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]). 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). 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. 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
