I don´t know how, but the google mail has changed the applicative functor operator after (,) Left and Rigth by "<-".
2013/6/19 Alberto G. Corona <agocor...@gmail.com> > Hi, > > This is just to let you know the promising results of some experimentation: > > Formlets are about applicative instances, but what about monadic > instances? What a Monad instance of formlets means? I recently experimented > with this and the results are very interesting and powerful- It mixes the > best of web forms, with the flexibility of console applications. ???!!!!!! > > > Althoug this example is for the formlets of the MFlow > <https://github.com/agocorona/MFlow>framework , it can be ported to other > formlet implementations. Although the MFLow formlets include web formatting > that is not supported in other formlets implementations. Static HTML > templating don´t work well with monadic formlets, so it is important to > include the formatting as a part of the computation: > > import MFlow.Wai.Blaze.Html.All > > dynamicForm= wform $ do > (n,s) <- (,) <- p << "Who are you?" > ++> getString Nothing <! hint "name" <++ br > <*> getString Nothing <! hint "surname" <++ br > <** submitButton "ok" <++ br > > flag <- b << "do you " ++> getRadio[radiob "work?",radiob "study?"] > <++ br > > r<-case flag of > "work" -> pageFlow "l" > $ Left <- b << "do you enjoy your work? " > ++> getBool True "yes" "no" > <** submitButton "ok" <++ br > > "study"-> pageFlow "r" > $ Right <- b << "do you study in " > ++> getRadio[radiob "University" > ,radiob "High School"] > > p << ("You are "++n++" "++s) ++> > case r of > Left fl -> p << ("You work and it is " ++ show fl ++ " that you > enjoy your work") > ++> noWidget > > Right stu -> p << ("You study at the " ++ stu) > ++> noWidget > > > hint s= [("placeholder",s)] > onClickSubmit= [("onclick","this.form.submit()")] > radiob s n= text s ++> setRadio s n <! onClickSubmit > > Here wform, getBool, getString , getRadio etc are formlet elements > > The first sentence is an applicative composition that generate a 2 tuple, > to show that applicative and monadic can be mixed. the operations ++> add > html to the formlet. the operatior <! add attributes to the formlet > element.. noWidget is a dumb formlet that does not validate. > > The second monadic statement is an election between two options. The > beauty of the monadic instance is that the rest of the form can vary > depending on the previous answers. Since the formlets validate the input, > unless the election is made, the radio will not validate, so the monadic > execution will be aborted beyond any unanswered question, so nothing will > appear after the question. The rest of the form will appear when the user > choose one of the two options. once one or the other option is chosen, then > another binary question is presented. (either he likes his work or where he > study). When the questions are finised, the results are presented. > I hope that you get the idea. The benefit is not only the familiar coding > and presentation of a sequential console application: Since the form > encloses all the fields, At any time the user can change previous inputs > and the form will reflect these changes. For example if the user change > from work to study (second statements) the "where do you study will appear > and the work related questions and answers will disappear. That is > wonderfully useful for heavily interactive applications. > > There is a problem however and it is the issue of the formlet > identifiers. Unlike in an applicative presentation, now the number and type > of the formlets will vary, so the response to a previous form create a new > kind of form, and the post response can be misinterpreted. To avoid that , > the pageFlow call creates fixed field labels for each branch of execution. > > I will release a version of MFlow that support this kind of monadic > composition of fomlets, but In essence it is nothing but to add Monad > instance to formlets. A single server procedure, that executes the formlet > code can support all the interaction so any framework can do it. The > usability of that is huge:It is possible to interact in a web page in a > console style with questions and answers with the versatitly of a dynamic > foms: Any modification in the form change the subsequent flow of > interaction. Another application of this monadic style is to ease multistep > processes such are registration, check-out and payment ad so on. Even a > entire interactive dynamic application can be coded in a single page. > > And no javascript is needed!. > > > To run this formlet in MFlow: > > main=do > addMessageFlows > [("" , transient $ runFlow $ ask dynamicForm )] > > wait $ run port waiMessageFlow > > > This video show how the presentation of this example vary with the user > input: > > http://youtu.be/DryBQc9agFg > > > I hope that you find the idea interesting. If you want to experiment > with this in MFlow, I have to say that the implementation of this feature > is in an early stage. The code is in the head branch > > https://github.com/agocorona/MFlow/tree/head > > > > Alberto. > -- Alberto.
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