[Newbies] Re: Adding methods to Integers...

[Klaus D. Witzel]

On Fri, 13 Apr 2007 13:39:08 +0200, Bert Freudenberg wrote:

> On Apr 13, 2007, at 13:27 , Klaus D. Witzel wrote:
>
>> Hi Bert,
>>
>> on Thu, 12 Apr 2007 18:31:55 +0200, you wrote:
>>
>>> This is actually wrong.
>>
>> :)
>>
>>> Only SmallIntegers are special [*].
>>>
>>> What happens is this: When you add two SmallIntegers (like "3 + 4"),  
>>> and the result is a SmallInteger, the result is calculated in the  
>>> bytecode directly. Otherwise, a regular send of #+ is performed.
>>
>> Right.
>>
>>> From there, everything else happens in the image,
>>
>> Not really. (Integer>>#+ aNumber) sends (self digitAdd: aNumber) which  
>> is implemented as <primitive: 'primDigitAdd' module: 'LargeIntegers'>  
>> which is part of the VM. Of course the LargeIntegers module may be  
>> absent, have failed to load, may not like the argument, etc.
>
> No, this is an *optional* primitive. It's there purely to speed up  
> computation and can be safely removed.

Sure, but this thread is not about what happens when the optional  
primitive is removed, and I was not reflecting that, either. I was rather  
discussing the point when the primitive does *not* fail on one of  
Patrick's subclasses and, what the returned species is.

> You could change the Integer classes to handle subclasses properly (via  
> species etc.). So far, this has not been necessary. My point was that  
> this (unlike SmallIntegers) is *not* hard-coded in the VM.

I think it depends on operand order. When the LargeIntegers module is  
invoked (in my previous example when sending + myLargeInteger to  
SmallInteger 1) then a "hard-coded" instance of LargePositiveIntegers is  
returned.

The attached class can be used (together with my previous example) to  
illustrate my point. The class does not inherit from some default large  
integer class and the primitive does not fail, regardless of operand  
order. I hope I didn't base my argument on a bug or mistake.

FWIW I do not disagree with anything about your argument, except a bit  
with "hard-coded".

> - Bert -

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