Hi Bruno,
2013/2/12 Bruno P. Kinoshita <ki...@apache.org> > Hi Benedikt, > > Thanks for taking a look at the github repo and for posting your thoughts > here. > > If I understand it correctly, your concern is: > > - In the github repo, a BinaryFunction is a Binary, and a Binary is an > Arity. > > - But at same time, it is intuitive that a BinaryFunction "has" an arity, > which is binary. > Is that right? If so, I think it's a question of changing the > nomenclature. The issue started because in functional languages like > Haskell, a functor has a broader meaning (e.g.: a list is a functor in > Haskell [1]). > Yes, I guess it boils down to this :) As Matt has pointed out, there does not seem to be a name for the superset of things that have an arity and "SomethingThatHasArity" really is a bad name :) > > Maybe we could revert this changes, or find a better name? I thought about > something like Operation or Operator, but in project lambda, the interface > BinaryOperator extends BiFunction [2]. So maybe it would be confusing too, > if the user was used to Java 8 (assuming both interfaces are released with > Java 8). Yes, this may confuse users. Better prevent collisions with core java terminology. > What do you think? Back to Functors (and maybe document the difference > from haskell and [functor]?), or do you have some other name in mind? > Academics papers might be a good place to find a better name. > Sorry, as I'm no expert on functional programming I don't know the terminology in that domain. The question is, what is the superset of Predicates, Functions and Procedures (those are the concepts in [functor] that have an arity, right?). This superset seems to be "functor". I haven't understood yet, why you think it is a bad name. Again: If it practical to just call it Arity, then you should go ahead (pragmatism wins over oo purism ;-) Benedikt > > Thanks!! > > [1] http://en.wikibooks.org/wiki/Haskell/Applicative_Functors > [2] > http://download.java.net/lambda/b76/docs/api/java/util/function/BinaryOperator.html > > Bruno P. Kinoshita > http://kinoshita.eti.br > http://tupilabs.com > > > ----- Original Message ----- > > From: Benedikt Ritter <brit...@apache.org> > > To: Commons Developers List <dev@commons.apache.org> > > Cc: > > Sent: Tuesday, February 12, 2013 2:45 PM > > Subject: Re: [functor] Change default arity of Function, Predicate and > Procedure > > > > Hi Matt, > > > > 2013/2/12 Matt Benson <gudnabr...@gmail.com> > > > >> Hi Benedikt, > >> So what you are pointing out is the "is a" vs. "has > > a" dichotomy? To an > >> extent, I see your point. I could argue that the semantics of the word > >> "implements" perhaps leaves a bit of so-called wiggle room on the > > is a/has > >> a subject. > > > > > > Now we are mixing things up. I was referring to the inheritance > > relationships between the interfaces. > > > > The java "implements" keyword is a different concept. Indeed, I'm > > not sure > > if it (or the notion of Interfaces) is part of the OO paradigm at all. > > There is an interesting paper about this topic (what are the core > conecpts > > of object orientation?) [1]... > > > > Anyway the reason I'm bringing this rather academic topic up is, that I > > believe that a clear object-orient design will lead to a better (= easier > > to understand) API. People will work with the API. They will browse the > > type hierarchy to understand how things are tied together. > > This will lead to situations like: "okay, I have a BinaryFunction... what > > is a BinaryFuncation? Ah, it's a Binary... what is a Binary? A Binary > seems > > to be an Arity... wait.. what?" > > > > Maybe I can make myself clearer by giving a less abstract example. > > Consider the following set of thinks: Cars, Trucks, Motorcycles. > > They all have wheels of some sort. How would you model this using > > Interfaces? > > I'm sure you wouldn't define an interface "Wheel" that is > > extended by Car, > > Truck and Motorcycle. > > Instead you would probably define "Vehicle" with a > > "getNumberOfWheels()" > > method and let Car, Truck and Motorcycle extend Vehicle. > > This is what I meant when I said "Arity is not a superset of > > functors". it > > is a property, like the number of Wheels is a property of all vehicles. > > > > Again, this is all very academic. If you see it fit to create Arity and > > have the different functors extend it, then do it :-) > > > > > >> This could devolve into a long discussion of the most > >> semantically correct place to use "implements Arity*" vs. > > "extends Arity*" > >> throughout the API, but the final result, IMO, is that the intent of > any > >> given concrete class is clear enough, and Arity|Nullary|Unary|Binary|ad > >> infinitum seems more convenient than e.g. > > "SomethingThatHasArity", etc. > >> > > > > I agree! > > > > > >> > >> Does that make sense? > >> > > > > As I said, I think pragmatism should win over OO purism :) > > > > > >> > >> Matt > >> > > > > Benedikt > > > > [1] http://dl.acm.org/citation.cfm?id=1113040 > > > >> > >> > >> On Tue, Feb 12, 2013 at 7:29 AM, Benedikt Ritter <brit...@apache.org> > >> wrote: > >> > >> > Hi Guys, > >> > > >> > I've had a look at the github repo and let me say at first that > > I'm no > >> > expert in functional programming. So maybe what I'm talking is > > complete > >> > nonsense :) > >> > > >> > From what I learned about the concept of arity at wikipedia it seems > > that > >> > an arity is a property of a functor. > >> > One could say: "A binary functor has an arity of two" > > (right?!) > >> > > >> > In the github repo you introduced an inheritance relationship between > >> > functors and arity. > >> > This maybe a good thing to do from a pracmatic POV because all > > functors > >> > share the fact that say have an arity. > >> > > >> > From an object oriented POV inheritance is more then pure reuse. When > >> > defining an inheritance relationship between concept Super and > concept > >> Sub > >> > we basically say "Every instance of Sub is also an instance of > > Super" or > >> > short "Every Sub is also a Super" > >> > > >> > Now coming back to functors you have introduced a relationship that > > says > >> > "Every BinaryFunction is a Binary and every Binary is an > > Arity". > >> > Keeping in mind that arity is only a property of a functor (rather > > than a > >> > superset) this seems strange (from an OO POV). > >> > But as I'm no expert on functional programming this maybe the > > right thing > >> > to do... :) > >> > > >> > just my 2 cents :) > >> > Benedikt > >> > > >> > > >> > > >> > 2013/2/11 Bruno P. Kinoshita <ki...@apache.org> > >> > > >> > > Hi Matt! > >> > > > >> > > Great! I'll commit these changes tomorrow if there are no > > objections. > >> > > > >> > > Thanks! > >> > > > >> > > Bruno P. Kinoshita > >> > > http://kinoshita.eti.br > >> > > http://tupilabs.com > >> > > > >> > > > >> > > ----- Original Message ----- > >> > > > From: Matt Benson <gudnabr...@gmail.com> > >> > > > To: Commons Developers List <dev@commons.apache.org> > >> > > > Cc: > >> > > > Sent: Monday, February 11, 2013 8:39 PM > >> > > > Subject: Re: [functor] Change default arity of Function, > > Predicate > >> and > >> > > Procedure > >> > > > > >> > > > Hi Bruno, > >> > > > No objections here about the Arity interfaces. I see that > > your > >> > master > >> > > > branch also contains changes to migrate Unary* to * and * to > >> Nullary*. > >> > > > Personally I am satisfied to align with lambda/guava if > > noone else > >> > > objects. > >> > > > > >> > > > Thanks, > >> > > > Matt > >> > > > > >> > > > > >> > > > On Mon, Feb 11, 2013 at 4:25 PM, Bruno P. Kinoshita < > >> > > > brunodepau...@yahoo.com.br> wrote: > >> > > > > >> > > >> Hi Matt, all, > >> > > >> > >> > > >> I'm messing with [functor] in my GitHub mirror [1]. > > You can find > >> the > >> > > >> commits in the master branch [2]. > >> > > >> > >> > > >> The Arity->Unary/Binary/Nullary interfaces look > > good. If there are > >> no > >> > > >> objections I would like to commit this change to the > > trunk in SVN. > >> > > >> > >> > > >> There are other changes that I'll omit in this > > commit, but will > >> start > >> > > > new > >> > > >> threads here in the mailing list :o) > >> > > >> > >> > > >> Thank you in advance! > >> > > >> > >> > > >> [1] https://github.com/kinow/functor > >> > > >> [2] https://github.com/kinow/functor/commits/master > >> > > >> > >> > > >> Bruno P. Kinoshita > >> > > >> http://kinoshita.eti.br > >> > > >> http://tupilabs.com > >> > > >> > >> > > >> > >> > > >> >________________________________ > >> > > >> > From: Bruno P. Kinoshita <ki...@apache.org> > >> > > >> >To: Commons Developers List > > <dev@commons.apache.org>; " > >> > > >> gudnabr...@gmail.com" <gudnabr...@gmail.com> > >> > > >> >Sent: Wednesday, January 30, 2013 3:58 PM > >> > > >> >Subject: Re: [functor] Change default arity of > > Function, Predicate > >> > and > >> > > >> Procedure > >> > > >> > > >> > > >> >I think it makes sense and is clear what is does. > >> > > >> > > >> > > >> >I thought in using {arity}Operation, but in Java 8 > > there are > >> > > interfaces > >> > > >> like BinaryOperator, and BinaryOperator extends > > BiFunction, so it > >> > > would be > >> > > >> confusing to users having something like interface > > BinaryFunction > >> > > extends > >> > > >> BinaryOperation in [functor]. > >> > > >> > > >> > > >> >Bruno P. Kinoshita > >> > > >> >http://kinoshita.eti.br > >> > > >> >http://tupilabs.com > >> > > >> > > >> > > >> > > >> > > >> >----- Original Message ----- > >> > > >> >> From: Matt Benson <gudnabr...@gmail.com> > >> > > >> >> To: Bruno P. Kinoshita > > <brunodepau...@yahoo.com.br> > >> > > >> >> Cc: Commons Developers List > > <dev@commons.apache.org> > >> > > >> >> Sent: Wednesday, January 30, 2013 1:29 PM > >> > > >> >> Subject: Re: [functor] Change default arity of > > Function, > >> Predicate > >> > > > and > >> > > >> Procedure > >> > > >> >> > >> > > >> >> What about: > >> > > >> >> > >> > > >> >> Arity (Marker) > >> > > >> >> |_Nullary extends Arity > >> > > >> >> |_Unary<A> extends Arity > >> > > >> >> |_Binary<L, R> extends Arity > >> > > >> >> > >> > > >> >> ? > >> > > >> >> > >> > > >> >> Matt > >> > > >> >> > >> > > >> >> > >> > > >> >> On Tue, Jan 29, 2013 at 6:09 PM, Bruno P. > > Kinoshita < > >> > > >> >> brunodepau...@yahoo.com.br> wrote: > >> > > >> >> > >> > > >> >>> In Haskell you define your functions and > > its arity. > >> > > >> >>> > >> > > >> >>> // nullary function > >> > > >> >>> a :: () => () -> String > >> > > >> >>> a = "Hello World" > >> > > >> >>> > >> > > >> >>> // unary function > >> > > >> >>> b :: (Integral c) => c -: String > >> > > >> >>> b x = "Hello Integral" > >> > > >> >>> > >> > > >> >>> I think in Clojure and Scala you can > > define the arity of the > >> > > > function > >> > > >> too. > >> > > >> >>> > >> > > >> >>> For the users of [functor] I think it > > would be easier to > >> > > > migrate their > >> > > >> >>> code to Java 8, or use it with Java 8, if > > both [functor] and > >> > > > Java 8 > >> > > >> >>> Function classes had similar behaviour. > > That would be > >> > > > interesting > >> > > >> >>> especially if the lambda project provided > > a backport jar. > >> > > >> >>> > >> > > >> >>> [functor] and lambda project provide 1 > > and 2 arities by > >> > > > default, but > >> > > >> >>> lambda doesn't provide nullary > > interfaces (or at least I > >> > > > couldn't > >> > > >> >> find them > >> > > >> >>> in java.util.functions). > >> > > >> >>> > >> > > >> >>> Cheers > >> > > >> >>> > >> > > >> >>> Bruno P. Kinoshita > >> > > >> >>> http://kinoshita.eti.br > >> > > >> >>> http://tupilabs.com > >> > > >> >>> > >> > > >> >>> > >> > > >> >>> ----- Original Message ----- > >> > > >> >>> > From: Matt Benson > > <gudnabr...@gmail.com> > >> > > >> >>> > To: Commons Developers List > >> > > > <dev@commons.apache.org>; Bruno P. > >> > > >> >>> Kinoshita > > <brunodepau...@yahoo.com.br> > >> > > >> >>> > Cc: > >> > > >> >>> > Sent: Tuesday, January 29, 2013 8:57 > > PM > >> > > >> >>> > Subject: Re: [functor] Change > > default arity of Function, > >> > > > Predicate > >> > > >> and > >> > > >> >>> Procedure > >> > > >> >>> > > >> > > >> >>> > What about in pure functional > > languages e.g. Haskell? > >> > > >> >>> > > >> > > >> >>> > Matt > >> > > >> >>> > > >> > > >> >>> > > >> > > >> >>> > On Tue, Jan 29, 2013 at 4:55 PM, > > Bruno P. Kinoshita < > >> > > >> >>> > brunodepau...@yahoo.com.br> > > wrote: > >> > > >> >>> > > >> > > >> >>> >> Hi all, > >> > > >> >>> >> > >> > > >> >>> >> In Java 8 and Guava the default > > arity of a Function > >> > > > is 1, but in > >> > > >> >>> [functor] > >> > > >> >>> >> it is 0, IOW, in Java 8 and > > Guava a Function is by > >> > > > default a > >> > > >> >>> UnaryFunction, > >> > > >> >>> >> while in [functor] it is a > > NullaryFunction. > >> > > >> >>> >> > >> > > >> >>> >> What do you guys think of > > changing the default > >> > > > arity of Function, > >> > > >> >>> >> Procedure and Predicate in > > [functor] to 1, rather > >> > > > than 0? > >> > > >> >>> >> > >> > > >> >>> >> Cheers > >> > > >> >>> >> > >> > > >> >>> >> Bruno P. Kinoshita > >> > > >> >>> >> http://kinoshita.eti.br > >> > > >> >>> >> http://tupilabs.com > >> > > >> >>> >> > >> > > >> >>> >> > >> > > >> >> > >> > > > > > --------------------------------------------------------------------- > >> > > >> >>> >> To unsubscribe, e-mail: > >> > > > dev-unsubscr...@commons.apache.org > >> > > >> >>> >> For additional commands, > > e-mail: > >> > > > dev-h...@commons.apache.org > >> > > >> >>> >> > >> > > >> >>> >> > >> > > >> >>> > > >> > > >> >>> > >> > > >> >> > >> > > >> > > >> > > >> > >> > > >> --------------------------------------------------------------------- > >> > > >> >To unsubscribe, e-mail: > > dev-unsubscr...@commons.apache.org > >> > > >> >For additional commands, e-mail: > > dev-h...@commons.apache.org > >> > > >> > > >> > > >> > > >> > > >> > > >> > > >> > > >> > > >> > >> > > > > >> > > > >> > > > > --------------------------------------------------------------------- > >> > > To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org > >> > > For additional commands, e-mail: dev-h...@commons.apache.org > >> > > > >> > > > >> > > >> > > >> > -- > >> > http://people.apache.org/~britter/ > >> > http://www.systemoutprintln.de/ > >> > http://twitter.com/BenediktRitter > >> > http://github.com/britter > >> > > >> > > > > > > > > -- > > http://people.apache.org/~britter/ > > http://www.systemoutprintln.de/ > > http://twitter.com/BenediktRitter > > http://github.com/britter > > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org > For additional commands, e-mail: dev-h...@commons.apache.org > > -- http://people.apache.org/~britter/ http://www.systemoutprintln.de/ http://twitter.com/BenediktRitter http://github.com/britter
