[Haskell-cafe] Either Monad and Laziness
I am currently trying to rewrite the Graphics.Pgm library from hackage to parse the PGM to a lazy array. Laziness and IO really do not mix. The problem is that even using a lazy array structure, because the parser returns an Either structure it is only possible to know if the parser was successful or not after the whole file is read, That is one of the problems. Unexpected memory blowups could be another problem. The drawbacks of lazy IO are well documented by now. The behaviour I want to achieve is like this: I want the program when compiled to read from a file, parsing the PGM and at the same time apply transformations to the entries as they are read and write them back to another PGM file. Such problems are the main motivation for iteratees, conduits, pipes, etc. Every such library contains procedures for doing exactly what you want. Please check Hackage. John Lato's iteratee library, for example, has procedure for handling sound (AIFF) files -- which may be very big. IterateeM has the TIFF decoder -- which is incremental and strict. TIFF is much harder to parse than PGM. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] IO vs MonadIO
Hi. Just a brief question. System.IO functions are defined in IO monad and have signatures like Foo - IO Bar. Would it be better to have all of them defined as (MonadIO m) = Foo - m Bar? What are the problems that would arise? Sergey ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] IO vs MonadIO
On 12 September 2012 18:24, Sergey Mironov ier...@gmail.com wrote: Hi. Just a brief question. System.IO functions are defined in IO monad and have signatures like Foo - IO Bar. Would it be better to have all of them defined as (MonadIO m) = Foo - m Bar? What are the problems that would arise? That would require MonadIO being defined in base, and might make some existing code fail due to lack of type signatures (though I suppose you could specify a default). -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com http://IvanMiljenovic.wordpress.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] IO vs MonadIO
On 12 September 2012 19:55, Ivan Lazar Miljenovic ivan.miljeno...@gmail.com wrote: On 12 September 2012 18:24, Sergey Mironov ier...@gmail.com wrote: Hi. Just a brief question. System.IO functions are defined in IO monad and have signatures like Foo - IO Bar. Would it be better to have all of them defined as (MonadIO m) = Foo - m Bar? What are the problems that would arise? That would require MonadIO being defined in base, and might make some existing code fail due to lack of type signatures (though I suppose you could specify a default). Oh, and you'd still need to define them all somewhere to work _for_ IO so you can then have the liftIO variants anyway. -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com http://IvanMiljenovic.wordpress.com -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com http://IvanMiljenovic.wordpress.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] type variable in class instance
If I understand, the SomeEvent event acts as a proxy to hide the diversity
of the events? That's interesting.
This way I don't have to use an heterogeneous list and a lot of casting...
On Wed, Sep 12, 2012 at 7:44 AM, o...@okmij.org wrote:
Let me see if I understand. You have events of different sorts: events
about players, events about timeouts, events about various
messages. Associated with each sort of event is a (potentially open)
set of data types: messages can carry payload of various types. A
handler specifies behavior of a system upon the reception of an
event. A game entity (player, monster, etc) is a collection of
behaviors. The typing problem is building the heterogeneous collection
of behaviors and routing an event to the appropriate handler. Is this
right?
There seem to be two main implementations, with explicit types and latent
(dynamic) types. The explicit-type representation is essentially HList
(a Type-indexed Record, TIR, to be precise). Let's start with the
latent-type representation. Now I understand your problem better, I
think your original approach was the right one. GADT was a
distraction, sorry. Hopefully you find the code below better reflects
your intentions.
{-# LANGUAGE ExistentialQuantification, DeriveDataTypeable #-}
{-# LANGUAGE StandaloneDeriving #-}
import Data.Typeable
-- Events sorts
data Player = Player PlayerN PlayerStatus
deriving (Eq, Show, Typeable)
type PlayerN = Int
data PlayerStatus = Enetering | Leaving
deriving (Eq, Show)
newtype Message m = Message m
deriving (Eq, Show)
deriving instance Typeable1 Message
newtype Time = Time Int
deriving (Eq, Show, Typeable)
data SomeEvent = forall e. Typeable e = SomeEvent e
deriving (Typeable)
-- They are all events
class Typeable e = Event e where -- the Event
predicate
what_event :: SomeEvent - Maybe e
what_event (SomeEvent e) = cast e
instance Event Player
instance Event Time
instance Typeable m = Event (Message m)
instance Event SomeEvent where
what_event = Just
-- A handler is a reaction on an event
-- Given an event, a handler may decline to handle it
type Handler e = e - Maybe (IO ())
inj_handler :: Event e = Handler e - Handler SomeEvent
inj_handler h se | Just e - what_event se = h e
inj_handler _ _ = Nothing
type Handlers = [Handler SomeEvent]
trigger :: Event e = e - Handlers - IO ()
trigger e [] = fail Not handled
trigger e (h:rest)
| Just rh - h (SomeEvent e) = rh
| otherwise = trigger e rest
-- Sample behaviors
-- viewing behavior (although viewing is better with Show since all
-- particular events implement it anyway)
view_player :: Handler Player
view_player (Player x s) = Just . putStrLn . unwords $
[Player, show x, show s]
-- View a particular message
view_msg_str :: Handler (Message String)
view_msg_str (Message s) = Just . putStrLn . unwords $
[Message, s]
-- View any message
view_msg_any :: Handler SomeEvent
view_msg_any (SomeEvent e)
| (tc1,[tr]) - splitTyConApp (typeOf e),
(tc2,_)- splitTyConApp (typeOf (undefined::Message ())),
tc1 == tc2 =
Just . putStrLn . unwords $ [Some message of the type, show tr]
view_msg_any _ = Nothing
viewers = [inj_handler view_player, inj_handler view_msg_str, view_msg_any]
test1 = trigger (Player 1 Leaving) viewers
-- Player 1 Leaving
test2 = trigger (Message str1) viewers
-- Message str1
test3 = trigger (Message (2::Int)) viewers
-- Some message of the type Int
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[Haskell-cafe] [ANN] Cumino 0.2 - Now supports pretty indentation through stylish-haskell
Hi everyone, in case you have missed it, I've released a Vim plugin called Cumino: http://adinapoli.github.com/cumino/ It does one simple thing: It allows communication between Vim and tmux, in particular to a ghci session. With Cumino you can fire-up Vim, load a ghci session and interact with it with only few keystrokes. The plugin also supports visual selection: you can select for example a function (even with all its signature!) and you can send it to ghci. The visual selection supports imports, custom types and typeclasses. It's a simple idea but so damn useful, imho. This release also adds the possibility to prettify the code using the excellent stylish-haskell: select a snippet, simply indent in the usual way ( = ) and voilà, now your code is indented! Feedback are highly appreciated, as well as contributions. There are still some issues with some terminals (for example urxvt does not work right now) but the plugin has been tested against gnome-terminal, xterm and mlterm. I'll post in reddit too for completeness! Bye! Alfredo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [ANN] Cumino 0.2 - Now supports pretty indentation through stylish-haskell
Are urxvt-related issues documented somewhere? On 09/12/2012 05:03 PM, Alfredo Di Napoli wrote: There are still some issues with some terminals (for example urxvt does not work right now) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] guards in applicative style
Hi Haskellers, Suppose I have two list and I want to calculate the cartesian product between the two of them, constrained to a predicate. In List comprehension notation is just result = [ (x, y) | x - list1, y -list2, somePredicate x y ] or in monadic notation result = do x - list1 y - list2 guard (somePredicate x y) return $ (x,y) Then I was wondering if we can do something similar using an applicative style result = (,) $ list1 * list2 (somePredicate ???) The question is then, there is a way for defining a guard in applicative Style? Thanks in advance, Felipe Zapata. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Either Monad and Laziness
Thanks for all the tips! The iteratees seem worth checking out. I'll see what I can do and will report back if I come up with something. Eric On 12 September 2012 03:03, o...@okmij.org wrote: I am currently trying to rewrite the Graphics.Pgm library from hackage to parse the PGM to a lazy array. Laziness and IO really do not mix. The problem is that even using a lazy array structure, because the parser returns an Either structure it is only possible to know if the parser was successful or not after the whole file is read, That is one of the problems. Unexpected memory blowups could be another problem. The drawbacks of lazy IO are well documented by now. The behaviour I want to achieve is like this: I want the program when compiled to read from a file, parsing the PGM and at the same time apply transformations to the entries as they are read and write them back to another PGM file. Such problems are the main motivation for iteratees, conduits, pipes, etc. Every such library contains procedures for doing exactly what you want. Please check Hackage. John Lato's iteratee library, for example, has procedure for handling sound (AIFF) files -- which may be very big. IterateeM has the TIFF decoder -- which is incremental and strict. TIFF is much harder to parse than PGM. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] guards in applicative style
I'm no expert at all, but I would say no. guard type is: guard :: MonadPlus m = Bool - m () and MonadPlus is a monad plus (ehm...) mzero and mplus (http://en.wikibooks.org/wiki/Haskell/MonadPlus). On the other hand Applicative is less than a monad (http://www.haskell.org/haskellwiki/Applicative_functor), therefore guard as is cannot be defined. But, in your specific example, with lists, you can always use filter: filter (uncurry somePredicate) ((,) $ list1 * list2 (somePredicate ???)) hth, L. On Wed, Sep 12, 2012 at 3:40 PM, felipe zapata tifonza...@gmail.com wrote: Hi Haskellers, Suppose I have two list and I want to calculate the cartesian product between the two of them, constrained to a predicate. In List comprehension notation is just result = [ (x, y) | x - list1, y -list2, somePredicate x y ] or in monadic notation result = do x - list1 y - list2 guard (somePredicate x y) return $ (x,y) Then I was wondering if we can do something similar using an applicative style result = (,) $ list1 * list2 (somePredicate ???) The question is then, there is a way for defining a guard in applicative Style? Thanks in advance, Felipe Zapata. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Either Monad and Laziness
On 12 September 2012 11:46, Eric Velten de Melo ericvm...@gmail.com wrote: Thanks for all the tips! The iteratees seem worth checking out. I'll see what I can do and will report back if I come up with something. Eric On 12 September 2012 03:03, o...@okmij.org wrote: I am currently trying to rewrite the Graphics.Pgm library from hackage to parse the PGM to a lazy array. Laziness and IO really do not mix. The problem is that even using a lazy array structure, because the parser returns an Either structure it is only possible to know if the parser was successful or not after the whole file is read, That is one of the problems. Unexpected memory blowups could be another problem. The drawbacks of lazy IO are well documented by now. The behaviour I want to achieve is like this: I want the program when compiled to read from a file, parsing the PGM and at the same time apply transformations to the entries as they are read and write them back to another PGM file. Such problems are the main motivation for iteratees, conduits, pipes, etc. Every such library contains procedures for doing exactly what you want. Please check Hackage. John Lato's iteratee library, for example, has procedure for handling sound (AIFF) files -- which may be very big. IterateeM has the TIFF decoder -- which is incremental and strict. TIFF is much harder to parse than PGM. It would be really awesome, though, if it were possible to use a parser written in Parsec with this, in the spirit of avoiding code rewriting and enhancing expressivity and abstraction. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [ANN] Cumino 0.2 - Now supports pretty indentation through stylish-haskell
So, suppose that I'm in a terminal vim session, and I want to start ghci (in the current terminal). What do I do? localleadercc starts a new terminal, which is not what I want. On Wed, Sep 12, 2012 at 3:03 PM, Alfredo Di Napoli alfredo.dinap...@gmail.com wrote: Hi everyone, in case you have missed it, I've released a Vim plugin called Cumino: http://adinapoli.github.com/cumino/ It does one simple thing: It allows communication between Vim and tmux, in particular to a ghci session. With Cumino you can fire-up Vim, load a ghci session and interact with it with only few keystrokes. The plugin also supports visual selection: you can select for example a function (even with all its signature!) and you can send it to ghci. The visual selection supports imports, custom types and typeclasses. It's a simple idea but so damn useful, imho. This release also adds the possibility to prettify the code using the excellent stylish-haskell: select a snippet, simply indent in the usual way ( = ) and voilà, now your code is indented! Feedback are highly appreciated, as well as contributions. There are still some issues with some terminals (for example urxvt does not work right now) but the plugin has been tested against gnome-terminal, xterm and mlterm. I'll post in reddit too for completeness! Bye! Alfredo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [ANN] Cumino 0.2 - Now supports pretty indentation through stylish-haskell
Hi, I'm not in front of the pc now, but afair the problem was related to opening a new urxvt window FROM a running urxvt. More details soon :) Sent from my iPad On 12/set/2012, at 15:18, Matvey Aksenov matvey.akse...@gmail.com wrote: Are urxvt-related issues documented somewhere? On 09/12/2012 05:03 PM, Alfredo Di Napoli wrote: There are still some issues with some terminals (for example urxvt does not work right now) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [ANN] Cumino 0.2 - Now supports pretty indentation through stylish-haskell
Could you please tell me what your desired behaviour would be? In praticular, do you want a ghci session in another tab or in a tmux pane perhaps? Otherwise I can't see any viable way to let vim and ghci cooperate inside the SAME window. Bye, Alfredo Sent from my iPad On 12/set/2012, at 17:05, Roman Cheplyaka r...@ro-che.info wrote: So, suppose that I'm in a terminal vim session, and I want to start ghci (in the current terminal). What do I do? localleadercc starts a new terminal, which is not what I want. On Wed, Sep 12, 2012 at 3:03 PM, Alfredo Di Napoli alfredo.dinap...@gmail.com wrote: Hi everyone, in case you have missed it, I've released a Vim plugin called Cumino: http://adinapoli.github.com/cumino/ It does one simple thing: It allows communication between Vim and tmux, in particular to a ghci session. With Cumino you can fire-up Vim, load a ghci session and interact with it with only few keystrokes. The plugin also supports visual selection: you can select for example a function (even with all its signature!) and you can send it to ghci. The visual selection supports imports, custom types and typeclasses. It's a simple idea but so damn useful, imho. This release also adds the possibility to prettify the code using the excellent stylish-haskell: select a snippet, simply indent in the usual way ( = ) and voilà, now your code is indented! Feedback are highly appreciated, as well as contributions. There are still some issues with some terminals (for example urxvt does not work right now) but the plugin has been tested against gnome-terminal, xterm and mlterm. I'll post in reddit too for completeness! Bye! Alfredo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Either Monad and Laziness
At Wed, 12 Sep 2012 12:04:31 -0300, Eric Velten de Melo wrote: It would be really awesome, though, if it were possible to use a parser written in Parsec with this, in the spirit of avoiding code rewriting and enhancing expressivity and abstraction. There is http://hackage.haskell.org/package/attoparsec-conduit and http://hackage.haskell.org/package/attoparsec-enumerator, which turn attoparsec parsers into enumerators/conduits, and http://hackage.haskell.org/package/attoparsec-parsec, which is a compatibility layer between attoaparsec and parsec. Good luck :). -- Francesco * Often in error, never in doubt ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [ANN] Cumino 0.2 - Now supports pretty indentation through stylish-haskell
On Wed, Sep 12, 2012 at 11:25 AM, Alfredo Di Napoli alfredo.dinap...@gmail.com wrote: I'm not in front of the pc now, but afair the problem was related to opening a new urxvt window FROM a running urxvt. More details soon :) urxvt defaults to using a client-server model for all terminals, IIRC (we have a warning about it in the xmonad documentation as well since it messes up ManageHooks). There's possibly some option to disable this and force an independent terminal. -- brandon s allbery allber...@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [ANN] Cumino 0.2 - Now supports pretty indentation through stylish-haskell
If such a possibility exists, I would be happy to fix the urxvt support :) Bear in mind, though, that the Cumino terminal is only needed for the Ghci session, so you can use your favourite terminal to run Vim :) A. urxvt defaults to using a client-server model for all terminals, IIRC (we have a warning about it in the xmonad documentation as well since it messes up ManageHooks). There's possibly some option to disable this and force an independent terminal. -- brandon s allbery allber...@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Invitation to connect on LinkedIn
Hi, Correct me if I am wrong, but by looking at the way the message is created, I think, LinkedIn is acting a kind of spammer these days. Shall we lodge protest against it as a community? As an aside, can we not automatically delete all messages to haskell mailing-lists whose from field contains LinkedIn (and the likes of it) in it? -Damodar On Wed, Sep 12, 2012 at 9:12 PM, Sakari Joinen via LinkedIn mem...@linkedin.com wrote: [image: LinkedIn Logo] http://www.linkedin.com/ Steve, Sakari Joinen wants to connect with you on LinkedIn. Sakari Joinen Senior QA Engineer at Rocketpack View Profile »http://www.linkedin.com/e/uc6lxc-h70llpqy-2x/rso/203924390/GIO8/name/2590796_I425561150_15/eml-comm_invm-b-pro_txt-inv28/?hs=falsetok=0etVV1LByeHlo1 Accepthttp://www.linkedin.com/e/uc6lxc-h70llpqy-2x/XvIdBwmueHfd6vFMPXXdLaqreCbl5oOSpPTFPU/blk/I425561150_15/0UcDpKqiRzolZKqiRybmRSrCBvrmRLoORIrmkZt5YCpnlOt3RApnhMpmdzgmhxrSNBszYRclYMdj4NdzkRczh9bThqd3kOp5tMbP0TdjgMd3wNdzwLrCBxbOYWrSlI/eml-comm_invm-b-in_ac-inv28/?hs=falsetok=0SXF1g5wqeHlo1 You are receiving Invitation emails. Unsubscribehttps://www.linkedin.com/e/uc6lxc-h70llpqy-2x/XvIdBwmueHfd6vFMPXXdLaqreCbl5oOSpPTFPU/prv/?hs=falsetok=1cq1jVz5SeHlo1. This email was intended for Steve Severance (Principal at Alpha Heavy Industries). Learn why we included thishttp://www.linkedin.com/e/uc6lxc-h70llpqy-2x/plh/http%3A%2F%2Fhelp%2Elinkedin%2Ecom%2Fapp%2Fanswers%2Fdetail%2Fa_id%2F4788/-GXI/?hs=falsetok=38T1PPvOmeHlo1. © 2012, LinkedIn Corporation. 2029 Stierlin Ct. Mountain View, CA 94043, USA ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Invitation to connect on LinkedIn
I believe these are the effect of linkedin harvesting your email contacts, and then a blanket invite all link that you can click. Whether it's linkedin who's spamming, or the person who forgot to uncheck certain mailing lists, that's more of a moral debate.. kris On Wed, Sep 12, 2012 at 2:21 PM, damodar kulkarni kdamodar2...@gmail.comwrote: Hi, Correct me if I am wrong, but by looking at the way the message is created, I think, LinkedIn is acting a kind of spammer these days. Shall we lodge protest against it as a community? As an aside, can we not automatically delete all messages to haskell mailing-lists whose from field contains LinkedIn (and the likes of it) in it? -Damodar On Wed, Sep 12, 2012 at 9:12 PM, Sakari Joinen via LinkedIn mem...@linkedin.com wrote: [image: LinkedIn Logo] http://www.linkedin.com/ Steve, Sakari Joinen wants to connect with you on LinkedIn. Sakari Joinen Senior QA Engineer at Rocketpack View Profile »http://www.linkedin.com/e/uc6lxc-h70llpqy-2x/rso/203924390/GIO8/name/2590796_I425561150_15/eml-comm_invm-b-pro_txt-inv28/?hs=falsetok=0etVV1LByeHlo1 Accepthttp://www.linkedin.com/e/uc6lxc-h70llpqy-2x/XvIdBwmueHfd6vFMPXXdLaqreCbl5oOSpPTFPU/blk/I425561150_15/0UcDpKqiRzolZKqiRybmRSrCBvrmRLoORIrmkZt5YCpnlOt3RApnhMpmdzgmhxrSNBszYRclYMdj4NdzkRczh9bThqd3kOp5tMbP0TdjgMd3wNdzwLrCBxbOYWrSlI/eml-comm_invm-b-in_ac-inv28/?hs=falsetok=0SXF1g5wqeHlo1 You are receiving Invitation emails. Unsubscribehttps://www.linkedin.com/e/uc6lxc-h70llpqy-2x/XvIdBwmueHfd6vFMPXXdLaqreCbl5oOSpPTFPU/prv/?hs=falsetok=1cq1jVz5SeHlo1. This email was intended for Steve Severance (Principal at Alpha Heavy Industries). Learn why we included thishttp://www.linkedin.com/e/uc6lxc-h70llpqy-2x/plh/http%3A%2F%2Fhelp%2Elinkedin%2Ecom%2Fapp%2Fanswers%2Fdetail%2Fa_id%2F4788/-GXI/?hs=falsetok=38T1PPvOmeHlo1. © 2012, LinkedIn Corporation. 2029 Stierlin Ct. Mountain View, CA 94043, USA ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Help a young graduate haskeller to land its dream job
Hi everyone, If this mail sound strange to you, you are free to ignore it. My name is Alfredo Di Napoli and I'm a 24-year-old programmer from Rome, Italy. I've graduated in May and I'm currently working as an intern for a company involved in the defence field. In my spare time, though, I study functional programming, especially Haskell. FP is my true passion and I'm another dreamer trying to land the job he loves. In a nutshell I'm looking for every possibility to do Haskell/functional programming in Europe/North Europe. I'm throwing this stone into this pond because life has endless possibilities, who knows? :) A disclaimer, though: I'm not an expert Haskeller, but I'm very passionate about technology and I love learning (I've obviously already read LYAH and RWH). You can find more information about me (including my CV if interested) here: www.alfredodinapoli.com Oh! One last thing! I would be very grateful to everyone willing to spent two minutes of his time giving me any kind of suggestion about the FP job world or how to prepare/improve myself for the foreseeable future. Thanks again, and sorry for the OT/spammish plug. Humbly, Alfredo Di Napoli ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Invitation to connect on LinkedIn
On Wed, Sep 12, 2012 at 2:21 PM, damodar kulkarni kdamodar2...@gmail.comwrote: Correct me if I am wrong, but by looking at the way the message is created, I think, LinkedIn is acting a kind of spammer these days. Shall we lodge protest against it as a community? What happens is that anyone who joins is pushed to run their contact list through them to look for connections, then LinkedIn sends an invitation to any address not already noted as a member. So it's spammy but in an especially slimy user-initiated way. -- brandon s allbery allber...@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] [Hackage] Bug report and proposal
Hello, I found a bug: source points to the wrong page. [1] I know that bugs should be reported via Github. But I don't have an account and don't want to create one. There might be others who don't want to use Github. Why rely on external bug tracker? I assume that it has been chosen because of its features, but it doesn't have the most important one (i.e. anonymous posting). What's better: to have more features or to have less bugs? Is it possible to move away from Github? What about a separate mailing list for bugs? I'm sorry if this sounds to harsh; I'm not good at writing. I don't want to attack or blame anyone. I'm also sorry if this message is not appropriate, but I haven't found a better place. [1] http://hackage.haskell.org/packages/archive/base/latest/doc/html/Prelude.html#v:seq Cheers ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [ANN] Cumino 0.2 - Now supports pretty indentation through stylish-haskell
On Wed, Sep 12, 2012 at 1:36 PM, Alfredo Di Napoli alfredo.dinap...@gmail.com wrote: If such a possibility exists, I would be happy to fix the urxvt support :) Actually I went back through it and it should only be an issue if urxvtc is used; urxvt should always be standalone. Unless they went and made it too smart for its own good, in which case there might be some option to make it behave the old way. See http://www.haskell.org/haskellwiki/Xmonad/General_xmonad.hs_config_tips#Terminal_emulator_factoriesfor details. (I am assuming the problem is urxvt recognizes itself and uses the terminal factory to rub off a new window in the same process, which can't be given separate configuration information and can't be communicated with via xterm-style raw pty mode etc.) -- brandon s allbery allber...@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Help a young graduate haskeller to land its dream job
Hi Alfredo, You might look at the various bigdata companies. I was surprised by how many of them are using Scala or Clojure - it's definitely over 50%. Looks like FP is really gaining traction in this area. On Wed, Sep 12, 2012 at 11:48 AM, Alfredo Di Napoli alfredo.dinap...@gmail.com wrote: Hi everyone, If this mail sound strange to you, you are free to ignore it. My name is Alfredo Di Napoli and I'm a 24-year-old programmer from Rome, Italy. I've graduated in May and I'm currently working as an intern for a company involved in the defence field. In my spare time, though, I study functional programming, especially Haskell. FP is my true passion and I'm another dreamer trying to land the job he loves. In a nutshell I'm looking for every possibility to do Haskell/functional programming in Europe/North Europe. I'm throwing this stone into this pond because life has endless possibilities, who knows? :) A disclaimer, though: I'm not an expert Haskeller, but I'm very passionate about technology and I love learning (I've obviously already read LYAH and RWH). You can find more information about me (including my CV if interested) here: www.alfredodinapoli.com Oh! One last thing! I would be very grateful to everyone willing to spent two minutes of his time giving me any kind of suggestion about the FP job world or how to prepare/improve myself for the foreseeable future. Thanks again, and sorry for the OT/spammish plug. Humbly, Alfredo Di Napoli ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Eugene Kirpichov http://www.linkedin.com/in/eugenekirpichov We're hiring! http://tinyurl.com/mirantis-openstack-engineer ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] guards in applicative style
Lorenzo is correct, but actually for the wrong reason. =) The *type* of guard is a historical accident, and the fact that it requires MonadPlus doesn't really tell us anything. Let's take a look at its implementation: guard :: (MonadPlus m) = Bool - m () guard True = return () guard False = mzero 'return' is not specific to Monad; we could just as well use 'pure'. 'mzero' is a method of 'MonadPlus' but there is no reason we can't use 'empty' from the 'Alternative' class. So we could define guardA :: Alternative f = Bool - f () guardA True = pure () guardA False = empty (As another example, consider the function 'sequence :: Monad m = [m a] - m [a]'. Actually this function does not need Monad at all, it only needs Applicative.) However, guardA is not as useful as guard, and it is not possible to do the equivalent of the example shown using a list comprehension with a guard. The reason is that whereas monadic computations can make use of intermediate computed values to decide what to do next, Applicative computations cannot. So there is no way to generate values for x and y and then pass them to 'guardA' to do the filtering. guardA can only be used to conditionally abort an Applicative computation using information *external* to the Applicative computation; it cannot express a condition on the intermediate values computed by the Applicative computation itself. -Brent On Wed, Sep 12, 2012 at 03:52:03PM +0100, Lorenzo Bolla wrote: I'm no expert at all, but I would say no. guard type is: guard :: MonadPlus m = Bool - m () and MonadPlus is a monad plus (ehm...) mzero and mplus (http://en.wikibooks.org/wiki/Haskell/MonadPlus). On the other hand Applicative is less than a monad (http://www.haskell.org/haskellwiki/Applicative_functor), therefore guard as is cannot be defined. But, in your specific example, with lists, you can always use filter: filter (uncurry somePredicate) ((,) $ list1 * list2 (somePredicate ???)) hth, L. On Wed, Sep 12, 2012 at 3:40 PM, felipe zapata tifonza...@gmail.com wrote: Hi Haskellers, Suppose I have two list and I want to calculate the cartesian product between the two of them, constrained to a predicate. In List comprehension notation is just result = [ (x, y) | x - list1, y -list2, somePredicate x y ] or in monadic notation result = do x - list1 y - list2 guard (somePredicate x y) return $ (x,y) Then I was wondering if we can do something similar using an applicative style result = (,) $ list1 * list2 (somePredicate ???) The question is then, there is a way for defining a guard in applicative Style? Thanks in advance, Felipe Zapata. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Invitation to connect on LinkedIn
My heart skipped a beat when I saw myself on here. Then I saw I was the target. For the record I am morally opposed to inbox harvesting, although LinkedIn keeps recommending that I do just that. Steve On Wed, Sep 12, 2012 at 11:49 AM, Brandon Allbery allber...@gmail.comwrote: On Wed, Sep 12, 2012 at 2:21 PM, damodar kulkarni kdamodar2...@gmail.comwrote: Correct me if I am wrong, but by looking at the way the message is created, I think, LinkedIn is acting a kind of spammer these days. Shall we lodge protest against it as a community? What happens is that anyone who joins is pushed to run their contact list through them to look for connections, then LinkedIn sends an invitation to any address not already noted as a member. So it's spammy but in an especially slimy user-initiated way. -- brandon s allbery allber...@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [ANN] Cumino 0.2 - Now supports pretty indentation through stylish-haskell
Ah, okay. I was just confused by the fact that it uses tmux, and thought that I was misusing it. Yes, I also usually keep ghci in a separate window (and I am an xmonad user, too). I just thought that this offers a different experience and wanted to try it out. Anyway, thanks for clarifying. On Wed, Sep 12, 2012 at 5:24 PM, Alfredo Di Napoli alfredo.dinap...@gmail.com wrote: Hi Roman, Cumino was thought to operate in another terminal. Personally, but this is only a personal taste, having to switch between terminal tabs or tmux panes is not the fastest workflow. Being an Xmonad user, i can easily swap between terminals (read ghci and vim) simply with mod + j or mod + k. So the answer to your answer is: You can't, Cumino will always start in another terminal window. Is the same behaviour of Slime, though. Sent from my iPad On 12/set/2012, at 17:06, Roman Cheplyaka r...@ro-che.info wrote: So, suppose that I'm in a terminal vim session, and I want to start ghci (in the current terminal). What do I do? localleadercc starts a new terminal, which is not what I want. On Wed, Sep 12, 2012 at 3:03 PM, Alfredo Di Napoli alfredo.dinap...@gmail.com wrote: Hi everyone, in case you have missed it, I've released a Vim plugin called Cumino: http://adinapoli.github.com/cumino/ It does one simple thing: It allows communication between Vim and tmux, in particular to a ghci session. With Cumino you can fire-up Vim, load a ghci session and interact with it with only few keystrokes. The plugin also supports visual selection: you can select for example a function (even with all its signature!) and you can send it to ghci. The visual selection supports imports, custom types and typeclasses. It's a simple idea but so damn useful, imho. This release also adds the possibility to prettify the code using the excellent stylish-haskell: select a snippet, simply indent in the usual way ( = ) and voilà, now your code is indented! Feedback are highly appreciated, as well as contributions. There are still some issues with some terminals (for example urxvt does not work right now) but the plugin has been tested against gnome-terminal, xterm and mlterm. I'll post in reddit too for completeness! Bye! Alfredo ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [Hackage] Bug report and proposal
On 13 September 2012 04:53, Stayvoid stayv...@gmail.com wrote: Hello, I found a bug: source points to the wrong page. [1] I know that bugs should be reported via Github. But I don't have an account and don't want to create one. There might be others who don't want to use Github. Why rely on external bug tracker? I assume that it has been chosen because of its features, but it doesn't have the most important one (i.e. anonymous posting). What's better: to have more features or to have less bugs? Is it possible to move away from Github? What about a separate mailing list for bugs? Whilst in general I agree with you, people have complained previously about needing to subscribe to librar...@haskell.org for bug reports for boot libraries, or for needing to get a Trac login, etc. If, however, _no_ login is required, then the system is open to spamming :s I'm sorry if this sounds to harsh; I'm not good at writing. I don't want to attack or blame anyone. I'm also sorry if this message is not appropriate, but I haven't found a better place. [1] http://hackage.haskell.org/packages/archive/base/latest/doc/html/Prelude.html#v:seq Cheers ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com http://IvanMiljenovic.wordpress.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] guards in applicative style
Brent Yorgey byor...@seas.upenn.edu wrote:
However, guardA is not as useful as guard, and it is not possible to
do the equivalent of the example shown using a list comprehension with
a guard. The reason is that whereas monadic computations can make use
of intermediate computed values to decide what to do next, Applicative
computations cannot. So there is no way to generate values for x and
y and then pass them to 'guardA' to do the filtering. guardA can only
be used to conditionally abort an Applicative computation using
information *external* to the Applicative computation; it cannot
express a condition on the intermediate values computed by the
Applicative computation itself.
To continue this story, from most applicative functors you can construct
a category, which is interesting for non-monads. Let's examine the
SparseStream functor, which is not a monad:
data SparseStream a =
SparseStream {
headS :: Maybe a,
tailS :: SparseStream a
}
This is an applicative functor,
instance Applicative SparseStream where
pure x = let str = SparseStream (Just x) str in str
SparseStream f fs * SparseStream x xs =
SparseStream (f * x) (fs * xs)
but with a little extension it becomes a category, the wire category:
newtype Wire a b = Wire (a - (Maybe b, Wire a b))
This is like SparseStream, but for each head/tail pair it wants an
argument. Given a Category instance you can now actually make use of
guardA without resorting to monadic combinators:
guardA p . myStream
This is conceptually how Netwire's applicative FRP works and how events
are implemented.
Greets,
Ertugrul
--
Not to be or to be and (not to be or to be and (not to be or to be and
(not to be or to be and ... that is the list monad.
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Re: [Haskell-cafe] [ANN] Cumino 0.2 - Now supports pretty indentation through stylish-haskell
On Wed, Sep 12, 2012 at 01:03:49PM +, Alfredo Di Napoli wrote: Hi everyone, in case you have missed it, I've released a Vim plugin called Cumino: http://adinapoli.github.com/cumino/ It does one simple thing: It allows communication between Vim and tmux, in particular to a ghci session. With Cumino you can fire-up Vim, load a ghci session and interact with it with only few keystrokes. The plugin also supports visual selection: you can select for example a function (even with all its signature!) and you can send it to ghci. The visual selection supports imports, custom types and typeclasses. It's a simple idea but so damn useful, imho. This release also adds the possibility to prettify the code using the excellent stylish-haskell: select a snippet, simply indent in the usual way ( = ) and voilà, now your code is indented! Feedback are highly appreciated, as well as contributions. There are still some issues with some terminals (for example urxvt does not work right now) but the plugin has been tested against gnome-terminal, xterm and mlterm. I'll post in reddit too for completeness! Nice bridge between vim and tmux! Would you mind add supporting for `urxvtc'? urxvtc's -e option is followed by a list of options instead of a string. urxvtc -e sh -c 'echo a' xterm -e echo a ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
