December 2012 - Pharo-dev - lists.pharo.org

Re: [Pharo-project] Interval protocol

by Nicolas Cellier

Beware, Range exists in other languages (python, etc..). We should check if they correspond to a Smalltalk Interval or a mathematical Interval. If they correspond to a Smalltalk Interval, that will be one more un-necessary trap. Note that we rarely use Interval, we just use #to: or #to:by:, so we could as well rename Interval->Range. And postpone creation of Mathematical Interval which is most likely unused in kernel image. Nicolas 2012/12/16 StÃ©phane Ducasse <stephane.ducasse(a)inria.fr>: > I agree so we should introduce Range. > Did not you or camillo started to have Range? > It can be a really nice class. > > Stef > On Dec 16, 2012, at 4:55 PM, Igor Stasenko wrote: > >> So, to my sense a behavior of Interval is overloaded.. >> it tries to be too many things at once: >> - be an interval in math sense (which is infinite set if used for Real numbers) >> - be a "collection" of numbers which you can enumerate (implies that >> it is finite). >> >> to me, i would be much happier if we could have two different and >> non-intersecting entities: >> >> - Enumeration. This one indeed can be used as a collection. i.e. >> "give me all integer numbers lying between values A and B, count each >> C-th number" >> Like that, >> (1 to: 1.5 by: 1) is enumeration which contains a single element. >> and #last should be = 1 >> >> - Interval (Range). A pure interval in math sense: defines a Set of >> numbers lying between numbers A and B, inclusive, where A <= B. Not >> enumerable, therefore no 'step' variable, instead what it could have, >> is flags to indicate whether interval endpoints included into interval >> or not.. i.e. (a,b) vs [a,b] vs [a,b) vs (a,b]. >> >> Not supporting enumeration (no #do: , no #add: no #at: etc). You can, >> however intersect, merge or diff two intervals etc.. same operations >> which you doing on sets (but that would require another entity - >> interval set). And of course, you can test whether some number lies >> within given interval or not. >> >> The reason i started this topic is because some code were using >> 'range' for variables which holding intervals.. >> Now what you think is more appropriate protocol for something called >> 'range', this: >> >> x := range first >> y := range last >> >> or this: >> >> x := range start >> y := range end >> >> >> -- >> Best regards, >> Igor Stasenko. >> > >

Dec. 16, 2012

Re: [Pharo-project] Interval protocol

by StÃ©phane Ducasse

I agree so we should introduce Range. Did not you or camillo started to have Range? It can be a really nice class. Stef On Dec 16, 2012, at 4:55 PM, Igor Stasenko wrote: > So, to my sense a behavior of Interval is overloaded.. > it tries to be too many things at once: > - be an interval in math sense (which is infinite set if used for Real numbers) > - be a "collection" of numbers which you can enumerate (implies that > it is finite). > > to me, i would be much happier if we could have two different and > non-intersecting entities: > > - Enumeration. This one indeed can be used as a collection. i.e. > "give me all integer numbers lying between values A and B, count each > C-th number" > Like that, > (1 to: 1.5 by: 1) is enumeration which contains a single element. > and #last should be = 1 > > - Interval (Range). A pure interval in math sense: defines a Set of > numbers lying between numbers A and B, inclusive, where A <= B. Not > enumerable, therefore no 'step' variable, instead what it could have, > is flags to indicate whether interval endpoints included into interval > or not.. i.e. (a,b) vs [a,b] vs [a,b) vs (a,b]. > > Not supporting enumeration (no #do: , no #add: no #at: etc). You can, > however intersect, merge or diff two intervals etc.. same operations > which you doing on sets (but that would require another entity - > interval set). And of course, you can test whether some number lies > within given interval or not. > > The reason i started this topic is because some code were using > 'range' for variables which holding intervals.. > Now what you think is more appropriate protocol for something called > 'range', this: > > x := range first > y := range last > > or this: > > x := range start > y := range end > > > -- > Best regards, > Igor Stasenko. >

Dec. 16, 2012

Re: [Pharo-project] Interval protocol

by Igor Stasenko

So, to my sense a behavior of Interval is overloaded.. it tries to be too many things at once: - be an interval in math sense (which is infinite set if used for Real numbers) - be a "collection" of numbers which you can enumerate (implies that it is finite). to me, i would be much happier if we could have two different and non-intersecting entities: - Enumeration. This one indeed can be used as a collection. i.e. "give me all integer numbers lying between values A and B, count each C-th number" Like that, (1 to: 1.5 by: 1) is enumeration which contains a single element. and #last should be = 1 - Interval (Range). A pure interval in math sense: defines a Set of numbers lying between numbers A and B, inclusive, where A <= B. Not enumerable, therefore no 'step' variable, instead what it could have, is flags to indicate whether interval endpoints included into interval or not.. i.e. (a,b) vs [a,b] vs [a,b) vs (a,b]. Not supporting enumeration (no #do: , no #add: no #at: etc). You can, however intersect, merge or diff two intervals etc.. same operations which you doing on sets (but that would require another entity - interval set). And of course, you can test whether some number lies within given interval or not. The reason i started this topic is because some code were using 'range' for variables which holding intervals.. Now what you think is more appropriate protocol for something called 'range', this: x := range first y := range last or this: x := range start y := range end -- Best regards, Igor Stasenko.

Dec. 16, 2012

Re: [Pharo-project] Interval protocol

by StÃ©phane Ducasse

On Dec 16, 2012, at 4:21 PM, Nicolas Cellier wrote: > Ah, i also forgot this feature: > > (2 to: 3) at: 1.5 -> 2.5 > > It's fun I'm not sure that this is the adjective that came to my mind.

Dec. 16, 2012

Re: [Pharo-project] Interval protocol

by StÃ©phane Ducasse

On Dec 16, 2012, at 4:11 PM, Sven Van Caekenberghe wrote: > I am probably stupid but this sounds crazy. > > Most people will have a pretty good idea of what an interval is from mathematics. > Stating that it is a finite, countable progression from a start to a stop with a step is more precise and makes sense. > > Now, [a,b] with b<a will seem wrong from this perspective. > > It could well be that Interval is (ab)used somewhere with b<a but is that a reason to allow this ? > > IMO, the specific cursor usage should have its own data structureâ¦ Yes :) I'm as stupid as you :)

Dec. 16, 2012

[Pharo-project] about isAbstractClass

by StÃ©phane Ducasse

Hi guys I will deprecate isAbstractClass and introduce defineAbstractMethods. why? because as soon as we have an abstract method in Object nearly all the classes becomes abstract and this does not make sense. Now I can understand that we want to know if a class defineAbstractMethods and sometimes taking into account inheritance. http://code.google.com/p/pharo/issues/detail?id=7123 Stef

Dec. 16, 2012

Re: [Pharo-project] Interval protocol

by Nicolas Cellier

Ah, i also forgot this feature: (2 to: 3) at: 1.5 -> 2.5 It's fun 2012/12/16 StÃ©phane Ducasse <stephane.ducasse(a)inria.fr>: > >>> For hash, I wonder if it would not be easier to just drop #(2 3) = (2 >>> to: 3) and let it answer false. > > + 1 > to me there are not equal! > > Stef > >>> We have hasSameElementsThan: or isSameSequenceThan: for that purpose. >>> >> or we haven't (? can't remember), but should have. >> >>> Nicolas >>> >>>> >>>> >> > >

Dec. 16, 2012

Re: [Pharo-project] Interval protocol

by StÃ©phane Ducasse

>> For hash, I wonder if it would not be easier to just drop #(2 3) = (2 >> to: 3) and let it answer false. + 1 to me there are not equal! Stef >> We have hasSameElementsThan: or isSameSequenceThan: for that purpose. >> > or we haven't (? can't remember), but should have. > >> Nicolas >> >>> >>> >

Dec. 16, 2012

Re: [Pharo-project] Interval protocol

by StÃ©phane Ducasse

O > > Currently: > > (3 to: 2) first -> 3. > (3 to: 2) last -> 2. > > But: > (2 to: 4 by: 3) last -> 2 > > Try to guess the logic behind thisâ¦ ;D > >> >> I see. But does it make sense to have (thinking aloud)? >> (3 to: 2) start -> 3 >> (3 to: 2) end -> 2 >> probably? > > Yes, I did that refactoring in Squeak 3.9, but I was sure it would be > rejected, too many methods were changed (TextMorph ParagraphEditor & > co). See http://bugs.squeak.org/view.php?id=6454 > > You also know that breaking the classes we use for browsing/debugging > is a dangerous sport ;) oh yes like CharacterScanner and Event :) > The simplest thing would be to add a few message to TextLineInterval > (first, last, ...) and move it somewhere else in hierarchy, because I > don't think it shares that much with Interval. > - I guess we don't use much of Collection protocol in TextLineInterval > - it spoils first/last uniformity > - it can't handle Interval step > - ... > >> >> So we should improve that. >> If what I said is correct and you confirm it I will open a bug entry >> Stef >> >> > > I found http://bugs.squeak.org/view.php?id=7002 indicating that most > weirdness of Interval were corrected, but I'm quite sure it still has > other reported or non reported bugs, except hash. > > I can still do an infinite loop with to:do: and Float, > 2 - Float epsilon to: 2 by: Float epsilon/4 do: [:i | Transcript cr; > show: i printString] > > but Interval>>do: is correct: (well I warned you, some rounding occurs...) > (2 - Float epsilon to: 2 by: Float epsilon/4) do: [:i | Transcript cr; > show: i printString] > > For hash, I wonder if it would not be easier to just drop #(2 3) = (2 > to: 3) and let it answer false. > We have hasSameElementsThan: or isSameSequenceThan: for that purpose. If you have changes that you want to propose for Pharo please go. I think that I will spend most of my charisma holidays fixing bugs :) Stef

Dec. 16, 2012

Re: [Pharo-project] Interval protocol

by Sven Van Caekenberghe

I am probably stupid but this sounds crazy. Most people will have a pretty good idea of what an interval is from mathematics. Stating that it is a finite, countable progression from a start to a stop with a step is more precise and makes sense. Now, [a,b] with b<a will seem wrong from this perspective. It could well be that Interval is (ab)used somewhere with b<a but is that a reason to allow this ? IMO, the specific cursor usage should have its own data structureâ¦ On 16 Dec 2012, at 11:04, Nicolas Cellier <nicolas.cellier.aka.nice(a)gmail.com> wrote: > What Frank means is that Smalltalk Interval are countable (and most are finite). > > However, the original usage of Interval was for Text editing, and an > Interval from 5 to: 4 means that the cursor is before (after?) > position 5. That's why Interval is a strange beast, not exactly > polymorphic to an Array of Number. Those two views have introduced a > number of unconsistencies in the library... > > Last thing, I don't recommend using Interval of Float, (1.5 to: 1.6 > by: 0.01), rather use Integer or Fraction. You never know where the > Float Interval really ends, it's progression is generally not > constant, and to:do: used to behaved differently than do: > > Nicolas > > 2012/12/16 Igor Stasenko <siguctua(a)gmail.com>: >> On 16 December 2012 09:26, Frank Shearar <frank.shearar(a)gmail.com> wrote: >>> On 16 December 2012 01:06, Igor Stasenko <siguctua(a)gmail.com> wrote: >>>> On 15 December 2012 23:45, Chris Muller <asqueaker(a)gmail.com> wrote: >>>>>> and i always hitting the wall with my head again and again.. because >>>>>> there's no such protocol >>>>>> and instead (after opening browser and looking at class, i figuring >>>>>> that i should use #first/#last, but it is completely unintuitive to >>>>>> me).. >>>>> >>>>> Me too, when I was using what I knew would only ever need to be, >>>>> simply, an Interval. >>>>> >>>>> Later the complexity increased and it would be either a Interval or >>>>> Array of numbers. It was a transparent / painless improvement. After >>>>> gaining that appreciation, now I think of Intervals as just "efficient >>>>> Arrays" and think naturally to use #first / #last. >>>>> >>>> >>>> Well, my math background prevents me from thinking this way. >>>> Since in math, intervals are defined on sets of numbers. >>>> (like Real set).. you cannot treat it as array , simply because there >>>> is an infinite number >>>> of values inside any non-empty interval, and you cannot enumerate them. >>> >>> But it's a subset of the integers, not the reals! >>> >> what? >> then how you explain this: >> >> (1.5 to: 1.6 by: 0.01) collect: [:i | i ] >> >>> frank >>> >>>> -- >>>> Best regards, >>>> Igor Stasenko. >>>> >>> >> >> >> >> -- >> Best regards, >> Igor Stasenko. >> >

Dec. 16, 2012