Squeak-dev April 1998

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107 participants
279 discussions

Re: Equivalent of addSubView:in: in Squeak
by Tim Olson 27 Apr '98

27 Apr '98

>however, the following code, which should display a transparent View >containing two subviews in it, a gray subview which a black border, and a >black subview with a gray border, does not work properly: > >"Example code in Philippe Dugerdil's Smalltalk-80, Programmation par Objets, >Presses Polytechniques et Universitaires Romandes, 1990" >| v v1 v2 | >v := View new. >v1 := View new. >v2 := View new. >v borderWidth: 1. >v1 insideColor: Color gray. >v2 insideColor: Color black. >v window: v window viewport: (300@250 corner: 400@300). >v addSubView: v1 in: (0@0 extent: 0.5(a)0.5) borderWidth: 2. >v addSubView: v1 in: (0.5(a)0.5 extent: 1@1) borderWidth: 2. ^^ ^^^ You are using v1 here when you mean v2, and the extent you want is probably 0.5(a)0.5, not 1@1. -- tim

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Newbie's question: how do you create a chessboard in Squeak?
by Philippe de Rochambeau 27 Apr '98

27 Apr '98

Which of the addSubView commands would you use to create a chessboard-like View containing 9 subviews? ----------------- | XXXX VVVV XXXX | | XXXX VVVV XXXX | | XXXX VVVV XXXX | | VVVV XXXX VVVV | | VVVV XXXX VVVV | | VVVV XXXX VVVV | | XXXX VVVV XXXX | | XXXX VVVV XXXX | | XXXX VVVV XXXX | ------------------ I have tried using the "addSubView viewport:" command, computing each subview's position based upon its neighbor's. However, that seems unnecessarily tedious. Is there a better way of doing it? Is there any algorithm in Squeak Smalltalk that lets you emulate Java's FlowLayout algorithm? Many thanks. Philippe de Rochambeau

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Sound under Linux ?
by Mark Andrew 27 Apr '98

27 Apr '98

Has anyone got sound working for Squeak under Linux ? I downloaded the Squeak unix source and managed to rebuild it but couldn't see anything concerning sound that I dared to touch. Thanks Mark Andrew

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Equivalent of addSubView:in: in Squeak
by Philippe de Rochambeau 27 Apr '98

27 Apr '98

What is the equivalent of: v := View new. ..... v window: v window viewport: (300@250 corner: 400@300). "This is the problematic line" v addSubView: v1 in: (0@0 extent: 0.5(a)0.5) borderWidth: 2. in Squeak Smalltalk? addSubView:in: does not seem to exist in Squeak. Another question: why "v window: v window"? If v is a View, why do you need to tell it that its window is its own (v's) window? Many thanks. Philippe de Rochambeau

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Re: HELP! formalizing OO
by Tansel Ersavas 27 Apr '98

27 Apr '98

Florin Mateoc wrote: > > At 08:54 PM 24/04/98 -0700, Alan wrote: [... Alan's good stuff deleted] > Alan, > > Thank you for your reply. I would say though that math looks to me like it > is still ticking, even if it is much more formal than in its early days. > And I think that the efforts towards formalization have helped its > progress. Metamathematics or, more general, thinking about the thought > process, are still very useful tools, even if not universal panaceas (sigh...) Florin, Alan is known to be 20 to 50 years ahead of his time. I know where his heart is but by his own words in last years OOPSLA opening speech we are not "there" where we reach anywhere near the complexity of biological systems yet. Still computer programs are the most complex systems human beings have ever created so far. I agree with Alan that the current mathematics hasn't got sufficient tools that can make sense of object oriented systems. The reason for this is an average object oriented system in terms of its combinatorial complexity makes up a non-linear system far beyond the reach of current mathematical techniques. Mathematics as is today does not have the techniques that can be applied to an arbitrary non-trivial non-linear system. When mathematicians face a complex non-linear system they either try to go into messy linearization techniques to convert the darn thing into something that they can apply their techniques to, or all together call it a yucky system and avoid it; and I am afraid most non-trivial OO systems are in this second category. I suspect what you're looking for is something in the lines of relational database theory so that by means of something or some mechanism similar to "normal forms" so that one can apply the magic of formulas to prove a design's correctness; in fact OO was long criticized (yawn) that it didn't have something similar to that. If this is an assignment, then you can fake it by finding some attempts to address the issue such as [1] and [2]. You can also look at FOOD (formal OO development) FOOM (formal OO methodology) or even very appropriately named FOOL (Yes, you guessed it, formal OO language:). If you are genuinely looking for an answer then I recommend that you look far beyond the existing mathematical techniques, because you won't find the answers there. [1] Formal Object-Oriented Development,Springer-Verlag, Formal Approaches to Computing and Information Technology Series Editor: Professor S.A.Schuman [2] Formal Object-Oriented Development of Software Systems using LOTOS , Paul Gibson > Regards, > > Florin Tansel

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Re: the case for two's complement
by sqrmax＠cvtci.com.ar 27 Apr '98

27 Apr '98

Hi Ian. >Beeler M., Gosper, R.W. and Schroeppel, R., "HAKMEM", MIT AI Memo 239, Feb. 29, 1972. YES! A GOSPERISM FROM HAKMEM! >[...] >By this strategy, consider the universe, or, more precisely, algebra: > >let X = the sum of many powers of two = ...111111 >now add X to itself; X + X = ...111110 >thus, 2X = X - 1 so X = -1 >therefore algebra is run on a machine (the universe) which is twos-complement. This is great. Thanks! By the way, there are integer numbers with infinite digits that satisfy x^2 = x (not 0 neither 1). Andres.

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InterpreterSimulator fails
by Aik-Siong Koh 26 Apr '98

26 Apr '98

I executed the follow line on a virgin squeak 1.31 on WinNT 4.0 (InterpreterSimulator new openOn: Smalltalk imageName) test and got an out of bounds exception when it was "swapping bytes in foreign image". My Dell Latitude CP notebook has 128MB RAM and 3.5GB harddisk. Squeak was running on my D: drive which has 1GB or more free space. The same error occured with DynamicInterpreterSimulator. Thanks for your help. Aik-Siong Koh

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Re: bit shifting
by Dan Ingalls 26 Apr '98

26 Apr '98

Folks - First of all, thanks to the several people who answered my questions about whether they had found it to be either useful or enlightening to do bit manipulation with negative numbers. Out of all the correspondence, other than motherhood arguments, the only mention of any useful aspect of this came from Wim Boot: >Yes. If you have a bit vector of arbitrary size and you want to clear >certain bits the normal way is to bitAnd: with a negative number. It's >the only practical way to preserve an unknown number of bits to the left. I'm still mildly opposed to bit manipulation on negative numbers, mainly for simplicity, although ANSI compliance is a weak second reason. To that end I have assembled a changeSet that does away with logic on negative numbers without breaking LargeInteger division. It also adds the method bitClear: aMask "Return a number equal to the receiver, except with all bits cleared that are set in mask." ^ (self bitOr: aMask) - aMask which seems to do a fine job of clearing bit fields regardless of number size. These changes will be available for test as part of the forthcoming 2.0 beta release (we're shooting for 1st week of May, by the way). Also included will be a faster and more accurate print routine from Tim Olson, an isPositive/isNegative protocol (from me) to replace the methods that the mathematicians hate, and a number of Fraction speedups from Leandro Caniglia and colleagues. ------------------------------------------------------------- That all said, of course, I sympathize with the folks who consider it non-uniform to forbid logic on negative numbers. After all, isn't Squeak supposed to be simple and general? Now, I believe that this is the only place where Squeak would reveal the underlying representation of negative numbers. And -- guess what -- the ACTUAL representation is not really two's complement at all! It's not one's complement either. It is a mixed strategy in which SmallIntegers are two's complement, and LargeIntegers are sign-and-magnitude. I am on the verge of implementing a uniform extension of bit logic to negative numbers (just to silence the nit-pickers ;-), but I have the following question: If bit manipulation is the only place where we reveal the representation of negative numbers, then why on earth choose two's complement? Sign-and-magnitude would be a much simpler choice, because bit-wise logic is the same regardless of sign, and it would be a trivial uniform interpretation (it would also tie in perfectly with the actual implementation of our LargeIntegers). Even one's complement would seem to make more sense, since the relationship between a positive number and its negative is a simple bitwise complement. So, if we were to reveal a specific bit representation for the purpose of allowing logic on negative numbers, can anyone explain why it should be two's complement? - Dan

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Re: Bug in Rectangle>>containsPoint:?
by David Stes 26 Apr '98

26 Apr '98

Dan Ingalls wrote: > > Squeak's model goes straight back to the original implementation of > BitBlt on the Alto in 1974. The concept is indeed zero-width coordinates > between pixels, and it has stood the time well. I keep being impressed by reading this sort of thing (I mean, to hear BitBlt is from 1974). Sometimes people report things on this list like "I downloaded a package, which was written a couple of years ago", and then they say it works fine with Squeak (which didn't exist back then). Nice.

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Re: HELP! formalizing OO
by Alan C. Kay 26 Apr '98

26 Apr '98

At 1:50 AM -0400 4/25/98, Florin Mateoc wrote: -- snip -- >Alan, > >Thank you for your reply. I would say though that math looks to me like it >is still ticking, even if it is much more formal than in its early days. >And I think that the efforts towards formalization have helped its >progress. Metamathematics or, more general, thinking about the thought >process, are still very useful tools, even if not universal panaceas (sigh...) Florin -- I totally agree that math is still ticking -- that's why I said that computers are already math. We are doing math, but of a new kind, and it could hardly be more formal. What we don't have yet for most of our stuff is "parsimonious beauty" and powerful metaviewpoints for thinking about computing. We are perhaps still in a Babylonian stage waiting for the Greeks to come along. However, as a card carrying mathematician, I don't believe that the trappings of classical math -- set theory, etc. -- will help. Cheers, Alan

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