The Gospel of Alan (was Re: [squeak-dev] Re: Instance variable access in superclasses)

Bert Freudenberg bert at freudenbergs.de
Wed Nov 26 16:18:00 UTC 2008


On 26.11.2008, at 09:48, Igor Stasenko wrote:

> 2008/11/26 Trygve Reenskaug <trygver at ifi.uio.no>:
>>
>> On 26.11.2008 05:32, Igor Stasenko wrote:
>>>
>>> 1. Everything is an object
>>> 2. Objects communicate by sending and receiving messages (in terms  
>>> of
>>> objects)
>>> 3. Objects has their own memory (in terms of objects)
>>> ----
>>> 4. Every object is an instance of class (which must be an object)
>>> 5. The class holds the shared behavior for its instances (in the  
>>> form
>>> of objects in a program list)
>>> 6. To eval a program list, control is passed to the first object and
>>> the remainder is treated as its message
>>>
>>> so, where in these statements you find anything about inheritance,  
>>> or
>>> something where it says that subclass(es) should have any  
>>> assumptions
>>> about the ways how superclass is storing its instances in memory,  
>>> and
>>> therefore a subclass allowed to directly manipulate the object's  
>>> state
>>> without consulting with superclass?
>>
>> I'm afraid Alan wasn't as precise as he should have been here.
>
> I think he did this intentionally, because a precise parts is up to
> implementation.
> The principles above is most generic ones. Btw, notice a line between
> 3 and 4, its not just a random stroke - its actually shows a first
> step from most generic to more specific.


Just a meta remark - I find it highly amusing how people dissect the  
Gospel of Alan, even interpreting it literally. He must get quite a  
chuckle from that ;)

- Bert -





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