- Pharo-users - lists.pharo.org

Re: [Pharo-users] type checking in Smalltalk
by Denis Kudriashov March 30, 2017

March 30, 2017

2017-03-30 16:03 GMT+02:00 Marc Hanisch via Pharo-users < pharo-users(a)lists.pharo.org>: > It is advised not to use the message isKindOf: in applications. > > I do understand that it is not a good idea to do different operations > depending on the kind of an object in one method. But in my (Javascript) > production code I do a lot of checking if an argument to a function is > "instanceof" someObject. When it is not the expected type of object, an > exception is thrown. I do this to ensure that someone (=another developer) > does not by accident passes a wrong type into my method. > > Reading this, I realized, that I never saw such type-checking in Pharo > production code. > In Pharo you will got DNU error automatically when object will receive message which it *d*oes *n*ot *u*nderstands. Then Pharo will show debugger to investigate and fix the problem. This is called dynamic typing and I guess JS will do something similar. So I wonder why you need custom error when program breaks types.

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Re: [Pharo-users] type checking in Smalltalk
by Alexandre Bergel March 30, 2017

March 30, 2017

Hi Marc, > Reading this, I realized, that I never saw such type-checking in Pharo production code. So the question is, what are recommended design principles for that problem in Smalltalk? Do you use what is called duck typing? I have carefully studied the topic of type checking in the past. I came to the conclusion that type errors are too easy to fix to justify a support in the language. There are always exceptions, for example, if you wish to provide guaranties and proof on some aspect of the language, interesting to hardware driver developers and critical software developers. In that case, you may want to have type annotation, maybe. But all in all, static type checking is more a distraction than a real benefit for practitioners in my opinion. Cheers, Alexandre

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type checking in Smalltalk
by Marc Hanisch March 30, 2017

March 30, 2017

Hello, I have a question which is more related to software engineering than to Pharo, but I hope that someone can give me an useful hint ;-) In Pharo By Example 5, Page 308, in the Chapter "Introspection", it is written: "Although these features (type inspection) are especially useful for imple- menting development tools, they are normally not appropriate for typical applications. Asking an object for its class, or querying it to discover which messages it understands, are typical signs of design problems, since they violate the principle of encapsulation." It is advised not to use the message isKindOf: in applications. I do understand that it is not a good idea to do different operations depending on the kind of an object in one method. But in my (Javascript) production code I do a lot of checking if an argument to a function is "instanceof" someObject. When it is not the expected type of object, an exception is thrown. I do this to ensure that someone (=another developer) does not by accident passes a wrong type into my method. Reading this, I realized, that I never saw such type-checking in Pharo production code. So the question is, what are recommended design principles for that problem in Smalltalk? Do you use what is called duck typing? Thanks for any advice :-) Marc

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Re: Neural Networks in Pharo
by Alidra Abdelghani March 29, 2017

March 29, 2017

Hi Oleksandr, Since you are interested in the implementation aspect of neural networks, may be you should take a look on heuristiclab (http://dev.heuristiclab.com/trac.fcgi/wiki) a general framework for developing heuristic algorithms (not only neural networks, actually). The interesting part is that the focus is on the implementation aspects too. The approach adopted by the developers is a Software Product Line one which seems to bring significant improvement to the way the code can be reused and adapted to different/new problems. Have a nice journey with Pharo ;) Abdelghani > On 21 Mar 2017, at 10:22, pharo-users-request(a)lists.pharo.org wrote: > > From: Oleksandr Zaytsev <olk.zaytsev(a)gmail.com <mailto:olk.zaytsev@gmail.com>> > To: pharo-users(a)lists.pharo.org <mailto:pharo-users@lists.pharo.org> > Subject: [Pharo-users] Neural Networks in Pharo > Message-ID: > <CAEp0UzuU-sMvgJyWtQSuMOQFu1JX1joyy48U8s08XAfZix8JjA(a)mail.gmail.com <mailto:CAEp0UzuU-sMvgJyWtQSuMOQFu1JX1joyy48U8s08XAfZix8JjA@mail.gmail.com>> > Content-Type: text/plain; charset="utf-8" > > Hello. > > I'm implementing Neural Networks in Pharo as part of my thesis > (object-oriented approaches to neural networks implementation). It would be > really nice to receive some feedback. So if you have any ideas, > recommendations, or critique, please, write me. What are the existing > projects or common pitfalls that I should consider? Maybe, you can > recommend me some nice book or paper on a related topic. I would be > grateful for any kind of feedback. > > Here is the repository: http://smalltalkhub.com/#!/~Oleks/NeuralNetwork <http://smalltalkhub.com/#!/~Oleks/NeuralNetwork>. > It's not much, but I'm working on it. > > Yours sincerely, > Oleksandr

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Build instructions for building threaded 6.0 VM on linux
by Alistair Grant March 29, 2017

March 29, 2017

Hi Everyone, Would someone please point me to instructions on how to build the 6.0 threaded VM for linux (Ubuntu). Thanks! Alistair

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Fast drag option, not really fast
by Hilaire March 29, 2017

March 29, 2017

Hi, Will it be possible to have the really *fast* drag option back as we had in old time and does in Squeak? Even over LAN X11 exported display, the fast drag option is slow. Obvisouly graphic translucent operations can't be fast. As far as I can rewind, fast drag is slow since at least Pharo3 Hilaire -- Dr. Geo http://drgeo.eu

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FileSystemDirectoryEntry>>#size may be wrong/misleading for symLinks
by PAUL DEBRUICKER March 28, 2017

March 28, 2017

This is on Pharo 5, on a mac. It reports the size of the symlink and not the linked file. So when I'd expect a size around 70kB its reporting 51B. Is there a way to get the size of the linked file? doing a 'reference contents size' isn't giving me the correct size either. In some cases it is off by hundreds of bytes. Thanks Paul

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SSL Exception on running the first example of Live Object Programming mooc
by Ahdach Mohamed March 28, 2017

March 28, 2017

Hi All, Newbie to Pharo (48 hours). I'm going through the excellent mooc by Stephane D. and his team. I've installed Pharo and run into an error when trying to run my second expression. Here it is: (ZnEasy getPng:'http://pharo.org/web/files/pharo.png') asMorph openInWindow And I have the following error: "SSL Exception: connect failed". What am I missing? Mohamed

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meaning of orange losange beside a protocol
by Ahdach Mohamed March 28, 2017

March 28, 2017

Hi, Whats the meaning of an orange losange at the left of a protocol, actually initialization Is there a list of the meanings of the icons one sees at the left of packages, classes, protocols and methods? Mohamed

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loading petitParser
by Stephane Ducasse March 28, 2017

March 28, 2017

Hi in the deep into pharo book it is written Gofer new smalltalkhubUser: 'Moose' project: 'PetitParser'; package: 'ConfigurationOfPetitParser'; load. (Smalltalk at: #ConfigurationOfPetitParser) perform: #loadDefault But this is not correct. There is no loadDefault. Should I change it? Stef

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