latest additions:

• A monad for reactive programming part 2 describes the monadic reactive mechanism of hplayground

• A Tutorial for creating client side applications using haste and hplayground

• ajax with de-inversion of control

• WebSockets with de-inversion of control

• A accounting application example that show how to include a javascript library -the google chart library- as a widget.

Create applications in the browser as fast as easy as console applications and have reactive, window-oriented and spreadsheet-like behaviours for free.

So you translate your inputs and outputs from console calls to playground widgets and with no more modifications you have reactive and spreadsheet behaviours.

Hplayground uses the same MFlow combinators running in the browser with the Haste compiler

This program creates two input boxes and present the sum below them:

    import Haste.HPlay.View
    import Control.Applicative


    main= runBody action

    action :: Widget ()
    action = do
         r  <- (+) <$> inputInt Nothing `wake` OnKeyPress <++ br
                   <*> inputInt Nothing `wake` OnKeyPress <++ br
         p  (show r) ++> noWidget

Each widget creates his own rendering and manage his own events, that can be propagated or not down trough the monadic computation and trigger modifications in the DOM.

There is an IDE for Haste and hplayground it is running At:

http://tryplayg.herokuapp.com

With many examples.

You can install this IDE locally or in an Heroku instance. Follow the instructions at:

https://github.com/agocorona/tryhplay

Additionally you can see a more complex example: the hplay-todo, the todoMVC project for hplayground.

The todo application running

Under the hood there is the good old formlet concept. It uses monadic and applicative combinators The same ones used by MFlow in the server side. While the server side widgets of MFlow produce blaze-html output converted to bytestrings, playground construct a builder function that creates a tree in the HTML DOM when executed. This builder (perch) is monoidal so the formlet can aggregate subtrees. When some event happens in the widget subtree, the widget executes his code and reconstruct itself. If it return a valid result and it is in a monadic computation the tree continues recreating itself downstream by executing further widgets in the monadic sequence. If the event is raised within a widget that does not generate a valid result (return empty) the remaining widgets continue unchanged and unevaluated.

Non-local modifications of the DOM works with the new "at" primitive. Option buttons, checkboxes and drop-down buttons works with the same syntax than MFlow.

The Cell module has Lens-like primitives for updates of form elements and experimental math operations with form elements as spreadsheet cells. Currently it is at the beginning.

https://registry.hub.docker.com/u/agocorona/tryhplay/

Contains everything necessary to use hplayground

install the ghc compiler

install Haste:

>cabal install haste-compiler
>haste-boot

install perch

>haste-inst install haste-perch

clone hplayground

>git clone http://github.com/agocorona/hplayground

install hplayground:

>haste-inst install

or install it from Hackage using cabal:

>haste-inst install hplayground

compile

>cd src
>hastec Main.hs --output-html

hastec uses ghc internally so you can expect ordinary ghc error messages in your development.

Browse the Main.html file. In windows simply execute it in the command line:

>Main.html

you can also see it executing at

 http://mflowdemo.herokuapp.com/noscript/wiki/browserwidgets

Main.html and Main.js is included in the repo so you can execute it in your PC

Execute it in the same directory where Main.js is, since it references it assuming that it is in the current folder