- Pharo-users - lists.pharo.org

Re: [Pharo-users] ZnClient - how suppress popup notifications

by Sven Van Caekenberghe

Hi Jimmie, > On 2 Sep 2020, at 20:29, Jimmie Houchin <jlhouchin(a)gmail.com> wrote: > > > Before I get to my problem. I want to thank Sven for the huge effort that had to be made to provide all of the Zinc networking tools. Thank you. Thanks, you're welcome. > I am using ZnClient in an app. It is working fine. But I do not want any UI Notifications. This will eventually be headless on a server. But right now in development when the internet goes out I get a pop up from NameLookupFailure which offers me the options of "Give Up" or "Retry". > > I need to suppress this popup. I already have Error handling code which will catch NameLookupFailure among many other network based errors. I know this is confusing, but this is not a problem. You can simply catch the NameLookupFailure and this will work as expected. The problem is the custom/overwritten NameLookupFailure>>#defaultAction which is doing UI stuff (although this gets handled differently in a headless image as well). IMHO this should be removed. ZnClientTest>>#testIfFailNonExistingHost is an example that does more or less what you want. > Also, is there a better way to check if the network is up other than simply making a request and either getting a successful response or an Error? This is not such an easy problem to solve. Doing something simple, like accessing a known host, is one way (but never 100% since that host might be down on itself). There is also the problem of timeouts (i.e. very slow networks). One of my experimental projects, https://github.com/svenvc/NeoDNS, does contains something called NeoNetworkState that tests internet connectivity by doing a DNS call. But this probably goes to far. HTH, Sven > Thanks for any help. > > > Jimmie

Sept. 2, 2020

ZnClient - how suppress popup notifications

by Jimmie Houchin

Before I get to my problem. I want to thank Sven for the huge effort that had to be made to provide all of the Zinc networking tools. Thank you. I am using ZnClient in an app. It is working fine. But I do not want any UI Notifications. This will eventually be headless on a server. But right now in development when the internet goes out I get a pop up from NameLookupFailure which offers me the options of "Give Up" or "Retry". I need to suppress this popup. I already have Error handling code which will catch NameLookupFailure among many other network based errors. Also, is there a better way to check if the network is up other than simply making a request and either getting a successful response or an Error? Thanks for any help. Jimmie

Sept. 2, 2020

Re: [Pharo-users] Scaled decimals comparisons

by StÃ©phane Ducasse

Richard we are really interested in improving Pharo on that aspect. Now Iâm really not good with such domain. Can you send us some code and tests? S. > On 2 Sep 2020, at 12:31, Richard O'Keefe <raoknz(a)gmail.com> wrote: > > The behaviour of ScaledDecimal in Squeak and Pharo is > - different from what the ANSI Smalltalk standard says > - different from what other Smalltalks do (not that they agree) > - completely different from decimal arithmetic in COBOL, PL/I, or SQL > - seriously confusing. > > What you EXPECT is an exact rational number that is equal to an > integer divided by a power of 10, so that the printed > representation faithfully represents the value with no error. > What you GET in Pharo is a rational number that PRINTS with > a given number of decimal places but that is all. > > Thus we expect that > x := 10/3 asScaledDecimal: 2. > x asString ==> '3.33s2' > y := x+x+x. > y asString ==> '9.99s2' > But no, y asString => '10.00s2'. > > Here's what the comment in the VW class FixedPoint says: > "There are two possible ways to express FixedPoint numbers. One is as a scaled Integer, but the problem here is that you can lose precision during intermediate calculations. For example, a property that seems useful is that the calculation (1.000 / 7 * 7) should give you back the number 1.000. > > For this reason, we have adopted an alternative representation, which is a slight variation on Fraction. The number is expressed as the ratio of a numerator to a denominator, with the addition of a precision that is used for printing and for rounding. The number is not usually rounded off to its scale, but if an intermediate result must be rounded to its scale before being used, the messages #roundedToScale and #truncatedToScale may be used." > > The last sentence in the first paragraph is one I cannot agree with. > If I want a calculation where (1/7 * 7) gives me back 1, then I use > exact Fractions. If I am using ScaledDecimal, it is because I *want* > fixed point decimal numbers, with the properties appropriate to fixed > point decimal numbers. Wanting something that I could use to talk to > databases like MariaDB I found that I had to write my own FixedPoint > class, only to find that VW called ScaledDecimal FixedPoint. *Sigh*. > > Unless and until the current ScaledDecimal is ripped out and buried > in an unmarked grave at a crossroad with a stake through its heart, > you may wish to add VW-compatibility methods > > roundedToScale > |t| > t := 10 raisedToInteger: scale. > ^(numerator * t / denominator) rounded / t asScaledDecimal: scale > > truncatedToScale > |t| > t := 10 raisedToInteger: scale. > ^(numerator * t / denominator) truncated / t asScaledDecimal: scale > > and then use > > aScaledDecimal roundedToScale = anotherOne roundedToScale > > Note that the ANSI standard, which was agreed to by a whole bunch of > Smalltalk experts, says "A <scaledDecimal> converted to a <Fraction> > will be a fraction having the same numeric value but having an integer > numerator and a denominator which is ten raised to > the power of the <scaledDecimal>âs scale factor." > Try "(10.00s2 / 3) asFraction" in your Smalltalk, and if the > result has a denominator of 3, SOMEONE stuffed up. > > > > > On Tue, 1 Sep 2020 at 16:08, Esteban Maringolo <emaringolo(a)gmail.com <mailto:emaringolo@gmail.com>> wrote: > Hi, > > I was doing some basic calculations based on a formula, and I wanted > to convert the result to a scaled decimal in order to avoid having > these "loose" decimals in 10th position or something similar. > > So I did the following: > 82 - (2 * 35.9) - (0 / 2) * (113/121) asScaledDecimal: 1 -> 9.5s1 > > But When I do this in a test: > (82 - (2 * 35.9) - (0 / 2) * (113/121) asScaledDecimal: 1) = 9.5s1 > > It fails because the comparison returns false. > > I guess this is the proper behavior, but I'd expected that the > conversion from a Float to a scaled decimal would have eliminated the > extra precision from the formula. > > I can do a roundTo: 0.1 before converting, but I'd like to know what > would be the proper way of dealing with this. > > Thanks! > > Esteban A. Maringolo > -------------------------------------------- StÃ©phane Ducasse http://stephane.ducasse.free.fr / http://www.pharo.org 03 59 35 87 52 Assistant: Aurore Dalle FAX 03 59 57 78 50 TEL 03 59 35 86 16 S. Ducasse - Inria 40, avenue Halley, Parc Scientifique de la Haute Borne, BÃ¢t.A, Park Plaza Villeneuve d'Ascq 59650 France

Sept. 2, 2020

Epicea and multiple images - mixed changes

by Davide Varvello

Hi Guys, Did you notice that if there are 2 or more images in the same directory, Epicea shows the changes of all of them? I think it shouldn't. Cheers Davide -- Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html

Sept. 2, 2020

Re: [Pharo-users] Can it do this way ?

by Roelof Wobben

Sept. 2, 2020

Re: [Pharo-users] Can it do this way ?

by Roelof Wobben

Correct. This is a exercism task. and yes, there are no variables given but that does not in my oponion means that I cannot add a instance or a class variable I myself was thinking about adding two instance variables named digits which hold the first 9 characters and a variable named controlDigit Can I do it then this way 1) Check if the string is empty , if so return false otherwise made a new object like this in IsValidIsbn isValidIsbn: aString Â Â Â if aString isEmpty Â Â Â Â Â ifTrue: [False] Â Â Â Â ifFalse: [ self new Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â digits := something. Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â controlDigit := something.] I can also do what I think you are describing isValidIsbn: AString Â Â if aString isEmpty Â Â Â Â Â Â ifTrue: [ ^false] Â Â Â Â Â Â ifFalse: [ISBN isValidIsbn10] and then as you describe so have a isValidISBN10 method in the class side where IÂ do the check there soÂ the class ISBN has the two instance variables digits and controlDigit Roelof

Sept. 2, 2020

Re: [Pharo-users] Can it do this way ?

by Richard O'Keefe

There is simply no point in "taking the first nine numbers out". And there shouldn't BE a test for the string being empty, anywhere. '' '-' '---' and so on should all be handled the same way. Oh well, what stops you doing digits := aString select: [:each | each ~= $-]. digits size = 10 ifFalse: [^false]. lastDigit := digits la ost. digits := digits copyFrom: 1 to: 9. ( (lastDigit = $X or: [lastDigit isDigit]) and: [ digits allSatisfy: #isDigit] ) ifFalse: [^false]. Now my code does not do this, but it is just 16 lines of code with nothing that it would make sense to extract. On Wed, 2 Sep 2020 at 22:24, Roelof Wobben <r.wobben(a)home.nl> wrote: > Yep, I know that isValidIsbn is the method that must output if a isbn is > valid or not. > > What I want to do is take the first 9 characters out so I can convert > them to a array of numbers where I can do the calculation on. > And take out the last char so I can seperate test if that is a valid > char. So between the 0 and 9 or a X > > I do not think I would have do all the checks in that only method > because it would be a very big method then. > > but if I understand you well also the test if a string is empty should > be called from the isValidIsbn method or even checked there. > > Roelof > > >

Sept. 2, 2020

Re: [Pharo-users] Scaled decimals comparisons

by Richard O'Keefe

The behaviour of ScaledDecimal in Squeak and Pharo is - different from what the ANSI Smalltalk standard says - different from what other Smalltalks do (not that they agree) - completely different from decimal arithmetic in COBOL, PL/I, or SQL - seriously confusing. What you EXPECT is an exact rational number that is equal to an integer divided by a power of 10, so that the printed representation faithfully represents the value with no error. What you GET in Pharo is a rational number that PRINTS with a given number of decimal places but that is all. Thus we expect that x := 10/3 asScaledDecimal: 2. x asString ==> '3.33s2' y := x+x+x. y asString ==> '9.99s2' But no, y asString => '10.00s2'. Here's what the comment in the VW class FixedPoint says: "There are two possible ways to express FixedPoint numbers. One is as a scaled Integer, but the problem here is that you can lose precision during intermediate calculations. For example, a property that seems useful is that the calculation (1.000 / 7 * 7) should give you back the number 1.000. For this reason, we have adopted an alternative representation, which is a slight variation on Fraction. The number is expressed as the ratio of a numerator to a denominator, with the addition of a precision that is used for printing and for rounding. The number is not usually rounded off to its scale, but if an intermediate result must be rounded to its scale before being used, the messages #roundedToScale and #truncatedToScale may be used." The last sentence in the first paragraph is one I cannot agree with. If I want a calculation where (1/7 * 7) gives me back 1, then I use exact Fractions. If I am using ScaledDecimal, it is because I *want* fixed point decimal numbers, with the properties appropriate to fixed point decimal numbers. Wanting something that I could use to talk to databases like MariaDB I found that I had to write my own FixedPoint class, only to find that VW called ScaledDecimal FixedPoint. *Sigh*. Unless and until the current ScaledDecimal is ripped out and buried in an unmarked grave at a crossroad with a stake through its heart, you may wish to add VW-compatibility methods roundedToScale |t| t := 10 raisedToInteger: scale. ^(numerator * t / denominator) rounded / t asScaledDecimal: scale truncatedToScale |t| t := 10 raisedToInteger: scale. ^(numerator * t / denominator) truncated / t asScaledDecimal: scale and then use aScaledDecimal roundedToScale = anotherOne roundedToScale Note that the ANSI standard, which was agreed to by a whole bunch of Smalltalk experts, says "A <scaledDecimal> converted to a <Fraction> will be a fraction having the same numeric value but having an integer numerator and a denominator which is ten raised to the power of the <scaledDecimal>âs scale factor." Try "(10.00s2 / 3) asFraction" in your Smalltalk, and if the result has a denominator of 3, SOMEONE stuffed up. On Tue, 1 Sep 2020 at 16:08, Esteban Maringolo <emaringolo(a)gmail.com> wrote: > Hi, > > I was doing some basic calculations based on a formula, and I wanted > to convert the result to a scaled decimal in order to avoid having > these "loose" decimals in 10th position or something similar. > > So I did the following: > 82 - (2 * 35.9) - (0 / 2) * (113/121) asScaledDecimal: 1 -> 9.5s1 > > But When I do this in a test: > (82 - (2 * 35.9) - (0 / 2) * (113/121) asScaledDecimal: 1) = 9.5s1 > > It fails because the comparison returns false. > > I guess this is the proper behavior, but I'd expected that the > conversion from a Float to a scaled decimal would have eliminated the > extra precision from the formula. > > I can do a roundTo: 0.1 before converting, but I'd like to know what > would be the proper way of dealing with this. > > Thanks! > > Esteban A. Maringolo > >

Sept. 2, 2020

Re: [Pharo-users] Can it do this way ?

by Roelof Wobben

Yep, I know that isValidIsbn is the method that must output if a isbn is valid or not. What I want to do is take the first 9 characters out so I can convert them to a array of numbers where I can do the calculation on. And take out the last char so I can seperate test if that is a valid char. So between the 0 and 9 or a X I do not think I would have do all the checks in that only method because it would be a very big method then. but if I understand you wellÂ also the test if a string is empty should be called from the isValidIsbn method or even checked there. Roelof

Sept. 2, 2020

Re: [Pharo-users] Can it do this way ?

by Richard O'Keefe

Briefly, you cannot and (for a different reason) you should not. The IsbnVerifierTest class defines the API; the method must be isValidIsbn: aString and it MUST be on the instance side. The reason why you shouldn't is that an empty string should NOT be a special case. This is a problem where the design style described by Dijkstra in "A Discipline of Programming" and further fleshed out by Reynolds and Gries in related books pays off. You want to inspect all the characters of the string once each in a single left-to-right loop. On Wed, 2 Sep 2020 at 18:19, Roelof Wobben via Pharo-users < pharo-users(a)lists.pharo.org> wrote: > Hello, > > I have now a challenge where I have to validate a ISBN number. > > Can I do something like this on the class side : > > (string isEmpty) > ifTrrue: [ ^ false] > ifFalse: [ digits:= something. > controlDigit := something. > self validateISBNNumber] > > where on the validateISBNNumber I use the instance variables digits and > controlDigit to validate the ISBN number on the instance side. > > Roelof > > > > > > > >

Sept. 2, 2020