Re: [Haskell-cafe] equational reasoning

* Tillmann Rendel [2009-02-19 22:43:24+0100] > Roman Cheplyaka schrieb: >> Evaluation order matters for operational semantics, not for axiomatic. >> And even in operational semantics Church–Rosser theorem should prevent >> getting different results (e.g. 0 and error) for different evaluation >> or

Re: [Haskell-cafe] Hoogle and Network.Socket

On 2009 Feb 19, at 13:19, Svein Ove Aas wrote: If you say so, but.. Unix domain sockets? sendFd? I can't speak to sendFd, but BITD OS/2 had AF_LOCAL (the portable version of AF_UNIX; same API) sockets. There's no particular reason aside from unwillingness that Windows wouldn't support it

[Haskell-cafe] Re: Looking for pointfree version (Kim-Ee Yeoh) (02/12)

>Kim-Ee Yeoh said: >On the same note, does anyone have ideas >for the following snippet? Tried the pointfree >package but the output was useless. >pointwise op (x0,y0) (x1,y1) = (x0 `op` x1, y0 `op` y1) First sorry for the delay in getting to this.. been behind on projects so had some days of

Re: [Haskell-cafe] Re: Overloading functions based on arguments?

On Feb 19, 2009, at 9:09 AM, John A. De Goes wrote: Let's try a little test: 1. If the parameter is a tree, what do you think "flatten" would do? I would imagine that it would be "join" on trees -- i.e. take a tree of trees and turn it into a tree. But perhaps it would be arbitrarily

Re: [Haskell-cafe] A typeclass for Data.Map etc?

Eugene Kirpichov wrote: Looks like such a thing would be useful; as for now, I see at least two applications: Data.Map and Data.Trie (bytestring-trie) - it's a pity that they have rather similar interfaces, but the latter lacks many methods and some are named in a different way. Are there any

Re: [Haskell-cafe] Haskell.org GSoC

On Feb 18, 2009, at 4:43 AM, Max Bolingbroke wrote: 2009/2/18 Sterling Clover : The punchline: With GHC plugins, it should be possible, and reasonable, to add a proper unit system for Haskell. Alas, GHC plugins cannot change the type system - only meddle with the compilation strategy or ana

Re: [Haskell-cafe] A typeclass for Data.Map etc?

On Thu, Feb 19, 2009 at 10:18 AM, Jamie Brandon wrote: >> Maybe this is of interest: >> http://hackage.haskell.org/cgi-bin/hackage-scripts/package/gmap > > The edison api is much more stable. The gmap api was already in place > when I started working on it but I would prefer to at some point make

Re: [Haskell-cafe] Re: garbage collector woes

On Feb 19, 2009, at 3:41 PM, Don Stewart wrote: Is the solution written up somewhere so we can point to that next time? :) Well, the applicability to the community at large is probably minimal, but my misadventure follows... The MySQL C API has "statements" that are associated with a dat

Re: [Haskell-cafe] Re: garbage collector woes

waterson: > On Feb 17, 2009, at 12:22 PM, Chris Waterson wrote: > >> I'm at wits end with respect to GHC's garbage collector and would very >> much appreciate a code review of my MySQL driver for HDBC, which is >> here: >> >> >>

Re: [Haskell-cafe] package for algebraic structures

On Thu, 19 Feb 2009, Wolfgang Jeltsch wrote: Am Donnerstag, 19. Februar 2009 00:17 schrieben Sie: Do you mean this one: ? There is currently no code for this, is there? ??? http://hackage.haskell.org/cgi-bin/hackage-scripts/package/numeric-

Re: [Haskell-cafe] package for algebraic structures

Wolfgang Jeltsch schrieb: > Am Donnerstag, 19. Februar 2009 00:17 schrieben Sie: >> Do you mean this one: ? > > There is currently no code for this, is there? http://hackage.haskell.org/cgi-bin/hackage-scripts/package/numeric-prelude http://darcs.h

Re: [Haskell-cafe] Re: Overloading functions based on arguments?

On 20 Feb 2009, at 3:24 am, John A. De Goes wrote: It is precisely this abuse of notation which makes, for instance, statistics textbooks impossible to read (without already knowing the material). Hmmm, I don't find statistics books difficult to read. I'm interested in a technique called

Re: [Haskell-cafe] ANNOUNCE: pqueue-mtl, stateful-mtl

Ryan, I didn't get your question after the first read, so here's an actual answer to it -- What I want to preserve about ST is the existence of a guaranteed safe runST, really. I tend to do algorithms and data structures development, which almost never requires use of IO, or references of any kin

Re: [Haskell-cafe] A typeclass for Data.Map etc?

On Thu, Feb 19, 2009 at 01:51:44PM +0300, Eugene Kirpichov wrote: > Is there a typeclass for mappings with a Data.Map-like interface, with > stuff like: empty, insert, insertWithKey, unionWith etc. ? > And, probably, a similar typeclass for mutable mappings like Data.Hashtable. Here is one I wrote

Re: [Haskell-cafe] Paper draft: "Denotational design with type class morphisms"

May be I am reading it wrong Shouldn't the second "instance" in "The instance's meaning is the meaning's instance" be plural as "meaning's instances" rather than "meaning's instance"? I am reading it similar to the "you are who you know" saying. It seems to say that the meaning of your d

Re: [Haskell-cafe] equational reasoning

Roman Cheplyaka schrieb: Evaluation order matters for operational semantics, not for axiomatic. And even in operational semantics Church–Rosser theorem should prevent getting different results (e.g. 0 and error) for different evaluation orders. Let's consider omega = omega const omega 42

Re: [Haskell-cafe] equational reasoning

On Thu, 2009-02-19 at 23:06 +0200, Roman Cheplyaka wrote: > * Wouter Swierstra [2009-02-19 11:58:38+0100] > > There are several problems with this approach. > > > > For example, I can show: > > > > const 0 (head []) = 0 > > > > But if I pretend that I don't know that Haskell is lazy: > > > > const

[Haskell-cafe] equational reasoning

* Wouter Swierstra [2009-02-19 11:58:38+0100] > There are several problems with this approach. > > For example, I can show: > > const 0 (head []) = 0 > > But if I pretend that I don't know that Haskell is lazy: > > const 0 (head []) = const 0 (error ) = error ... Where does the last equality

Re: [Haskell-cafe] Haskell.org GSoC

Alberto G. Corona wrote: Wouldn't it be better to achieve the goals you describe with a dependently typed programming language? But I wonder how a dependent typed language can express certain properties, for example, the distributive property between the operation + and * in a ring or simply t

Re: [Haskell-cafe] ANNOUNCE: pqueue-mtl, stateful-mtl

Oh, sweet beans. I hadn't planned to incorporate mutable references -- my code uses them highly infrequently -- but I suppose that since mutable references are really equivalent to single-threadedness where referential transparency is concerned, that could be pulled off -- I would still want a Sta

Re: [Haskell-cafe] ANNOUNCE: pqueue-mtl, stateful-mtl

So, why not use this definition? Is there something special about ST you are trying to preserve? -- minimal complete definition: -- Ref, newRef, and either modifyRef or both readRef and writeRef. class Monad m => MonadRef m where type Ref m :: * -> * newRef :: a -> m (Ref m a) readRef

Re: [Haskell-cafe] Paper draft: "Denotational design with type class morphisms"

Hi, Thanks for this very interesting and inspiring paper. I'm certainly going to try some other data types, and see what kind of implementations you get when using the TCM property. I was wondering if any of this could be automated, given the semantic function? If not in Haskell, then cou

Re: [Haskell-cafe] forall & ST monad

Jonathan Cast-2 wrote: > > Taking the `let open' syntax from `First-class > Modules for Haskell' [1], we can say > > let open runST' = runST in > let > ref = runST' $ newSTRef 0 > !() = runST' $ writeSTRef ref 1 > !() = runST' $ writeSTRef ref 2 > in runST' $ readSTRef ref >

Re: [Haskell-cafe] Hoogle and Network.Socket

2009/2/19 Bryan O'Sullivan : > On Wed, Feb 18, 2009 at 6:50 PM, Thomas DuBuisson > wrote: >> >> I recall that Niel made sure hoogle doesn't search through >> non-portable libraries (a shame), but I thought Network.Socket could >> be used on Windows and yet Hoogle does not give any results for >> '

Re: [Haskell-cafe] A typeclass for Data.Map etc?

> Maybe this is of interest: > http://hackage.haskell.org/cgi-bin/hackage-scripts/package/gmap The edison api is much more stable. The gmap api was already in place when I started working on it but I would prefer to at some point make it a superset of the edison api. No sense in having more than o

Re: [Haskell-cafe] Hoogle and Network.Socket

On Wed, Feb 18, 2009 at 6:50 PM, Thomas DuBuisson < thomas.dubuis...@gmail.com> wrote: > I recall that Niel made sure hoogle doesn't search through > non-portable libraries (a shame), but I thought Network.Socket could > be used on Windows and yet Hoogle does not give any results for > 'socket' or

Re: [Haskell-cafe] Hoogle and Network.Socket

Niel, Outside of flags to enable display of modules specific to each major platform (+windows, +posix, +osx) I see two options. This all depends on hoogle having some sort of list of modules for each platform, which I believe would be the main problem. 1) Show all the functions (when the number

Re: [Haskell-cafe] Hoogle and Network.Socket

Hi http://haskell.org/hoogle/?q=socket+%2Bnetwork By default it searches the libraries supplied with Windows apart from Network (for various technical reasons). If you add +network it will then search the network library. What libraries should Hoogle search by default? What flags should be avail

Re: [Haskell-cafe] How to create an online poll

2009/2/19 Luke Palmer > 2009/2/19 Rick R > >> I think the capabilities community including E and Coyotos/BitC have >> extensively addressed this topic. Coyotos is taking the correct approach for >> trusted voting platform. Since, even if your software is trustworthy, it >> can't be trusted if th

Re: [Haskell-cafe] How to create an online poll

2009/2/19 Luke Palmer : > 2009/2/19 Rick R >> >> I think the capabilities community including E and Coyotos/BitC have >> extensively addressed this topic. Coyotos is taking the correct approach for >> trusted voting platform. Since, even if your software is trustworthy, it >> can't be trusted if t

Re: [Haskell-cafe] How to create an online poll

2009/2/19 Rick R > I think the capabilities community including E and Coyotos/BitC have > extensively addressed this topic. Coyotos is taking the correct approach for > trusted voting platform. Since, even if your software is trustworthy, it > can't be trusted if the OS on which it runs is suspec

[Haskell-cafe] ANNOUNCE: Cabal-1.6.0.2 and cabal-install-0.6.2

I'm pleased to announce point-releases of the Cabal library and the cabal-install command line tool. If you are already using cabal-install then you can upgrade both using: $ cabal update $ cabal install Cabal cabal-install New users you can get it from: http://haskell.org/cabal/downloa

Re: [Haskell-cafe] How to create an online poll

I think the capabilities community including E and Coyotos/BitC have extensively addressed this topic. Coyotos is taking the correct approach for trusted voting platform. Since, even if your software is trustworthy, it can't be trusted if the OS on which it runs is suspect. However, we might have a

Re: [Haskell-cafe] A typeclass for Data.Map etc?

2009/2/19 Eugene Kirpichov : > > Is there a typeclass for mappings with a Data.Map-like interface, with > stuff like: empty, insert, insertWithKey, unionWith etc. ? Maybe this is of interest: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/gmap Peter ___

Re: [Haskell-cafe] Uses of `fix' combinator

Thankyou everyone. This was most helpful. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

Re: [Haskell-cafe] Re: Overloading functions based on arguments?

I agree that type classes should not be used for this purpose. That's part of the reason I support "linguistic overloading" -- to stop the type class abuse. Type classes should be used, as you say, when there are algorithms that work for arbitrary members -- i.e. the type class encodes

Re: [Haskell-cafe] Haskell.org GSoC

Unfortunately the "proofs" in dependently typed languages are extremely long and tedious to write. Some kind of compiler proofing tool could ease the pain, but I do not think it has low enough complexity for a GSoC project. I wouldn't say that. Here's the complete proof script in Coq provi

Re: [Haskell-cafe] Re: Overloading functions based on arguments?

On Thu, Feb 19, 2009 at 7:09 AM, John A. De Goes wrote: > > On Feb 14, 2009, at 2:29 PM, Luke Palmer wrote: > >> To me, typeclasses are at their best when you have a real abstraction to >> encode. >> > > I agree. > > If you are having trouble using a typeclass and need C++-style ad-hoc >> overlo

Re: [Haskell-cafe] Uses of `fix' combinator

Each data type in Haskell contains one element, which is usually "invisible". It's called "bottom" and denoted by (_|_). Naturally (_|_) of type Int and (_|_) of type Char are different; however, they are denoted as if they are the same, 'cause there isn't much difference between them. Anyw

Re: [Haskell-cafe] Uses of `fix' combinator

By the way, the fact that "least" is in the sense of "least defined" explains why fix (2^) gives an undefined: The least defined fixpoint of any strict function (f : f _|_ = _|_) is, by definition, undefined. And (2^) is strict. 2009/2/19 Derek Elkins : > On Thu, 2009-02-19 at 17:00 +0300, Khudyak

Re: [Haskell-cafe] ANNOUNCE: pqueue-mtl, stateful-mtl

It does. In the most recent version, the full class declaration runs class MonadST m where type StateThread m liftST :: ST (StateThread m) a -> m a and the StateThread propagates accordingly. Louis Wasserman wasserman.lo...@gmail.com On Thu, Feb 19, 2009 at 2:10 AM, Sittampalam, Ganesh < gane

Re: [Haskell-cafe] Re: Overloading functions based on arguments?

On Feb 14, 2009, at 11:28 PM, wren ng thornton wrote: John A. De Goes wrote: On Feb 13, 2009, at 2:11 PM, Jonathan Cast wrote: The compiler should fail when you tell it two mutually contradictory things, and only when you tell it two mutually contradictory things. By definition, it's not a cont

Re: [Haskell-cafe] Uses of `fix' combinator

Hello Khudyakov, Thursday, February 19, 2009, 5:00:03 PM, you wrote: > I have two questions. How could this function be used? I'm unable to imagine > any. Naive approach lead to nothing (no surprise): fix (1:) -- Best regards, Bulatmailto:bulat.zigans...@gmail.com

[Haskell-cafe] Re[2]: Ready for testing: Unicode support for Handle I/O

Hello Khudyakov, Thursday, February 19, 2009, 4:06:06 PM, you wrote: >> i think that FilePath=String is ok, we just need to use utf8 string >> encoding on unix/macs and utf-16 encoding with *W functions on >> Windows. i have implemented such support inside my own application, and >> would be happ

Re: [Haskell-cafe] forall & ST monad

On Thu, 2009-02-19 at 05:53 -0800, Kim-Ee Yeoh wrote: > There's a lot to chew on (thank you!), but I'll just take something > I can handle for now. > > > Dan Doel wrote: > > > > An existential: > > > > exists a:T. P(a) > > > > is a pair of some a with type T and a proof that a satisfies P

Re: [Haskell-cafe] Haskell.org GSoC

Am Donnerstag, 19. Februar 2009 14:50 schrieb John A. De Goes: > Unfortunately the "proofs" in dependently typed languages are > extremely long and tedious to write. Some kind of compiler proofing > tool could ease the pain, but I do not think it has low enough > complexity for a GSoC project. I w

Re: [Haskell-cafe] Re: [darcs-users] darcs and Google Summer of Code

Am Donnerstag, 19. Februar 2009 12:37 schrieb Malcolm Wallace: > > > Unless Google's changed things, the organization gets 500$ for each > > > project. What the Darcs organization does with that, who knows. > > > > Yes, who knows. The Haskell organization didn't give a cent > > to the mentors, as f

Re: [Haskell-cafe] Re: Overloading functions based on arguments?

On Feb 14, 2009, at 2:29 PM, Luke Palmer wrote: To me, typeclasses are at their best when you have a real abstraction to encode. I agree. If you are having trouble using a typeclass and need C++-style ad- hoc overloading, it's likely you are trying to encode a "fake" abstraction -- one th

Re: [Haskell-cafe] Uses of `fix' combinator

On Thu, 2009-02-19 at 17:00 +0300, Khudyakov Alexey wrote: > Hello, > > While browsing documentation I've found following function > > > -- | @'fix' f@ is the least fixed point of the function @f@, > > -- i.e. the least defined @x@ such that @f x = x...@. > > fix :: (a -> a) -> a > > fix f = let

[Haskell-cafe] Uses of `fix' combinator

Hello, While browsing documentation I've found following function > -- | @'fix' f@ is the least fixed point of the function @f@, > -- i.e. the least defined @x@ such that @f x = x...@. > fix :: (a -> a) -> a > fix f = let x = f x in x I have two questions. How could this function be used? I'm u

Re: [Haskell-cafe] A typeclass for Data.Map etc?

On Thu, Feb 19, 2009 at 2:46 PM, Mark Wotton wrote: > On Thu, Feb 19, 2009 at 9:51 PM, Eugene Kirpichov > wrote: >> Greetings, >> >> Is there a typeclass for mappings with a Data.Map-like interface, with >> stuff like: empty, insert, insertWithKey, unionWith etc. ? >> And, probably, a similar ty

Re: [Haskell-cafe] forall & ST monad

There's a lot to chew on (thank you!), but I'll just take something I can handle for now. Dan Doel wrote: > > An existential: > > exists a:T. P(a) > > is a pair of some a with type T and a proof that a satisfies P (which has > type > P(a)). In Haskell, T is some kind, and P(a) is some t

Re: [Haskell-cafe] Haskell.org GSoC

Yes, this is indeed the point. Right now we express properties that a type class should obey, but there is no compiler assistance to prove or verify them. A compiler aware of "properties" can do additional symbolic manipulation to increase performance. Surely there has been some researc

Re: [Haskell-cafe] Haskell.org GSoC

Unfortunately the "proofs" in dependently typed languages are extremely long and tedious to write. Some kind of compiler proofing tool could ease the pain, but I do not think it has low enough complexity for a GSoC project. Regards, John A. De Goes N-BRAIN, Inc. The Evolution of Collabor

Re: [Haskell-cafe] A typeclass for Data.Map etc?

On Thu, Feb 19, 2009 at 9:51 PM, Eugene Kirpichov wrote: > Greetings, > > Is there a typeclass for mappings with a Data.Map-like interface, with > stuff like: empty, insert, insertWithKey, unionWith etc. ? > And, probably, a similar typeclass for mutable mappings like Data.Hashtable. > > Looks lik

Re: [Haskell-cafe] Haskell.org GSoC

Am Donnerstag, 19. Februar 2009 11:35 schrieb Alberto G. Corona: > 2009/2/19 Wolfgang Jeltsch > > > Am Donnerstag, 19. Februar 2009 02:22 schrieb sylvain: > > > Haskell is a nice, mature and efficient programming language. > > > By its very nature it could also become a nice executable formal > >

Re: [Haskell-cafe] forall & ST monad

On Thursday 19 February 2009 7:22:48 am Kim-Ee Yeoh wrote: > Jonathan Cast-2 wrote: > > Summary: Existential types are not enough for ST. You need the rank 2 > > type, to guarantee that *each* application of runST may (potentially) > > work with a different class of references. (A different state

[Haskell-cafe] Re[2]: Ready for testing: Unicode support for Handle I/O

Hello Simon, Thursday, February 19, 2009, 3:21:03 PM, you wrote: > Correct - I'm aware that there's a problem with filenames, but it hasn't > been tackled yet. There probably isn't anything sensible that we can do > without changing FilePath into an ADT. i think that FilePath=String is ok, we j

Re: [Haskell-cafe] forall & ST monad

Jonathan Cast-2 wrote: > > Summary: Existential types are not enough for ST. You need the rank 2 > type, to guarantee that *each* application of runST may (potentially) > work with a different class of references. (A different state thread). > Interesting. What's going on in the example tha

[Haskell-cafe] Re: Ready for testing: Unicode support for Handle I/O

Bulat Ziganshin wrote: Hello Khudyakov, Saturday, February 7, 2009, 4:01:57 PM, you wrote: How do you plan to handle filenames? Currently FilePath is simply a string. i think that this patch does nothing to unicode filenames support Correct - I'm aware that there's a problem with filenames

Re: [Haskell-cafe] Re: [darcs-users] darcs and Google Summer of Code

> > Unless Google's changed things, the organization gets 500$ for each > > project. What the Darcs organization does with that, who knows. > > Yes, who knows. The Haskell organization didn't give a cent > to the mentors, as far as I know. Am I wrong here? That is correct. The haskell.org mento

Re: [Haskell-cafe] Haskell.org GSoC

This could look like: module Integer where .. theorem read_parses_what_show_shows : (a :: Integer, Show a, Read a) => show . read a = id a proof axiom There are several problems with this approach. For example, I can show: const 0 (head []) = 0 But if I pretend that I don't k

[Haskell-cafe] Re: How to create an online poll

Ketil Malde wrote: > Rick R writes: > >> I'm sure Premier Election Solutions (formerly Diebold) can provide us with >> an online voting solution. > > You know, while the recent voting scandals have been milked for all > they're worth by the open source community, FP has been very quiet > about it

[Haskell-cafe] A typeclass for Data.Map etc?

Greetings, Is there a typeclass for mappings with a Data.Map-like interface, with stuff like: empty, insert, insertWithKey, unionWith etc. ? And, probably, a similar typeclass for mutable mappings like Data.Hashtable. Looks like such a thing would be useful; as for now, I see at least two applica

Re: [Haskell-cafe] Haskell.org GSoC

2009/2/19 Wolfgang Jeltsch > Am Donnerstag, 19. Februar 2009 02:22 schrieb sylvain: > > Haskell is a nice, mature and efficient programming language. > > By its very nature it could also become a nice executable formal > > specification language, provided there is tool support. > > Wouldn't it be

[Haskell-cafe] Hoogle and Network.Socket

The Network.Socket module works fine on Windows. The original Winsock implementation was based on the Berkeley sockets api. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

Re: [Haskell-cafe] How to create an online poll

> "Ketil" == Ketil Malde writes: Ketil> gregg reynolds writes: >> I.e. war, plague.famine. etc. Ketil> No, those are quite outdated by now. The new horsemen of Ketil> the programming apocalypse are, of course, IO, Ketil> MutableState, LazyMemoryLeak, and Bottom. And wh

Re: [Haskell-cafe] Re: [darcs-users] darcs and Google Summer of Code

Am Donnerstag, 19. Februar 2009 05:10 schrieben Sie: > Wolfgang Jeltsch wrote: > > I’ve put myself as a potential mentor on the old Haskell SoC ticket > > (). However, > > one or two years ago I was told that mentoring is a very time-consumi

Re: [Haskell-cafe] package for algebraic structures

Am Donnerstag, 19. Februar 2009 00:17 schrieben Sie: > On Tue, 17 Feb 2009, Wolfgang Jeltsch wrote: > > Now, a package only for one class with one method seems like overkill. > > However, it could serve as a start for a package of all kinds of > > algebraic structures. So I called the package “alge

Re: [Haskell-cafe] Haskell.org GSoC

Am Donnerstag, 19. Februar 2009 02:22 schrieb sylvain: > Haskell is a nice, mature and efficient programming language. > By its very nature it could also become a nice executable formal > specification language, provided there is tool support. Wouldn’t it be better to achieve the goals you describ

Re: [Haskell-cafe] Hoogle and Network.Socket

On Thu, Feb 19, 2009 at 3:50 AM, Thomas DuBuisson wrote: > I recall that Niel made sure hoogle doesn't search through > non-portable libraries (a shame), but I thought Network.Socket could > be used on Windows and yet Hoogle does not give any results for > 'socket' or any other functions within Ne

RE: [Haskell-cafe] ANNOUNCE: pqueue-mtl, stateful-mtl

Henning Thielemann wrote: > On Mon, 16 Feb 2009, Louis Wasserman wrote: > >> Overnight I had the following thought, which I think could work >> rather well.  The most basic implementation of the idea is as >> follows: >> >> class MonadST s m | m -> s where >> liftST :: ST s a -> m a >> >> insta