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This approach to webdev (continuations) could be so cool. I just wish there was a framework on the level of django/rails so that I could feel comfortable using

This approach to webdev (continuations) could be so cool. I just wish there was a framework on the level of django/rails so that I could feel comfortable using it for a large product.

tbje 11y ago
The Lift web framework in Scala is somehow similar in that aspect. It has been used on multiple bigger sites like foursquare. I really like the approach compared to MVC.
- eggy 11y ago
  Racket does stateful and stateless servers, and the continuations are either stored on the server or the client per which type you choose to implement [1]. [1] https://docs.racket-lang.org/web-server/
long 11y ago
The FAQ doesn't mention anything about this -- can you explain how Seaside uses continuations?
- doublec 11y ago
  It uses continuations to hide the asynchronous nature of web requests and allows the flow between pages of a web app to be written in an imperative style. "Inverting back the inversion of control" describes the idea (in Scheme) https://pages.lip6.fr/Christian.Queinnec/PDF/www.pdf https://pages.lip6.fr/Christian.Queinnec/PDF/www.pdf Paul Graham used the idea in ViaWeb - and apparently got a patent on some aspect of it https://web.archive.org/web/20060323211251/http://paulgraham.infogami.com/blog/morepatents https://web.archive.org/web/20060323211251/http://paulgraham...
  - agumonkey 11y ago
    IIUC HN uses them too.
  - mbrock 11y ago
    There are a couple of continuation-based web frameworks for Ruby (Borges, Wee), but they're old and abandoned as far as I know. I suspect it didn't catch on because (1) people are afraid of continuations, and (2) web apps are typically designed in at least a pseudo-REST-like style, so the paradigm of "asking" the user (like "await" in ES6) isn't needed very often. But it's a cool thing to be able to do, especially for funnel-type flows, and other types of more complex session-based interactions. I wonder if there are any JavaScript inversion of control things for client side code. I've been working for the past week on a signup funnel with React and Flux, and it's just a big explicit state machine... which kind of works, but is also kind of tedious.
    - doublec 11y ago
      I think 'Ajax' killed continuation based web servers. See Avi Bryant's thoughts in this area from back then: https://web.archive.org/web/20060610180033/http://smallthought.com/avi/?p=14 https://web.archive.org/web/20060610180033/http://smallthoug... There were client side JavaScript continuation like things. Back in the mid-2000's there was Narrative JavaScript. I used it to implement threads and Alice ML style futures/promises on the client side: https://bluishcoder.co.nz/2006/06/05/more-concurrency-in-narrative.html https://bluishcoder.co.nz/2006/06/05/more-concurrency-in-nar...
    - klibertp 11y ago
      There's also Nagare in Python: http://www.nagare.org/trac/wiki/NagareTutorial http://www.nagare.org/trac/wiki/NagareTutorial IIRC it uses Stackless Python, not the standard interpreter, and I don't know how active its development is.
sriku 11y ago
Paul Graham's startup (way back) did this and he claims it was a competitive advantage. These days it doesn't feel like this approach offers enough.
- derefr 11y ago
  Not just way back; HN uses continuations. (Not in many user-visible places any more, but every link on the front page used to be one—expired "next page" continuation links were a frequent source of grumbling.) Note that you don't have to expire continuations, necessarily—you could actually persist them statelessly (i.e. without server-side state), by shipping their encoded representations to the client embedded into HMAC-signed links. You're basically giving the server a raw bytecode-eval endpoint, and then making sure that it only accepts code you yourself wrote. Kind of a crazy strategy compared to the standard predeclared REST API, but interestingly flexible.
  - dang 11y ago
    > their encoded representations What's an example of such a representation?
    - derefr 11y ago
      Now that you mention it, I can't think of very many languages that define a language-standard persistent encoding of a continuation on a closure. One that I can think of is Erlang. Here's the relevant section of the Erlang "External Term Format encoding" spec: http://erlang.org/doc/apps/erts/erl_ext_dist.html#id95269 http://erlang.org/doc/apps/erts/erl_ext_dist.html#id95269 Said spec is nominally "about" the wire protocol Erlang nodes use to communicate with one another in a distributed system. But the ETF format defined there is much more general, and is used all over the place (e.g. when persisting values in Erlang's DETS tables to disk.) It's what you get when you call Erlang's global term_to_binary/1 function. Erlang's ETF could probably be most closely compared to Python's "pickle" format. (Though, sadly, you can't pickle a lexical closure in Python.)
      - 11y ago
rakoo 11y ago
Never used it but Tir (https://github.com/mongrel2/Tir https://github.com/mongrel2/Tir), which runs on top of mongrel2, allows you to use continuation style if you wish to do so.
- aidenn0 11y ago
  Tir is currently without a maintainer and won't even install from the rocks file in the repository.

This approach to webdev (continuations) could be so cool. I just wish there was a framework on the level of django/rails so that I could feel comfortable using it for a large product.

tbje 11y ago

The Lift web framework in Scala is somehow similar in that aspect. It has been used on multiple bigger sites like foursquare. I really like the approach compared to MVC.

eggy 11y ago
Racket does stateful and stateless servers, and the continuations are either stored on the server or the client per which type you choose to implement [1]. [1] https://docs.racket-lang.org/web-server/

long 11y ago

The FAQ doesn't mention anything about this -- can you explain how Seaside uses continuations?

doublec 11y ago
It uses continuations to hide the asynchronous nature of web requests and allows the flow between pages of a web app to be written in an imperative style. "Inverting back the inversion of control" describes the idea (in Scheme) https://pages.lip6.fr/Christian.Queinnec/PDF/www.pdf https://pages.lip6.fr/Christian.Queinnec/PDF/www.pdf Paul Graham used the idea in ViaWeb - and apparently got a patent on some aspect of it https://web.archive.org/web/20060323211251/http://paulgraham.infogami.com/blog/morepatents https://web.archive.org/web/20060323211251/http://paulgraham...
- agumonkey 11y ago
  IIUC HN uses them too.
- mbrock 11y ago
  There are a couple of continuation-based web frameworks for Ruby (Borges, Wee), but they're old and abandoned as far as I know. I suspect it didn't catch on because (1) people are afraid of continuations, and (2) web apps are typically designed in at least a pseudo-REST-like style, so the paradigm of "asking" the user (like "await" in ES6) isn't needed very often. But it's a cool thing to be able to do, especially for funnel-type flows, and other types of more complex session-based interactions. I wonder if there are any JavaScript inversion of control things for client side code. I've been working for the past week on a signup funnel with React and Flux, and it's just a big explicit state machine... which kind of works, but is also kind of tedious.
  - doublec 11y ago
    I think 'Ajax' killed continuation based web servers. See Avi Bryant's thoughts in this area from back then: https://web.archive.org/web/20060610180033/http://smallthought.com/avi/?p=14 https://web.archive.org/web/20060610180033/http://smallthoug... There were client side JavaScript continuation like things. Back in the mid-2000's there was Narrative JavaScript. I used it to implement threads and Alice ML style futures/promises on the client side: https://bluishcoder.co.nz/2006/06/05/more-concurrency-in-narrative.html https://bluishcoder.co.nz/2006/06/05/more-concurrency-in-nar...
  - klibertp 11y ago
    There's also Nagare in Python: http://www.nagare.org/trac/wiki/NagareTutorial http://www.nagare.org/trac/wiki/NagareTutorial IIRC it uses Stackless Python, not the standard interpreter, and I don't know how active its development is.

sriku 11y ago

Paul Graham's startup (way back) did this and he claims it was a competitive advantage. These days it doesn't feel like this approach offers enough.

derefr 11y ago
Not just way back; HN uses continuations. (Not in many user-visible places any more, but every link on the front page used to be one—expired "next page" continuation links were a frequent source of grumbling.) Note that you don't have to expire continuations, necessarily—you could actually persist them statelessly (i.e. without server-side state), by shipping their encoded representations to the client embedded into HMAC-signed links. You're basically giving the server a raw bytecode-eval endpoint, and then making sure that it only accepts code you yourself wrote. Kind of a crazy strategy compared to the standard predeclared REST API, but interestingly flexible.
- dang 11y ago
  > their encoded representations What's an example of such a representation?
  - derefr 11y ago
    Now that you mention it, I can't think of very many languages that define a language-standard persistent encoding of a continuation on a closure. One that I can think of is Erlang. Here's the relevant section of the Erlang "External Term Format encoding" spec: http://erlang.org/doc/apps/erts/erl_ext_dist.html#id95269 http://erlang.org/doc/apps/erts/erl_ext_dist.html#id95269 Said spec is nominally "about" the wire protocol Erlang nodes use to communicate with one another in a distributed system. But the ETF format defined there is much more general, and is used all over the place (e.g. when persisting values in Erlang's DETS tables to disk.) It's what you get when you call Erlang's global term_to_binary/1 function. Erlang's ETF could probably be most closely compared to Python's "pickle" format. (Though, sadly, you can't pickle a lexical closure in Python.)
    - 11y ago

rakoo 11y ago

Never used it but Tir (https://github.com/mongrel2/Tir https://github.com/mongrel2/Tir), which runs on top of mongrel2, allows you to use continuation style if you wish to do so.

aidenn0 11y ago
Tir is currently without a maintainer and won't even install from the rocks file in the repository.