Lua Alchemy Getting Sweeter in v02a

Thanks to Alexander Lua Alchemy now has sugar! What this means is you no longer need to make calls like the following in the Lua Alchemy code:

as3.call(myvar, "someCall", param1, param2)

Instead you can make calls that look like native Lua code:

myvar.someCall(param1, param2)

This includes chaining calls like a.b.c().d

Below is a preview of the release:

Note that the demo above requires Flash Player 10 (required by Alchemy and my use of the local file system to allow opening/saving files). It is also hosted here where it can take up a full browser screen and is much easier to read.

You will notice in the demo code a great number of calls to as3.tolua(xxx). These calls convert ActionScript types into Lua types where possible. We removed all automatic conversion from AS3 to Lua types for performance reasons - each time you cross the Lua<->C<->AS3 boundary you have to pay the Alchemy wrapper performance tax.

For more information on the upcoming release of v0.2a (official downloads available in the next few days) see:

• HISTORY for v0.2a


• Lua Alchemy Homepage

Lua Alchemy v0.1a Released

The first release of Lua Alchemy has been released; the library SWC, demo, and code can be downloaded from here:
http://code.google.com/p/lua-alchemy/

Since my preview post (which is now running the same demo code) we have

• Added many Lua scripting samples.
• Fixed some memory leaks.
• Cleaned up function callbacks created in Lua which would typically be used for event listeners.
  

Below is a preview of the release:

Note that the demo above requires Flash Player 10 (required by Alchemy and my use of the local file system to allow opening/saving files). It is also hosted here where it can take up a full browser screen and is much easier to read.

The next version will include syntax sugar so instead of calling as3.call(var, "function", param) you could call var.function(param) and similar calls to make calling ActionScript code look the same as calling Lua code.

LuaAlchemy Project v.1a Preview

Since my last post my experiment to make Lua a runtime scripting language in Flash using Alchemy has become a full open source project located here:
http://code.google.com/p/lua-alchemy/

I even have a partner named Alexander Gladysh whom I met on the Lua boards.

We are approaching a V.1a release of the project. Using LuaAlchemy you can now create any ActionScript class available at runtime, get/set properties, call functions, and set event listeners (actually you can return a Lua function to use as an ActionScript function). The Lua to ActionScript interface is a little raw right now but we plan on adding some Lua sugar to make accessing ActionScript objects, classes, and namespaces in Lua look and feel like using Lua objects.

Below is a preview of the release:

Note that the demo above requires Flash Player 10 (required by Alchemy and my use of the local file system to allow opening/saving files). It is also hosted here where it can take up a full browser screen and is much easier to read.

Along the way to this release we have encountered a few problems which I will discuss. The first problem was speed. Although the Alchemy V.4a compiled code was fast enough for our purposes, it was about 30 times slower running a life simulator written in Lua than natively compiled Lua. The release of Alchemy V.5a has made life run 4 times faster so progress is being made (v.4a had some debug code compiled in that slowed things down).

The second problem has been gluegen. Gluegen is a tool to help you create wrappers around C code that takes a mix of C and ActionScript code to generate C and ActionScript wrappers. Unfortunately this seems to interfear with CLibInit.setSprite() which we wanted to use to provide a sprite that Lua could use for stdin, stdout, and stderr. Glugen created code creates and inits CLibInit as static members and you seemingly need to call setSprite() before init(). We worked around that problem by providing an output TextArea in the demo below, but we plan on writing the wrapper ourselves and not using gluegen at all.

The third problem is related to garbage collection in Flash and Lua. To make Lua functions usable as an ActionScript function we call AS3_Function() to create an ActionScript function that calls a C callback function passing in some contextual data. This data includes some Lua references in a malloced structure and we would like to know when it isn't needed anymore so it can be released. We haven't figured out any way for Alchemy to tell us when the object is no longer needed. A future version will do some cleanup when the lua_state is closed.

Overall our experience has been a positive one and Alchemy is still in Alpha.

Lua ActionScript Alchemy

At Adobe MAX 2008 San Francisco, Alchemy was released. Alchemy was once known as FlaCC or Cassava and is a C/C++ to ActionScript compiler.

Alchemy works by translating C/C++ code to ActionScript through a LLVM compiler which instead of producing machine or bytecode produces ActionScript. The translated C/C++ code uses a big ActionScript ByteArray as the C/C++ heap and stack. The performance of alchemy is slow if you martial data from C/C++ code to ActionScript or back but faster (supposedly up to 10 times faster) than ActionScript code you write yourself for data intensive actions where everything operates in the C/C++ memory space - speed improvements over AS code are also due to LLVM doing code optimization which is missing from the normal AS compiler.

After downloading and setting up Alchemy, I started trying to port over a few C/C++ libraries. The following libraries have given me some trouble mainly with needing to adjust makefiles or the ./configure script: Angband, Nethack, guile, Python, Ruby, ARToolkitPlus, SDL, and Squeak. I haven't given up on them but I wasn't in the mood to do battle with Makefiles; I wanted to learn Alchemy.

My success came with compiling the scripting language Lua 5.1.4 and embedding it into a Flex application. The following proof of concept can run a Lua script which returns one or more values and are shown in the Lua Stack Panel. Lua can make the following calls into Flex:

• getTextAreaProperty(property_name) - Returns the given property of the text area in the lower left hand corner.
  
• setTextAreaProperty(property_name, value) - Sets the given property on the text area in the lower left hand corner (must accept string values).
  
• callTextAreaFunction(function_name[, param1, ..., paramN]) - Calls a function on the text area in the lower left hand corner (must accept string values).
  
• average(value1, ..., valueN) - Returns the average and sum of the given values.
  

Note that the demo above requires Flash Player 10 (required by Alchemy and my use of the local file system to allow opening/saving files). It is also hosted here.

Should I continue working on this library, I'd want to allow Lua to create and call functions on any arbitrary ActionScript class. Alchemy is still in beta and does have its own problems - not everything builds easily and while pure Alchemy code can be faster than ActionScript, marshaling from ActionScript to C/C++ code and back can slow things down - for example life.lua takes 4 seconds with the standard compile of Lua and 13 minutes! with the Alchemy build. Still it works quite well for my purposes of embedding a runtime scripting language into my Flex applications.

For more information check out the following blog posts:

• http://www.automatastudios.com/2008/11/21/understanding-adobe-alchemy
• http://docs.google.com/View?docid=dg7w6sqr_8fbhvz6d6
• http://techblog.floorplanner.com/2008/11/23/alchemy-first-looks
• http://www.theregister.co.uk/2008/12/02/adobe_alchemy/

Edit: Created a google code project to share efforts in using Alchemy to embed Lua in ActionScript. Uploaded the proof of concept:

• http://code.google.com/p/lua-alchemy
• http://code.google.com/p/lua-alchemy/downloads/list
  

FlaCC (C/C++ to Flash Compiler)

More news on the C/C++ to Flash compiler, now called FlaCC. With this tool developed by Scott Petersen at Adobe would allow almost any arbitrary C/C++ code to be compiled down to ActionScript bytecode to run on the Flash player. I first heard of this at MAX 2007 and there will be a session at MAX 2008 on this (plus hints it will be in keynotes).

While we wait here are a few links to some more recent news:

• http://www.peterelst.com/blog/2008/10/05/more-information-on-flacc/
• From LLVM Dev Meeting
  
  • http://llvm.org/devmtg/2008-08/Petersen_FlashCCompiler.pdf
  • http://llvm.org/devmtg/2008-08/Petersen_FlashCCompiler_Hi.m4v
    

The MAX 2008 Session is "Using C++ Libraries in Flash Player and Adobe AIR" Monday, November 17, 2:00 pm - 3:00 pm. I'm looking forward to that session.

360|Flex

This coming August, I'll be heading out to San Jose to attend the 360 Flex conference:
http://www.360conferences.com/360flex/

I'm new to the Flex scene (almost a year now) and came from a background of 14 years of C++ cross-platform application development so it is exciting and different to immerse myself in the new culture. This is the first 360 I will have attended and only the second conference related to Flex (the first being MAX 2007 in Chicago). I'm now fortunate enough to be working for Universal Mind (as a contractor) and when I saw all the people taking vacation to attend 360, I knew I had to attend.

Of particular interest to me are sessions teaching frameworks, component building, design patterns, process (I'm a big process geek - how you do something is very important for maintainability), and low level programming. There are so many sessions that appeal to me at the same time that I'm going to have to make some rough decisions. Here is a list of the appealing sessions (fortunately I work with some of these people so I can pick their brain later):

• Pre-Conference stuff I cannot attend because my plane doesn't land until 2pm
  
  • James Huang - The R1-RPC/J Toolkit and the D.eval API
    
  • Ben Stucki/Ryan Campbell - OpenFlux
    
• Adam Flater - How to make your AIR app blow up with Merapi
• Alex Harui - Versioning Support for Large Applications and Portals
• Andrew Powell - Implementing BlazeDS
• Axel Jensen - Project Workflow (trac,svn,ANT,XML...)
• Ben Clinkinbeard - Concepts and Strategies for Creating Reusable Components
• Ben Stucki - How to Build a Framework
• Brad Umbaugh/RJ Owen - Diving Deep with the Flex Component Lifecycle
• Brian Weisenthal - Architecting real-time and collaborative applications in Flex
• Chet Haase - Filthy Rich [Flex] Clients
• Chris Scott - Introduction to the Swiz Framework for Flex
• Eric Ko - Reflective Programming
• Jacob Wright - Advanced ActionScript APIs
  
• Jeff Houser - How to Build Flex Components
  
• Jeff Tapper - Unraveling the hassle with Drag an Drop in AIR
• Jonathan Branam - Improve your programming by reading the Flex source code
• Josh Tynjala - Polishing Components for the Unwashed Masses
• Laura Arguello - Decoupling Flex Applications with Mate Framework
• H. Paul Robertson - Advanced AIR and SQLite: An optimization conversation
• Ryan Campbell - PlexiGlass (OpenFlux 3D Components)
• Samuel Asher Rivello - Creating an MMO from Scratch with Adobe Flex 3… in 59 minutes.
• Tom Gonzalez - Data Visualization and Dashboards with Flex
• Troy Gardner - Advanced State management, the Heirarchical State Design Pattern

PS: The 360|Flex team sent me a 1GB flash drive with content from 360|Flex Atlanta and Europe. I could pass it on to a lucky commenter.

ActionScript Cross Compiler Theories

This post is a bit late coming, but I'm trying to be good and post once a week.

Last year after Adobe MAX 2007, I posted a bit on the preview of a C++ to ActionScript compiler. This year there has been a little more buzz buzz on the subject. I've been curious how this might be done and have a few theories:

• Create a C++ parser/compiler to either produce Flash bytecodes or ActionScript. C++ is notoriously hard to parse so this would be quite a pain without something to get you started. There is a partial ANTLR grammar for C++ here.
  
• Create a gcc backend to produce Flash bytecodes. All gcc languages compile to intermediate languages called GIMPLE and GENERIC. Target platforms "merely" translate this intermediate form to the target platform. See this link for more information. This path would be the most generic solution and allow any gcc language to be compiled to flash.
• Leverage PyPy (a python VM generator and more) to create an ActionScript or Flash bytecode target. Of course this would only really help you use python unless you created a translator for C++, but flex-pypy is cool enough to mention.

Overall I think the gcc solution is the most likely and most powerful. I'm looking forward to the cross compiler and hope it will be included in Flex 4 as part of the broadening horizons theme.

Using ANTLR to create an Excel Like Formula Parser in Flex

Introduction
One of my first Flex programming projects was to write an Excel-like expression parser. This parser was written using the “shunting yard” algorithm by Edsger Dijkstra to transform infix notation to a reverse-polish notation (postfix) stack which is easily processed. That code isn't publicly available but the algorithms are described in a paper I wrote here.

I decided to re-write the expression evaluator using ANTLR. ANTLR is a parser generator that takes BNF-like notation and generates code for a target language. The default target language is Java, but there are many other target languages including an ActionScript target in the upcoming 3.1 version.

Flex Formula Evaluator
The actual Flex application is available here with source available. This is an example of a formula that can be evaluatedl feel free to copy and paste into the evaluator below (variables are noted in "[variable_name]"):
(1+2)*sum(9-8,5,17.5,[numarray])/if(or([string]="hello",1>5),2,99)
How Does it Work?
The formula parser begins with the ANTLR grammar found in Formula.g and FormulaTree.g (in src com.arcanearcade.antlr). ANTLR has 3 types of grammar rules:

• Lexer - Used to transform the character stream into a series of tokens. Lexer rule names are written in all capital letters. For example, the following code describes how to recognize variables which are any characters except [ or ] found between [ and ].
  

VARIABLE : '[' ~('[' | ']')+ ']';

• Parser - Walks though the tokens to form sentences in the grammar. Parser rules begin with lower case letters. The following example shows how to recognize a percent token, which is a number token followed by the percent sign (both described in the parser grammar). The '^' in the grammar is a special token that shows what the head of the created tree grammar looks like. So "50%" is transformed into a tree with an s-expression notation of "(% 50)" and will be evaluated to the value "0.5" by the tree grammar.
  

percent: NUMBER PERCENT^;

• Tree - This optional grammer taks the tree that can be created by parser grammar and with the help of native code snippets interprets the tree to produce output. While you can use code snippets directly in the parser, using a tree grammer allows you to reuse the lexer and parser for other languages and write a (usually simpler) tree parser for each target language. The following tree grammar shows how to evaluate addition where "6 + 7" was turned into "(+ 6 7)" by the parser and is evaluated to the number "13" by the ActionScript code between the {}
  

operation returns [Object value]
: ^(ADD a=expression b=expression)
{ $value = Number($a.value) + Number($b.value); }

The ANTLR tools parse the grammar files to produce native code as shown in the diagram below:
Code in FlexFormula.mxml evaluateFormula() takes a string, feeds it into the lexer, takes the output of the lexer feeds it into the parser, and then finally feeds that into the tree to evaluate the result. FormulaTree#addFunction() adds new spreadsheet functions like "sum" and "if" and FormulaTree#lookupVariable sets the function callback to retrieve variables.

What Next?
The expression parser isn't as friendly as it could be (it is just a demo). To improve the formula engine to the point it could be used in a spreadsheet the FormulaLexer, FormulaParser, and FormulaTree in a class that would:

• Add all the common function.
• Setup binding to watch for changes to the formula string and only call the lexer and parser when the formula changes.
• Setup a public and bindable variable for the result value.
• Add binding for all variables in an expression so when they change the tree can be re-evaluated.
• Improve error handling
  

C++ to ActionScript

One of the sneak peeks at Adobe MAX 2007 Chicago was a C++ to ActionScript translator by Scott Peterson. This was the most interesting of the sneak peeks for me in part because I was a C++ developer for 12 years (until 3 weeks ago) and because of the implications of the translator.

First check out the video here:
http://youtube.com/watch?v=0hX-Uh3oTcE

During the demo he showed:

• A C++ XSLT library turned into ActionScript
• A fractal program from C++ to ActionScript simulating green threads using ActionScripts asyncronous calls.
• Doom 2 running in Flash.

How does it work:

1. C/C++ code is translated to ActionScript 3
2. AS3 code is compiled into a SWF
3. Run the code on Flash/AIR
   

What does it mean:

• Easy porting useful open source C++ libraries/programs to ActionScript to run on the browser.
• Porting interpreters for languges like Ruby, PHP, Lua, Python, Smalltalk. ... to run on Flash.
• Writing your own DSL using ANTLR and porting the C code to ActionScript without having to write an ANTLR target language. I recently wrote a shunting yard algorithm Lexer and RPN parser in ActionScript for an Excel like language where this would have saved me some time (but not the fun of writing my own Lexer/Parser).

Scott Peterson, if you ever read this and want an alpha/beta tester I have two projects in mind:

• An AIR Subversion client.
• Porting the Squeak Smalltalk core to AS to match the Vista Smalltalk in Silverlight project.
  

What is Thermo?

Yesterday at Adobe MAX 2007 in Chicago, I had the pleasure of seeing a sneak peak at a potential future product of Adobe's codenamed Thermo. I'm a developer and not a designer and have never worked with a designer, but I can see the appeal of the product. Plus it is technically cool.

During the demo they took a UI mockup drawn in Adobe Photoshop with layers. Thermo converted that mockup int MXML. The converted MXML had new "graphics" tags that will be added to the language. The graphics tags draw (as you may guess) graphics primitives (boxes, lines, etc), text, images, etc. While not interactive yet, the mockup can be compiled as a Flex application.

Then the magic comes in. Graphics items are selected and turned into controls. For example a box with some text in it was turned into text input. Relatively simple yes, but the compiled Flex app was now interactive. Next they turned a row of Album images with a drawing of a scroll bar in it into a scrollable list of albums. Thermo took the images given to populate the list and could add data, import new images, or just duplicate the images so there was something to scroll.

Interaction was added to the application in the form of a rollover on the albums that zoomed in and showed the title and artist. Overall it was an impressive show of the transformation of graphics to an application.

The "Flex Roadmap" session shed some light on what might be going on behind the scenes in MXML for Thermo (and any other Flex development). From what I hear skinning a control isn't easy (I haven't done so) but the future version will make it easy. They will split the controls into a MVC like architecture with a Skin, Controller, and Model.

The Model encapsulates data, the controller behavior, and skin all of the UI. The skin is all done in declarative MXML using the graphics tags (including transitions). During this demo they showed how to skin a list control to look like a standard list, list with icons, behavior, turning a list into tabs, turing a list into an accordion.

I'm looking forward to the future of Flex.

Shifting Gears to Adobe Flex and C#

Times change and so do jobs. I'm starting a new job in two weeks working with rich internet applications - Microsoft SQL data store, C# middle-ware, and Adobe Flex GUI. None of which I have any professional experience but I'm eager to learn.

So what this means is that Squeak, Erlang, and Rails take something of a back seat while I learn the technologies for my new job. I plan on dabbling in Erlang and Rails for being the middle-ware for my own personal projects.

Meanwhile, I wrote a Sudoku solver in Flex for my algorithm analysis class.

http://www.arcanearcade.com/Flex/Sudoku/Sudoku.html

Overall I really like the Flex framework thus far. It is nice to know that Flash 9 has a 90% browser penetration, so it makes for a reliable platform for distributing my own Flex applications. The applications look really nice as well - as a Windows application developer I've always found most web applications not quite up to snuff.