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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 14:33, 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 <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. > 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 > I just want to check that before you are ask such questions, did you actually run this code? Because it would be fairly easy to see how close you are by evaluating it without #sumNumbers. i.e Please report what you see when evaluating this.... ``` collection := '8569 2478 0383 3437'. (collection reverse selectWithIndex: [:item :index | (index % 2 == 0) ifTrue: [item *2]] ) inspect ``` 3) check if its a valid number by doing this : > > > ^ (checkNumber % 10 == 0) > That would work, but there is a more intention revealing method... #isDivisibleBy: cheers -ben

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mentor question 4
by Roelof Wobben April 30, 2020

April 30, 2020

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Re: [Pharo-users] mentor question 3 is there a formula for this
by Richard Sargent April 29, 2020

April 29, 2020

Formula? Well, it's pretty straight forward. Let's start with the size of the diamond (it field, actually). In the example, there are two lines above and two lines below the "C" line. C-A = 2. This number looks useful. The dimension is 2+1+2 square. How many spaces before a letter? C-letter i.e. C-A = 2 C-B = 1 and C-C = 0 The same number of spaces after the second/last occurrence of the letter on the line. The number of spaces between the letters on a line is the size minus the number of spaces before and after plus the two copies of the current line's letter. For the "B" line, there is one space before and after, 2x"B", leaving 5 - 1 -1 - 2 = 1 space between. For the "A" line, the simple arithmetic would give you -1, which also confirms that just one "A" is appropriate with no space between first and last letter on the line. (For "A", it is first and last, once only.) After that, you just need to iterate ($A to: $C), ($(C-1) to: $A by: -1) and do the arithmetic. On Tue, Apr 28, 2020 at 1:23 AM Roelof Wobben via Pharo-users < pharo-users(a)lists.pharo.org> wrote: > Hello, > > I try now to solve this one : > > ntroduction > > The diamond kata takes as its input a letter, and outputs it in a diamond > shape. Given a letter, it prints a diamond starting with 'A', with the > supplied letter at the widest point. > Requirements > > - The first row contains one 'A'. > - The last row contains one 'A'. > - All rows, except the first and last, have exactly two identical > letters. > - All rows have as many trailing spaces as leading spaces. (This might > be 0). > - The diamond is horizontally symmetric. > - The diamond is vertically symmetric. > - The diamond has a square shape (width equals height). > - The letters form a diamond shape. > - The top half has the letters in ascending order. > - The bottom half has the letters in descending order. > - The four corners (containing the spaces) are triangles. > > Examples > > In the following examples, spaces are indicated by Â· characters. > > Diamond for letter 'A': > > A > > Diamond for letter 'C': > > Â·Â·AÂ·Â· > Â·BÂ·BÂ· > CÂ·Â·Â·C > Â·BÂ·BÂ· > Â·Â·AÂ·Â· > > > I noticed that if you take a quarter of it. you see this pattern > > 001 > 010 > 100 > > where a 0 is a space and a 1 is the character. > > Is there a easy way to make some sort of formula so I can make a output of this ? > > > Roelof > > >

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Re: [Pharo-users] can I divide a string into part of exactly n length
by Ben Coman April 29, 2020

April 29, 2020

On Tue, 28 Apr 2020 at 01:08, Roelof Wobben via Pharo-users < pharo-users(a)lists.pharo.org> wrote: > Op 27-4-2020 om 19:05 schreef Richard Sargent: > > On Mon, Apr 27, 2020 at 9:27 AM Roelof Wobben via Pharo-users < > pharo-users(a)lists.pharo.org> wrote: > >> Hello, >> >> I wonder if it is possible in Pharo to divide a string in lets say part >> of 3. >> so this : 'abcdefgh' >> >> would be 'abc def gh` >> > > Do you really want a single string with spaces inserted or do you want a > collection of substrings, each three characters (or less, for the last one)? > > > I need a single string with spaces inserted. > So maybe I have formulate my question wrong. Very difficult if English is > not your mother language and you were bad at school in languages a very > very long ago. > I didn't previously know of a method to do this, but I "guessed" what you needed might be related to "grouping", so I did... 'abcd' inspect. then in the Meta tab, starting at Collection, filtered on.... group* and worked up the hierarchy discovering #groupsOf:atATimeDo: in SequenceableCollection, which guesswork found could work like this... ``` input := 'abcdefghijk'. stream := String streamContents: [:s | input groupsOf: 3 atATimeDo: [ :group | s nextPutAll: group; nextPutAll: ' ']]. stream contents inspect. ``` One of the skills a new programmer needs to develop is to make those educated "guesses" and know where/how to test them. So I learnt a new method today. thx. cheers -ben

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Re: [Pharo-users] mentor question 1
by Ben Coman April 29, 2020

April 29, 2020

> but I do not have a clue what the aBlock is You say the method definition is... > linksTowards: anAddress do: aBlock and then later indicate its called like this... > linksTowards: aPacket destinationAddress do: [ :link | self send: aPacket via: link ] so in this case aBlock would be "[ :link | self send: aPacket via: link ]" Or was that not your question? Remember that "blocks are objects too". In the same way that curly brackets create an instance of Array... { 1 . 2 . 3 } inspect the square brackets create an instance of BlockClosure, or "block" for short. In Playground, compare evaluating the above inspect with evaluating the following... (i.e. type "inspect" and evaluate the whole thing) [ :x | x + 1 ] inspect then in bottom pane of that inspector, DoItAndGo evaluate the following... self value: 5 and you will see the result is 6 because #value: was sent to the block object that you inspected. HTH cheers -ben On Sun, 26 Apr 2020 at 00:48, Roelof Wobben via Pharo-users < pharo-users(a)lists.pharo.org> wrote: > Hello, > > Im doing the OOP book written by Ducassse and im now stuck at the > network-simulator. > Code so far can be found here : > https://github.com/RoelofWobben/Network-simulator > > Im stuck at 2 places > > 1) What for datatype is loopback ? Is it a string or something else. > The book is not telling that. > > 2) I have to make this method/function > > linksTowards: anAddress do: aBlock > "Simple flood algorithm: route via all outgoing links. > However, just loopback if the receiver node is the routing destination." > (address destination == loopback) > ifTrue: [self send: via: loopback ]; > ifFalse: [self send: via: anAddress] > > but I do not have a clue what the aBlock is and if im on the right path. > I know the solutions can be found online but then I do not learn anything. > > This is what is stated in the book : > > This method has to rely on some routing algorithm to identify which links > will transmit the packet > closer to its destination. Since some routing algorithms select more than > one link, we will implement routing as an iteration method, which > evaluates the given block for each selected link. > KANetworkNode >> send: aPacket > "Send aPacket, leaving the responsibility of routing to the node." > self > linksTowards: aPacket destinationAddress > do: [ :link | self send: aPacket via: link ] > One of the simplest routing algorithm is flooding: just send the packet > via every outgoing link. Obviously, this is a waste of bandwidth, but it > works without any knowledge of the network topology > beyond the list of outgoing links. > However, there is one case where we know how to route the packet: if the > destination address > matches the one of the current node, we can select the loopback link. The > logic of linksTowards:do: > is then: compare the packetâs destination address with the one of the > node, if it is the same, we > execute the block using the loopback link, else we simply iterate on the > outgoing links of the receiver. > KANetworkNode >> linksTowards: anAddress do: aBlock > "Simple flood algorithm: route via all outgoing links. > However, just loopback if the receiver node is the routing destination." > ... Your code ... > > > I hope someone can help me on the way or let me see which steps I had to > take to solve this on my own. > > Roelof > > >

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Re: [Pharo-users] mentor question 2.
by Richard O'Keefe April 29, 2020

April 29, 2020

String>> isValidBinary ^self allSatisfy: [:each | each = $0 or: [each = $1]] binaryToDecimal "The caller should ensure that self isValidBinary before calling this." ^self inject: 0 into: [:acc :each | acc*2 + (each codePoint - $0 codePoint)] On Mon, 27 Apr 2020 at 06:05, Roelof Wobben via Pharo-users <pharo-users(a)lists.pharo.org> wrote: > > Hello, > > I have to make some code that convert a binary to a decimal and im not > allowed to use the convert methods that Pharo has. > > So I have written this : > > > decimalFromBinary: aString > | result isValid | > isValid = self isValidBinary: aString. > isValid > ifTrue: [ result := 0. > aString reverse > withIndexDo: > [ :digit :index | result := result + (digit > digitValue * (2 raisedTo: index - 1)) ]. > ^ result ] > ifFalse: [ ^ nil ] > > isValidBinary: aString > ^ aString allSatisfy: [ :c | c = 0 or: [ c = 1 ] ] > > > but on the first method I see a message that the temp variables are read > before written. > and the second one I see a message that I use a or instead of searching > literals. > > Where did I think wrong here ? > > Roelof > >

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mentor question 3 is there a formula for this
by Roelof Wobben April 28, 2020

April 28, 2020

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Re: [Pharo-users] can I divide a string into part of exactly n length
by Richard O'Keefe April 27, 2020

April 27, 2020

|s1 s2| s1 := 'abcdefghijk'. s2 := String streamContents: [:s | s1 keysAndValuesDo: [:index :each | (index \\ 3 = 1 and: [1 < index]) ifTrue: [s space]. s nextPut: each]]. is perhaps a little simpler. I generally prefer to have Smalltalk do the counting for me. On Tue, 28 Apr 2020 at 07:25, Todd Blanchard via Pharo-users <pharo-users(a)lists.pharo.org> wrote: > > This works > > | s1 s2 | > s1 := 'abcdefghijk'. > s2 := String streamContents: [:s || in len | > in := ReadStream on: s1. > len := 0. > [in atEnd] whileFalse: [ > s nextPut: in next. > len := len + 1. > (in atEnd not and: [ (len \\ 3) = 0]) ifTrue: [ s space ] ] ] > > On Apr 27, 2020, at 10:07 AM, Roelof Wobben via Pharo-users <pharo-users(a)lists.pharo.org> wrote: > > > From: Roelof Wobben <r.wobben(a)home.nl> > Subject: Re: [Pharo-users] can I divide a string into part of exactly n length > Date: April 27, 2020 at 10:07:41 AM PDT > To: Richard Sargent <richard.sargent(a)gemtalksystems.com>, Any question about pharo is welcome <pharo-users(a)lists.pharo.org> > > > Op 27-4-2020 om 19:05 schreef Richard Sargent: > > On Mon, Apr 27, 2020 at 9:27 AM Roelof Wobben via Pharo-users <pharo-users(a)lists.pharo.org> wrote: >> >> Hello, >> >> I wonder if it is possible in Pharo to divide a string in lets say part >> of 3. >> so this : 'abcdefgh' >> >> would be 'abc def gh` > > > Do you really want a single string with spaces inserted or do you want a collection of substrings, each three characters (or less, for the last one)? > > > I need a single string with spaces inserted. > So maybe I have formulate my question wrong. Very difficult if English is not your mother language and you were bad at school in languages a very very long ago. > > Roelof > > > >

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Re: [Pharo-users] how can I test this
by Richard O'Keefe April 27, 2020

April 27, 2020

You wrote "I want to test if the response back to the sending node is the same string as the sending node is but then all uppercased." What is wrong with received = sent asUppercase ? If for some reason you don't like that, then received class = sent class and: [ received size = sent size and: [ received with: sent allSatisfy: [:r :s | r = s asUppercase]]] might do the job, but for two things. (1) SequenceableCollection>> with: another allSatisfy: testBlock "Extension of Collection>>allSatisfy: to test whether corresponding elements of two sequences already known to be the same length all satisfy the given test." self with: another do: [:x :y | (testBlock value: x value: y) ifFalse: [^false]]. ^true is not in Pharo 7. (2) Case conversion in Unicode is *not* a code-point by code-point mapping; it can change the length of a string. received = sent asUppercase is not just the simplest way, it's the safest. On Tue, 28 Apr 2020 at 05:04, Roelof Wobben via Pharo-users <pharo-users(a)lists.pharo.org> wrote: > > Op 27-4-2020 om 18:28 schreef Richard Sargent: > > On Mon, Apr 27, 2020 at 1:56 AM Roelof Wobben via Pharo-users <pharo-users(a)lists.pharo.org> wrote: >> >> Hello, >> >> I have to test the server which should return the string but then in >> uppercase. >> >> So far I have this : >> https://github.com/RoelofWobben/Network-simulator/blob/master/src/NetworkSi… >> >> but I fail to see how I can test that the package sending back is a >> uppercase string. > > > I think you need to rephrase this question. Either the String class hierarchy has a method named something like #isUppercase or Character does. If only Character has it, you would need to iterate over the received string testing each individual character. > > Or is your question more about getting the response back to the sending node? > > > yep, I want to test if the response back to the sending node is the same string as the sending node is but then all uppercased. > > Roelof >

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Re: [Pharo-users] how can I test this
by Roelof Wobben April 27, 2020

April 27, 2020

Op 27-4-2020 om 19:50 schreef Roelof Wobben via Pharo-users: This seems to be working testKaNetWorkServer Â Â Â | srcNode destNode link packet link2 packet2 recievedPackage | Â Â Â srcNode := KANetworkNode withAddress: #src. Â Â Â destNode := KANetworkServer withAddress: #dest. Â Â Â link := (KANetworkLink from: srcNode to: destNode) Â Â Â Â Â Â attach; Â Â Â Â Â Â yourself. Â Â Â link2 := (KANetworkLink from: destNode to: srcNode) Â Â Â Â Â Â attach; Â Â Â Â Â Â yourself. Â Â Â packet := KANetworkPacket from: #src to: #dest payload: 'test'. Â Â Â srcNode send: packet via: link. Â Â Â destNode consume: packet. Â Â Â packet2 := link2 packetsToTransmit first. Â Â Â srcNode receive: packet2 from: destNode. Â Â Â recievedPackage := srcNode arrivedPackets first. Â Â Â self assert: recievedPackage payload equals: 'TEST' I hope it is a good one.

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