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Re: [Pharo-dev] About abuse of inheritance

by Igor Stasenko

On 22 July 2013 16:52, Florin Mateoc <fmateoc(a)gmail.com> wrote: > Forget about quaternions! Are you really saying: specialization good, > generalization bad?!!! Well, at least in this case, your generalization is > indeed a bad one :) > > Generalization and specialization are duals of each other. We can do stupid > specializations just as easily as we can do stupid generalizations. Let's > take you example. Postman subclass: > PostmanWhoAlsoDeliversPizzasAndFliesToTheMoon is a specialization, not a > generalization. How is it any better? > > uh? Generalization is good. but you don't achieving it by subclassing. And that's exactly what i was pointing out: subclassing is intended for specialization, but not for generalization. And when you subclass for generalization you doing exactly what i am against. > > > On Mon, Jul 22, 2013 at 10:38 AM, Igor Stasenko <siguctua(a)gmail.com> wrote: >> >> On 22 July 2013 16:23, Nicolas Cellier >> <nicolas.cellier.aka.nice(a)gmail.com> wrote: >> > Because the quaternion (ar + ai * i + 0 * j + 0 * k) will behave exactly >> > like a complex (ar + ai * i) with respect to arithmetic (+ - * /) and >> > elementary functions (exp sin cos etc...). >> > >> all i know is that >> >> i*i = -1 >> >> that's what makes complex numbers quite different from other >> n-dimensional vector(s). >> and i never seen that you can mix complex algebra and linear algebra.. >> hence, i can imagine that you can subclass both from some abstract >> NDimensionalVector >> but not subclass one from another, because it makes no sense. >> >> >> > >> > 2013/7/22 Igor Stasenko <siguctua(a)gmail.com> >> >> >> >> On 22 July 2013 15:13, Florin Mateoc <fmateoc(a)gmail.com> wrote: >> >> > On 7/22/2013 8:44 AM, Igor Stasenko wrote: >> >> >> On 22 July 2013 14:13, Florin Mateoc <fmateoc(a)gmail.com> wrote: >> >> >>> I also liked the debate, so before it closes I want to throw my 2 >> >> >>> cents in: >> >> >>> >> >> >>> I don't think this is an issue about inheritance (vs composition), >> >> >>> it >> >> >>> is one >> >> >>> about multiple inheritance or lack thereof. You may want your >> >> >>> object >> >> >>> to be >> >> >>> an announcer of events, but almost always you will also want it to >> >> >>> be >> >> >>> something else as well. To me this suggests that Announcer should >> >> >>> be a >> >> >>> trait, not a class, so in a sense, indeed, you would "compose" your >> >> >>> classes >> >> >>> using it, but you would use trait composition instead of class >> >> >>> composition. >> >> >>> In VisualAge there is a huge hierarchy underneath >> >> >>> AbtObservableObject. >> >> >>> Sure, >> >> >>> there are many classes that want to participate in an observable >> >> >>> pattern, >> >> >>> but you should not be forced to inherit from a particular class in >> >> >>> order to >> >> >>> do that, so that is just another related example that would have >> >> >>> benefited >> >> >>> from traits. >> >> >>> >> >> >> Again, announcer of events means event source role. >> >> >> It is distinct from 'delivery service' role. >> >> >> >> >> >> When you write mail, you just drop it into mailbox, and then mr. >> >> >> Postman delivers it to receiver, >> >> >> but not directly yourself. >> >> >> That's what you get from specialization. >> >> >> But if you wanna play as mr. Postman, and also will deliver pizzas, >> >> >> and fly to the moon, >> >> >> this is called generalization, and straightly opposite to >> >> >> specialization. >> >> >> >> >> >> >> >> > >> >> > So what? The thing is, you want to do both. We think in both >> >> > directions. >> >> > Sometimes we generalize from the existing >> >> > knowledge, sometimes we specialize from the abstract. >> >> >> >> I say you what. If you go to extreme, then your object can do >> >> everything.. and so you end up with code like this everywhere: >> >> >> >> self foo: self bar with: self zork. >> >> >> >> Because your object knows everything, can do everything and don't >> >> needs anything. >> >> The only question which remains is why you using object-oriented >> >> language >> >> then? >> >> Why using classes, caring about inheritance, polymorphism , message >> >> passing etc, because >> >> if single object does all you need, you don't need all of above. >> >> >> >> My point is that if you don't need such concepts, just don't use >> >> them.. but if you using them, >> >> then please follow the rules. >> >> >> >> Same goes to Announcer. It defines the certain way how it should be >> >> used. And how its not. >> >> >> >> > A quaternion is a generalization in 4 dimensions, we did not get >> >> > complex >> >> > numbers by specializing from quaternions, it >> >> > was the other way around. >> >> > >> >> >> >> hmm? how that? i first time hear that they are related. >> >> Can you provide a real example where you can mix both of them >> >> interchangeably? >> >> Besides the fact that they both are partial case of n-dimentional >> >> vectors, they not sharing too much, >> >> because of different math and different uses. >> >> >> >> But anyways.. it seems like Announcement(s) model, to my thinking >> >> don't really fits well with >> >> observer pattern. >> >> Because in observer pattern you need only 2 roles: observer(s) and >> >> subject. >> >> You don't have nor need a mediator or 'event dispatcher', which >> >> represented by announcer. >> >> >> >> Implementing an observer pattern using Announcer is an overkill, to my >> >> thinking. >> >> Reflecting by your example, is like using quaternions where complex >> >> numbers is sufficient. >> >> >> >> I think more and more, in this regard, that Announcements is not a >> >> silver bullet and it has own limits >> >> and intended ways to use. >> >> For that matter, i think we should have more simple and elegant >> >> solution. >> >> Because subclassing from Announcer is not a solution. >> >> >> >> >> >> -- >> >> Best regards, >> >> Igor Stasenko. >> >> >> > >> >> >> >> -- >> Best regards, >> Igor Stasenko. >> > -- Best regards, Igor Stasenko.

July 22, 2013

Re: [Pharo-dev] About abuse of inheritance

by Florin Mateoc

Forget about quaternions! Are you really saying: specialization good, generalization bad?!!! Well, at least in this case, your generalization is indeed a bad one :) Generalization and specialization are duals of each other. We can do stupid specializations just as easily as we can do stupid generalizations. Let's take you example. Postman subclass: PostmanWhoAlsoDeliversPizzasAndFliesToTheMoon is a specialization, not a generalization. How is it any better? On Mon, Jul 22, 2013 at 10:38 AM, Igor Stasenko <siguctua(a)gmail.com> wrote: > On 22 July 2013 16:23, Nicolas Cellier > <nicolas.cellier.aka.nice(a)gmail.com> wrote: > > Because the quaternion (ar + ai * i + 0 * j + 0 * k) will behave exactly > > like a complex (ar + ai * i) with respect to arithmetic (+ - * /) and > > elementary functions (exp sin cos etc...). > > > all i know is that > > i*i = -1 > > that's what makes complex numbers quite different from other > n-dimensional vector(s). > and i never seen that you can mix complex algebra and linear algebra.. > hence, i can imagine that you can subclass both from some abstract > NDimensionalVector > but not subclass one from another, because it makes no sense. > > > > > > 2013/7/22 Igor Stasenko <siguctua(a)gmail.com> > >> > >> On 22 July 2013 15:13, Florin Mateoc <fmateoc(a)gmail.com> wrote: > >> > On 7/22/2013 8:44 AM, Igor Stasenko wrote: > >> >> On 22 July 2013 14:13, Florin Mateoc <fmateoc(a)gmail.com> wrote: > >> >>> I also liked the debate, so before it closes I want to throw my 2 > >> >>> cents in: > >> >>> > >> >>> I don't think this is an issue about inheritance (vs composition), > it > >> >>> is one > >> >>> about multiple inheritance or lack thereof. You may want your object > >> >>> to be > >> >>> an announcer of events, but almost always you will also want it to > be > >> >>> something else as well. To me this suggests that Announcer should > be a > >> >>> trait, not a class, so in a sense, indeed, you would "compose" your > >> >>> classes > >> >>> using it, but you would use trait composition instead of class > >> >>> composition. > >> >>> In VisualAge there is a huge hierarchy underneath > AbtObservableObject. > >> >>> Sure, > >> >>> there are many classes that want to participate in an observable > >> >>> pattern, > >> >>> but you should not be forced to inherit from a particular class in > >> >>> order to > >> >>> do that, so that is just another related example that would have > >> >>> benefited > >> >>> from traits. > >> >>> > >> >> Again, announcer of events means event source role. > >> >> It is distinct from 'delivery service' role. > >> >> > >> >> When you write mail, you just drop it into mailbox, and then mr. > >> >> Postman delivers it to receiver, > >> >> but not directly yourself. > >> >> That's what you get from specialization. > >> >> But if you wanna play as mr. Postman, and also will deliver pizzas, > >> >> and fly to the moon, > >> >> this is called generalization, and straightly opposite to > >> >> specialization. > >> >> > >> >> > >> > > >> > So what? The thing is, you want to do both. We think in both > directions. > >> > Sometimes we generalize from the existing > >> > knowledge, sometimes we specialize from the abstract. > >> > >> I say you what. If you go to extreme, then your object can do > >> everything.. and so you end up with code like this everywhere: > >> > >> self foo: self bar with: self zork. > >> > >> Because your object knows everything, can do everything and don't > >> needs anything. > >> The only question which remains is why you using object-oriented > language > >> then? > >> Why using classes, caring about inheritance, polymorphism , message > >> passing etc, because > >> if single object does all you need, you don't need all of above. > >> > >> My point is that if you don't need such concepts, just don't use > >> them.. but if you using them, > >> then please follow the rules. > >> > >> Same goes to Announcer. It defines the certain way how it should be > >> used. And how its not. > >> > >> > A quaternion is a generalization in 4 dimensions, we did not get > complex > >> > numbers by specializing from quaternions, it > >> > was the other way around. > >> > > >> > >> hmm? how that? i first time hear that they are related. > >> Can you provide a real example where you can mix both of them > >> interchangeably? > >> Besides the fact that they both are partial case of n-dimentional > >> vectors, they not sharing too much, > >> because of different math and different uses. > >> > >> But anyways.. it seems like Announcement(s) model, to my thinking > >> don't really fits well with > >> observer pattern. > >> Because in observer pattern you need only 2 roles: observer(s) and > >> subject. > >> You don't have nor need a mediator or 'event dispatcher', which > >> represented by announcer. > >> > >> Implementing an observer pattern using Announcer is an overkill, to my > >> thinking. > >> Reflecting by your example, is like using quaternions where complex > >> numbers is sufficient. > >> > >> I think more and more, in this regard, that Announcements is not a > >> silver bullet and it has own limits > >> and intended ways to use. > >> For that matter, i think we should have more simple and elegant > solution. > >> Because subclassing from Announcer is not a solution. > >> > >> > >> -- > >> Best regards, > >> Igor Stasenko. > >> > > > > > > -- > Best regards, > Igor Stasenko. > >

July 22, 2013

Re: [Pharo-dev] About abuse of inheritance

by Igor Stasenko

On 22 July 2013 16:23, Nicolas Cellier <nicolas.cellier.aka.nice(a)gmail.com> wrote: > Because the quaternion (ar + ai * i + 0 * j + 0 * k) will behave exactly > like a complex (ar + ai * i) with respect to arithmetic (+ - * /) and > elementary functions (exp sin cos etc...). > all i know is that i*i = -1 that's what makes complex numbers quite different from other n-dimensional vector(s). and i never seen that you can mix complex algebra and linear algebra.. hence, i can imagine that you can subclass both from some abstract NDimensionalVector but not subclass one from another, because it makes no sense. > > 2013/7/22 Igor Stasenko <siguctua(a)gmail.com> >> >> On 22 July 2013 15:13, Florin Mateoc <fmateoc(a)gmail.com> wrote: >> > On 7/22/2013 8:44 AM, Igor Stasenko wrote: >> >> On 22 July 2013 14:13, Florin Mateoc <fmateoc(a)gmail.com> wrote: >> >>> I also liked the debate, so before it closes I want to throw my 2 >> >>> cents in: >> >>> >> >>> I don't think this is an issue about inheritance (vs composition), it >> >>> is one >> >>> about multiple inheritance or lack thereof. You may want your object >> >>> to be >> >>> an announcer of events, but almost always you will also want it to be >> >>> something else as well. To me this suggests that Announcer should be a >> >>> trait, not a class, so in a sense, indeed, you would "compose" your >> >>> classes >> >>> using it, but you would use trait composition instead of class >> >>> composition. >> >>> In VisualAge there is a huge hierarchy underneath AbtObservableObject. >> >>> Sure, >> >>> there are many classes that want to participate in an observable >> >>> pattern, >> >>> but you should not be forced to inherit from a particular class in >> >>> order to >> >>> do that, so that is just another related example that would have >> >>> benefited >> >>> from traits. >> >>> >> >> Again, announcer of events means event source role. >> >> It is distinct from 'delivery service' role. >> >> >> >> When you write mail, you just drop it into mailbox, and then mr. >> >> Postman delivers it to receiver, >> >> but not directly yourself. >> >> That's what you get from specialization. >> >> But if you wanna play as mr. Postman, and also will deliver pizzas, >> >> and fly to the moon, >> >> this is called generalization, and straightly opposite to >> >> specialization. >> >> >> >> >> > >> > So what? The thing is, you want to do both. We think in both directions. >> > Sometimes we generalize from the existing >> > knowledge, sometimes we specialize from the abstract. >> >> I say you what. If you go to extreme, then your object can do >> everything.. and so you end up with code like this everywhere: >> >> self foo: self bar with: self zork. >> >> Because your object knows everything, can do everything and don't >> needs anything. >> The only question which remains is why you using object-oriented language >> then? >> Why using classes, caring about inheritance, polymorphism , message >> passing etc, because >> if single object does all you need, you don't need all of above. >> >> My point is that if you don't need such concepts, just don't use >> them.. but if you using them, >> then please follow the rules. >> >> Same goes to Announcer. It defines the certain way how it should be >> used. And how its not. >> >> > A quaternion is a generalization in 4 dimensions, we did not get complex >> > numbers by specializing from quaternions, it >> > was the other way around. >> > >> >> hmm? how that? i first time hear that they are related. >> Can you provide a real example where you can mix both of them >> interchangeably? >> Besides the fact that they both are partial case of n-dimentional >> vectors, they not sharing too much, >> because of different math and different uses. >> >> But anyways.. it seems like Announcement(s) model, to my thinking >> don't really fits well with >> observer pattern. >> Because in observer pattern you need only 2 roles: observer(s) and >> subject. >> You don't have nor need a mediator or 'event dispatcher', which >> represented by announcer. >> >> Implementing an observer pattern using Announcer is an overkill, to my >> thinking. >> Reflecting by your example, is like using quaternions where complex >> numbers is sufficient. >> >> I think more and more, in this regard, that Announcements is not a >> silver bullet and it has own limits >> and intended ways to use. >> For that matter, i think we should have more simple and elegant solution. >> Because subclassing from Announcer is not a solution. >> >> >> -- >> Best regards, >> Igor Stasenko. >> > -- Best regards, Igor Stasenko.

July 22, 2013

Re: [Pharo-dev] About abuse of inheritance

by Nicolas Cellier

Because the quaternion (ar + ai * i + 0 * j + 0 * k) will behave exactly like a complex (ar + ai * i) with respect to arithmetic (+ - * /) and elementary functions (exp sin cos etc...). 2013/7/22 Igor Stasenko <siguctua(a)gmail.com> > On 22 July 2013 15:13, Florin Mateoc <fmateoc(a)gmail.com> wrote: > > On 7/22/2013 8:44 AM, Igor Stasenko wrote: > >> On 22 July 2013 14:13, Florin Mateoc <fmateoc(a)gmail.com> wrote: > >>> I also liked the debate, so before it closes I want to throw my 2 > cents in: > >>> > >>> I don't think this is an issue about inheritance (vs composition), it > is one > >>> about multiple inheritance or lack thereof. You may want your object > to be > >>> an announcer of events, but almost always you will also want it to be > >>> something else as well. To me this suggests that Announcer should be a > >>> trait, not a class, so in a sense, indeed, you would "compose" your > classes > >>> using it, but you would use trait composition instead of class > composition. > >>> In VisualAge there is a huge hierarchy underneath AbtObservableObject. > Sure, > >>> there are many classes that want to participate in an observable > pattern, > >>> but you should not be forced to inherit from a particular class in > order to > >>> do that, so that is just another related example that would have > benefited > >>> from traits. > >>> > >> Again, announcer of events means event source role. > >> It is distinct from 'delivery service' role. > >> > >> When you write mail, you just drop it into mailbox, and then mr. > >> Postman delivers it to receiver, > >> but not directly yourself. > >> That's what you get from specialization. > >> But if you wanna play as mr. Postman, and also will deliver pizzas, > >> and fly to the moon, > >> this is called generalization, and straightly opposite to > specialization. > >> > >> > > > > So what? The thing is, you want to do both. We think in both directions. > Sometimes we generalize from the existing > > knowledge, sometimes we specialize from the abstract. > > I say you what. If you go to extreme, then your object can do > everything.. and so you end up with code like this everywhere: > > self foo: self bar with: self zork. > > Because your object knows everything, can do everything and don't > needs anything. > The only question which remains is why you using object-oriented language > then? > Why using classes, caring about inheritance, polymorphism , message > passing etc, because > if single object does all you need, you don't need all of above. > > My point is that if you don't need such concepts, just don't use > them.. but if you using them, > then please follow the rules. > > Same goes to Announcer. It defines the certain way how it should be > used. And how its not. > > > A quaternion is a generalization in 4 dimensions, we did not get complex > numbers by specializing from quaternions, it > > was the other way around. > > > > hmm? how that? i first time hear that they are related. > Can you provide a real example where you can mix both of them > interchangeably? > Besides the fact that they both are partial case of n-dimentional > vectors, they not sharing too much, > because of different math and different uses. > > But anyways.. it seems like Announcement(s) model, to my thinking > don't really fits well with > observer pattern. > Because in observer pattern you need only 2 roles: observer(s) and subject. > You don't have nor need a mediator or 'event dispatcher', which > represented by announcer. > > Implementing an observer pattern using Announcer is an overkill, to my > thinking. > Reflecting by your example, is like using quaternions where complex > numbers is sufficient. > > I think more and more, in this regard, that Announcements is not a > silver bullet and it has own limits > and intended ways to use. > For that matter, i think we should have more simple and elegant solution. > Because subclassing from Announcer is not a solution. > > > -- > Best regards, > Igor Stasenko. > >

July 22, 2013

Re: [Pharo-dev] About abuse of inheritance

by Igor Stasenko

On 22 July 2013 15:13, Florin Mateoc <fmateoc(a)gmail.com> wrote: > On 7/22/2013 8:44 AM, Igor Stasenko wrote: >> On 22 July 2013 14:13, Florin Mateoc <fmateoc(a)gmail.com> wrote: >>> I also liked the debate, so before it closes I want to throw my 2 cents in: >>> >>> I don't think this is an issue about inheritance (vs composition), it is one >>> about multiple inheritance or lack thereof. You may want your object to be >>> an announcer of events, but almost always you will also want it to be >>> something else as well. To me this suggests that Announcer should be a >>> trait, not a class, so in a sense, indeed, you would "compose" your classes >>> using it, but you would use trait composition instead of class composition. >>> In VisualAge there is a huge hierarchy underneath AbtObservableObject. Sure, >>> there are many classes that want to participate in an observable pattern, >>> but you should not be forced to inherit from a particular class in order to >>> do that, so that is just another related example that would have benefited >>> from traits. >>> >> Again, announcer of events means event source role. >> It is distinct from 'delivery service' role. >> >> When you write mail, you just drop it into mailbox, and then mr. >> Postman delivers it to receiver, >> but not directly yourself. >> That's what you get from specialization. >> But if you wanna play as mr. Postman, and also will deliver pizzas, >> and fly to the moon, >> this is called generalization, and straightly opposite to specialization. >> >> > > So what? The thing is, you want to do both. We think in both directions. Sometimes we generalize from the existing > knowledge, sometimes we specialize from the abstract. I say you what. If you go to extreme, then your object can do everything.. and so you end up with code like this everywhere: self foo: self bar with: self zork. Because your object knows everything, can do everything and don't needs anything. The only question which remains is why you using object-oriented language then? Why using classes, caring about inheritance, polymorphism , message passing etc, because if single object does all you need, you don't need all of above. My point is that if you don't need such concepts, just don't use them.. but if you using them, then please follow the rules. Same goes to Announcer. It defines the certain way how it should be used. And how its not. > A quaternion is a generalization in 4 dimensions, we did not get complex numbers by specializing from quaternions, it > was the other way around. > hmm? how that? i first time hear that they are related. Can you provide a real example where you can mix both of them interchangeably? Besides the fact that they both are partial case of n-dimentional vectors, they not sharing too much, because of different math and different uses. But anyways.. it seems like Announcement(s) model, to my thinking don't really fits well with observer pattern. Because in observer pattern you need only 2 roles: observer(s) and subject. You don't have nor need a mediator or 'event dispatcher', which represented by announcer. Implementing an observer pattern using Announcer is an overkill, to my thinking. Reflecting by your example, is like using quaternions where complex numbers is sufficient. I think more and more, in this regard, that Announcements is not a silver bullet and it has own limits and intended ways to use. For that matter, i think we should have more simple and elegant solution. Because subclassing from Announcer is not a solution. -- Best regards, Igor Stasenko.

July 22, 2013

[regression reporter]regression occurred

by no-reply＠ci.inria.fr

https://ci.inria.fr/pharo/job/Pharo-3.0-Update-Step-2-Validation/label=win/… 1 regressions found. KernelTests.Classes.ClassHierarchyTest.testSubclasses

July 22, 2013

[regression reporter]regression occurred

by no-reply＠ci.inria.fr

https://ci.inria.fr/pharo/job/Pharo-3.0-Update-Step-2-Validation/label=mac/… 1 regressions found. KernelTests.Classes.ClassHierarchyTest.testSubclasses

July 22, 2013

Re: [Pharo-dev] About abuse of inheritance

by Florin Mateoc

On 7/22/2013 8:44 AM, Igor Stasenko wrote: > On 22 July 2013 14:13, Florin Mateoc <fmateoc(a)gmail.com> wrote: >> I also liked the debate, so before it closes I want to throw my 2 cents in: >> >> I don't think this is an issue about inheritance (vs composition), it is one >> about multiple inheritance or lack thereof. You may want your object to be >> an announcer of events, but almost always you will also want it to be >> something else as well. To me this suggests that Announcer should be a >> trait, not a class, so in a sense, indeed, you would "compose" your classes >> using it, but you would use trait composition instead of class composition. >> In VisualAge there is a huge hierarchy underneath AbtObservableObject. Sure, >> there are many classes that want to participate in an observable pattern, >> but you should not be forced to inherit from a particular class in order to >> do that, so that is just another related example that would have benefited >> from traits. >> > Again, announcer of events means event source role. > It is distinct from 'delivery service' role. > > When you write mail, you just drop it into mailbox, and then mr. > Postman delivers it to receiver, > but not directly yourself. > That's what you get from specialization. > But if you wanna play as mr. Postman, and also will deliver pizzas, > and fly to the moon, > this is called generalization, and straightly opposite to specialization. > > So what? The thing is, you want to do both. We think in both directions. Sometimes we generalize from the existing knowledge, sometimes we specialize from the abstract. A quaternion is a generalization in 4 dimensions, we did not get complex numbers by specializing from quaternions, it was the other way around. Florin

July 22, 2013

[regression reporter]regression occurred

by no-reply＠ci.inria.fr

https://ci.inria.fr/pharo/job/Pharo-3.0-Update-Step-2-Validation/label=linu… 1 regressions found. KernelTests.Classes.ClassHierarchyTest.testSubclasses

July 22, 2013

[update 3.0] #30292

by Marcus Denker

30292 ----- 11211 clean up Watery2 theme https://pharo.fogbugz.com/f/cases/11211 11206 clean up externalInterrupt in old Debugger https://pharo.fogbugz.com/f/cases/11206 Diff information: http://smalltalkhub.com/mc/Pharo/Pharo30/main/Tools-MarcusDenker.1190.diff http://smalltalkhub.com/mc/Pharo/Pharo30/main/Polymorph-Widgets-MarcusDenke…

July 22, 2013