pure function, defined in applicative, is equivalent to return (In Haskell, in Fluokitten there is only pure).
I think I understand what is your question now. Since Clojure does not support polymorphysm based on the returning argument you cannot translate that Haskell code exactly. For such a case (when you want to keep operating in the same monad without knowing which one it is), a you have to provide an argument for m in f (but that's how Clojure works :), and then apply it partially or curry it: (defn f [m g] (comp (pure m) g g)) (def c+ (curry +)) (bind [1 2 3] (f [] (c+ 2)) or (>>= [1 2 3] (f [] (c+ 2)) If [] really hurts your aesthetic views maybe a macro (bind* or mdo) would help, since instead of [], any vector, let's say [1 2 3] would do, but then, it's a special case when you actually want the monad to stay the same. Thank you for helpful comments, BTW :) On Wednesday, July 3, 2013 12:03:45 AM UTC+2, Ben wrote: > > e.g., I'm not sure how to define the function "f" here: > > $ ghci > GHCi, version 7.4.1: http://www.haskell.org/ghc/ :? for help > Loading package ghc-prim ... linking ... done. > Loading package integer-gmp ... linking ... done. > Loading package base ... linking ... done. > Prelude> let f :: (Monad m) => (a -> a) -> a -> m a ; f g = return . g . > g > Prelude> Just 4 >>= f (2+) > Just 8 > Prelude> [[1]] >>= f (2:) > [[2,2,1]] > Prelude> import Control.Monad.State > Prelude Control.Monad.State> runState (get >>= f (+4)) 4 > Loading package transformers-0.2.2.0 ... linking ... done. > Loading package mtl-2.0.1.0 ... linking ... done. > (12,4) > Prelude Control.Monad.State> > > > > On Tue, Jul 2, 2013 at 2:45 PM, Ben Wolfson <wol...@gmail.com<javascript:> > > wrote: > >> I did look at the docs and I don't really get how to return a monadic >> value in the right monad, the way "return" does automatically. All the >> examples I saw have something like "vector" or "atom" or what-have-you. >> >> >> On Tue, Jul 2, 2013 at 2:41 PM, Dragan Djuric <drag...@gmail.com<javascript:> >> > wrote: >> >>> No, the second argument to bind only needs to be a function that takes a >>> plain value and return a monadic value; you do not need to specify anything >>> explicitly and it does not need to know what kind of monad it is operating >>> on. Whatever that function returns will be a monad that the eventual second >>> bind will operate on. >>> Moreover, Fluokitten supports vararg bind, so the function is actually >>> the last argument of bind in general case; it is the second argument only >>> if there are two args. >>> >>> Please note that Fluokitten does not have a built-in mdo (a syntactic >>> sugar for nested binds) for now. The reason is that Clojure itself has >>> native constructs that do many stuff that Haskell's do does, so I am not >>> yet sure why and if it would be useful, and if I add it how to make it >>> non-awkward. Of course, I am open to suggestions. >>> Also note that Fluokitten is not monad-centric, it has functors, >>> applicatives, etc and I plan to add more categorical concepts, so It is >>> different in that regard from other monadic Clojure libraries. That's why I >>> would like to suggest reading the docs, most of the stuff is significantly >>> different from other libs, and more similar (but simpler, due to the lack >>> of legacy) to Haskell's categorical stuff. >>> >>> >>> On Tuesday, July 2, 2013 9:15:10 PM UTC+2, Ben wrote: >>> >>>> I haven't played around with this but it looks as if the second >>>> argument to bind needs to know what kind of monad it's operating in, is >>>> that right? Would it be possible to write agnostic functions like this in >>>> this lib? >>>> >>>> monads.core> (defn tst-reader [f] >>>> (mdo env <- ask >>>> v <- (lift (f env)) >>>> (return (println "here I am")) >>>> (return v))) >>>> #'monads.core/tst-reader >>>> monads.core> (require '[monads.reader :as r] '[monads.identity :as i] >>>> '[monads.state :as st] '[monads.error :as e]) >>>> nil >>>> monads.core> (r/run-reader-t (r/t i/m) (tst-reader (comp return inc)) 5) >>>> here I am >>>> 6 >>>> monads.core> (r/run-reader-t (r/t e/m) (tst-reader (fn [_] (throw-error >>>> "early exit"))) 5) >>>> #<Either [:left early exit]> >>>> monads.core> (st/run-state (r/run-reader-t (r/t st/m) (tst-reader (fn >>>> [env] (>> (modify #(assoc % :env env)) (return (dec env))))) 5) {}) >>>> here I am >>>> #<Pair [4 {:env 5}]> >>>> monads.core> >>>> >>>> ? >>>> >>>> >>>> On Tue, Jul 2, 2013 at 11:07 AM, Dragan Djuric <drag...@gmail.com>wrote: >>>> >>>>> I am pleased to announce a first public release of new (and different) >>>>> "monads and friends" library for Clojure. >>>>> Extensive *documentation* is at >>>>> http://fluokitten.**uncomplicate.org<http://fluokitten.uncomplicate.org> >>>>> >>>>> Fluokitten is a Clojure library that implements category theory >>>>> concepts, such as functors, applicative functors, monads, monoids etc. in >>>>> idiomatic Clojure. >>>>> >>>>> Main project goals are: >>>>> >>>>> - Fit well into idiomatic Clojure - Clojure programmers should be >>>>> able to use and understand Fluokitten like any regular Clojure library. >>>>> - Fit well into Haskell monadic types conventions - programmers >>>>> should be able to reuse existing widespread monadic programming >>>>> know-how >>>>> and easily translate it to Clojure code. >>>>> - Be reasonably easy to learn - the code from the existing books, >>>>> articles and tutorials for learning monadic programming, which is >>>>> usually >>>>> written in Haskell should be easily translatable to Clojure with >>>>> Fluokitten. >>>>> - Offer good performance. >>>>> >>>>> Please give us your feedback, and we would also love if anyone is >>>>> willing to help, regardless of previous experience, so please *get >>>>> involved*. There are lots of things to be improved: >>>>> >>>>> - If you are a native English speaker, i would really appreciate >>>>> if you can help with correcting the English on the Fluokitten site and >>>>> in >>>>> the documentation. >>>>> - Contribute your example code (your own or the ports from Haskell >>>>> tutorials) to be added to Fluokitten tests. >>>>> - Contribute articles and tutorials. >>>>> - Do code review of the Fluokitten code and suggest improvements. >>>>> - If you find bugs, report them via Fluokitten issue tracker. >>>>> - If you have any additional suggestion, contact us here: >>>>> >>>>> http://fluokitten.**uncomplicate.org/articles/**community.html<http://fluokitten.uncomplicate.org/articles/community.html> >>>>> >>>>> >>>>> -- >>>>> -- >>>>> You received this message because you are subscribed to the Google >>>>> Groups "Clojure" group. >>>>> To post to this group, send email to clo...@googlegroups.com >>>>> >>>>> Note that posts from new members are moderated - please be patient >>>>> with your first post. >>>>> To unsubscribe from this group, send email to >>>>> clojure+u...@**googlegroups.com >>>>> >>>>> For more options, visit this group at >>>>> http://groups.google.com/**group/clojure?hl=en<http://groups.google.com/group/clojure?hl=en> >>>>> --- >>>>> You received this message because you are subscribed to the Google >>>>> Groups "Clojure" group. >>>>> To unsubscribe from this group and stop receiving emails from it, send >>>>> an email to clojure+u...@**googlegroups.com. >>>>> >>>>> For more options, visit >>>>> https://groups.google.com/**groups/opt_out<https://groups.google.com/groups/opt_out> >>>>> . >>>>> >>>>> >>>>> >>>> >>>> >>>> >>>> -- >>>> Ben Wolfson >>>> "Human kind has used its intelligence to vary the flavour of drinks, >>>> which may be sweet, aromatic, fermented or spirit-based. ... Family and >>>> social life also offer numerous other occasions to consume drinks for >>>> pleasure." [Larousse, "Drink" entry] >>>> >>>> -- >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Clojure" group. >>> To post to this group, send email to clo...@googlegroups.com<javascript:> >>> Note that posts from new members are moderated - please be patient with >>> your first post. >>> To unsubscribe from this group, send email to >>> clojure+u...@googlegroups.com <javascript:> >>> For more options, visit this group at >>> http://groups.google.com/group/clojure?hl=en >>> --- >>> You received this message because you are subscribed to the Google >>> Groups "Clojure" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to clojure+u...@googlegroups.com <javascript:>. >>> For more options, visit https://groups.google.com/groups/opt_out. >>> >>> >>> >> >> >> >> -- >> Ben Wolfson >> "Human kind has used its intelligence to vary the flavour of drinks, >> which may be sweet, aromatic, fermented or spirit-based. ... Family and >> social life also offer numerous other occasions to consume drinks for >> pleasure." [Larousse, "Drink" entry] >> >> > > > -- > Ben Wolfson > "Human kind has used its intelligence to vary the flavour of drinks, which > may be sweet, aromatic, fermented or spirit-based. ... Family and social > life also offer numerous other occasions to consume drinks for pleasure." > [Larousse, "Drink" entry] > > -- -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
