April 2020 - Pharo-users - lists.pharo.org

Re: [Pharo-users] mentor question 2.

by Roelof Wobben

April 27, 2020

Re: [Pharo-users] mentor question 2.

by PBKResearch

Roelof You maybe have enough mentors already, but there are some important features of this problem which can be of use in future. Your code solves the problem, but it could be improved in two ways, which make it simpler and clearer. 1. What is the purpose of the local variable 'isValid'? It provides somewhere to remember the result of your validity test. But you have no need to remember it; all you want to do is evaluate it, use it to determine the course of the program and then forget it. If you write: (self isValidBinary: aString) ifTrue: [..] ifFalse: [^nil] you will achieve the same result without introducing the local variable. It probably reads more clearly, revealing the intention of the code. (You can simplify further by replacing the ifFalse: clause with an unconditional ^nil; if the code reaches this point, we know it's false.) The general principle is: only introduce a named local variable if you need to remember something for later re-use. 2. It is not necessary to reverse the string in order to evaluate it; it is in fact easier to evaluate it from left to right. You have used the withIndexDo: method to supply the index and know the appropriate power of two to use. Instead you could multiply by two as you process each digit, which will automatically use the right power of two without ever needing to know what it is. You could write: result := 0. aString do: [:digit| result := result * 2 + digit digitValue]. ^result. This is a special case of a very useful general procedure for evaluating a polynomial. The digits of a binary number are the coefficients of a polynomial in x which is evaluated at x=2; similarly, a decimal number is a polynomial evaluated at x=10. I hope this is helpful. Peter Kenny From: Pharo-users <pharo-users-bounces(a)lists.pharo.org> On Behalf Of Roelof Wobben via Pharo-users Sent: 26 April 2020 19:52 To: pharo-users(a)lists.pharo.org Cc: Roelof Wobben <r.wobben(a)home.nl> Subject: Re: [Pharo-users] mentor question 2. Op 26-4-2020 om 20:17 schreef Sven Van Caekenberghe: > >> On 26 Apr 2020, at 20:10, Gabriel Cotelli <g.cotelli(a)gmail.com <mailto:g.cotelli@gmail.com> > wrote: >> >> In the first method you aren't doing an assignment, are sending the message = to the temp isValid, if you change the method to: >> 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 ] >> it should work. > There is a #reverseWithIndexDo: method > > Also, #digitValue might be considered a builtin method that you are > not allowed to use. Since you already did the #isValidBinary: test, > you could say > > (digit charCode - $0 charCode) > >> In the second one you're comparing characters with numbers, this will always return false because the number 0 is not the same as the character 0. >> Use >> isValidBinary: aString >> ^ aString allSatisfy: [ :c | c = $0 or: [ c = $1 ] ] or >> something like >> >> isValidBinary: aString >> ^ aString allSatisfy: [ :c | '01' includes: c ] >> >> On Sun, Apr 26, 2020 at 2:52 PM Roelof Wobben via Pharo-users <pharo-users(a)lists.pharo.org <mailto:pharo-users@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 >> >> > Thanks, this problem is solved. Roelof

April 27, 2020

how can I test this

by Roelof Wobben

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. Regards, Roelof

April 27, 2020

Re: [Pharo-users] mentor question 2.

by Roelof Wobben

Op 26-4-2020 om 20:17 schreef Sven Van Caekenberghe: > >> On 26 Apr 2020, at 20:10, Gabriel Cotelli <g.cotelli(a)gmail.com> wrote: >> >> In the first method you aren't doing an assignment, are sending the message = to the temp isValid, if you change the method to: >> 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 ] >> it should work. > There is a #reverseWithIndexDo: method > > Also, #digitValue might be considered a builtin method that you are not allowed to use. Since you already did the #isValidBinary: test, you could say > > (digit charCode - $0 charCode) > >> In the second one you're comparing characters with numbers, this will always return false because the number 0 is not the same as the character 0. >> Use >> isValidBinary: aString >> ^ aString allSatisfy: [ :c | c = $0 or: [ c = $1 ] ] >> or something like >> >> isValidBinary: aString >> ^ aString allSatisfy: [ :c | '01' includes: c ] >> >> On Sun, Apr 26, 2020 at 2:52 PM 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 >> >> > Thanks,Â this problem is solved. Roelof

April 26, 2020

Re: [Pharo-users] mentor question 2.

by Sven Van Caekenberghe

> On 26 Apr 2020, at 20:10, Gabriel Cotelli <g.cotelli(a)gmail.com> wrote: > > In the first method you aren't doing an assignment, are sending the message = to the temp isValid, if you change the method to: > 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 ] > it should work. There is a #reverseWithIndexDo: method Also, #digitValue might be considered a builtin method that you are not allowed to use. Since you already did the #isValidBinary: test, you could say (digit charCode - $0 charCode) > In the second one you're comparing characters with numbers, this will always return false because the number 0 is not the same as the character 0. > Use > isValidBinary: aString > ^ aString allSatisfy: [ :c | c = $0 or: [ c = $1 ] ] > or something like > > isValidBinary: aString > ^ aString allSatisfy: [ :c | '01' includes: c ] > > On Sun, Apr 26, 2020 at 2:52 PM 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 > >

April 26, 2020

Re: [Pharo-users] mentor question 2.

by Gabriel Cotelli

In the first method you aren't doing an assignment, are sending the message = to the temp isValid, if you change the method to: 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 ] it should work. In the second one you're comparing characters with numbers, this will always return false because the number 0 is not the same as the character 0. Use isValidBinary: aString ^ aString allSatisfy: [ :c | c = $0 or: [ c = $1 ] ] or something like isValidBinary: aString ^ aString allSatisfy: [ :c | '01' includes: c ] On Sun, Apr 26, 2020 at 2:52 PM 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 > > >

April 26, 2020

mentor question 2.

by Roelof Wobben

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 Â Â Â | result isValid | Â Â Â isValid = self isValidBinary: aString. Â Â Â isValid Â Â Â Â Â Â ifTrue: [ result := 0. Â Â Â Â Â Â Â Â Â aString reverse Â Â Â Â Â Â Â Â Â Â Â Â withIndexDo: Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â [ :digit :index | result := result + (digit digitValue * (2 raisedTo: index - 1)) ]. Â Â Â Â Â Â Â Â Â ^ result ] Â Â Â Â Â Â ifFalse: [ ^ nil ] isValidBinary: aString Â Â Â ^ 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 didÂ I think wrong here ? Roelof

April 26, 2020

Re: [Pharo-users] running Pharo8 in Digitalocean

by Ben Coman

Have you considered installing Ubuntu App from Microsoft App Store? cheers -ben On Sun, 19 Apr 2020 at 01:15, Sanjay Minni <sm(a)planage.com> wrote: > Hi, > > I am using a Windows 10 local machine and digitalocean ubuntu server > droplet > - how can I run pharo 8 remotedly in the windows 10 inbuilt powershell ssh > terminal - or any other method > > (I have successfully executed > # ./pharo Pharo.image eval --no-quit 'ZnServer startDefaultOn: 8080' > and connected from my local machine) >

April 26, 2020

Re: [Pharo-users] mentor wanted

by Roelof Wobben

Op 26-4-2020 om 06:30 schreef Richard O'Keefe: > Roelof, *I* was offering to write something. > > On Sat, 25 Apr 2020 at 19:47, Roelof Wobben via Pharo-users > <pharo-users(a)lists.pharo.org> wrote: >> Op 25-4-2020 om 08:30 schreef Richard Sargent: >> >> On Fri, Apr 24, 2020, 22:25 Richard O'Keefe <raoknz(a)gmail.com> wrote: >>> Roelof, I don't think CRC cards or the GRASP patterns or anything like that >>> addresses your immediate needs. Based on other questions of yours it >>> seems to me that your problem is not *organising* the responsibilities in an >>> OO program, but decomposing a problem into responsibilities in the first >>> place. I think this is perhaps the most important part of programming, and >>> the hardest to learn, not least because very few of us are good at teaching >>> it. We're not very good at teaching it in mathematics either. I do not think >>> your issues are anything to do with Pharo, Smalltalk, OOP, or programming >>> as such. >>> >>> One symptom of the general problem that I've noticed is that I see code as >>> a very fluid sort of thing where pieces can be moved around and recombined, >>> while many people think of code as something solid and rather brittle. >>> >>> I was thinking of writing up a short description of what I was thinking for a >>> RosettaCode example anyway. Would that help? >> >> Thank you, Richard. I appreciate your offering this. I am not a teacher, so your help is truly appreciated! >> >> >> >> Moment, I have to look if I understand you right. >> I think you have some strong points but the last one I did not understand well. >> >> Do I have to write for example for a exercism challenge a short description of that problem like people do with rosetta code challenges and example code ? >> >> Roelof >> oke, I also accept this offer also. The more angles I learn to solve this , the more I can use that in later challenges. and if I understand everything right , the solution is very simple linksTowards: anAddress do: aBlock Â Â Â "Simple flood algorithm: route via all outgoing links. However, just loopback if the receiver node is the routing destination." Â Â Â address = anAddress Â Â Â Â Â Â ifTrue: [ aBlock evaluate: loopback ] Â Â Â Â Â Â ifFalse: [ outgoingLinks do: aBlock ] and the flow is this : send: aPacket Â Â Â "Send aPacket, leaving the responsibility of routing to the node." Â Â Â self Â Â Â Â Â Â linksTowards: aPacket destinationAddress Â Â Â Â Â Â do: [ :link | self send: aPacket via: link ] so for linkTwowards the anAddress isÂ the `aPacket destinationAdress `Â and the aBlockÂ is ` [:link | self send: aPacket via: link ` so if the address is the loopback oneÂ it would be ` self send: aPacket via: loopback ` and send is this : send: aPacket via: aLink Â Â Â aLink emit: aPacket so that would beÂ ` loopback emit : aPackageÂ ` and that would lead to : emit: aPacket Â Â Â "Packets are not transmitted right away, but stored. Transmission is explicitly triggered later, by sending #transmit:." Â Â Â packetsToTransmit add: aPacket where packetsToTransmit is a OrderedCollection where the packet is added Waiting till the transmit method is called where the sending of a package is simulated. Roelof

April 26, 2020

Re: [Pharo-users] mentor wanted

by Richard O'Keefe

Roelof, *I* was offering to write something. On Sat, 25 Apr 2020 at 19:47, Roelof Wobben via Pharo-users <pharo-users(a)lists.pharo.org> wrote: > > Op 25-4-2020 om 08:30 schreef Richard Sargent: > > On Fri, Apr 24, 2020, 22:25 Richard O'Keefe <raoknz(a)gmail.com> wrote: >> >> Roelof, I don't think CRC cards or the GRASP patterns or anything like that >> addresses your immediate needs. Based on other questions of yours it >> seems to me that your problem is not *organising* the responsibilities in an >> OO program, but decomposing a problem into responsibilities in the first >> place. I think this is perhaps the most important part of programming, and >> the hardest to learn, not least because very few of us are good at teaching >> it. We're not very good at teaching it in mathematics either. I do not think >> your issues are anything to do with Pharo, Smalltalk, OOP, or programming >> as such. >> >> One symptom of the general problem that I've noticed is that I see code as >> a very fluid sort of thing where pieces can be moved around and recombined, >> while many people think of code as something solid and rather brittle. >> >> I was thinking of writing up a short description of what I was thinking for a >> RosettaCode example anyway. Would that help? > > > Thank you, Richard. I appreciate your offering this. I am not a teacher, so your help is truly appreciated! > > > > Moment, I have to look if I understand you right. > I think you have some strong points but the last one I did not understand well. > > Do I have to write for example for a exercism challenge a short description of that problem like people do with rosetta code challenges and example code ? > > Roelof >

April 26, 2020