[web-devel] [Haskell-cafe] ANNOUNCE: MFlow 3.0

Wed Jul 10 21:32:53 CEST 2013

My plan is to synchronize MFlow servers using cloud Haskell since the state
serialization is small. I´m working on it.  However continuation based
frameworks can not synchronize state.  There is "swarm" in scala that
generate portable continuations but this is not used in the context of web
application since the state in a continuation is big and can not be
synchronized fast enough. In other languages these states are not even
portable between machines.

2013/7/10 Alexander Kjeldaas <alexander.kjeldaas at gmail.com>

> Here are some common-lisp web frameworks using continuations:
>
> http://common-lisp.net/project/cl-weblocks/
> http://common-lisp.net/project/ucw/features.html
>
> What always worried me with these frameworks is how they could be made
> robust in case of failures.  Storing all state in a database backend often
> makes it possible to isolate failures.  However, it seems to me that it is
> be possible to solve this in Haskell where state can be serialized and
> synchronized between multiple machines using Cloud Haskell, something that
> is error-prone or impossible in other languages.  But that step has never
> been taken.
>
> Alexander
>
>
> On Wed, Jul 10, 2013 at 4:48 PM, Alberto G. Corona <agocorona at gmail.com>wrote:
>
>> Thanks Adrian. The racket people where pioneers in this idea I think.
>>
>> There is another web framework in Ocaml, Osigen that it is also
>> continuation based. MFlow is not continuation-based but it also define the
>> navigation as a sequence. But only Seaside (and now MFlow) supports many
>> flows in the same page. See for example this:
>>
>> [PDF] *Seaside* – A *Multiple* Control *Flow* Web Application Framework<http://www.google.es/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=3&cad=rja&ved=0CEwQFjAC&url=http%3A%2F%2Fscg.unibe.ch%2Farchive%2Fpapers%2FDuca04eSeaside.pdf&ei=WnPdUYHPI-Ly7Aaa0oHQDA&usg=AFQjCNFxwsFQc9QsQCNPRFfD4t6ReQtP5g&sig2=_klwtzxIKW5UzAOUDOvFCw>
>>
>> There is also other: Apache Coccoon that run in a special kind of
>> JavaScript. The continuation-based frameworks have the reputation of
>> storing a lot of application state and to be non  scalable. MFlow
>> uses backtracking and It does not have these problems.
>>
>>
>> 2013/7/10 Adrian May <adrian.alexander.may at gmail.com>
>>
>>> Oh how nice!
>>>
>>> I have been looking at MFlow a lot lately and I think it's got something
>>> quite special that Yesod, Happstack, etc don't seem to have, at least, not
>>> as far as I know. I mean, look at this:
>>>
>>> sumWidget= pageFlow "sum" $ do
>>>
>>>       n1 <- p << "Enter first number"  ++> getInt Nothing <** submitButton "enter" <++ br
>>>
>>>
>>>
>>>
>>>
>>>       n2 <- p << "Enter second number" ++> getInt Nothing <** submitButton "enter" <++ br
>>>
>>>
>>>
>>>
>>>
>>>       n3 <- p << "Enter third number"  ++> getInt Nothing <** submitButton "enter" <++ br
>>>
>>>
>>>
>>>
>>>
>>>       p <<  ("The result is: "++show (n1 + n2 + n3))  ++>  wlink () << b << " menu"
>>>
>>>
>>>
>>>
>>>
>>>       <++ p << "you can change the numbers in the boxes to see how the result changes"
>>>
>>> Is that pretty or what? That's the code for this:
>>>
>>> http://mflowdemo.herokuapp.com/noscript/fviewmonad
>>>
>>> To me that's a real technological step over and above the usual servlets
>>> paradigm and I'd love to see more people getting involved. It seems like
>>> Yesod and Happstack have a lot more manpower behind them, but unless I've
>>> missed something, MFlow is going somewhere new and should be helped along.
>>>
>>> Adrian.
>>>
>>> PS. Besides Seaside, Racket is playing with the same ideas. They (Jay
>>> McCarthy) have something to say about performance but I didn't quite
>>> understand it.
>>>
>>>
>>>
>>> On 10 July 2013 06:41, Alberto G. Corona <agocorona at gmail.com> wrote:
>>>
>>>> The third version of MFlow is out.
>>>>
>>>> http://hackage.haskell.org/package/MFlow
>>>>
>>>> MFlow is an all-heterodox web application framework, but very
>>>> haskellish.
>>>>
>>>> Now MFlow support restful URLs.  It is the first stateful web framework
>>>> to my knowledge that supports it. The type safe routes are implicitly
>>>> expressed as normal monadic code within a navigation monad. The application
>>>> look as a normal imperative console application, but the navigation monad
>>>> goes back and forth to match the path of the URL. The user has control of
>>>> the state, that can roll-back or not when the navigation goes back
>>>> depending on the application needs. The state is in the form of normal
>>>> Haskell variables In a monadic computation, with the weird addition of
>>>> backtracking.
>>>>
>>>> The menu of the application below is implemented as an imperative-like
>>>> syntax, but the application navigate forward and backward to synchronize
>>>> with the requests of the web browser:
>>>> http://mflowdemo.herokuapp.com/
>>>>
>>>> This version support  in-page flows.
>>>>  What is that? look at this example:
>>>>
>>>> http://mflowdemo.herokuapp.com/noscript/fviewmonad
>>>>
>>>> These flows are implemented as formlets with a monad instance, and
>>>> callbacks which change the look. I call them "widgets":
>>>>
>>>>
>>>> http://haskell-web.blogspot.com.es/2013/06/the-promising-land-of-monadic-formlets.html
>>>>
>>>>
>>>> Each page may have many  of these active widgets, each one running
>>>> their own flow. These widgets refresh themselves trough Ajax if they are
>>>> enclosed in the primitive "autoRefresh". If there is no Ajax or JavaScript
>>>> available, they gracefully degrade by refreshing the entire page:
>>>>
>>>> http://mflowdemo.herokuapp.com/noscript/combination
>>>>
>>>>
>>>> http://haskell-web.blogspot.com.es/2013/06/and-finally-widget-auto-refreshing.html
>>>>
>>>> The page flows and the multiflow idea was inspired in Seaside<http://www.seaside.st/>,
>>>> a great Smalltalk web framework and adapted to the pure recursive nature of
>>>> Haskell and the formlets.
>>>>
>>>> It also support some JQuery widgets integrated: modal and not modal
>>>> dialogs, datePicker and other active widgets that handle other widgets.
>>>>
>>>> It also support the older features: persistent state, WAI, blaze-html
>>>> and others integration, server process timeouts, Ajax, requirements,
>>>>  content management, caching of widget rendering and all the other
>>>> previous stuff.
>>>>
>>>> I wish to thank some people for their feedback. Specially Adrian May
>>>> for his feedback and interest
>>>>
>>>>
>>>> --
>>>> Alberto.
>>>>
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>>>>
>>>>
>>>
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>>>
>>
>>
>> --
>> Alberto.
>>
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>>
>>
>

-- 
Alberto.
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