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Re: [Pharo-users] mentor question 4
by Richard O'Keefe May 2, 2020

May 2, 2020

This sounds very much like the Luhn test task at RosettaCode. https://rosettacode.org/wiki/Luhn_test_of_credit_card_numbers except that there it is described as working on the digits of an integer. (1) There are two approaches to traversing a sequence in reverse. (A) Reverse the sequence, then traverse the copy forward. aString reverse do: [:each | ...] (B) Just traverse the sequence in reverse aString reverseDo: [:each | ...] My taste is for the second. (2) There are two approaches to deleting spaces. (A) Make a copy of the string without spaces. x := aString reject: [:each | each = Character space]. x do: ... (B) Ignore spaces as you go: (i) aString do: [:each | each = Character space ifFalse: [...]] (ii) aString select: [:each | each ~= Character space] thenDo: [:each | ...] Combining (1A) and (2A) you get very obvious code: (aString reject: [:each | each = Character space]) reverse do: [:digit } ...] Combining (1B) and (2Bi) you get more efficient code: aString reverseDo: [:digit | digit = Character space ifFalse: [ ...]] By the way, let's start by checking that the character in the string *are* digits or spaces: (aString allSatisfy: [:each | each isDigit or: [each = Character s[ace]]) ifFalse: [^false], (3) There are two approaches to doubling the even digits. (A) Make a new string that starts as a copy and change every second digit from the right. (B) Simply *act* as if this has been done; keep track of whether the current digit position is even or odd and multiply by 1 or 2 as appropriate. nextIsOdd := true. aString reverseDo: [:digit | digit = Character space ifFalse: [ nextIsOdd ifTrue: [oddSum := ...] ifFalse: [evenSum := ...]. nextIsOdd := nextIsOdd not]]. I *like* code that traverses a data structure exactly once and allocates no intermediate garbage, so I'd be making (B) choices. But I am not at all sure that it is right for *you* at this stage. Your goal is to get practice in making code that is obviously correct and lends itself to testing. I think in your case it makes more sense to make the (A) choices. You can write some code that reverses a string (using the built-in method) and test that it does what you expect. You can write some code that checks whether a string contains only digits and spaces, and test that. You can write some code that returns a space-less copy, and test that. You can write some code that returns the even (odd) elements of a sequence, and test those. SequenceableCollection>> withIndexSelect: aBlock |index| index := 0. ^self select: [:each | aBlock value: each value: (index := index + 1)] evenElements ^self withIndexSelect: [:each :index | index even] oddElements ^self withIndexSelect: [:each :index | index odd] The easiest way to convert a string to numbers and add up the numbers is to use #detectSum, as in aString oddElements detectSum: [:char | char digitValue] How do you find #digitValue? By looking in Character. #detectSum:? Collection enumeration methods. Using the (A) approach will give you lots of little methods, which you can comment and above all TEST, so that each mistake will be in just one small method. This is a typical functional programming "lots of little functions" approach. On Thu, 30 Apr 2020 at 18:33, Roelof Wobben via Pharo-users <pharo-users(a)lists.pharo.org> wrote: > > Hello, > > I hope I can discuss my approch to this problem : > > Given a number determine whether or not it is valid per the Luhn formula. > > The Luhn algorithm is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers and Canadian Social Insurance Numbers. > > The task is to check if a given string is valid. > > Validating a Number > > Strings of length 1 or less are not valid. Spaces are allowed in the input, but they should be stripped before checking. All other non-digit characters are disallowed. > > Example 1: valid credit card number > > 4539 1488 0343 6467 > > The first step of the Luhn algorithm is to double every second digit, starting from the right. We will be doubling > > 4_3_ 1_8_ 0_4_ 6_6_ > > If doubling the number results in a number greater than 9 then subtract 9 from the product. The results of our doubling: > > 8569 2478 0383 3437 > > Then sum all of the digits: > > 8+5+6+9+2+4+7+8+0+3+8+3+3+4+3+7 = 80 > > If the sum is evenly divisible by 10, then the number is valid. This number is valid! > > > my idea was to do these steps > > 1) reverse the input. > > 2) use this to double every second digit and calculate the sum of all the numbers : > > checkNumber := (collection reverse selectwith index: [:item :index | (index % 2 == 0) . IfTrue: [item *2]] ) sumNumbers > > 3) check if its a valid number by doing this : > > > ^ (checkNumber % 10 == 0) > > > is this a good game plan or has it flaws or can I do it better ? > > Regards, > > > Roelof > >

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Package Browser (AKA 6-paned Browser) and Pharo package organization
by stephen＠heaveneverywhere.com May 1, 2020

May 1, 2020

Hello friends, Iâm getting started with Pharo after decades using VisualWorks and Squeak; itâs pretty wonderful what you all have assembled! My question is related to what we used to teach as the first law of software reuse: âYou canât reuse it if you canât find it,â and the related software engineering "principle of least astonishment." When I fire up Pharo, the system browser presents me with a list of several hundred categories (from AST to Zodiac) in a system with over 8000 classes. The system categorization makes no sense since I donât know the naming conventions and so many packages have cute but quite non-descriptive names (Zinc? Metacello? Calypso?). In Smalltalk-80, the class category names were organized as a 2-level hierarchy where the top-level were items such as Magnitudes, Collections, Streams, Graphics, Text, System, Tools, Files, etc. This made it easy to find (e.g.,) the browser source code by looking in the Tools package for the class category Tools-Browser. Even packages with cute names (like my own âSirenâ), were categorized for ease of finding; e.g., the Siren classes were in class categories like Music-Events and Music-Magnitudes. Parsing the class category names on the first instance of $- made it possible to build 6-paned Browsers (called package pane browser in Squeak). (We acknowledged that this violates the âzero/one/infinity" rule.) Is something like this available for Pharo? I looked through the Calypso browser code and itâs so over-engineered (IMHO) that itâd take me several days to figure out how to implement this (it was about 1.5 pages of code in Smalltalk-80). If Pharo had a browser that scaled better and a reorganization/simplification of the class categories to use names that were more self-explanatory, it would be *much* easier for new users (in fact, for all users) to find their way around. I apologize for the stepping on toes... Stephen Pope -- Stephen Travis Pope Santa Barbara, California, USA http://HeavenEverywhere.com <http://heaveneverywhere.com/> http://FASTLabInc.com <http://fastlabinc.com/> https://vimeo.com/user19434036/videos <https://vimeo.com/user19434036/videos> http://heaveneverywhere.com/Reflections --

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Automating release announcements
by Gabriel Cotelli May 1, 2020

May 1, 2020

Hi!, Anyone here is moderator in the Pharo Users list? I want to automate the release announcement of projects in github/ba-st org. I'm using sendgrid to send the e-mails and I'm getting a returning mail saying: "Your message to Pharo-users awaits moderator approval". I subscribed previously to the list the e-mail account used as mail sender. Thank you for your help! Gabriel

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[ANN] Willow v13.0.0 [v13.0.0] released!
by Buenos Aires Smalltalk April 30, 2020

April 30, 2020

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Re: [Pharo-users] mentor question 4
by Richard Sargent April 30, 2020

April 30, 2020

See below. On Thu, Apr 30, 2020 at 10:58 AM Roelof Wobben via Pharo-users < pharo-users(a)lists.pharo.org> wrote: > and also not with this one : > > cardNumber := '4539 1488 0343 6467'. > oddSum := 0. > evenSum := 0. > nextIsOdd := false. > cardNumber reverseDo: [:digit | > digit = Character space ifFalse: [ > nextIsOdd > ifFalse: [oddSum := oddSum + (digit asString asInteger ) ] > ifTrue: [(((digit asString asInteger) * 2) > 9) > ifTrue: [evenSum := evenSum + ((digit asString asInteger) * 2) - 9 ] > ifFalse: [ evenSum := evenSum + (digit asString asInteger) * 2 ]]. > nextIsOdd := nextIsOdd not]]. > ^ evenSum > > > > > Op 30-4-2020 om 18:30 schreef Roelof Wobben: > > Op 30-4-2020 om 16:16 schreef Roelof Wobben: > >> nextIsOdd := true. > >> aString reverseDo: [:digit | > >> digit = Character space ifFalse: [ > >> nextIsOdd > >> ifTrue: [oddSum := ...] > >> ifFalse: [evenSum := ...]. > >> nextIsOdd := nextIsOdd not]]. > > > > hmm, > > > > Still no luck with this code : > > > > cardNumber := '4539 1488 0343 6467'. > > oddSum := 0. > > evenSum := 0. > > nextIsOdd := true. > > cardNumber reverseDo: [:digit | > > digit = Character space ifFalse: [ > > nextIsOdd > > ifTrue: [oddSum := oddSum + digit asInteger ] > > ifFalse: [evenSum := ((digit asInteger * 2) > 9) > > ifTrue: [evenSum + ((digit asInteger * 2) - 9) ] > > ifFalse: [ evenSum + (digit asInteger * 2) ]]. > > nextIsOdd := nextIsOdd not]]. > > ^ oddSum + evenSum > With the one change to use #digitValue instead of #asInteger (which answers the code point), the above example works. | evenSum oddSum | cardNumber := '4539 1488 0343 6467'. oddSum := evenSum := 0. nextIsOdd := true. cardNumber reverseDo: [:digit | digit = Character space ifFalse: [ nextIsOdd ifTrue: [oddSum := oddSum + digit digitValue ] ifFalse: [evenSum := ((digit digitValue * 2) > 9) ifTrue: [evenSum + ((digit digitValue * 2) - 9) ] ifFalse: [ evenSum + (digit digitValue * 2) ]]. nextIsOdd := nextIsOdd not]]. ^ oddSum + evenSum gives me 80 for the answer. A few (mostly) minor points: - I don't see why "reverse" is necessary. Of course if you use #do:, nextIsOdd needs to start with true. - repeating the "digit digitValue" or other variations adds clutter and reduces clarity - ((digit digitValue * 2) - 9) is not unreasonable, but could be simplified. What is the largest integer X such that 2xX<=9? > > > the answer schould be 57 where I get 1157 > > > > So some debugging to do > > > > >

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NeoCSV - how to parse a string with unescaped quoted string inside it?
by PAUL DEBRUICKER April 30, 2020

April 30, 2020

Hi - This is on Pharo 7 with Neo-CSV-Core-SvenVanCaekenberghe.28 In a CSV file I have several instances of records like "123","asdf", "one two "three" four five", "5678" When that line is parsed instead of an Array with 4 records '123' 'asdf' 'one two "three" four five' '5678' I instead get '123' 'asdf' '"one two "three" four five"' '"5678"' Is there a standard way or setting for handing strings with quoted strings in them? I'd like to end up with the expected result rather than the result I'm getting. Thanks Paul

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Re: [Pharo-users] mentor question 4
by StÃ©phane Ducasse April 30, 2020

April 30, 2020

It looks like a cool problem from where did you take it? > I hope I can discuss my approch to this problem : > > Given a number determine whether or not it is valid per the Luhn formula. > > The Luhn algorithm <https://en.wikipedia.org/wiki/Luhn_algorithm> is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers and Canadian Social Insurance Numbers. > > The task is to check if a given string is valid. > > I like people that are always thinking in string as if a collection of number would not make it :) > Validating a Number > > Strings of length 1 or less are not valid. Spaces are allowed in the input, but they should be stripped before checking. All other non-digit characters are disallowed. > > Example 1: valid credit card number > > 4539 1488 0343 6467 > The first step of the Luhn algorithm is to double every second digit, starting from the right. We will be doubling > > 4_3_ 1_8_ 0_4_ 6_6_ > If doubling the number results in a number greater than 9 then subtract 9 from the product. The results of our doubling: > > 8569 2478 0383 3437 > Then sum all of the digits: > > 8+5+6+9+2+4+7+8+0+3+8+3+3+4+3+7 = 80 > If the sum is evenly divisible by 10, then the number is valid. This number is valid! > > > > my idea was to do these steps > > 1) reverse the input. > > 2) use this to double every second digit and calculate the sum of all the numbers : > > checkNumber := (collection reverse selectwith index: [:item :index | (index % 2 == 0) . IfTrue: [item *2]] ) sumNumbers > you can also 1 to: xx by: 2 do: > 3) check if its a valid number by doing this : > > > ^ (checkNumber % 10 == 0) > > > > is this a good game plan or has it flaws or can I do it better ? > > Regards, > > > Roelof > > > > > -------------------------------------------- StÃ©phane Ducasse http://stephane.ducasse.free.fr / http://www.pharo.org 03 59 35 87 52 Assistant: Julie Jonas 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

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[ANN] RenoirSt v7.0.1 [v7.0.1] released!
by Buenos Aires Smalltalk April 30, 2020

April 30, 2020

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Re: [Pharo-users] mentor question 4
by Ben Coman April 30, 2020

April 30, 2020

On Thu, 30 Apr 2020 at 16:46, Roelof Wobben via Pharo-users < pharo-users(a)lists.pharo.org> wrote: > Op 30-4-2020 om 10:31 schreef Ben Coman: > > collection := '8569 2478 0383 3437'. > > (collection reverse selectWithIndex: [:item :index | (index % 2 == 0) > > ifTrue: [item *2]] ) inspect > > > I see a error and the non-even numbers are nill now. > > but after some figgeling this seems to work : > Great that you worked it out for yourself !!! "figgeling" is a very important part of programming. > > collection := '8569247803833437' asArray. > checkNumber := (collection reverse withIndexCollect: [:item :index | > (index % 2 == 0) ifTrue: [item asInteger *2] ifFalse: [item asInteger]] > ) sum inspect > ^ checkNumber isDivisibleBy: 10 > That looks like it would work, but the inspect is redundant now you know how it works. An important take away from this is that when you are confused by what is happening, you need to LOOK at each spot you data is transformed, where "inspect" is your friend, particular running it from the debugger. -------------------------------- Now there is another path you might try, but first I want to stress that I didn't know this answer a minute ago - I only just discovered it !! So this answer is not based on something magic I knew directly, but on my approach to guess, search and test within the system. I was considering how you were dealing with "every second digit" and considered a general description of this was "pairs". I _wondered_ whether Pharo had any methods dealing with "pairs" ? Spotter is a good place to ask this question, so I... Pressed <Shift-Enter> Typed... pair #i to see if there were any implementors containing the word "pair" and discovered SequenceableCollection>>#pairsCollect: 3. First time I've seen that method, I wonder how it works? The method comment gives a clue that the block takes two arguments. So lets try-the-simplest-possible-thing... ( '123456' pairsCollect: [ :a :b | a ] ) inspect ==> #($1 $3 $5) So that looks useful. Try experimenting with it yourself. cheers -ben

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Fwd: Statement about the VM
by ducasse April 30, 2020

April 30, 2020

> Begin forwarded message: > > From: StÃ©phane Ducasse <stephane.ducasse(a)inria.fr> > Subject: Statement about the VM > Date: 27 April 2020 at 18:06:09 CEST > To: Any question about pharo is welcome <pharo-users(a)lists.pharo.org>, Pharo Development List <pharo-dev(a)lists.pharo.org> > > As promised the consortium engineering team composed of G. Polito, P. Tesone, E. Lorenzano, M. Denker, C. Demarey and S. Ducasse > produced a statement about the Pharo VM. This statement was reviewed by the Pharo board and follows decisions taken during the > 2019 consortium general assembly held during PharoDays. > > S. Ducasse on the behalf of the consortium > > > > > > > > -------------------------------------------- > StÃ©phane Ducasse > http://stephane.ducasse.free.fr <http://stephane.ducasse.free.fr/> / http://www.pharo.org <http://www.pharo.org/> > 03 59 35 87 52 > Assistant: Julie Jonas > 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 >

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