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From Gordon Smith <gosm...@adobe.com>
Subject RE: Falcon compiler source code / Falcon architecture
Date Thu, 19 Jan 2012 19:05:08 GMT
Until we release specs, Javadoc, or code for Falcon, here is a very brief overview of Falcon's
architecture:

Falcon is designed from the beginning to support compiling multiple targets in multiple projects
in a workspace (as you have in an IDE like Flash Builder). By contrast, asc was designed to
compile a single AS file, and then mxmlc was built on top of that.

Falcon uses multiple threads to compile multiple files at the same time. The more cores you
have, the faster it goes.

Critical data structures such as the symbol table (which stores information about which classes
are known, what methods they have, etc.) are shared across the entire workspace, to minimize
memory usage.

Critical data structures are maintained in memory to support both compilation and IDS code
intelligence in an efficient and consistent way. For example: If you open a file in the IDE,
Falcon builds a syntax tree and symbol table for it to support intelligent editing. Compiling
the file requires just one additional code generation step. By contrast, in the current Flash
Builder which uses the compiler in the SDK, Flash Builder builds its own parse trees and symbol
tables to support editing, and then when you compile the compiler in the SDK builds another
set of parse trees and symbol tables. This is slow and a waste of memory.

Falcon understands .as, .mxml, .css, and .properties files.

The parse trees for AS consist of nodes from about 100 classes, such as LiteralNode, BinaryOperatorNode,
FunctionNode, ClassNode. The parse trees for MXML consist of nodes from about 50 classes,
such as MXMLDocumentNode, MXMLInstanceNode, MXMLScriptNode, etc. The ActionScript-y parts
of MXML are represented by AS nodes inside of MXML nodes.

The symbol table consists of objects representing the things your code defines, such as ClassDefiniition,
FunctionDefinition, and VariableDefinition, arranged into a hierarchy of scope objects.

Falcon uses 3rd-party grammars like JFlex, ANTLR, and JBurg to generate various lexers, parsers,
and code generators.

MXML is compiled directly to ABC, not to ActionScript source code or an ActionScript parse
tree.

- Gordon Smith, Adobe

P.S. After working on the Flex framework since its inception for about 8 years, I joined the
Falcon team 18 months ago.



-----Original Message-----
From: Raju Bitter [mailto:rajubitter@googlemail.com] 
Sent: Thursday, January 19, 2012 2:10 AM
To: flex-dev@incubator.apache.org
Subject: Re: Falcon compiler source code / Falcon architecture

2012/1/19 Alex Harui <aharui@adobe.com>:
> I was in the Falcon code in November.  It was way easier to figure out 
> how to make changes than with MXMLC.  Even if it is not documented, I 
> think it will be easier to make progress that with the Falcon code base.
I agree, that sounds like it would be much better to use the Falcon code base. There are normally
fewer community members with much experience in language/compiler design, and the cleaner
the architecture is, the better for the community.
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