Stephen --

Yes, it works fine from the outside where one has to send messages, but
it's the inside case of:
      foo <- 59
that Smalltalk-80 lets you do that I don't like. This absolutely means
munge that variable and there is no override possible -- I like self's
gentler and more general approach that handles this from the inside as
well. In other words: of course I think we should use accessors (that was
one of my earliest ahas!) -- As I said, what I don't like is that Smalltalk
permits the above case (and so many people can't refrain from using it,
only to get bitten by the early binding later on ....)

Cheers,

Alan

-----

At 2:30 PM -0800 7/30/99, Stephen Pope wrote:
>Alan Kay wrote:
>>
>> I agree Andreas -- but we could also point the finger at Smalltalk-80 and
>> ask why doesn't it have a slot class that would allow us to change the
>> meaning without having to worry about what the code looks like ...
>>  [ ... ]
>> I think that the Self way is pretty good and clean, since it extends
>> referential transparency one more level. A little more of a metadescription
>> would make things even nicer and more useful ...
>
>Far be it for me to pick an argument with Alan, but I think that
>Smalltalk's accessing messages are just what he's looking for. If you
>only refer to an instance variable in the getter/setter accessing
>methods, you can change it freely, and the rest of your code never has
>to know. If you use any of the goodies for automatically generating
>accessing methods, then you never have to see any state except when you
>define a class.
>
>Back when I taught Smalltalk regularly, we used the example of 2-D
>points, which have methods such as x, y, x:, y:, r, theta, r: and
>theta:. A client of this class has no idea or concern whether it
>actually stores its coordinates using Cartesian or polar coordinates.
>Only a benchmark test of the relative cost of translation and rotation
>operations will tell, and if you do one of these much more than the
>other, you're free to change the storage format of points with no other
>side-effects.
>
>--
>
>Stephen Travis Pope  --  http://www.create.ucsb.edu/~stp
>stp at create.ucsb.edu  --  stp9 at cornell.edu