Klaus D. Witzel puso en su mail :

> List,
> 
> haven't you heard that Smalltalk and Squeak do not directly support
> multiple inheritance, time and again? But that Perl, Python and Ruby do
> (to some extent)?
> - http://www.google.com/search?q=python+ruby+multiple+inheritance
> 
> Well, that is not the case for Smalltalk since the time that VMs are
> implemented by using the specs of the Blue Book.
> 
> I have attached a small .st file which demonstrates that the *unchanged*
> VM *must* support multiple inheritance (for message sends), or else it
> won't work properly. It's a matter of view on what the VM does for you :-D
> 
> With the exception of support code for exceptions [pun intended] the
> attached examples work on VMs which implement the super send from the Blue
> Book.
> 
> The first example demonstrates that multiple inheritance works; in this
> example it is also checked that the requesting method qualifies (that the
> instances qualify is checked at fileIn time).
> 
> The second example does a message tally and shows that there is less than
> 50% overhead when possible walkbacks are guarded at every multiple
> inheritance message send.
> 
> The third example employs the existing method cache of the VM (the
> original Squeak VM) for multiple inheritance message sends and thus
> minimizes the overhead to less than 5% (and the demo is written in .st
> code :-)
> 
> Again, this all exists *unchanged* for decades. It only had to be brought
> to the surface?
> 
> -------
> 
> I would be very interested to see if my examples run on other platforms
> and VMs, please post your experience. Thank you.
> 
> It'd be equally interesting if the approach had been used before.
> 
> /Klaus
> ?
> 


DoIt: " MessageTally spyOn: [ | aCupWith |
        aCupWith := CaffeeWithMilk newLatteMacchiato.
        10000 timesRepeat: [aCupWith veryMuchSugar]] "

Here I got on Mac

 1267 tallies, 1273 msec.

**Tree**
99.8% {1270ms} CaffeeWithMilk>>veryMuchSugar
  47.0% {598ms} CaffeeWithMilk>>DoIt
    |46.7% {594ms} ProcessorScheduler>>nextReadyProcess
    |  22.7% {289ms} LinkedList>>isEmpty
    |  22.6% {288ms} Array(SequenceableCollection)>>reverseDo:
  26.8% {341ms} CaffeeWithMilk(Object)>>doesNotUnderstand:
    |12.2% {155ms} MessageNotUnderstood(Exception)>>signal
    |  |11.8% {150ms} MethodContext(ContextPart)>>handleSignal:
    |  |  7.5% {95ms} BlockContext>>valueWithPossibleArgs:
    |11.5% {146ms} MessageNotUnderstood>>message:
  22.3% {284ms} CaffeeWithMilk(SuperclassX)>>internalSwitchSenderToParent:
    |17.7% {225ms} UndefinedObject(Object)>>->
    |  |16.0% {204ms} Association>>key:value:
    |2.7% {34ms} CompiledMethod>>numLiterals
  3.1% {39ms} BlockContext>>onDNU:do:

**Leaves**
22.7% {289ms} LinkedList>>isEmpty
22.6% {288ms} Array(SequenceableCollection)>>reverseDo:
16.0% {204ms} Association>>key:value:
11.5% {146ms} MessageNotUnderstood>>message:
9.0% {115ms} BlockContext>>valueWithPossibleArgs:

**Memory**
    old            +0 bytes
    young        -25,012 bytes
    used        -25,012 bytes
    free        +25,012 bytes

**GCs**
    full            0 totalling 0ms (0.0% uptime)
    incr        550 totalling 356ms (28.0% uptime), avg 1.0ms
    tenures        0
    root table    0 overflows


But your code deserve more deep study, and I thanks for it.

Edgar



	
	
		
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