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Re: [Pharo-project] Extending #< to compare all numbers
by Ken.Dickey Aug. 13, 2009

Aug. 13, 2009

"Schwab,Wilhelm K" <bschwab(a)anest.ufl.edu> > Floating point is not always what it seems. Â Hence my comment that IEEE floats get "the wrong answer fast". I have used interval math, continued fractions, and linear fractional transforms (a.k.a. exact reals). I agree that each representation has its challenges. Let's talk for a second about integers. 0 = (0+0i) --> true 1 = (1+0i) --> true 0 < 1 --> true (0+0i) < (1+0i) --> ?? which answer here gives me the least surprise ?? To put it another way (A = a) --> true (B = b) --> true (A < B) --> true (a < b) --> ?? what do you expect to see here ?? > By extension, I argue that > computer-represented complex numbers are not always what they seem, only > more so. Â Agreements: computers don't do math well. Computers approximate math. We would prefer to get the best approximations possible and be told when we are in deep waters. There are math systems (e.g. using interval arithmetic) which either complain that they can't come up with a sensible answer (all the bits are roundoff error) or go back and recompute with higher precision numeric representations in order to get X digits of correct precision. I am _not_ proposing to make Pharo into such a system. > Intuition resulting from lots of exposure to mathematicians suggests that > they consider this non-trivial but well-known. I don't consider "What Every Computer Scientist Should Know About Floating-Point Arithmetic" trivial -- especially for us non-mathematician users of numbers. [ http://docs.sun.com/source/806-3568/ncg_goldberg.html ] > If I am reading this correctly, defining $< is making a promise we can't > keep, or perhaps we simply should not try. Again, I am using unit tests as a fixed point. I want "if A=a and B=b and A<B then a<b" to work as I expect. I consider anything else to be deeply broken. > If you can find something that claims to produce a sensible ordering of > complex numbers, please post a reference. Â For now, my sense is that such a > thing cannot exist. I posted what I consider a sensible ordering which unit tests the property I care about. It happens to be a total ordering (not that I really care). I can certainly remove Complex>>< from the code, but I deeply dislike breaking basic logic on integers. I would prefer to have something more meaningful than "mathematicians can't agree on a theoretical ordering of complex numbers, so practical logic must fail". Do you really not believe that (0+0i) = 0 ?? Why, such numbers must be imaginary!! ;^) -KenD

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[Pharo-project] Packages that load in Pharo [WAS] [Ann] RFB/VNC fully configurable by code.
by Mariano Martinez Peck Aug. 13, 2009

Aug. 13, 2009

Miguel created this page: http://code.google.com/p/pharo/wiki/PackagesTestedInPharo so that we can add there all the packages that load (and work) ok in Pharo. I trying to add some but I found a problem: there is a column called "Package version". I have a same project (for example SqueakDBX) with several Packages in the same monticello repository. There isn't a version for a repository, but for a package. So, what should I do if I have several packages? Best, Mariano ---------- Forwarded message ---------- From: Miguel Enrique CobÃ¡ Martinez <miguel.coba(a)gmail.com> Date: 2009/8/12 Subject: Re: [Pharo-project] [Ann] RFB/VNC fully configurable by code. To: Pharo-project(a)lists.gforge.inria.fr El miÃ©, 12-08-2009 a las 18:18 -0100, Mariano Martinez Peck escribiÃ³: > > > What sort of packages should be put there? For example, I am woring in > SqueakDBX and Glorp and both of them work there. However, they are not > dev tools or something like. Thus, I don't understand which type or > packages should be added. Every package that loads and runs ok on pharo. This will motivate to port even more packages. I hope it will be a catalyzer because if we can show that a lot of packages are already running ok on pharo, the stability and maturity of pharo will make it a good platform to base new software and to port software from other smalltalk versions. So, if you have a package that load/runs, please by any means add it. -- Miguel CobÃ¡ http://miguel.leugim.com.mx _______________________________________________ Pharo-project mailing list Pharo-project(a)lists.gforge.inria.fr http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project

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[Pharo-project] There are still problem with keyboard shortcuts in Windows
by Mariano Martinez Peck Aug. 12, 2009

Aug. 12, 2009

Hi: this is broken since a lot of time (not new). It happens only on Windows I think (in Linux it works ok). I have preference duplicateAllControlAndAltKeys enabled. Browse: works ok with ctrl + b and alt + b Implementors: Only works with alt + m . ctrl + m doesnt work. Senders: works ok with alt + m and ctrl + m Inpect: Only works with alt + m . ctrl + m doesnt work. Close windows: Only works with alt + w. Ctrl + w is interpreted as undo (ctrl + z ) Undo: works ok with ctrl + z and alt + z Print it: works ok with ctrl + p and alt + p Do it: works ok with ctrl + d and alt + d In summary, there are problems with Implementors, Inspect and Close windows. At least, the one I tested, but there can be more. This happens not only with core but also with dev, both clean image. I am waiting someone to confirm this so that to open a bug ticket. anyone? Thanks Mariano

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Re: [Pharo-project] Complex neurotic
by Ken.Dickey Aug. 12, 2009

Aug. 12, 2009

St?phane Ducasse <stephane.ducasse(a)inria.fr> > What I would love is the following: that we get a good Complex package! > Since we can do method extensions in Smalltalk we can design a really > nice Complex > packages with its own tests. > We could publish for now Complex into PharoTaskForces or create a > PharoExternalPackages or whatever. If you point me to the package docs, I am happy to make a package. Note that the Complex cuts across a number of classes [Point,Float,Number,Object]. Is the desired behavior that (-1 sqrt) raise and exception when the Complex package is not loaded but return 1i when loaded? I presume that we could simply add the hyperbolic trig functions (and some tests) to Float? -KenD

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[Pharo-project] What others do [Scheme]
by Ken.Dickey Aug. 12, 2009

Aug. 12, 2009

> (< 0+0i 1+0i) #t > (sqrt -4) +2i ;; note exact 2, not 2.0 [extra credit] > (log -3) ;; known as #ln in Smalltalk 1.0986122886681098+3.141592653589793i > FYI, -KenD

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Re: [Pharo-project] Complex neurotic
by Ken.Dickey Aug. 12, 2009

Aug. 12, 2009

KenD> > Currently: > > > > -1 asComplex isNumber --> true > > ?1 asComplex isNumber -> true > > -1 asComplex < 1 asComplex --> error > > > > -4 sqrt --> error Igor Stasenko <siguctua(a)gmail.com>> > and it should. > Not many people using a complex numbers. And -4 is an integer number, > not complex number (i hope this non-objectionable?). And sqrt function > is not defined for real/integer numbers < 0 ,and should lead to error, > period. > If you change this behavior, some of code will fail to work correctly > , definitely. > But you are free to use something like: > -4 asComplex sqrt So you prefer (1 asFraction / 2) -> 1/2 , where (1/2) gives an error because 1 and 2 are not fractions? (-1 sqrt) is the definition of 1i . Other dynamic languages I use [Scheme, Lisp] which define complex numbers all give square roots of negative numbers. I am trying to approach the Principle of Least Surprise here. Computers are very bad at math, but we have learned painfully to work around this. I would like pre-computer high school math to "just work". IEEE Floats only guarantee the wrong answer fast, IMHO. I would like square roots of negative numbers to work like they did before I got a computer! 8^) 8^O 8^{ Cheers, -KenD

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[Pharo-project] Squeak 4.x should adopt Pharo 1.0
by Keith Hodges Aug. 12, 2009

Aug. 12, 2009

Dear All, As far as I see it the only sensible way ahead for squeak 3.11 is to adopt Pharo 1.0 as the next base version of squeak (i.e. 4.0), and to begin a series of initiatives to promote compatibility with squeak pieces that pharo doesn't support. The previous squeak 3.11 vision accepted, and now rejected, by the squeak board was to develop a process that would allow squeak to harvest the contributions of all the other forks, or other major initiatives, and for significant contributions to be shared by all the forks. All of a sudden there was an "oh no pharo is ahead of us" panic that ensued last month as a result of new squeak-dev people that were not involved in, nor seemed aware of the goals of the 3.11 process. Within this process Pharo may simply be viewed as a research project carried out on behalf of the wider squeak community, that will be harvestable in good time. However now that this idea is no longer going to be developed, we need to limit the number of diverging active forks as much as possible, rather than creating new ones ("trunk" makes the problem worse not better). Once the output of "trunk" is released in whatever form we will then have yet another base image to manage code for, and I don't think that that is an acceptable outcome. When it comes to the elections next year, if there is anyone who would like to run on the "Squeak to adopt Pharo" ticket, then I will vote for them. best regards Keith p.p.s. Bob is not going to be released as open source, if you would like the ability to build your images daily, and run the test suites against your deliverables, then please do email me for licensing terms.

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Re: [Pharo-project] Complex neurotic
by Ken.Dickey Aug. 12, 2009

Aug. 12, 2009

> AFAIK, one has to be careful ordering complex numbers: I am aware of this. Â There are a large number of ways to define #< for complex numbers -- and a large number of problems with each of them. What I object to are bad behaviors for things which are perfectly well defined. Currently: -1 asComplex isNumber --> true Â 1 asComplex isNumber -> true -1 asComplex < 1 asComplex --> error -4 sqrt --> error -3 ln -> NaN > If in doubt, I would #shouldNotImplement #< until we can get a conclusive > answer. Â An answer to what? Â I wrote the test cases first and then did code to make the tests pass. I am certainly open to alternate definitions, but I think if an object answers true to isNumber it should behave as a number. What would you expect of the following? -1 asFloat < 1 asFloat. -1 asNumber < 1 asNumber. -1 asFraction < 1 asFraction. -1 asComplex < 1 asComplex. One can add checks and make off-axis complex numbers fail (why?), but why cause the last case above to fail? Smalltalk is known for reasonable behaviors. Â E.g in Java (1/2) + (1/3) + 1/6) can yield zero (integer division truncates). I much prefer to get an exact 1. Why should I expect complex numbers to be unreasonable? $0.02, -KenD

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[Pharo-project] Extending #< to compare all numbers
by Ken.Dickey Aug. 12, 2009

Aug. 12, 2009

Greetings, Since there is some discussion around comparing using#< let me try to explain the context of my thinking. I am approaching this as a programmer and a user of mathematics, not as a mathematician. I prefer the Principle of Least Surprise. I prefer simple, easy to explain rules and simple implementations. I expect the following expressions all to answer true. 1/2 = 0.5. 1 = 1 asComplex. 1 = (1 + 0i). "same as the previous line" 0 < 1. 0 < 1 asComplex. Every number is-equivalent-to a complex number because 1 = (1 + 0i). [In the Scheme language every number _is_ a complex number, BTW]. So to me, saying that 0 and (1 asComplex) are not comparable is saying that 0 and 1 are also not comparable, because I consider them numerically the same as (0+0i) and (1+0i). My observation is that I don't want to lose properties. If A and B are numbers, I want them to be comparable on the real number line -- no matter how many other dimensions I add. If B is to the right on the real number line from A, then I expect (A < B) to answer true. I expect this to be true NO MATTER HOW MANY DIMENSIONS I ADD. To put this in context, say that I have an object which is a "basket of measurements" at a place and time (say position, density, temperature, pressure). Now if I add a new dimension, say electrical conductivity, I do not expect temperature comparisons to stop working. I can still compare temperatures between objects which lack the conductivity slot/measurement and those which have them. OK. Now to the extension. I suspect this is the root of the (potential) controversy. I chose to say that if the real/x component of a 2d number is equal, then one number may be considered less than another if the imaginary/y value is less. This means that (0+0i) < (0+1i) holds. These are the properties (and test cases) I care about. Currently, the definition for Complex>>< is just this (see below). This implies that (3+0i) < (3+1i) holds, even though the x/real components are equal. I think that this is OK. What do you think? Are there simpler, least surprising definitions for Complex>>< ? What useful properties/invariants/tests would you add? [As unit tests] Thanks for your thoughtful input. -KenD --------------------------------Complex < other "self < other if other's real-part is to the right or the real-parts are equal and the oher's imaginary part is larger" | otherCpx | otherCpx := other asComplex. ^self real < otherCpx real or: [self real = otherCpx real and: [self imag < otherCpx imag]] ---------------------------------

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[Pharo-project] right button still doesn't work on Windows
by Torsten Bergmann Aug. 12, 2009

Aug. 12, 2009

>With Pharo beta, right button still doesn't work out of the box >in Windows. Mariano, can you try the installer executable on http://pharo-project.org/pharo-download ? For me right button work out of the box on XP and Vista and the installer uses the same image as Damien provides on the download site. Bye Torsten -- Jetzt kostenlos herunterladen: Internet Explorer 8 und Mozilla Firefox 3 - sicherer, schneller und einfacher! http://portal.gmx.net/de/go/atbrowser

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