Squeak-dev April 1998

squeak-dev@lists.squeakfoundation.org

107 participants
279 discussions

Re:Version 2.0 -- What? When? Beta?
by Ryan Davis 28 Apr '98

28 Apr '98

>Version 2.0 will be entirely converted to pluggable views. This is already >done, including the elimination of over 40 classes! It will also be possible Are these 40 eliminations going to be documented w/ workarounds/replacements? If replacements is it possible to ship w/ symbols referencing the replacements (w/ an expectation that the symbols will not ship on the next release)? Ryan Davis -=- Zen Spider Software -=- mailto:zss@ZenSpider.com -=- http://www.ZenSpider.com/ -=- I know that you believe you understand what you think I said but, I'm not sure you realize that what you heard is not what I meant.

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Re: Introducing more meaning into inheritance
by David Farber 28 Apr '98

28 Apr '98

>> Integer size >>=> AlephNull > >To be consistent with the #do: issue, Integer size should not be null. We know >that we only deal with finite sets, we can take advantage of this knowledge, >which is not just an implementation detail. >It is true that SmallInteger does expose an implementation trick, but it is >a "bad" class anyway and we should get rid of it. AlephNull is not null. it is the number of elements in a non-recursively ennumerable set. this is an uncountable infinity of numbers. (or something like that. it is big, Big, BIG. see Cantor.) ((i'm not a mathematician. i just have a friend who, instead of "99 Bottles of beer on the wall" likes to sing "Aleph Null bottles of beer on the wall".)) dave -- j. david farber oo architect+mentor numenor labs incorporated in sunny boulder colorado dfarber(a)numenor.com www.numenor.com

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[Q] Ask on String manipulation
by Chun, Sung Jin 28 Apr '98

28 Apr '98

I want to make string like in ObjC; [ str concatSTR: 'Hello' ]; But in Smalltalk I cannot find it. And also I want printf like feature in error: like this; self error: 'Class %s', [ self name ] Can anyone teach me how I can do this ? Thanks in advance. ****************************************** I like N*Step's beauty, but Iove Freedom. ninja(a)aerohel.snu.ac.kr ---ObjC--- NSString* NSMyName = @"Chun, sungjin"; [ NSMyName fly ]; ---ObjC--- ******************************************

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Introducing more meaning into inheritance
by Krisztian Flautner 28 Apr '98

28 Apr '98

> (b) another thing we could do is to try to introduce more meaning into > inheritance. Right now there is no "algebra" that will tell us anything > useful about what a subclass might be relative to its super classes. Could you elaborate some more on this? I don't quite understand what you mean. When I think of added meaning related to inheritance, C++ comes to mind. There it is used both as a means of code reuse and type extension, causing designs to rely heavily (often unnecessarily) on inheritance. Could you give some example about what type of added meaning you are thinking about? Thanks, -- Kris

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Re: HELP! formalizing OO
by Steve Dekorte 28 Apr '98

28 Apr '98

Florin wrote: >..I would say though that math looks to me like it >is still ticking, An interesting thing about math/logic is that it can prove some of it's own limitations. I think I remember hearing about proofs of the insolvability of the n>2 body problem and of general solutions to finding the roots of polynomials above a certain order. If these problems are provably insolvablable, should we have much confidence in what seem to be the more complex problems of large programs being solvable? (By solvable I mean knowing everything about what they do without actually running them) I think most everyone sees that complex programs (like n>2-body problems) can't be analyzed without computation, so there are two choices. The top-down approach is to attempt to make programming langagues more analyzable before computation (Strong typing, etc) so correctness can be proven. This approach is basically out to eliminate the dynamic aspects of the system that lead to complexity. (Of course if Smalltalk can be written in ADA, how is ADA more provably correct or "safe"?) The bottom-up approach is to look for new ways of managing complexity so correctness is more probable. OO of the Smalltalk type is, IMO, an example of the 2nd approach. It looks at real the source of chaos - excessively coupled equations (via variables) and structures the langauge to make this problem easier to avoid. So while the top-down thinkers are unsuccessfully trying to make correctness provable, the bottom-up thinkers are successfully making correctness more probable. Steve

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sqAPIs *Update*
by Alejandro F. Reimondo 28 Apr '98

28 Apr '98

Hi, I have updated the sqAPI implementation adding some recomendations of Andreas Raab and Jim Benson. http://www.suagrWeb.com/Miniatures/downloads.html Cheers, Ale.

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Re: Good math/computation research (Was: HELP! formalizing OO)
by jecel＠lsi.usp.br 27 Apr '98

27 Apr '98

I can recomend the paper "The Paradigm Shift from Algorithms to Interaction" by Peter Wegner, Brown University. http://www.tiac.net/users/jsuth/papers/wegacm.pdf While some people have nasty things to say about this paper in particular and about the author's ideas in general, I really liked it and think it is a good argument about why objects have been much less "formal" than computing in general so far (and also why they are more powerfull). Cheers, -- Jecel

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HELP! formalizing OO
by Florin Mateoc 27 Apr '98

27 Apr '98

Could someone please point me to existing research in formalizing the OO approach (in relationship with fundamentals of Mathematics, Set Theory)? Thank you. Florin

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Simple Morphs
by Philippe de Rochambeau 27 Apr '98

27 Apr '98

Let us say that you create a Morphic World and add a SimpleButtonMorph and a TextMorph to it. How do you tell the SimpleButtonMorph to change the TextMorph's text? How do you refer to another Morph in a particular Morph's actions? When you create a Morph using the Morph palette, must you subclass the instance of the Morph you have just created before modifying some of its code (actions, etc.)? Philippe de Rochambeau

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Re: Introducing more meaning into inheritance
by Leandro Caniglia 27 Apr '98

27 Apr '98

David Stes wrote: >For example, I believe the following would NOT be a good inheritance >chain (but you may disagree) for Integer : > > SemiGroup > AdditiveSemiGroup > SemiMonoid > Monoid > AdditiveMonoid > Group > AdditiveGroup (abelian) > ... > Ring > IntegralDomain > Integer The problem here seems to be that while class Integer models each of the elements in Z, classes as Group or Ring refer to sets, not to elements. >After struggling a few years with classes like >"Integer-DegreeSparse-Recursive-VariableDense-Polynomial" as a subclass of >EuclideanDomain and result of some Polynomial constructing functor, I >just stopped doing it at that way, and I choose an interface centered >around objects with very *simple* names : > > Polynomial, Term, Monomial, BigInt, Symbol etc. I've used this approach too. In math, you have two kind of objects: elements and structures (objects in the sense of mathematical categories). For example, you may consider the field of Algebraic Numbers and, on the other hand, individual algebraic numbers as $\sqrt 2$. In Smalltalk, generally speaking, it is straitforward to model elements but it is more dificult to model structures. Still, it is possible to do that if you keep structures appart from elements. As an example, consider the class AlgebraicNumber, where instances are individual numbers. The role AlgebraicNumber plays in the system is similar to that of Integer. It is clear that you need a class for algebraic numbers because you have many diferent instances. But you don't need a class for the field of algebraic numbers (over Q); it is rather an instance of some other class. So you can model this field as an instance of some class Field. I call this class AlgebraicAmbient. >It is just that you can IMHO not carry over those concepts literally to >an object oriented programming language. Well, there's quite a few >languages out there that still do it, so I suspect this posting will be >controversial! In Smalltalk, I've used the concept of "Ambient" to recreate the structures. For example, you can model all the objects found in Linear Algebra: tuples, basis, subspaces, matrices, linear transformations, equations, etc. Doing so, I faced the problem of how to model the ambient space where all these objects live. Also I needed some knowledge about the scalars (are they a field, a ring or what?). I solved the problem using Smalltalk classes as LinearAmbient and AlgebraicAmbient. This is not the place to describe they here but let me say a few words about them: LinearAmbients model the linear spaces acting as the superset of linear subspaces (k^n, M_n(k), End(V), etc.). AlgebraicAmbients model the field of scalars (Z, Q, Z_p, k(x), Algebraic Numbers, etc.). Following this approach, if for example, V is a linear subspace in some LinearAmbient, you can easily construct the LinearAmbient End(V) of V-endomorphisms. Also you can construct ambients of tensor-products, direct sums, duals, etc. It is easy, clear and useful and was made using simple Smalltalk concepts. Of course, a lot of work must still be done. But mathematicians should explore deeper the current posibilities of Smalltalk, since some problems that seem to be in the paradigm are just design problems. Saludos, Leandro

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