI" by Peter Norvig.
i was amazed how elegant it is to add non-determinizm in form of amb
operator, via continuations in scheme:
http://www.ccs.neu.edu/home/dorai/t-y-scheme/t-y-scheme-Z-H-16.html