Hajax: Difference between revisions

Revision as of 07:17, 14 August 2006

Ajax applications are ‘stand-alone’ Web applications that execute into the browser environment, communicating with one or more server back-ends only to get raw data.

Ajax applications can be written using either:

Native libraries/frameworks in JavaScript/HMTML/CSS and/or Flash.
- Examples being dojo and Rialto (see the Open Directory Ajax page for more).
Higher-level languages that are compiled into native browser code.
- Examples being the Google Web Toolkit for Java and OpenLaszlo, for the high-level UI language Laszlo.

Hajax is a proposal to create a Haskell-based tool to program 'stand-alone' Ajax applications.

The main advantages of Hajax would be:

Web development using a very-high level language with extensive compile-time checks
No plugins (e.g. a Java VM) required on the user browser
No Haskell server back-end required (Hajax applications would communicate with back-ends written in any language).

Likely disadvantages with respect to native Ajax solutions are:

An additional compilation step
Lower performance

Hajax would consist of the following modules:

A Haskell compiler able to generate, directly or indirectly, native browser code.
Generic Haskell libraries (a port of a subset of the standard Haskell Libraries.
User interface framework and libraries.
(Optionally) A development environment.

Compiler

Requirements:

Support for Haskell 98 + most popular extensions.
Fast compilation.
Compact and efficient compiled code.

Compiler Design alternatives

Direct Compilation

Haskell code is directly compiled to JavaScript.

Advantage: possibly higher run-time performance, thanks to a more direct mapping between Haskell and JavaScript.

An example of this approach is Dimitry Golubovsky’s nhc98 to JavaScript Compiler, see [1] and in particular [2].

Two-Stages Compilation

Haskell code is compiled into an intermediate format (bytecodes or C--) that is then compiled to JavaScript.

For example: yhc to yhc bytecode to JavaScript (via the yhc bytecode API or similarly with GHCi bytecodes.

Advantage: much faster to develop as there would be less or no changes required in the compiler and the bytecode to JavaScript compilation should be straightforward.

Compiler Targets

Possible targets for the compiler are:

JavaScript/HTML/CSS
Flash
The OpenLaszlo kernel (currently under development) that can be executed in either Flash or HTML/Web browsers.

Generic Haskell Libraries

Libraries that would be useful include:

Prelude
Generic functional and mutable data structures
Parser/Regex libraries

UI Framework and Libraries

Most of the Haskell frameworks developed for GUI programming (see Libraries_and_tools/GUI_libraries) or Web programming (e.g. HSPClientside, see a full list at Libraries_and_tools/Web_programming) could be adapted for Hajax.

The libraries would include:

A complete set of UI widgets
Network libraries for browser-to-server communication

Development Environment

It should be relatively easy to adapt existing Haskell development environments like EclipseFP to work with Hajax.

Existing AJAX Applications Written in Haskell

HERA is written in Haskell and JavaScript. HERA uses asynchronous HTTP requests and Haskell threads to attempt many shallow rewrites quickly, in order to offer the user sensible choices. HERA would be a great stress test for Hajax.

@@ Line 3: / Line 3: @@
 Ajax applications can be written using either:
-* Native libraries/frameworks in JavaScript/HMTML/CSS. Examples being [http://www.dojotoolkit.org/ dojo] and [http://rialto.application-servers.com/wiki/ Rialto] (see the [http://dmoz.org/Computers/Programming/Languages/JavaScript/AJAX/ Open Directory Ajax page] for more).
+* Native libraries/frameworks in JavaScript/HMTML/CSS and/or Flash.
-* Higher-level languages that are compiled into JavaScript/HTML/CSS and/or Flash. Examples being the [http://code.google.com/webtoolkit Google Web Toolkit] for Java and [http://www.openlaszlo.org OpenLaszlo], for the high-level UI language Laszlo.
+** Examples being [http://www.dojotoolkit.org/ dojo] and [http://rialto.application-servers.com/wiki/ Rialto] (see the [http://dmoz.org/Computers/Programming/Languages/JavaScript/AJAX/ Open Directory Ajax page] for more).
+* Higher-level languages that are compiled into native browser code.
+** Examples being the [http://code.google.com/webtoolkit Google Web Toolkit] for Java and [http://www.openlaszlo.org OpenLaszlo], for the high-level UI language Laszlo.
-Hajax is a proposal to create a Haskell-based tool to program Ajax applications.
+Hajax is a proposal to create a Haskell-based tool to program 'stand-alone' Ajax applications.
 The main advantages of Hajax would be:
@@ Line 39: / Line 41: @@
 ==== Two-Stages Compilation ====
-Haskell code is compiled into an intermediate format (bytecodes or [http://en.wikipedia.org/wiki/C-- C--]) that is then compiled to JavaScript. For example: [http://www-users.cs.york.ac.uk/~ndm/yhc/  yhc] to yhc bytecode to JavaScript (via the [http://www.eecs.tufts.edu/~rdocki01/yhc-bytecode.html yhc bytecode API] or similarly with GHCi bytecodes.
+Haskell code is compiled into an intermediate format (bytecodes or [http://en.wikipedia.org/wiki/C-- C--]) that is then compiled to JavaScript.
+For example: [http://www-users.cs.york.ac.uk/~ndm/yhc/  yhc] to yhc bytecode to JavaScript (via the [http://www.eecs.tufts.edu/~rdocki01/yhc-bytecode.html yhc bytecode API] or similarly with GHCi bytecodes.
 Advantage: much faster to develop as there would be less or no changes required in the compiler and the bytecode to JavaScript compilation should be straightforward.
@@ Line 56: / Line 60: @@
 == UI Framework and Libraries ==
-Most of the Haskell frameworks developed for GUI programming (see [[Libraries_and_tools/GUI_libraries]]) or Web programming (e.g. [http://www.dtek.chalmers.se/~bjornson/soc/ HSPClientside], see a full list at  [[http://www.haskell.org/haskellwiki/Libraries_and_tools/Web_programming]]) could be adapted for Hajax.
+Most of the Haskell frameworks developed for GUI programming (see [[Libraries_and_tools/GUI_libraries]]) or Web programming (e.g. [http://www.dtek.chalmers.se/~bjornson/soc/ HSPClientside], see a full list at  [[Libraries_and_tools/Web_programming]]) could be adapted for Hajax.
 The libraries would include:
@@ Line 67: / Line 71: @@
 == Existing AJAX Applications Written in Haskell ==
-* [http://www.haskell.org/haskellwiki/Haskell_Equational_Reasoning_Assistant HERA] is written in Haskell and JavaScript. HERA uses asynchronous HTTP requests and Haskell threads to attempt many shallow rewrites quickly, in order to offer the user sensible choices. HERA would a great stress test for Hajax.
+* [http://www.haskell.org/haskellwiki/Haskell_Equational_Reasoning_Assistant HERA] is written in Haskell and JavaScript. HERA uses asynchronous HTTP requests and Haskell threads to attempt many shallow rewrites quickly, in order to offer the user sensible choices. HERA would be a great stress test for Hajax.