[Laszlo-user] Laszlo function as Array.sort argument

[André Bargull]

Another riddle for Tucker:

I can call:
_root.Debug.write("%s: %d - %d", arguments.callee, n1, n2);

But I cannot call:
_root.Debug.write("%s: %d - %d (%s)", arguments.callee, n1, n2, 
Debug);//or i.e. global, canvas etc. breaks, too

So, in which context does get Array#sort(..) called?

> It _is_ getting called.  For some reason, your Debug.write is failing  
> to send any output:
>
> lzx> Debug.trace(canvas, 'laszloMethod')
> lzx> [1,2,3].sort(canvas.laszloMethod)
> TRACE: [394491.00] laszloMethod.apply(?undefined?, [1, 2])
> laszloMethod( 1 , 2 )
> TRACE: [394501.00] laszloMethod -> 0
> TRACE: [394505.00] laszloMethod.apply(?undefined?, [1, 3])
> laszloMethod( 1 , 3 )
> TRACE: [394512.00] laszloMethod -> 0
> TRACE: [394516.00] laszloMethod.apply(?undefined?, [1, 2])
> laszloMethod( 1 , 2 )
> TRACE: [394523.00] laszloMethod -> 0
> TRACE: [394527.00] laszloMethod.apply(?undefined?, [2, 3])
> laszloMethod( 2 , 3 )
> TRACE: [394536.00] laszloMethod -> 0
> ?Array(3)#15| [1, 2, 3]?
> lzx>
>
> Oh, hah-hah.  I see why.  Because laslzoMethod is a method, it expects  
> a 'this' argument, and our compiler inserts an implicit `with (this)`  
> around your method body, but you are calling it as a function, and  
> `this` is undefined in that case (see the trace output above).  So  
> your code is turning into `with (undefined)` and I bet that causes the  
> global reference to Debug to fail.  Amusingly, tracing the method  
> makes the debug output work.  I can't really explain that.
>
> If you were to make a closure to call your method, it should work:
>
> lzx> Debug.untrace(canvas, 'laszloMethod')
> lzx> [1,2,3].sort(function (a, b) { return canvas.laszloMethod(a, b) })
> laszloMethod( 1 , 2 )
> laszloMethod( 1 , 3 )
> laszloMethod( 1 , 2 )
> laszloMethod( 2 , 3 )
> ?Array(3)#57| [1, 2, 3]?
> lzx>
>
> On 2008-01-09, at 14:28 EST, Pablo Kang wrote:
>
>   
>>  Btw, I know that I can call a laszloMethod from a Javascript  
>>  function like:
>>
>>   <method name="javascriptFunction" args="n1,n2">
>>       return canvas.laszloMethod(n1,n2);
>>   </method>
>>
>>  What I want to know is why it is I can't pass in the the  
>>  laszloMethod directly.
>>
>>  Thanks,
>>  pablo
>>
>>  On Wed, 9 Jan 2008, Pablo Kang wrote:
>>
>>     
>>>  Anyone know why passing in a function defined with an LZX method  
>>>  tag into Array.sort doesn't work? Here's a test case:
>>>
>>>  <canvas debug="true">
>>>
>>>    <method name="laszloMethod" args="n1,n2">
>>>       Debug.write('laszloMethod(', n1, ',', n2, ')');
>>>        return 0;
>>>    </method>
>>>
>>>    <script>
>>>        function javascriptFunction(n1,n2) {
>>>            Debug.write('javascriptFunction(', n1, ',', n2 ,')');
>>>            return 0;
>>>        }
>>>    </script>
>>>
>>>    <handler name="oninit">
>>>        var arr = [ 1,2,3 ];
>>>
>>>        Debug.write('-- Javascript Function --');
>>>        arr.sort( javascriptFunction );
>>>
>>>        Debug.write('-- Laszlo Method --------');
>>>        arr.sort( canvas.laszloMethod );
>>>    </handler>
>>>
>>>  </canvas>
>>>
>>>  pablo
>>>
>>>
>>>
>>>       
>
>