[Laszlo-dev] Constraint function generator

[Donald Anderson]

On Feb 20, 2008, at 5:05 AM, P T Withington wrote:

> On 2008-02-19, at 19:00 EST, Donald Anderson wrote:
>
>> Henry,
>>
>> I have the constraint function generator mostly ready.
>>
>> First question - do we need an option to compute meta references?
>> That's apparently a compile time option, but I don't see when it's  
>> turned on.
>
> That was a failed experiment.  Correct, but determined to be too  
> slow.  For now, we are just keeping the code as a reference  
> implementation, turned off.  It is trying to solve the problem that  
> if a constraint says `a.b.c`, we only listen for `c` changing in  
> `a.b`; if `b` changes in `a`, we won't notice.

Okay, I'll leave that code untouched.
>
>
>> In my current version, I am accepting as arguments 1) the name of  
>> the original function,
>> and 2) the source for the function, for the moment I expect the  
>> source
>> to look just like what you are now generating.
>>
>> I am returning the source of a function with the name  
>> XXX_dependencies.
>
> I agree with you and Henry that it will be more useful going forward  
> if you accept an arbitrary expression (as a string) and return the  
> expression that computes the dependencies for that (also as a  
> string).  Thus, to retrofit your code to the current "pattern" you  
> would analyze the expression that is the second argument to  
> setAttribute in the current constraint functions.
>
> Are you doing this in RingDing?  I think that would be the best  
> place, since then we can test against the known-working test cases.

At the moment I'm in devildog, but there's nothing that's branch- 
specific at this point.
As for testing, if you want me to retrofit the current code in  
compiler/NodeModel.java to use this
directly, well that could be done and tested in either branch, right?
The branch doesn't matter to me - but whether I retrofit (or merely  
provide
a new internal API) does...

>> For example, input source is this: (culled from where this string  
>> is made in NodeModel.java):
>>
>> ===
>> function $base$2Fbasefocusview$2Elzx_282_41_x_always () {
>> #pragma 'constraintFunction'
>>
>> #pragma 'withThis'
>> this.setAttribute("x",
>> #beginAttribute
>>
>> #file base/basefocusview.lzx
>> #line 282
>>                                        -classroot.offset
>> #endAttribute
>> )}
>> ===
>>
>> Output source is currently:
>>
>> ===
>> /* -*- file: Compiler.substitute#-1.1 -*- */
>> function $base$2Fbasefocusview$2Elzx_282_41_x_always_dependencies  
>> () {
>> #pragma "warnUndefinedReferences=false";
>> with (this) {
>> return [classroot, "offset"]
>> }}
>> ===
>>
>> I'm thinking instead I could accept simply '-classroot.offset'
>> and return just the text of the statements:
>> with (this) {
>>   return [classroot, "offset"]
>> }
>
> I would leave out the `with (this)` and have that be an implicit  
> burden on the callee.  (Especially because that is implicit in JS2  
> method bodies).

Will do.

>> Then you could name the function whatever you want or
>> use it as a function expression.  Or I could return just the
>> array (as an expression) like '[classroot, "offset"]' .  It depends
>> on how you plan to use it,  vs. how much of the details you need to  
>> know.
>>
>> - Don
>>
>> --
>>
>> Don Anderson
>> Java/C/C++, Berkeley DB, systems consultant
>>
>> voice: 617-547-7881
>> email: dda at ddanderson.com
>> www: http://www.ddanderson.com
>>
>>
>>
>>
>


--

Don Anderson
Java/C/C++, Berkeley DB, systems consultant

voice: 617-547-7881
email: dda at ddanderson.com
www: http://www.ddanderson.com