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Re: [Pharo-users] can I make this so the vm would not be not responsibe when running the tests

by Ben Coman

Hi Richard, Just fyi, the aim of Exercism is not to teach programming. Its aim is for experienced programmers to fast-start in new languages. It just happens to that new programmers also use Exercism and there is some catering in the exercise text for this. The grains exercise provides a nice vehicle for programmers to familiarize themselves with recursion in Pharo, and the hint for the exercise says "These kinds of problems (where an answer is dependent on a previous) one are often called recursion" which is why Roelof is approaching the problem this way. That said, any solution will do. Your advice on alternative considerations is insightful and always good to read. cheers -ben On Mon, 6 Jan 2020 at 00:25, Richard O'Keefe <raoknz(a)gmail.com> wrote: > I did not ask why you were validating input. > I asked about why you *repeatedly* validated input. > > Think of it this way: > publicMethod: arg1 also: arg2 > ... check arg1 ... > ... check arg2 ... > ^self privateMethod: arg1 also: arg2 > > privateMethod: arg1 also: arg2 > ... trust that arg1 and arg2 are valide ... > ... recursive calls use #privateMethod:andAlso: ... > ... not #publicMethod:andAlso: and must ensure ... > ... that arguments are valid by construction ... > > In my solution to the "Grains" exercism, I have > atSquare: n -- checks its argument > total ^(1 bitShift: 64) - 1 > You are required to implement these two methods, true. > You are NOT required to implement #total by calling #atSquare:. > Not even once. Nor is #atSquare: required to be recursive. > > On Mon, 6 Jan 2020 at 02:05, Roelof Wobben <r.wobben(a)home.nl> wrote: > > > > Hello Ricard. > > > > You mean when I calcualate the total of a board. > > That is because on when I had to calculate the number of a particular > > field there were tests where the number was lower then zero or higher > > then 64 which makes no sense. > > > > But im open for a solution where on a particular field I could check for > > that and for the total I do not need that part. > > > > Roelof > > > > > > > > Op 5-1-2020 om 13:58 schreef Richard O'Keefe: > > > Time microsecondsToRun: [ > > > |n| > > > n := (2 raisedToInteger: 8 * 8) - 1. > > > Transcript > > > nextPutAll: 'The number of grains on an 8x8 chessboard is '; > > > print: n; cr; endEntry]. > > > <PRINT-IT> > > > On my laptop, this reports 194 microseconds. > > > > > > Why would you use recursion, anyway? > > > > > > Time microsecondsToRun: [ > > > |n| > > > n := (1 to: 8 * 8) inject: 0 into: [:acc :each | acc+acc+1]. > > > Transcript > > > nextPutAll: 'The number of grains on an 8x8 chessboard is '; > > > print: n; cr; endEntry]. > > > <PRINT-IT> > > > On the same laptop, this reports 118 microseconds. > > > > > > One of the lessons of 'functional' languages, promptly adopted by > Smalltalk, is > > > to encapsulate control structures into reusable methods, such as > #inject:into:, > > > more commonly known as `foldl` in functional languages. It's then > none of > > > my business whether such a method works by recursion, iteration, or > gangs > > > of otherwise seasonally unemployed Christmas elves. > > > > > > In my own Smalltalk library, > > > (GeometricSeries new: 64 from: 1 byFactor: 2) sum > > > only takes 15 microseconds. > > > > > > I do note that you are calling validateInput repeatedly. Why? > > > > > > > > > On Sun, 5 Jan 2020 at 07:41, Roelof Wobben via Pharo-users > > > <pharo-users(a)lists.pharo.org> wrote: > > >> Oke, > > >> > > >> So I can better not use recursion for this problem if I understand > you well, Richard. > > >> > > >> Roelof > > >> > > >> > > >> > > >> Op 4-1-2020 om 19:02 schreef Richard Sargent: > > >> > > >> On Sat, Jan 4, 2020 at 9:47 AM Roelof Wobben via Pharo-users < > pharo-users(a)lists.pharo.org> wrote: > > >>> Hello, > > >>> > > >>> For a exercism challenge I need to calculate the total grains on a > > >>> chessboard. > > >>> So I did : > > >>> > > >>> atSquare: anInteger > > >>> self validateInput: anInteger. > > >>> ^ anInteger = 1 > > >>> ifTrue: [ 1 ] > > >>> ifFalse: [ 2 * (self atSquare: anInteger - 1) ] > > >>> > > >>> > > >>> but when I run the tests , the vm seems to be not responsive for > some 4 > > >>> - 5 seconds. > > >>> > > >>> Is there a way I can use this code and take care that the vm stays > > >>> responsive. > > >> > > >> What do you want the VM to do in addition to calculating that sum > while it is calculating that sum? > > >> > > >> > > >> The best way to keep the VM responsive is to take a page from Gauss' > notebook and pay attention to the numbers[1]. Let's consider the first four > squares and extrapolate from there. > > >> > > >> In binary, the squares hold the following grains: 2r1, 2r10, r2100, > and 2r1000. When we add them up, we get 2r1111. If we use Gauss' tricks, we > can notice that 2r1111 is equal to 2r10000 - 1. So, the sum of the grains > on the first 4 squares is 2^5 - 1. You can easily generalize that pattern, > of course. Then your program can calculate the answer quickly. > > >> > > >> > > >> [1] The story goes that Gauss' teacher was frustrated with his > student's abilities and set him a challenge to occupy him for some time: > sum the numbers from 1 through 100. Gauss immediately answered 5,050, much > to his teacher's chagrin. > > >> > > >>> Regards, > > >>> > > >>> Roelof > > >>> > > >>> > > > >

Jan. 5, 2020

Re: [Pharo-users] How can we celebrate the 50th anniversary of Smalltalk?

by tbrunz

Did Smalltalk start with Smalltalk-72 or Smalltalk-80? (Or 1969, when work on it began..??) ST-72 was an internal release; ST-80 was its first public release, in 1980. I've always thought that 1980 was the birthday, so this year it turns 40... Am I wrong? What's the consensus? Is it customary to go by the project start date, the first stable version, the first release to the public, or what? -- Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html

Jan. 5, 2020

Re: [Pharo-users] Prof Stef questions

by tbrunz

Your problem has to do with understanding how the 'ifTrue:ifFalse:' message is evaluated. This expression 1 < 2 ifTrue: [100] ifFalse: [42]. evaluates to '100'; it does not evaluate to "a block that will return 100 when evaluated". The blocks that make up the arguments to 'ifTrue:ifFalse:' will be selectively evaluated at run-time, by the receiver of the message, when the receiver makes the determination of which block to evaluate. In your modification, you mistakenly assume that one of the two block arguments will selected and returned verbatim (to be evaluated later in another context), but this is not how it works. When you write 'ifTrue: [:x|x+1]', and the receiver of the message is 'True', then 'True' will attempt to evaluate your block argument. But your block argument requires an argument itself, which is missing -- Hence the error that results. What you want is an "ifTrue:' argument block that will itself evaluate to another block that you can assign to 'a'. The fix is simple: Just enclose it in another set of '[ ]' like so: |a| a := 1 < 2 ifTrue: [ [:x|x+1] ] ifFalse: [42]. a value: 20. And the result will be '21', as intended. -Ted -- Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html

Jan. 5, 2020

Re: [Pharo-users] Prof Stef questions

by Richard Sargent

On Sun, Jan 5, 2020 at 8:08 AM xap <xap(a)router.33mail.com> wrote: > hi, I'm starting out w/ pharo (as my first smalltalk-ish language). am on > Windows 7 professional; downloaded 64-bit, pharo 8 64-bit development; then > downgraded to pharo 7, 32-bit stable. > I went through Prof Stef, and find 1 place of unexpected behavior: > > Prof Stef/Conditionals: > > "no surprises, prints 100" > 1 < 2 > ifTrue: [100] > ifFalse: [42]. > > "i added a, as below, and get an error -- i would've expected a to refer to > the block, and to be evaluable later, similar to the just prior example in > ProfStef/Block assignation" > > |a| > a := 1 < 2 > ifTrue: [:x|x+1] > ifFalse: [42]. > a value: 20. > > What am I missing, pls? > It is always a good idea to describe in detail what behaviour you did observe. "get an error" is the same as "it didn't work". It turns out that you are NOT assigning a Block to the temporary variable a. You are *evaluating* one of the two blocks in the #ifTrue:ifFalse: expression. Remember that the arguments to #ifTrue: and #ifFalse: are blocks that will be evaluated if the receiver is the correct Boolean. In this case, before there is a value to assign to a, the #ifTrue: block gets evaluated (since 1 is < 2). But, it is a one argument block and there is no value available for that argument. You should have been given the opportunity to open the debugger when the error occurred, and you would have been able to see the stack and recognize that the error occurred in the execution of the #ifTrue:ifFalse: method. I won't give you the answer at this point, as you should be able to figure it out now. Just remember that the expression essentially looks like aBoolean ifTrue: [anExpression] ifFalse: [anotherExpression] > > > > -- > Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html > >

Jan. 5, 2020

Re: [Pharo-users] Prof Stef questions

by Santiago Dandois

Hi, I haven't run your code, but I guess that the validation of the number of arguments of the block is failing. The block [ 42 ] is a block with zero arguments, but when you do a value: 20, you are calling it with one argument. So it fails. Happy Coding! Santiago Dandois El dom., 5 ene. 2020 a las 13:08, xap (<xap(a)router.33mail.com>) escribiÃ³: > hi, I'm starting out w/ pharo (as my first smalltalk-ish language). am on > Windows 7 professional; downloaded 64-bit, pharo 8 64-bit development; then > downgraded to pharo 7, 32-bit stable. > I went through Prof Stef, and find 1 place of unexpected behavior: > > Prof Stef/Conditionals: > > "no surprises, prints 100" > 1 < 2 > ifTrue: [100] > ifFalse: [42]. > > "i added a, as below, and get an error -- i would've expected a to refer to > the block, and to be evaluable later, similar to the just prior example in > ProfStef/Block assignation" > > |a| > a := 1 < 2 > ifTrue: [:x|x+1] > ifFalse: [42]. > a value: 20. > > What am I missing, pls? > > > > > -- > Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html > >

Jan. 5, 2020

Prof Stef questions

by xap

hi, I'm starting out w/ pharo (as my first smalltalk-ish language). am on Windows 7 professional; downloaded 64-bit, pharo 8 64-bit development; then downgraded to pharo 7, 32-bit stable. I went through Prof Stef, and find 1 place of unexpected behavior: Prof Stef/Conditionals: "no surprises, prints 100" 1 < 2 ifTrue: [100] ifFalse: [42]. "i added a, as below, and get an error -- i would've expected a to refer to the block, and to be evaluable later, similar to the just prior example in ProfStef/Block assignation" |a| a := 1 < 2 ifTrue: [:x|x+1] ifFalse: [42]. a value: 20. What am I missing, pls? -- Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html

Jan. 5, 2020

Re: [Pharo-users] How can we celebrate the 50th anniversary of Smalltalk?

by James Foster

> On Jan 5, 2020, at 7:39 AM, ponyatov <dponyatov(a)gmail.com> wrote: > > The best tribute to 50th anniversary will be the implementation of > distributed multi-user VM. How would that be different from GemStone?

Jan. 5, 2020

Re: [Pharo-users] How can we celebrate the 50th anniversary of Smalltalk?

by ponyatov

The best tribute to 50th anniversary will be the implementation of distributed multi-user VM. -- Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html

Jan. 5, 2020

Re: [Pharo-users] is this better regarding naming thigs

by Sven Van Caekenberghe

> On 5 Jan 2020, at 15:06, Roelof Wobben via Pharo-users <pharo-users(a)lists.pharo.org> wrote: > > > From: Roelof Wobben <r.wobben(a)home.nl> > Subject: is this better regarding naming thigs > Date: 5 January 2020 at 15:06:18 GMT+1 > To: Any question about pharo is welcome <pharo-users(a)lists.pharo.org> > > > Hello > > In a earlier question I get a remark to think better about naming things. > Now I did a challene where I have to find anagrams of a given word in a collection, > > So I did this : > > findAnagramsCandidates: aCollection subject: aWord > | charBag | > charBag := aWord asLowercase asBag. > ^ aCollection > reject: > [ :word | (word sameAs: aWord) or: [ word asLowercase asBag ~= charBag ] ] > > > is my naming here better or can i improved and if so how ? It is good. Possible alternatives: aCollectionOfWords instead of aCollection, I would even dare to use words/wordsCollection and word, since I am not a big fan of the 'a' and 'an' prefixes. Also the argument to the reject block is often called each or eachWord, but this is more of a tradition, word is OK too (but it would then conflict with naming the argument word). > Regards, > > Roelof > > > >

Jan. 5, 2020

Re: [Pharo-users] why is my css not found in a seaside project

by Sven Van Caekenberghe

> On 5 Jan 2020, at 14:46, Roelof Wobben via Pharo-users <pharo-users(a)lists.pharo.org> wrote: > > > From: Roelof Wobben <r.wobben(a)home.nl> > Subject: Re: [Pharo-users] why is my css not found in a seaside project > Date: 5 January 2020 at 14:46:24 GMT+1 > To: pharo-users(a)lists.pharo.org > > > I think I found the answer myself > > when I put this in the RootComponent > > updateRoot: anHtmlRoot > super updateRoot: anHtmlRoot. > anHtmlRoot stylesheet url: (PaintingLibrary urlOf: #mainCss) > > and this on the class side of the RootComponent > > > initialize > | app | > app := WAAdmin > register: #stRootComponent > asApplicationAt: 'Paintings2'. > app addLibrary: PaintingLibrary > > > then I see some css. The page looks not what I expect but that can be changed. > > So does the code I have now on my github page well or do I use the components still the wrong way ? What you write above is correct, it is what I meant. Good that you figured it out ! > Roelof > > > > Op 5-1-2020 om 12:48 schreef Roelof Wobben: >> Op 5-1-2020 om 11:36 schreef Roelof Wobben via Pharo-users: >> >> hmm, >> >> It looks like I had to do it like this : https://github.com/RoelofWobben/paintings >> for registering the project but I see then that the rootcomponent is not changed and that still the css is not found or used. >> >> >> So please help. >> >> Roelof >> > > > >

Jan. 5, 2020