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From Gordon Smith <gosm...@adobe.com>
Subject Re: [FlaconJS] pseudo emitter algorithm
Date Sat, 01 Dec 2012 05:48:08 GMT
The BURM is the Bottom-Up Rewrite Machine that the BURG or Bottom-Up Rewrite Generator generates.
A BURM reduces subtrees within an AST to an output format such as ABC or JS, starting with
leaf nodes and working its way upward.

Sent from my iPad

On Nov 30, 2012, at 8:45 PM, "Alex Harui" <aharui@adobe.com> wrote:

> BURM?  What does that stand for anyway?  It might as well have been Burmese.
> It will take a while to understand :-)
> On 11/30/12 5:36 PM, "Gordon Smith" <gosmith@adobe.com> wrote:
>>> I don't know SWF format and JBurg
>> The SWF and ABC formats are irrelevant if you want to generate JS code, so you
>> wouldn't need to learn them.
>> If you don't want to learn about the BURM I suppose you could try generating
>> JS code directly from the AST. I don't know enough about FalconJS to know
>> whether the BURM approach produces more efficient code. Understanding the BURM
>> is not terribly hard, though. There are three main ideas:
>> 1. A BURM pattern like
>>    Pattern labeledBreakStmt
>>    BreakID(IdentifierID(void));
>> describes a subtree within the AST; in this case, it is describing the subtree
>>    BreakNode
>>        IdentifierNode
>> that represents code like "break foo";
>> 2. A BURM rule like
>>    statement = Pattern labeledBreakStmt: 0
>>    JBurg.Reduction reducer.reduce_labeledBreakStmt(__p);
>> tells the BURM what to do when it finds such a subtree: namely, call the Java
>> method reduce_labeledBreakStmt() in the ASGeneratingReducer, which has a slew
>> of "reduce_XXX()" methods for reducing various subtrees.
>> 3. The result of a "reduction" can be any Java object which somehow represents
>> the subtree that got reduced. Often this is an InstructionList but it can be
>> anything. This Java object can then be used in other patterns to describe more
>> general or recursive patterns, as in
>>    Pattern blockStmt
>>    BlockID(statement stmts*);
>> For example, this says that a block statement is a BlockNode with multiple
>> child nodes which have been reduced to a 'statement'.
>> The BURM patterns and rules should be mostly the same whether you are
>> generating ABC or JS, because they depend on the AS node patterns that are
>> being noticed and reduced. So I really think you'd be doing most of your work
>> inside the JSGeneratingReducer. I believe this was Bernd's approach when he
>> developed FalconJS. You just make the reduce_XXX() method produce JS strings
>> rather than ABC InstructionLists.
>> - Gordon
>> -----Original Message-----
>> From: Michael Schmalle [mailto:apache@teotigraphix.com]
>> Sent: Friday, November 30, 2012 4:11 PM
>> To: flex-dev@incubator.apache.org
>> Subject: RE: [FlaconJS] pseudo emitter algorithm
>> Quoting Gordon Smith <gosmith@adobe.com>:
>>> I didn't follow the whole discussion. Is the issue that you were
>>> planning to work on MXML->JS but Alex and I think
>>> MXML->datastructure is a better approach? You don't have to accept
>>> what we say. :)
>>> - Gordon
>> The conversation was about exploring a straight AST to JS convertor
>> and bypassing the JS emitting using SWF reducer.
>> My point was in the discussion that I don't know SWF format and JBurg
>> so trying to maintain FalconJS in it's current state would be hard for
>> a lot of developers.
>> A lot of cross compilers just work with the straight AST in our case
>> the IASNode or IDefinition frameworks.
>> I also thought having this ability would allow other targets to be
>> implemented more quickly IE Java android or something...
>> What do you think?
>>> -----Original Message-----
>>> From: Michael Schmalle [mailto:apache@teotigraphix.com]
>>> Sent: Friday, November 30, 2012 3:55 PM
>>> To: flex-dev@incubator.apache.org
>>> Subject: RE: [FlaconJS] pseudo emitter algorithm
>>> Well considering the conversation between you two, I will ditch
>>> pretty much all I said in the last 3 days. This is what I get for
>>> living on a mountain...
>>> I have interest in the non-flash player stuff, so I guess I will
>>> keep up with your conversations.
>>> For now, I will focus on testing the compiler and trying to get in a
>>> groove somehow dealing with that. I'm going to try and document more
>>> of the compiler on the wiki. Gordon feel free the correct me if I'm
>>> wrong in places.
>>> And, I will try to really understand Alex's prototype and see if I
>>> can get my brain wrapped around that to help with some simple test
>>> components.
>>> Mike
>>> Quoting Gordon Smith <gosmith@adobe.com>:
>>>> That sounds fine. We'll work in parallel:
>>>> Me: MXML->ABC
>>>> You: MXML->datastructure, first for use in AS/ABC, then for use in JS
>>>> - Gordon
>>>> -----Original Message-----
>>>> From: Alex Harui [mailto:aharui@adobe.com]
>>>> Sent: Friday, November 30, 2012 3:29 PM
>>>> To: flex-dev@incubator.apache.org
>>>> Subject: Re: [FlaconJS] pseudo emitter algorithm
>>>> On 11/30/12 3:22 PM, "Gordon Smith" <gosmith@adobe.com> wrote:
>>>>> MXML->JS doesn't exist and is not the way to go.
>>>>> MXML->datastructure is a good idea. Alex will do it first for
>>>>> MXML->interpretation
>>>>> by JS and later for interpretation by an ABC library written in AS.
>>>> I'm pretty sure I had this all working last year in AS.  I just have
>>>> to dust it off.  Right now it is easier/faster for me to debug in AS,
>>>> so I will probably do the AS version first, but I will be keeping all
>>>> of the old ABC code paths around.  Right now there is some global flag
>>>> that determines which code paths to go down.  I might tie that to some
>>>> new property in flex-config.xml or something like that.
>>>> --
>>>> Alex Harui
>>>> Flex SDK Team
>>>> Adobe Systems, Inc.
>>>> http://blogs.adobe.com/aharui
>>> --
>>> Michael Schmalle - Teoti Graphix, LLC
>>> http://www.teotigraphix.com
>>> http://blog.teotigraphix.com
> -- 
> Alex Harui
> Flex SDK Team
> Adobe Systems, Inc.
> http://blogs.adobe.com/aharui

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