From bertram.felgenhauer at googlemail.com  Sun Jun  1 00:29:02 2008
From: bertram.felgenhauer at googlemail.com (Bertram Felgenhauer)
Date: Sun Jun  1 00:21:54 2008
Subject: [Haskell-cafe] type-level integers using type families
In-Reply-To: <48416FA4.7040402@gmail.com>
References: <483E1FCF.9000101@gmail.com>
	<66615E96-5F85-4DAD-A280-1CEBF356B682@cse.unsw.edu.au>
	<483FEFB0.3060904@di.unipi.it> <48416FA4.7040402@gmail.com>
Message-ID: <20080601042902.GA4221@zombie.inf.tu-dresden.de>

Peter Gavin wrote:
> Roberto Zunino wrote:
>> Maybe he wants, given
>>   cond :: Cond x y z => x -> y -> z
>>   tt :: True
>>   true_exp  :: a
>>   false_exp :: <<<untypable>>>
>> that
>>   cond tt true_exp false_exp :: a
>> That is the type of false_exp is "lazily inferred", so that type errors
>> do not make inference fail if they show up in an unneeded place.
>
> Yes, that's exactly what I want, but for type families (not MPTC). I think 
> it could be done if the type arguments were matched one at a time, across 
> all visible instances.

What do you think of the following idea?

Using naive type level natural numbers,

> data Zero
> newtype Succ a = Succ a

Booleans,

> data True
> data False

comparison,

> type family (:<:) x y
> type instance (Zero   :<: Succ a) = True
> type instance (Zero   :<: Zero  ) = False
> type instance (Succ a :<: Zero  ) = False
> type instance (Succ a :<: Succ b) = a :<: b

difference,

> type family Minus x y
> type instance Minus a        Zero     = a
> type instance Minus (Succ a) (Succ b) = Minus a b

and a higher order type level conditional,

> type family Cond2 x :: (* -> * -> *) -> (* -> * -> *) -> * -> * -> *
> type First2  (x :: * -> * -> *) (y :: * -> * -> *) = x
> type Second2 (x :: * -> * -> *) (y :: * -> * -> *) = y
> type instance Cond2 True  = First2
> type instance Cond2 False = Second2

we can define division as follows:

> type family Div x y
> type DivZero x y = Zero
> type DivStep x y = Succ (Div (Minus0 x y) y)
> type instance Div x y = Cond2 (x :<: y) DivZero DivStep x y

It's not exactly what you asked for, but I believe it gets the effect
that you wanted.

Enjoy,

Bertram
From thomas.dubuisson at gmail.com  Sun Jun  1 02:11:22 2008
From: thomas.dubuisson at gmail.com (Thomas M. DuBuisson)
Date: Sun Jun  1 01:59:44 2008
Subject: [Haskell-cafe] [ANN] Bindings to Xen Control (xenctrl.h)
Message-ID: <1212300682.2448.14.camel@Clunker>

All,
I'm just getting started with hsXenCtrl [1] as both a fun way to play
with Xen and become proficient with Haskell FFI.  Once I get my
community.haskell.org account squared away I'll likely setup a public
darcs repo (and a homepage somewhere).

As for modules: I intend to expand on the trival FFI bindings in
System.Xen.CBindings and there'll be a higher level interface in
System.Xen (functions will standardize on returning Either or throwing
exceptions, hiding the xc_handle open/close, etc).

Typical Disclaimers:
The _only_ thing I've actually done with this, just tonight, is pause /
unpause domains.  API is subject to change!  Only my exact build of Xen
is sure to work, and no promise even then.

TomMD

[1] http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hsXenCtrl

From dons at galois.com  Sun Jun  1 02:31:40 2008
From: dons at galois.com (Don Stewart)
Date: Sun Jun  1 02:24:41 2008
Subject: [Haskell-cafe] [ANN] Bindings to Xen Control (xenctrl.h)
In-Reply-To: <1212300682.2448.14.camel@Clunker>
References: <1212300682.2448.14.camel@Clunker>
Message-ID: <20080601063140.GA1200@scytale.galois.com>

thomas.dubuisson:
> All,
> I'm just getting started with hsXenCtrl [1] as both a fun way to play
> with Xen and become proficient with Haskell FFI.  Once I get my
> community.haskell.org account squared away I'll likely setup a public
> darcs repo (and a homepage somewhere).
> 
> As for modules: I intend to expand on the trival FFI bindings in
> System.Xen.CBindings and there'll be a higher level interface in
> System.Xen (functions will standardize on returning Either or throwing
> exceptions, hiding the xc_handle open/close, etc).
> 
> Typical Disclaimers:
> The _only_ thing I've actually done with this, just tonight, is pause /
> unpause domains.  API is subject to change!  Only my exact build of Xen
> is sure to work, and no promise even then.
> 
> TomMD
> 
> [1] http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hsXenCtrl

Good stuff. Perhaps the synopsis should include a link or description of
the typical use cases/ thinks we might achieve?

-- Don
From apfelmus at quantentunnel.de  Sun Jun  1 03:37:39 2008
From: apfelmus at quantentunnel.de (apfelmus)
Date: Sun Jun  1 03:30:40 2008
Subject: [Haskell-cafe] Re: appending an element to a list
In-Reply-To: <48414C2B.9010606@daimi.au.dk>
References: <483EE208.2010601@inf.fu-berlin.de>	<483EF36B.5040100@daimi.au.dk>	<48404039.6030605@cisco.com>	<48405717.20206@daimi.au.dk>	<87r6bja609.fsf@hbox.dyndns.org>	<3c4d5adf0805302159o23113ad2sb24754e02789bb06@mail.gmail.com>
	<48414C2B.9010606@daimi.au.dk>
Message-ID: <g1tjk4$c4i$1@ger.gmane.org>

Tillmann Rendel wrote:
> Abhay Parvate wrote:
>> I think I would like to make another note: when we talk about the complexity
>> of a function, we are talking about the time taken to completely evaluate
>> the result. Otherwise any expression in haskell will be O(1), since it 
>> just creates a thunk.
> 
> I don't like this notion of complexity, since it seems not very suited 
> for the analysis of composite expression in Haskell.
> 
> Is this intuitive view generalizable to arbitrary datatypes (instead of 
> lists) and formalized somewhere?

See also the thread section beginning with

   http://thread.gmane.org/gmane.comp.lang.haskell.cafe/34398/focus=34435



Regards,
apfelmus

From vigalchin at gmail.com  Sun Jun  1 04:00:27 2008
From: vigalchin at gmail.com (Galchin, Vasili)
Date: Sun Jun  1 03:53:13 2008
Subject: [Haskell-cafe] modelling C in Haskell ..
In-Reply-To: <F77D2BD2-3BF5-48FA-8B51-723305860036@fastmail.fm>
References: <5ae4f2ba0805292346y217d799du8a3e097a1e004e7a@mail.gmail.com>
	<B38D65AC-A9E6-4C12-B9D3-A2285477BBEE@fastmail.fm>
	<5ae4f2ba0805300029s69b1a1fdn73e07fe17b458b10@mail.gmail.com>
	<F77D2BD2-3BF5-48FA-8B51-723305860036@fastmail.fm>
Message-ID: <5ae4f2ba0806010100j3788d29bj4aa0f5f4e3a8c5a8@mail.gmail.com>

my knowledge of point-free is from category theory. in what sense is Haskell
point-free handle namespace pollution?

Kind regards, Vasili

On Fri, May 30, 2008 at 3:23 AM, Jonathan Cast <jonathanccast@fastmail.fm>
wrote:

> On 30 May 2008, at 12:29 AM, Galchin, Vasili wrote:
>
>  compactness in writing and also namespace pollution .. ;^)
>>
>
> I know what the advantages of C's notation are.  But getting the best
> notation out of Haskell generally doesn't happen by trying to make your code
> look like C.
>
> So the general answer to questions of the form `C can do x; can Haskell' is
> `No'.  Don't do it like in C.  It won't be idiomatic, it won't be elegant,
> and neither of us will like the results.  Understand the features of Haskell
> that make your program compact, point-free (how Haskell handles namespace
> pollution), and elegant and use those.  This will require a different
> factoring of your program vs. C.  Sorry, but that's life.
>
> jcc
>
>
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From aruiz at um.es  Sun Jun  1 06:20:03 2008
From: aruiz at um.es (Alberto Ruiz)
Date: Sun Jun  1 06:12:51 2008
Subject: [Haskell-cafe] Re: hmatrix
In-Reply-To: <e26d18e40805311209h4cd37689u30fe65e2ebd6c21e@mail.gmail.com>
References: <e26d18e40805311209h4cd37689u30fe65e2ebd6c21e@mail.gmail.com>
Message-ID: <484277D3.9020604@um.es>

Anatoly Yakovenko wrote:
> What is the most efficient way to update a position in a matrix or a
> vector?  I came up with this:
> 
> updateVector :: Vector Double -> Int -> Double -> Vector Double
> updateVector vec pos val = vec `add` v2
>    where
>       v2 = fromList $ (replicate (pos) 0.0) ++ ((val - (vec @>
> pos)):(replicate ((dim vec)- pos - 1) 0.0))
> 
> but this seems pretty inefficient to me.
> 
> thanks,
> Anatoly
> 

It is probably more efficient to use subVector and join (implemented by 
copyArray):

updateVector' v pos val
     | pos == 0        = join [b,c]
     | pos == dim v -1 = join [a,b]
     | otherwise       = join [a,b,c]
     where a = subVector 0 pos v
           b = fromList [val]
           c = subVector (pos+1) (dim v -pos-1) v

 > updateVector' (fromList [1,2,3,4,5]) 2 57
5 |> [1.0,2.0,57.0,4.0,5.0]

(The three cases are required because empty vectors are not currently 
allowed.)

Something similar can be done for matrices using flatten and reshape.

Although vectors and matrices in this library are immutable and intended 
to be manipulated as a whole by higher level functions, this kind of 
update functions may often be useful. I will include them soon.

Alberto
From bertram.felgenhauer at googlemail.com  Sun Jun  1 14:44:46 2008
From: bertram.felgenhauer at googlemail.com (Bertram Felgenhauer)
Date: Sun Jun  1 14:37:38 2008
Subject: [Haskell-cafe] [ANNOUNCE] git-darcs-import 0.1
Message-ID: <20080601184446.GA27750@zombie.inf.tu-dresden.de>

Hi,

I'm pleased to announce yet another tool for importing darcs repositories
to git. Unlike darcs2git [1] and darcs-to-git [2], it's written in
Haskell, on top of the darcs2 source code. The result is a much faster
program - it can convert the complete ghc 6.9 branch (without libraries)
in less than 15 minutes on my slightly dated machine (Athlon XP 2500+),
which is quite fast [3]. Incremental updates work, too.

The program is still rough around the edges, and there's some cosmetical
work to do, especially with respect to converting author names. The
program should recover from most errors, as long as nobody else modifies
the destination repository.

Nevertheless, it seems quite useable already. I hope somebody finds
this useful.

You can grab the source at

   http://int-e.home.tlink.de/haskell/git-darcs-import-0.1.tar.bz2

Look at the README for further information.

Credits go to:
    David Roundy and all contributors for darcs2. The code base is
    surprisingly pleasant to work with.

    And of course, Linus Torvalds, Junio Hamano and all other git
    contributors.

Enjoy,

Bertram

[1] http://repo.or.cz/w/darcs2git.git?a=shortlog
[2] http://git.sanityinc.com/?p=darcs-to-git.git
[3] http://nominolo.blogspot.com/2008/05/thing-that-should-not-be-or-how-to.html
From aeyakovenko at gmail.com  Sun Jun  1 14:45:09 2008
From: aeyakovenko at gmail.com (Anatoly Yakovenko)
Date: Sun Jun  1 14:37:55 2008
Subject: [Haskell-cafe] Re: hmatrix
In-Reply-To: <484277D3.9020604@um.es>
References: <e26d18e40805311209h4cd37689u30fe65e2ebd6c21e@mail.gmail.com>
	<484277D3.9020604@um.es>
Message-ID: <e26d18e40806011145y4200e294yf8ffe08a426636b7@mail.gmail.com>

do you have any plans to provide an interface for inplace updates?

On Sun, Jun 1, 2008 at 3:20 AM, Alberto Ruiz <aruiz@um.es> wrote:
> Anatoly Yakovenko wrote:
>>
>> What is the most efficient way to update a position in a matrix or a
>> vector?  I came up with this:
>>
>> updateVector :: Vector Double -> Int -> Double -> Vector Double
>> updateVector vec pos val = vec `add` v2
>>   where
>>      v2 = fromList $ (replicate (pos) 0.0) ++ ((val - (vec @>
>> pos)):(replicate ((dim vec)- pos - 1) 0.0))
>>
>> but this seems pretty inefficient to me.
>>
>> thanks,
>> Anatoly
>>
>
> It is probably more efficient to use subVector and join (implemented by
> copyArray):
>
> updateVector' v pos val
>    | pos == 0        = join [b,c]
>    | pos == dim v -1 = join [a,b]
>    | otherwise       = join [a,b,c]
>    where a = subVector 0 pos v
>          b = fromList [val]
>          c = subVector (pos+1) (dim v -pos-1) v
>
>> updateVector' (fromList [1,2,3,4,5]) 2 57
> 5 |> [1.0,2.0,57.0,4.0,5.0]
>
> (The three cases are required because empty vectors are not currently
> allowed.)
>
> Something similar can be done for matrices using flatten and reshape.
>
> Although vectors and matrices in this library are immutable and intended to
> be manipulated as a whole by higher level functions, this kind of update
> functions may often be useful. I will include them soon.
>
> Alberto
>
From pieter at laeremans.org  Sun Jun  1 18:18:36 2008
From: pieter at laeremans.org (Pieter Laeremans)
Date: Sun Jun  1 18:11:20 2008
Subject: [Haskell-cafe] Ghc / cgi static linking
Message-ID: <ddacd4a70806011518v2b65d010r56e60ca9bf0a530c@mail.gmail.com>

Hello,

I'm researching the use of Haskell to replace some perl scripts (in a web app).
The app is deployed with a webhosting provider.

CGI scripts can be executed =>  I can use Haskell. I've tried some
hello world cgi scripts, compiled them on the same linux
the hosting company uses and deployed them. It worked!

But I would like to implement a search feature for the website.  For
Java/php/perl there 's lucene.
For haskell there 's holumbus. Unfortunately, sqlite is a requirement
for holumbus. It is not installed at the server of the
hosting company.

Is it possible to staticly link the sqlite3 library using ghc ?

And are there other lucene like libs available like holumbus for haskell ?

thanks in advance,

Pieter



-- 
Pieter Laeremans <pieter@laeremans.org>
From dons at galois.com  Sun Jun  1 18:26:00 2008
From: dons at galois.com (Don Stewart)
Date: Sun Jun  1 18:18:48 2008
Subject: [Haskell-cafe] Ghc / cgi static linking
In-Reply-To: <ddacd4a70806011518v2b65d010r56e60ca9bf0a530c@mail.gmail.com>
References: <ddacd4a70806011518v2b65d010r56e60ca9bf0a530c@mail.gmail.com>
Message-ID: <20080601222600.GE4759@scytale.galois.com>

pieter:
> Hello,
> 
> I'm researching the use of Haskell to replace some perl scripts (in a web app).
> The app is deployed with a webhosting provider.
> 
> CGI scripts can be executed =>  I can use Haskell. I've tried some
> hello world cgi scripts, compiled them on the same linux
> the hosting company uses and deployed them. It worked!
> 
> But I would like to implement a search feature for the website.  For
> Java/php/perl there 's lucene.
> For haskell there 's holumbus. Unfortunately, sqlite is a requirement
> for holumbus. It is not installed at the server of the
> hosting company.
> 
> Is it possible to staticly link the sqlite3 library using ghc ?

Yes, it is entirely possible to statically link entire CGI apps.

For example, this simple program,

    import Database.SQLite
    main = print "hey, test this"

when compiled as $ ghc A.hs --make is dynamically linked against:

    $ ldd A
    A:
        Start            End              Type Open Ref GrpRef Name
        0000000000000000 0000000000000000 exe  1    0   0      A
        0000000041a85000 0000000041ee5000 rlib 0    1   0      /usr/local/lib/libsqlite3.so.9.0
        0000000049b04000 0000000049f1d000 rlib 0    1   0      /usr/lib/libm.so.2.3
        0000000042213000 000000004264f000 rlib 0    1   0      /usr/local/lib/libgmp.so.7.0
        0000000047d0e000 00000000481e0000 rlib 0    1   0      /usr/lib/libc.so.42.0
        0000000047900000 0000000047900000 rtld 0    1   0      /usr/libexec/ld.so

Now, we can just pass some linker flags through to statically link this lot,

    $ ghc A.hs --make -optl-static -no-recomp
    $ ldd A                                  
    ldd: A: not a dynamic executable
    $ file A
    A: ELF 64-bit LSB executable, AMD64, version 1, for OpenBSD, statically linked, not stripped

I've added this information to the web programming FAQ,

    haskell.org/haskellwiki/Practical_web_programming_in_Haskell#Deploying_statically_linked_applications

Note it also works for fastcgi, which when combined with Haskell's lightweight
threads, makes a good option for performance-oriented web apps.

-- Don
From peteg42 at gmail.com  Sun Jun  1 21:27:56 2008
From: peteg42 at gmail.com (Peter Gammie)
Date: Sun Jun  1 21:21:09 2008
Subject: [Haskell-cafe] Ghc / cgi static linking
In-Reply-To: <20080601222600.GE4759@scytale.galois.com>
References: <ddacd4a70806011518v2b65d010r56e60ca9bf0a530c@mail.gmail.com>
	<20080601222600.GE4759@scytale.galois.com>
Message-ID: <12F6690C-C370-4C25-B080-ADC3975318EC@gmail.com>

On 02/06/2008, at 5:26 AM, Don Stewart wrote:

> pieter:
> Yes, it is entirely possible to statically link entire CGI apps.

You might want to watch out for a bug in GHC 6.8.2 that means GHC's "- 
static" flag doesn't work. (At least for me, at least on Debian: the "- 
lpthread" flag is passed before the "-lrt" one, and symbols are left  
unresolved as a result.) Apparently the near-to-release 6.8.3 will fix  
this issue.

Presumably dons is using a more recent GHC than 6.8.2, or other (BSD?)  
platforms are not affected.

Note also you may have to tweak sundry .cabal files to add "extra- 
libraries" fields. As an example, I added this to HSQL's PostgreSQL  
backend to get it to statically link:

extra-libraries: pq, crypt, pthread

(If anyone cares you need to build PostgreSQL without kerberos as that  
doesn't seem to statically link any more.)

cheers
peter

-- 
http://peteg.org/

From dons at galois.com  Sun Jun  1 21:31:00 2008
From: dons at galois.com (Don Stewart)
Date: Sun Jun  1 21:23:45 2008
Subject: [Haskell-cafe] Ghc / cgi static linking
In-Reply-To: <12F6690C-C370-4C25-B080-ADC3975318EC@gmail.com>
References: <ddacd4a70806011518v2b65d010r56e60ca9bf0a530c@mail.gmail.com>
	<20080601222600.GE4759@scytale.galois.com>
	<12F6690C-C370-4C25-B080-ADC3975318EC@gmail.com>
Message-ID: <20080602013100.GJ4759@scytale.galois.com>

peteg42:
> On 02/06/2008, at 5:26 AM, Don Stewart wrote:
> 
> >pieter:
> >Yes, it is entirely possible to statically link entire CGI apps.
> 
> You might want to watch out for a bug in GHC 6.8.2 that means GHC's "- 
> static" flag doesn't work. (At least for me, at least on Debian: the "- 
> lpthread" flag is passed before the "-lrt" one, and symbols are left  
> unresolved as a result.) Apparently the near-to-release 6.8.3 will fix  
> this issue.
> 
> Presumably dons is using a more recent GHC than 6.8.2, or other (BSD?)  
> platforms are not affected.

Yeah, that's the case.
  
> Note also you may have to tweak sundry .cabal files to add "extra- 
> libraries" fields. As an example, I added this to HSQL's PostgreSQL  
> backend to get it to statically link:
> 
> extra-libraries: pq, crypt, pthread
> 
> (If anyone cares you need to build PostgreSQL without kerberos as that  
> doesn't seem to statically link any more.)
> 

Hey Pete,

Can you add these caveats to the wiki page?

    haskell.org/haskellwiki/Practical_web_programming_in_Haskell#Deploying_statically_linked_applications
From donn at avvanta.com  Sun Jun  1 22:08:38 2008
From: donn at avvanta.com (Donn Cave)
Date: Sun Jun  1 22:00:44 2008
Subject: [Haskell-cafe] haskell compiler on NetBSD amd64
In-Reply-To: <20080510093512.GA27361@matstaff04.nuigalway.ie>
References: <20080509222119.cfe30daa.donn@avvanta.com>
	<20080510093512.GA27361@matstaff04.nuigalway.ie>
Message-ID: <20080601190838.61e222e3.donn@avvanta.com>

On Sat, 10 May 2008 10:35:12 +0100
Emil Skoeldberg <emil.skoldberg@nuigalway.ie> wrote:

> On Fri, May 09, 2008 at 10:21:19PM -0700, Donn Cave wrote:
> > So here I am with 64 bit Athlon hardware, running amd64
> > NetBSD (a.k.a. x86_64), reasonably motivated to compile
> > Haskell.
> 
> So, we are in the same boat then!

OK, for you and me and probably no one else in the world, I have
built 6.8.2, and for a short time I have it on-line - at my ISP's
site, http://www.avvanta.com/~donn/   ... append file name, which
is ghc-6.8.2-netbsd-amd64.tar.bz2   Size is ca. 54 Mb.

When you want to use this to build future ghc releases, you'll
probably have to modify libbfd.so to get GNU ar to index one
or two of the larger libraries.  I believe the release itself
will work fine without this mod - ld uses the same library, but
I think only ar has the problem.

That cost me a lot of time.  The other thing that cost me some
time was the gmp dist in ghc-6.6.1, which didn't fully configure
for the platform.  The rest was reasonably straightforward.
I built 6.6.1 .hc files on OpenBSD.

-- 
Donn Cave <donn@avvanta.com>
From dons at galois.com  Sun Jun  1 22:34:10 2008
From: dons at galois.com (Don Stewart)
Date: Sun Jun  1 22:27:22 2008
Subject: [Haskell-cafe] haskell compiler on NetBSD amd64
In-Reply-To: <20080601190838.61e222e3.donn@avvanta.com>
References: <20080509222119.cfe30daa.donn@avvanta.com>
	<20080510093512.GA27361@matstaff04.nuigalway.ie>
	<20080601190838.61e222e3.donn@avvanta.com>
Message-ID: <20080602023410.GK4759@scytale.galois.com>

donn:
> On Sat, 10 May 2008 10:35:12 +0100
> Emil Skoeldberg <emil.skoldberg@nuigalway.ie> wrote:
> 
> > On Fri, May 09, 2008 at 10:21:19PM -0700, Donn Cave wrote:
> > > So here I am with 64 bit Athlon hardware, running amd64
> > > NetBSD (a.k.a. x86_64), reasonably motivated to compile
> > > Haskell.
> > 
> > So, we are in the same boat then!
> 
> OK, for you and me and probably no one else in the world, I have
> built 6.8.2, and for a short time I have it on-line - at my ISP's
> site, http://www.avvanta.com/~donn/   ... append file name, which
> is ghc-6.8.2-netbsd-amd64.tar.bz2   Size is ca. 54 Mb.
> 
> When you want to use this to build future ghc releases, you'll
> probably have to modify libbfd.so to get GNU ar to index one
> or two of the larger libraries.  I believe the release itself
> will work fine without this mod - ld uses the same library, but
> I think only ar has the problem.
> 
> That cost me a lot of time.  The other thing that cost me some
> time was the gmp dist in ghc-6.6.1, which didn't fully configure
> for the platform.  The rest was reasonably straightforward.
> I built 6.6.1 .hc files on OpenBSD.

Great work, let's get it up on the download page,

    http://haskell.org/ghc/download_ghc_682.html

-- Don
From donn at avvanta.com  Sun Jun  1 23:50:12 2008
From: donn at avvanta.com (Donn Cave)
Date: Sun Jun  1 23:42:18 2008
Subject: [Haskell-cafe] haskell compiler on NetBSD amd64
In-Reply-To: <20080602023410.GK4759@scytale.galois.com>
References: <20080509222119.cfe30daa.donn@avvanta.com>
	<20080510093512.GA27361@matstaff04.nuigalway.ie>
	<20080601190838.61e222e3.donn@avvanta.com>
	<20080602023410.GK4759@scytale.galois.com>
Message-ID: <20080601205012.6973f74a.donn@avvanta.com>

On Sun, 1 Jun 2008 19:34:10 -0700
Don Stewart <dons@galois.com> wrote:

> Great work, let's get it up on the download page,
> 
>     http://haskell.org/ghc/download_ghc_682.html
>

Suits me, but now that I've had a chance to compile a little
more Haskell with it, I think I might like to fix up a couple
things.  I'm not promising to make ghci work, though that would
be nice, but mainly I'm talking about linker warnings attached
to a couple of "compatibility" functions that got linked in
when the more POSIX compliant versions would have been found
if e.g. stdlib.h had been included.  opendir(), unsetenv(), etc.
So if that's agreeable, don't take the file I put on-line, I'll
build up another one.

thanks

-- 
Donn Cave <donn@avvanta.com>
From thomas.dubuisson at gmail.com  Mon Jun  2 00:19:24 2008
From: thomas.dubuisson at gmail.com (Thomas M. DuBuisson)
Date: Mon Jun  2 00:07:35 2008
Subject: [Haskell-cafe] [ANN] Bindings to Xen Control (xenctrl.h)
In-Reply-To: <20080601063140.GA1200@scytale.galois.com>
References: <1212300682.2448.14.camel@Clunker>
	<20080601063140.GA1200@scytale.galois.com>
Message-ID: <1212380364.2448.39.camel@Clunker>

Don,
I'll throw future work ideas in the next releases cabal.  The most
obvious doors opened are Haskell rewrites of the current Xen
infrastructure (virt-install, xm, xend).  Slightly more interesting
tasks could be (warning: random thoughts):

1) HAPPS server that can manage Xen domains (without requiring python
libs or System.cmd)
2) Network or BSD socket based remote management programs in Haskell.
haxr or session-types might be of use here.
3) With the functions that can alter the CPUs availability, more complex
rules or sharing arrangements could be implemented.  Same concept
applies to other resources such as PCI and memory allocation.  Seeing as
Xen doesn't over-commit memory, a guest VM program that detects low/high
memory situations and reports to the host for policy controlled
balloning (adjustment of VM allocated memory) would be kind of fun...
but probably complete overkill for any user of Xen.

Right now I think the bindings are enough for an 'xm' replacement but
nothing more.  I've over doubled the number of functions bound just now.
There will probably be regular releases for the next few weeks as I find
time.

Thomas

On Sat, 2008-05-31 at 23:31 -0700, Don Stewart wrote: 
> thomas.dubuisson:
> > All,
> > I'm just getting started with hsXenCtrl [1] as both a fun way to play
> > with Xen and become proficient with Haskell FFI.  Once I get my
> > community.haskell.org account squared away I'll likely setup a public
> > darcs repo (and a homepage somewhere).
> > 
> > As for modules: I intend to expand on the trival FFI bindings in
> > System.Xen.CBindings and there'll be a higher level interface in
> > System.Xen (functions will standardize on returning Either or throwing
> > exceptions, hiding the xc_handle open/close, etc).
> > 
> > Typical Disclaimers:
> > The _only_ thing I've actually done with this, just tonight, is pause /
> > unpause domains.  API is subject to change!  Only my exact build of Xen
> > is sure to work, and no promise even then.
> > 
> > TomMD
> > 
> > [1] http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hsXenCtrl
> 
> Good stuff. Perhaps the synopsis should include a link or description of
> the typical use cases/ thinks we might achieve?
> 
> -- Don

From abhay.parvate at gmail.com  Mon Jun  2 01:04:07 2008
From: abhay.parvate at gmail.com (Abhay Parvate)
Date: Mon Jun  2 00:56:51 2008
Subject: [Haskell-cafe] Re: appending an element to a list
In-Reply-To: <g1tjk4$c4i$1@ger.gmane.org>
References: <483EE208.2010601@inf.fu-berlin.de> <483EF36B.5040100@daimi.au.dk>
	<48404039.6030605@cisco.com> <48405717.20206@daimi.au.dk>
	<87r6bja609.fsf@hbox.dyndns.org>
	<3c4d5adf0805302159o23113ad2sb24754e02789bb06@mail.gmail.com>
	<48414C2B.9010606@daimi.au.dk> <g1tjk4$c4i$1@ger.gmane.org>
Message-ID: <3c4d5adf0806012204p25133bdaxbc22955b70f094ff@mail.gmail.com>

I somehow thought it would be easy to talk about complexity of calculating
individual elements in an infinite list should be sufficient, but that seems
to be involved, and my over-generalization doesn't seem to work. Thanks for
the link; particularly it has reference to Wadler's papers exactly on this
problem.

Abhay

On Sun, Jun 1, 2008 at 1:07 PM, apfelmus <apfelmus@quantentunnel.de> wrote:

> Tillmann Rendel wrote:
>
>> Abhay Parvate wrote:
>>
>>> I think I would like to make another note: when we talk about the
>>> complexity
>>> of a function, we are talking about the time taken to completely evaluate
>>> the result. Otherwise any expression in haskell will be O(1), since it
>>> just creates a thunk.
>>>
>>
>> I don't like this notion of complexity, since it seems not very suited for
>> the analysis of composite expression in Haskell.
>>
>> Is this intuitive view generalizable to arbitrary datatypes (instead of
>> lists) and formalized somewhere?
>>
>
> See also the thread section beginning with
>
>  http://thread.gmane.org/gmane.comp.lang.haskell.cafe/34398/focus=34435
>
>
>
> Regards,
> apfelmus
>
>
> _______________________________________________
> Haskell-Cafe mailing list
> Haskell-Cafe@haskell.org
> http://www.haskell.org/mailman/listinfo/haskell-cafe
>
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From vigalchin at gmail.com  Mon Jun  2 01:07:11 2008
From: vigalchin at gmail.com (Galchin, Vasili)
Date: Mon Jun  2 00:59:54 2008
Subject: [Haskell-cafe] ghc 6.8.2 issue
Message-ID: <5ae4f2ba0806012207i2797be95kf773d0cf75d6b39@mail.gmail.com>

Hello,

      I have been developing new code for the "unix" package. I have run
into what I think are ghc 6.8.2 anomalies but couldn't see a pattern.
Possibly now I do. I have been using the 32-bit x86 ghc binary that I
downloaded from http://www.haskell.org and running on Ubuntu Linux. I am
pretty I can repeat now. Everything is ok until I do "sudo runhaskell
Setup.hs install" which installs a new "unix" package that I just built. Of
course the "intall" installs into /usr/local/lib/unix-2.3.0.0/ghc-6.8.2. The
"install" seems to destroy some ghc compiler state under /usr/local ... This
is of course just a theory. However, once I re-install ghc et. al. from the
binary download then things are ok again. I have tried the ghc re-install at
least 4 times. Hope I am not misleading anybody .. just trying to help!

Kind regards, Vasili
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From yann at kierun.org  Mon Jun  2 03:48:21 2008
From: yann at kierun.org (Yann Golanski)
Date: Mon Jun  2 03:41:08 2008
Subject: [Haskell-cafe] Re: Images and GUIs in Haskell
In-Reply-To: <20080601040910.545853dc@solaris>
References: <62728db30805311530x6c28431fwf2615a18fac343cb@mail.gmail.com>
	<20080601014052.5658743f@solaris>
	<62728db30805311800s472cc708rf50bd77a70c65eb3@mail.gmail.com>
	<20080601040910.545853dc@solaris>
Message-ID: <20080602074821.GC1271@kierun.org>

Quoth Achim Schneider on Sun, Jun 01, 2008 at 04:09:10 +0200
> I would go for GL(U(T)), as it's as good for 2d primitives as SDL will
> ever be, has excellent cross-platform support and allows you to go 3d
> if you want to. There's also some very decent event handling.

You can use R as well. http://www.r-project.org/

-- 
yann@kierun.org             -= H+ =-             www.kierun.org
   PGP:   009D 7287 C4A7 FD4F 1680  06E4 F751 7006 9DE2 6318
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From jules at jellybean.co.uk  Mon Jun  2 05:10:16 2008
From: jules at jellybean.co.uk (Jules Bean)
Date: Mon Jun  2 05:02:59 2008
Subject: [Haskell-cafe] GHCi panic
In-Reply-To: <48406AC1.4090003@btinternet.com>
References: <48406AC1.4090003@btinternet.com>
Message-ID: <4843B8F8.9070309@jellybean.co.uk>

Andrew Coppin wrote:
> I don't suppose this will surprise anybody greatly, but...
> 
> Apparently if you write a Haskell module that is 400 KB in size and 
> defines a single CAF consisting of a 45,000-element [String], GHCi 
> panics when attempting to load it interpretted, and hits a stack 
> overflow attempting to load it compiled.

qv http://hackage.haskell.org/trac/ghc/ticket/2002
From aruiz at um.es  Mon Jun  2 05:37:14 2008
From: aruiz at um.es (Alberto Ruiz)
Date: Mon Jun  2 05:29:57 2008
Subject: [Haskell-cafe] Re: hmatrix
In-Reply-To: <e26d18e40806011145y4200e294yf8ffe08a426636b7@mail.gmail.com>
References: <e26d18e40805311209h4cd37689u30fe65e2ebd6c21e@mail.gmail.com>	
	<484277D3.9020604@um.es>
	<e26d18e40806011145y4200e294yf8ffe08a426636b7@mail.gmail.com>
Message-ID: <4843BF4A.2080800@um.es>

Anatoly Yakovenko wrote:
> do you have any plans to provide an interface for inplace updates?

Yes, I will try to write a simple version of Data.Array.ST...

> On Sun, Jun 1, 2008 at 3:20 AM, Alberto Ruiz <aruiz@um.es> wrote:
>> Anatoly Yakovenko wrote:
>>> What is the most efficient way to update a position in a matrix or a
>>> vector?  I came up with this:
>>>
>>> updateVector :: Vector Double -> Int -> Double -> Vector Double
>>> updateVector vec pos val = vec `add` v2
>>>   where
>>>      v2 = fromList $ (replicate (pos) 0.0) ++ ((val - (vec @>
>>> pos)):(replicate ((dim vec)- pos - 1) 0.0))
>>>
>>> but this seems pretty inefficient to me.
>>>
>>> thanks,
>>> Anatoly
>>>
>> It is probably more efficient to use subVector and join (implemented by
>> copyArray):
>>
>> updateVector' v pos val
>>    | pos == 0        = join [b,c]
>>    | pos == dim v -1 = join [a,b]
>>    | otherwise       = join [a,b,c]
>>    where a = subVector 0 pos v
>>          b = fromList [val]
>>          c = subVector (pos+1) (dim v -pos-1) v
>>
>>> updateVector' (fromList [1,2,3,4,5]) 2 57
>> 5 |> [1.0,2.0,57.0,4.0,5.0]
>>
>> (The three cases are required because empty vectors are not currently
>> allowed.)
>>
>> Something similar can be done for matrices using flatten and reshape.
>>
>> Although vectors and matrices in this library are immutable and intended to
>> be manipulated as a whole by higher level functions, this kind of update
>> functions may often be useful. I will include them soon.
>>
>> Alberto
>>
> 
From duncan.coutts at worc.ox.ac.uk  Mon Jun  2 06:38:20 2008
From: duncan.coutts at worc.ox.ac.uk (Duncan Coutts)
Date: Mon Jun  2 06:28:00 2008
Subject: [Haskell-cafe] ghc 6.8.2 issue
In-Reply-To: <5ae4f2ba0806012207i2797be95kf773d0cf75d6b39@mail.gmail.com>
References: <5ae4f2ba0806012207i2797be95kf773d0cf75d6b39@mail.gmail.com>
Message-ID: <1212403100.15010.133.camel@localhost>


On Mon, 2008-06-02 at 00:07 -0500, Galchin, Vasili wrote:
> Hello,
> 
>       I have been developing new code for the "unix" package. I have
> run into what I think are ghc 6.8.2 anomalies but couldn't see a
> pattern. Possibly now I do. I have been using the 32-bit x86 ghc
> binary that I downloaded from http://www.haskell.org and running on
> Ubuntu Linux. I am pretty I can repeat now. Everything is ok until I
> do "sudo runhaskell Setup.hs install" which installs a new "unix"
> package that I just built. Of course the "intall" installs
> into /usr/local/lib/unix-2.3.0.0/ghc-6.8.2. The "install" seems to
> destroy some ghc compiler state under /usr/local ...

That sounds right. You're replacing the unix-2.3.0.0 library that comes
with ghc-6.8.2 with your own version. It is highly unlikely to be ABI
compatible with the one you are replacing and so all the other packages
that already depends on the existing unix-2.3.0.0 library end up broken.
You'd expect this kind of breakage to be exposed as link errors and
segfaults.

I suggest you do not replace any of the libraries that come with ghc. To
be more precise, it is perfectly ok to *add new versions* but it is not
ok to *replace existing versions* without rebuilding all the other libs
that depend on it.

Make sense?

So if you really want to make changes to the unix lib, make sure you
change the version number too. I also suggest not installing the
packages as root, just install them locally. That way you can guarantee
you never mess up your ghc install. You would be able to revert to a
clean ghc install just by removing your
~/.ghc/$arch/ghc-6.8.2/package.conf file which will unregister *all*
locally registered packages. To unregister individual packages use
ghc-pkg --user unregister $pkgname

Duncan

From nominolo at googlemail.com  Mon Jun  2 06:42:15 2008
From: nominolo at googlemail.com (Thomas Schilling)
Date: Mon Jun  2 06:35:12 2008
Subject: [Haskell-cafe] [ANNOUNCE] git-darcs-import 0.1
In-Reply-To: <20080601184446.GA27750@zombie.inf.tu-dresden.de>
References: <20080601184446.GA27750@zombie.inf.tu-dresden.de>
Message-ID: <8D4BA8BD-D3A2-4B56-B18E-FD6EA7A81D45@googlemail.com>


On 1 jun 2008, at 20.44, Bertram Felgenhauer wrote:

> Hi,
>
> I'm pleased to announce yet another tool for importing darcs  
> repositories
> to git. Unlike darcs2git [1] and darcs-to-git [2], it's written in
> Haskell, on top of the darcs2 source code. The result is a much faster
> program - it can convert the complete ghc 6.9 branch (without  
> libraries)
> in less than 15 minutes on my slightly dated machine (Athlon XP 2500 
> +),
> which is quite fast [3]. Incremental updates work, too.
>
Nice!  Do you happen to also have a darcs (or Git) repository somewhere?

/ Thomas
--
Monkey killing monkey killing monkey over pieces of the ground.
Silly monkeys give them thumbs they forge a blade
And where there's one they're bound to divide it
Right in two

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From bertram.felgenhauer at googlemail.com  Mon Jun  2 08:05:03 2008
From: bertram.felgenhauer at googlemail.com (Bertram Felgenhauer)
Date: Mon Jun  2 07:57:51 2008
Subject: [Haskell-cafe] [ANNOUNCE] git-darcs-import 0.1
In-Reply-To: <8D4BA8BD-D3A2-4B56-B18E-FD6EA7A81D45@googlemail.com>
References: <20080601184446.GA27750@zombie.inf.tu-dresden.de>
	<8D4BA8BD-D3A2-4B56-B18E-FD6EA7A81D45@googlemail.com>
Message-ID: <20080602120503.GB4258@zombie.inf.tu-dresden.de>

Thomas Schilling wrote:
>
> On 1 jun 2008, at 20.44, Bertram Felgenhauer wrote:
[git-darcs-import]
>
> Nice!  Do you happen to also have a darcs (or Git) repository somewhere?

I've uploaded my (git) repo to repo.or.cz, see
    http://repo.or.cz/w/git-darcs-import.git

Patches are welcome.

enjoy,

Bertram
From devriese at cs.tcd.ie  Mon Jun  2 09:05:11 2008
From: devriese at cs.tcd.ie (Edsko de Vries)
Date: Mon Jun  2 08:57:56 2008
Subject: [Haskell-cafe] hs-plugins compile error
Message-ID: <20080602130511.GA24905@netsoc.tcd.ie>

Hi,

I'm getting the compilation error that is actually logged on Hackage:

http://hackage.haskell.org/cgi-bin/hackage-scripts/package/plugins

Below is a small diff file that resolves these problems; I don't know
what the proper protocol is for submitting these diffs but it may be
useful to someone.

- E 

diff -ur plugins-1.2-orig/src/System/Plugins/Env.hs plugins-1.2/src/System/Plugins/Env.hs
--- plugins-1.2-orig/src/System/Plugins/Env.hs	2008-06-02 14:57:59.000000000 +0100
+++ plugins-1.2/src/System/Plugins/Env.hs	2008-06-02 15:00:25.000000000 +0100
@@ -73,7 +73,7 @@
 
 import Control.Concurrent.MVar  ( MVar(), newMVar, withMVar )
 
-import Distribution.Package
+import Distribution.Package hiding (packageName)
 import Text.ParserCombinators.ReadP
 
 import qualified Data.Map as M
diff -ur plugins-1.2-orig/src/System/Plugins/PackageAPI.hs plugins-1.2/src/System/Plugins/PackageAPI.hs
--- plugins-1.2-orig/src/System/Plugins/PackageAPI.hs	2008-06-02 14:57:59.000000000 +0100
+++ plugins-1.2/src/System/Plugins/PackageAPI.hs	2008-06-02 14:59:49.000000000 +0100
@@ -40,7 +40,7 @@
 
 #if CABAL == 1 || __GLASGOW_HASKELL__ >= 604
 import Distribution.InstalledPackageInfo
-import Distribution.Package
+import Distribution.Package hiding (depends, packageName)
 #else
 import System.Plugins.Package
 #endif
diff -ur plugins-1.2-orig/src/System/Plugins/ParsePkgConfCabal.hs plugins-1.2/src/System/Plugins/ParsePkgConfCabal.hs
--- plugins-1.2-orig/src/System/Plugins/ParsePkgConfCabal.hs	2008-06-02 14:57:59.000000000 +0100
+++ plugins-1.2/src/System/Plugins/ParsePkgConfCabal.hs	2008-06-02 14:58:56.000000000 +0100
@@ -6,7 +6,7 @@
   ) where
 
 import Distribution.InstalledPackageInfo
-import Distribution.Package
+import Distribution.Package hiding (depends)
 import Distribution.Version
 
 import Data.Char             ( isSpace, isAlpha, isAlphaNum, isUpper, isDigit )

From richardg at richardg.name  Mon Jun  2 09:39:39 2008
From: richardg at richardg.name (Richard Giraud)
Date: Mon Jun  2 09:32:24 2008
Subject: [Haskell-cafe] Mutually Recursive Modules
Message-ID: <4843F81B.7060808@richardg.name>

Hello

I'm using GHC 6.8.2 with mutally recursive modules.  I'm familiar with 
how to do simple cases in GHC ({-# SOURCE #-} and .hs-boot files) but I 
can't figure out how to get it to work for a particular set of modules.

Is it known (i.e., proven) that GHC 6.8.2 can compile any set of 
mutually recursive modules without refactoring?  Are there known 
limitations?

Thanks,

Richard G.
From isaacdupree at charter.net  Mon Jun  2 09:55:25 2008
From: isaacdupree at charter.net (Isaac Dupree)
Date: Mon Jun  2 09:48:05 2008
Subject: [Haskell-cafe] Mutually Recursive Modules
In-Reply-To: <4843F81B.7060808@richardg.name>
References: <4843F81B.7060808@richardg.name>
Message-ID: <4843FBCD.8000001@charter.net>

Richard Giraud wrote:
> Hello
> 
> I'm using GHC 6.8.2 with mutally recursive modules.  I'm familiar with 
> how to do simple cases in GHC ({-# SOURCE #-} and .hs-boot files) but I 
> can't figure out how to get it to work for a particular set of modules.
> 
> Is it known (i.e., proven) that GHC 6.8.2 can compile any set of 
> mutually recursive modules without refactoring?  Are there known 
> limitations?

With the old (6.2 and before) .hi-boot scheme where there was no 
abstraction in boot-files, it could probably do anything that it could 
do.  But I'm not convinced with .hs-boot... it can resolve one level of 
cycle, and I don't know how to *prove* that it *can't* do any given 
thing, but I strongly suspect there are things it can't do.  Luckily, it 
is very often the case that your code will be better off anyway if 
refactored to have less module recursion. (though not always.)

-Isaac
From g9ks157k at acme.softbase.org  Mon Jun  2 10:08:38 2008
From: g9ks157k at acme.softbase.org (Wolfgang Jeltsch)
Date: Mon Jun  2 10:01:32 2008
Subject: [Haskell-cafe] Re: Damnit, we need a CPAN.
In-Reply-To: <20080530220930.6dff9dfa@solaris>
References: <20080529173830.3aae4434@solaris>
	<200805301834.16537.g9ks157k@acme.softbase.org>
	<20080530220930.6dff9dfa@solaris>
Message-ID: <200806021608.39009.g9ks157k@acme.softbase.org>

Am Freitag, 30. Mai 2008 22:09 schrieb Achim Schneider:
> [?]

> I'm generally very interested in declarative GUI programming, but not
> nearly enough acquainted with the whole topic to judge one project's
> approach over the other. I just followed standard scientific evaluation
> technique to select the projects to consider: The ones with the most and
> most recent activity win.
>
> So far, my impression is that documentation is severely lacking, but
> then I'm too busy watching Babylon 5 right now and did not get more
> than half an hour or so looking at grapefruit.

Okay, I think we?ll improve API documentation and then make a release, despite 
Grapefruit not being production quality yet.  I hope, you?ll find it 
useful. :-) 

Best wishes,
Wolfgang
From aditya_siram at hotmail.com  Mon Jun  2 10:37:11 2008
From: aditya_siram at hotmail.com (Aditya Siram)
Date: Mon Jun  2 10:29:57 2008
Subject: [Haskell-cafe] What is the maturity of Haskell Web Frameworks
Message-ID: <BLU108-W49A501FFE2AC204EE805FDF4BB0@phx.gbl>


I am building a web-app that, in broad strokes, allows a leader to assign tasks to team members and allows team members to accept/reject/pick tasks that they want to do. 

I really like Haskell and I would like to use it to implement the solution. Are frameworks like Happs ready? Not so much in terms of documentation, but in functionality and stability. 

-Deech
_________________________________________________________________
Give to a good cause with every e-mail. Join the i?m Initiative from Microsoft.
http://im.live.com/Messenger/IM/Join/Default.aspx?souce=EML_WL_ GoodCause
From isaacdupree at charter.net  Mon Jun  2 10:45:31 2008
From: isaacdupree at charter.net (Isaac Dupree)
Date: Mon Jun  2 10:38:12 2008
Subject: [Haskell-cafe] Default definitions for associated type synonyms
In-Reply-To: <52f14b210805300710k366731d6w340231d6eef3ef19@mail.gmail.com>
References: <52f14b210805300710k366731d6w340231d6eef3ef19@mail.gmail.com>
Message-ID: <4844078B.1010201@charter.net>

Dreixel wrote:
> Hello,
> 
> Does anyone know if it is possible to specify a default definition for an
> associated type synonym? When I tried:
> 
> class A a where
>>   type B a = a
>>
> 
> GHC (version 6.9.20080309) told me: "Type declaration in a class must be a
> kind signature or synonym default". However, when I look at the parser I see
> no way to specify such synonym default. Is this possible?

I'm curious... so, cc'ing glasgow-haskell-users mailinglist because the 
question is more likely to be noticed by relevant people there.

> Thanks,
> Z? Pedro
From stefan at cs.uu.nl  Mon Jun  2 10:50:00 2008
From: stefan at cs.uu.nl (Stefan Holdermans)
Date: Mon Jun  2 10:42:48 2008
Subject: [Haskell-cafe] Default definitions for associated type synonyms
In-Reply-To: <4844078B.1010201@charter.net>
References: <52f14b210805300710k366731d6w340231d6eef3ef19@mail.gmail.com>
	<4844078B.1010201@charter.net>
Message-ID: <9AAEC7D1-A1C3-4124-B2B0-E1F9F3E4675D@cs.uu.nl>

Isaac,

>> Does anyone know if it is possible to specify a default definition  
>> for an
>> associated type synonym?


According to http://hackage.haskell.org/trac/ghc/wiki/TypeFunctionsStatus 
  defaults for associated types is still a TODO.

Cheers,

   Stefan
From daniel at dbpatterson.com  Mon Jun  2 10:57:04 2008
From: daniel at dbpatterson.com (Daniel Patterson)
Date: Mon Jun  2 10:47:10 2008
Subject: [Haskell-cafe] What is the maturity of Haskell Web Frameworks
In-Reply-To: <BLU108-W49A501FFE2AC204EE805FDF4BB0@phx.gbl>
References: <BLU108-W49A501FFE2AC204EE805FDF4BB0@phx.gbl>
Message-ID: <20080602105704.1e4dc5ed@patagonia.local>

You definitely could use HAppS for that, but considering that it sounds like a
pretty small/lightweight app, you might want to check out hvac
( http://fmapfixreturn.wordpress.com/2008/03/23/ ), which is a newer (but
still surprisingly full-featured) web framework. It is pretty
lightweight, and might be easier to get working for your purposes.

Daniel

On Mon, 2 Jun 2008 09:37:11 -0500
Aditya Siram <aditya_siram@hotmail.com> wrote:

> 
> I am building a web-app that, in broad strokes, allows a leader to assign
> tasks to team members and allows team members to accept/reject/pick tasks
> that they want to do. 
> 
> I really like Haskell and I would like to use it to implement the solution.
> Are frameworks like Happs ready? Not so much in terms of documentation, but
> in functionality and stability. 
> 
> -Deech
> _________________________________________________________________
> Give to a good cause with every e-mail. Join the i?m Initiative from
> Microsoft. http://im.live.com/Messenger/IM/Join/Default.aspx?souce=EML_WL_
> GoodCause_______________________________________________ Haskell-Cafe mailing
> list Haskell-Cafe@haskell.org
> http://www.haskell.org/mailman/listinfo/haskell-cafe
From marco-oweber at gmx.de  Mon Jun  2 11:16:36 2008
From: marco-oweber at gmx.de (Marc Weber)
Date: Mon Jun  2 11:09:20 2008
Subject: [Haskell-cafe] What is the maturity of Haskell Web Frameworks
In-Reply-To: <BLU108-W49A501FFE2AC204EE805FDF4BB0@phx.gbl>
References: <BLU108-W49A501FFE2AC204EE805FDF4BB0@phx.gbl>
Message-ID: <20080602151636.GA20757@gmx.de>

On Mon, Jun 02, 2008 at 09:37:11AM -0500, Aditya Siram wrote:
> 
> I am building a web-app that, in broad strokes, allows a leader to assign tasks to team members and allows team members to accept/reject/pick tasks that they want to do. 
> 
> I really like Haskell and I would like to use it to implement the solution. Are frameworks like Happs ready? Not so much in terms of documentation, but in functionality and stability. 
Me too, but in this case if it's only about assigning tasks you should
consider using existing solutions such as flysrpay or mantis http://www.mantisbt.org/
Maybe they fit your needs ?

mit freundlichem Gruss
Marc Weber
From nominolo at googlemail.com  Mon Jun  2 12:13:33 2008
From: nominolo at googlemail.com (Thomas Schilling)
Date: Mon Jun  2 12:06:27 2008
Subject: [Haskell-cafe] Damnit, we need a CPAN.
In-Reply-To: <20080529161307.GA17931@scytale.galois.com>
References: <20080529173830.3aae4434@solaris>
	<404396ef0805290847w41cb7635ud6f655a9c096f28e@mail.gmail.com>
	<20080529110555.3d08fcb6@Eridanus.javasnob.homelinux.net>
	<20080529161307.GA17931@scytale.galois.com>
Message-ID: <E3E18D96-B25B-4287-885F-8D3CCCD1F757@googlemail.com>


On 29 maj 2008, at 18.13, Don Stewart wrote:

>> Hackage and Cabal are nice, but a command line tool for automatically
>> searching Hackage and installing Hackage packages (like the cpan
>> program, or easy_install) would be nice.  Unless I haven't done my
>> homework and this tool exists...
>>
>
> This tool exists. It is called 'cabal-install'. To try out one of
> today's new packages:
>
>     $ cabal update
>     $ cabal install category-extras
>


Another nice feature:  Say you want to hack on the darcs version of a  
project, but you need to install the dependencies.  If the project is  
Cabalised you can build and install the darcs version as well as all  
dependencies by calling 'cabal install' with no arguments inside the  
project directory.

   $ darcs get <project>
   $ cd <project>
   $ cabal install

/ Thomas
--
Push the envelope.  Watch it bend.



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From tphyahoo at gmail.com  Mon Jun  2 12:42:08 2008
From: tphyahoo at gmail.com (Thomas Hartman)
Date: Mon Jun  2 12:34:51 2008
Subject: [Haskell-cafe] cabal install fail for happs-hsp-template
Message-ID: <910ddf450806020942n4bc2fac8kc454aeda446b77ee@mail.gmail.com>

Can cabal install be made to work for this package?
*****
thartman@thartman-laptop:~>sudo cabal install happs-hsp-template
[sudo] password for thartman:
cabal: internal error: could not construct a valid install plan.
The proposed (invalid) plan contained the following problems:
Package Cabal is required by several packages, but they require
inconsistent versions:
  package ghc-6.8.2 requires Cabal-1.2.3.0
  package plugins-1.2 requires Cabal-1.5.2


thartman@thartman-laptop:~>cabal --version
cabal-install version 0.4.7
using version 1.3.11 of the Cabal library
thartman@thartman-laptop:~>ghc --version
The Glorious Glasgow Haskell Compilation System, version 6.8.2
thartman@thartman-laptop:~>ghc-pkg list | grep -i ghc
/usr/local/lib/ghc-6.8.2/package.conf:
    (ghc-6.8.2), haskell-src-1.0.1.1, haskell98-1.0.1.0, hpc-0.5.0.0,
From tphyahoo at gmail.com  Mon Jun  2 12:59:24 2008
From: tphyahoo at gmail.com (Thomas Hartman)
Date: Mon Jun  2 12:52:06 2008
Subject: [Haskell-cafe] Re: cabal install fail for happs-hsp-template
In-Reply-To: <910ddf450806020942n4bc2fac8kc454aeda446b77ee@mail.gmail.com>
References: <910ddf450806020942n4bc2fac8kc454aeda446b77ee@mail.gmail.com>
Message-ID: <910ddf450806020959i368abde0ud1080acc23734a0b@mail.gmail.com>

I just noticed this is also reported as a 6.8 build failure on hackage itself.

http://hackage.haskell.org/cgi-bin/hackage-scripts/package/happs-hsp-template

2008/6/2 Thomas Hartman <tphyahoo@gmail.com>:
> Can cabal install be made to work for this package?
> *****
> thartman@thartman-laptop:~>sudo cabal install happs-hsp-template
> [sudo] password for thartman:
> cabal: internal error: could not construct a valid install plan.
> The proposed (invalid) plan contained the following problems:
> Package Cabal is required by several packages, but they require
> inconsistent versions:
>  package ghc-6.8.2 requires Cabal-1.2.3.0
>  package plugins-1.2 requires Cabal-1.5.2
>
>
> thartman@thartman-laptop:~>cabal --version
> cabal-install version 0.4.7
> using version 1.3.11 of the Cabal library
> thartman@thartman-laptop:~>ghc --version
> The Glorious Glasgow Haskell Compilation System, version 6.8.2
> thartman@thartman-laptop:~>ghc-pkg list | grep -i ghc
> /usr/local/lib/ghc-6.8.2/package.conf:
>    (ghc-6.8.2), haskell-src-1.0.1.1, haskell98-1.0.1.0, hpc-0.5.0.0,
>
From aeyakovenko at gmail.com  Mon Jun  2 13:06:40 2008
From: aeyakovenko at gmail.com (Anatoly Yakovenko)
Date: Mon Jun  2 12:59:21 2008
Subject: [Haskell-cafe] Re: hmatrix
In-Reply-To: <4843BF4A.2080800@um.es>
References: <e26d18e40805311209h4cd37689u30fe65e2ebd6c21e@mail.gmail.com>
	<484277D3.9020604@um.es>
	<e26d18e40806011145y4200e294yf8ffe08a426636b7@mail.gmail.com>
	<4843BF4A.2080800@um.es>
Message-ID: <e26d18e40806021006y7277edcbn556971a87380bad0@mail.gmail.com>

>> do you have any plans to provide an interface for inplace updates?
>
> Yes, I will try to write a simple version of Data.Array.ST...
>

I can try to help you, although I still dont quite grok monads.
Wouldn't it be more efficient to use StorableArray, so you can cast
from and to C?  I am not sure how vectors and matrixes are represented
in C, but I imagine it should be possible to manipulate them without
resorting to copying between haskell and C.
From dons at galois.com  Mon Jun  2 13:21:31 2008
From: dons at galois.com (Don Stewart)
Date: Mon Jun  2 13:14:14 2008
Subject: [Haskell-cafe] What is the maturity of Haskell Web Frameworks
In-Reply-To: <BLU108-W49A501FFE2AC204EE805FDF4BB0@phx.gbl>
References: <BLU108-W49A501FFE2AC204EE805FDF4BB0@phx.gbl>
Message-ID: <20080602172131.GA7534@scytale.galois.com>

aditya_siram:
> 
> I am building a web-app that, in broad strokes, allows a leader to
> assign tasks to team members and allows team members to
> accept/reject/pick tasks that they want to do. 
> 
> I really like Haskell and I would like to use it to implement the
> solution. Are frameworks like Happs ready? Not so much in terms of
> documentation, but in functionality and stability. 

HAppS is nice (see hpaste.org for example, which is nice and simple, and
has been running for over a year).

Another nice option in Haskell is using something like HStringTemplate
or the xhtml combinators  with fastcgi hooked into GHC's concurrency
mechanisms.

You can find *many* more things here,

    http://hackage.haskell.org/packages/archive/pkg-list.html#cat:Network
    http://hackage.haskell.org/packages/archive/pkg-list.html#cat:Web
From bulat.ziganshin at gmail.com  Mon Jun  2 13:21:34 2008
From: bulat.ziganshin at gmail.com (Bulat Ziganshin)
Date: Mon Jun  2 13:16:45 2008
Subject: [Haskell-cafe] Re: hmatrix
In-Reply-To: <e26d18e40806021006y7277edcbn556971a87380bad0@mail.gmail.com>
References: <e26d18e40805311209h4cd37689u30fe65e2ebd6c21e@mail.gmail.com>
	<484277D3.9020604@um.es>
	<e26d18e40806011145y4200e294yf8ffe08a426636b7@mail.gmail.com>
	<4843BF4A.2080800@um.es>
	<e26d18e40806021006y7277edcbn556971a87380bad0@mail.gmail.com>
Message-ID: <814976210.20080602212134@gmail.com>

Hello Anatoly,

>> Yes, I will try to write a simple version of Data.Array.ST...
> Wouldn't it be more efficient to use StorableArray, so you can cast

there is some difference between them - MutableByteArray# (used for
STUArray) is movable Haskell object which is subject to GC while
StorableArray has a fixed address and allocated through C malloc().
this makes MBA more appropriate for small arrays while SA should be
used for large ones because GC makes memory usage of program 3 times
larger


-- 
Best regards,
 Bulat                            mailto:Bulat.Ziganshin@gmail.com

From dons at galois.com  Mon Jun  2 13:24:01 2008
From: dons at galois.com (Don Stewart)
Date: Mon Jun  2 13:16:50 2008
Subject: [Haskell-cafe] hs-plugins compile error
In-Reply-To: <20080602130511.GA24905@netsoc.tcd.ie>
References: <20080602130511.GA24905@netsoc.tcd.ie>
Message-ID: <20080602172401.GB7534@scytale.galois.com>

Thanks, 

if possible, could you construct this as a patch against the darcs
branch, which lives here:

    http://code.haskell.org/~dons/code/hs-plugins

Cheers,
  Don

devriese:
> Hi,
> 
> I'm getting the compilation error that is actually logged on Hackage:
> 
> http://hackage.haskell.org/cgi-bin/hackage-scripts/package/plugins
> 
> Below is a small diff file that resolves these problems; I don't know
> what the proper protocol is for submitting these diffs but it may be
> useful to someone.
> 
> - E 
> 
> diff -ur plugins-1.2-orig/src/System/Plugins/Env.hs plugins-1.2/src/System/Plugins/Env.hs
> --- plugins-1.2-orig/src/System/Plugins/Env.hs	2008-06-02 14:57:59.000000000 +0100
> +++ plugins-1.2/src/System/Plugins/Env.hs	2008-06-02 15:00:25.000000000 +0100
> @@ -73,7 +73,7 @@
>  
>  import Control.Concurrent.MVar  ( MVar(), newMVar, withMVar )
>  
> -import Distribution.Package
> +import Distribution.Package hiding (packageName)
>  import Text.ParserCombinators.ReadP
>  
>  import qualified Data.Map as M
> diff -ur plugins-1.2-orig/src/System/Plugins/PackageAPI.hs plugins-1.2/src/System/Plugins/PackageAPI.hs
> --- plugins-1.2-orig/src/System/Plugins/PackageAPI.hs	2008-06-02 14:57:59.000000000 +0100
> +++ plugins-1.2/src/System/Plugins/PackageAPI.hs	2008-06-02 14:59:49.000000000 +0100
> @@ -40,7 +40,7 @@
>  
>  #if CABAL == 1 || __GLASGOW_HASKELL__ >= 604
>  import Distribution.InstalledPackageInfo
> -import Distribution.Package
> +import Distribution.Package hiding (depends, packageName)
>  #else
>  import System.Plugins.Package
>  #endif
> diff -ur plugins-1.2-orig/src/System/Plugins/ParsePkgConfCabal.hs plugins-1.2/src/System/Plugins/ParsePkgConfCabal.hs
> --- plugins-1.2-orig/src/System/Plugins/ParsePkgConfCabal.hs	2008-06-02 14:57:59.000000000 +0100
> +++ plugins-1.2/src/System/Plugins/ParsePkgConfCabal.hs	2008-06-02 14:58:56.000000000 +0100
> @@ -6,7 +6,7 @@
>    ) where
>  
>  import Distribution.InstalledPackageInfo
> -import Distribution.Package
> +import Distribution.Package hiding (depends)
>  import Distribution.Version
>  
>  import Data.Char             ( isSpace, isAlpha, isAlphaNum, isUpper, isDigit )
> 
> _______________________________________________
> Haskell-Cafe mailing list
> Haskell-Cafe@haskell.org
> http://www.haskell.org/mailman/listinfo/haskell-cafe
From ben.franksen at online.de  Mon Jun  2 14:40:14 2008
From: ben.franksen at online.de (Ben Franksen)
Date: Mon Jun  2 14:33:09 2008
Subject: [Haskell-cafe] Re: modelling C in Haskell ..
References: <5ae4f2ba0805292346y217d799du8a3e097a1e004e7a@mail.gmail.com>
	<B38D65AC-A9E6-4C12-B9D3-A2285477BBEE@fastmail.fm>
	<5ae4f2ba0805300029s69b1a1fdn73e07fe17b458b10@mail.gmail.com>
	<F77D2BD2-3BF5-48FA-8B51-723305860036@fastmail.fm>
	<5ae4f2ba0806010100j3788d29bj4aa0f5f4e3a8c5a8@mail.gmail.com>
Message-ID: <g21eqe$aig$1@ger.gmane.org>

Galchin, Vasili wrote:
> my knowledge of point-free is from category theory. in what sense is
> Haskell point-free handle namespace pollution?

In the sense that you can write e.g.

  f = g . h

instead of

  f x = g (h x)

thereby avoiding the need to give a name the argument to f.

Cheers
Ben

BTW,
A: No.
Q: Should I include quotations after my reply?

From ben.franksen at online.de  Mon Jun  2 14:53:30 2008
From: ben.franksen at online.de (Ben Franksen)
Date: Mon Jun  2 14:46:22 2008
Subject: [Haskell-cafe] Re: modelling C in Haskell ..
References: <5ae4f2ba0805292346y217d799du8a3e097a1e004e7a@mail.gmail.com>
Message-ID: <g21fja$enk$1@ger.gmane.org>

Galchin, Vasili wrote:
>
> typedef struct blah
> {
>        int val1;
> 
>        union {
> 
>            int  val2;
> 
>            struct {
> 
>                  int val3;
> 
>                  int val4;
>            }
>        }
> }    C_type;
> 
> question: in Haskell, can I embed definition of the "union" inside of the
> C typedef, i.e. recursion definition? Or must I have a separate definition
> for the "union" which I "instantiate" inside the Haskell "typedef", i.e.
> Haskell "data"?

No. Each definition of a data type must occur at the top-level. Also,
Haskell has only a very weak record system, a deficit that is generally
agreed to be one of Haskell's greatest weaknesses.

Like jcc, I'd also be interested what concrete problem prompted your
question. While I have often found it annoying that in Haskell e.g. record
labels are global in scope, I have never encountered a situation where I
wanted to have lexically nested data type declarations.

Cheers
Ben

From keith at oreilly.com  Mon Jun  2 14:56:46 2008
From: keith at oreilly.com (Keith Fahlgren)
Date: Mon Jun  2 14:49:29 2008
Subject: [Haskell-cafe] What is the maturity of Haskell Web Frameworks
In-Reply-To: <20080602172131.GA7534@scytale.galois.com>
References: <BLU108-W49A501FFE2AC204EE805FDF4BB0@phx.gbl>
	<20080602172131.GA7534@scytale.galois.com>
Message-ID: <4844426E.7010101@oreilly.com>

On 6/2/08 10:21 AM, Don Stewart wrote:
> aditya_siram:
>> I am building a web-app that, in broad strokes, allows a leader to
>> assign tasks to team members and allows team members to
>> accept/reject/pick tasks that they want to do. 
>>
>> I really like Haskell and I would like to use it to implement the
>> solution. Are frameworks like Happs ready? Not so much in terms of
>> documentation, but in functionality and stability. 
> 
> HAppS is nice (see hpaste.org for example, which is nice and simple, and
> has been running for over a year).
> 
> Another nice option in Haskell is using something like HStringTemplate
> or the xhtml combinators  with fastcgi hooked into GHC's concurrency
> mechanisms.

If you're interested in the background of rolling your own web stuff, I like 
Paul Brown's description of building perpubplat here: http://mult.ifario.us/t/blog


HTH,
Keith

From devriese at cs.tcd.ie  Mon Jun  2 15:23:32 2008
From: devriese at cs.tcd.ie (Edsko de Vries)
Date: Mon Jun  2 15:16:15 2008
Subject: [Haskell-cafe] hs-plugins compile error
In-Reply-To: <20080602172401.GB7534@scytale.galois.com>
References: <20080602130511.GA24905@netsoc.tcd.ie>
	<20080602172401.GB7534@scytale.galois.com>
Message-ID: <20080602192332.GB24905@netsoc.tcd.ie>

Hi Don,

Is this the kind of thing you mean (I'm not really a darcs user; this is
the patch created by darcs record):

[Hide some names to remove ambiguity errors
Edsko de Vries <edsko@edsko.net>**20080602202001] {
hunk ./src/System/Plugins/Env.hs 76
-import Distribution.Package
+import Distribution.Package hiding (packageName)
hunk ./src/System/Plugins/PackageAPI.hs 43
-import Distribution.Package
+import Distribution.Package hiding (depends, packageName)
hunk ./src/System/Plugins/ParsePkgConfCabal.hs 9
-import Distribution.Package
+import Distribution.Package hiding (depends)
}

Edsko
From ekmett at gmail.com  Mon Jun  2 15:25:28 2008
From: ekmett at gmail.com (Edward Kmett)
Date: Mon Jun  2 15:18:12 2008
Subject: [Haskell-cafe] Re: [ANN] bloomfilter 1.0 - Fast immutable and
	mutable Bloom filters
In-Reply-To: <4841CFB2.1020203@cs.pdx.edu>
References: <48408014.30401@serpentine.com> <20080531005127.4b330ff7@solaris>
	<slrng433li.olb.wnoise@ofb.net> <20080531202904.45054b49@solaris>
	<4841CFB2.1020203@cs.pdx.edu>
Message-ID: <7fb8f82f0806021225l7bccc5det817cd572b1f0ca14@mail.gmail.com>

On Sat, May 31, 2008 at 6:22 PM, Jim Snow <jsnow@cs.pdx.edu> wrote:
> In practice, one might use something like 32 hash tables.  This yields a
> false positive rate of 1/(2^32).  Their most obvious application is to store
> the dictionary for a spell checker in a space-efficient way, though I have a
> friend who wrote a paper on using them for router caches.

One minor technicality is that you don't actually use k separate hash
tables. You use k separate hash functions, and hash using different
functions into the same physical table with a goal of having
approximately half of
the bits in the table set when all of your data is hashed.
From jstrait at moonloop.net  Mon Jun  2 15:48:12 2008
From: jstrait at moonloop.net (Jon Strait)
Date: Mon Jun  2 15:51:46 2008
Subject: [Haskell-cafe] Vancouver Haskell users meeting
Message-ID: <48444E7C.7050602@moonloop.net>

An HTML attachment was scrubbed...
URL: http://www.haskell.org/pipermail/haskell-cafe/attachments/20080602/205dcae6/attachment-0001.htm
From kr.angelov at gmail.com  Mon Jun  2 16:35:22 2008
From: kr.angelov at gmail.com (Krasimir Angelov)
Date: Mon Jun  2 16:28:04 2008
Subject: [Haskell-cafe] Implementing ParseChart with Data.Map
Message-ID: <c97c08d20806021335w734106c4m436eea10b5b20ff3@mail.gmail.com>

Hi,

I have to write ParseChart implementation with Data.Map/Set. The chart
is type like this:

type Chart k v = Map k (Set v)

now I need operation like:

insert :: k -> v -> Chart k v -> Maybe (Chart k v)

where the result is (Just _) if the (k,v) is actually added to the
chart or Nothing if it was already there and nothing have to be done.
The straight forward implementation is:

case Map.lookup k chart of
  Nothing -> Just (Map.insert k (Set.singleton v) chart)
  Just set | Set.member v set -> Nothing
               | otherwise            -> Just (Map.insert k
(Set.insert v set) chart)

The problem with this is that both the Map and the Set are traversed
twice. The first time from lookup/member and the second time from
insert. Does someone have an idea how to do this with the current
libraries?

There are the Map.updateLookupWithKey and the Map.alter functions:

updateLookupWithKey :: Ord k => (k -> a -> Maybe a) -> k -> Map k a ->
(Maybe a,Map k a)
alter :: Ord k => (Maybe a -> Maybe a) -> k -> Map k a -> Map k a

which are the closest that I need. The problem is that the first
doesn't allow the client function to be called if there isn't matching
key in the map and the second is doesn't allow to return value from
the client function. What I really need is an alterLook?p function:

alterLook?p :: Ord k => (Maybe a -> (b,Maybe a)) -> k -> Map k a -> (b,Map k a)

The chart manipulation is in the tight loop of my application so I
need fast code. Any other ideas?

Regards,
   Krasimir
From jstrait at moonloop.net  Mon Jun  2 16:45:26 2008
From: jstrait at moonloop.net (Jon Strait)
Date: Mon Jun  2 16:48:58 2008
Subject: [Haskell-cafe] Vancouver Haskell users meeting
Message-ID: <48445BE6.4090108@moonloop.net>

Anyone else here from Vancouver (Canada)?  I thought it would be great 
to have a little informal get-together at a local cafe and share how 
we're currently using Haskell, or really anything (problems,  
comparisons, useful software tools, etc.) in relation to Haskell.

I'm scheduling a meeting for this Thursday, June 5th. for 7PM at 
<http://www.waazubee.com/content/directions.php> Waazubee Cafe - 
http://www.waazubee.com/content/directions.php  (at Commercial Dr. and 
1st Ave.) 

They have wireless internet access.  I'll get a table near the back, 
bring my laptop, and will have a copy of Hudak's SOE book (the front 
cover is impossible to miss) out on the table.

If anyone wants to meet, but this Thursday is not a good day for you, 
let me know what days are better and we'll move the meeting.  If anyone 
is sure that they will come this Thursday, you might let me know, so I 
can have an idea about the resistance in changing the day, if needed.

Thanks,

Jon
From dons at galois.com  Mon Jun  2 17:09:21 2008
From: dons at galois.com (Don Stewart)
Date: Mon Jun  2 17:02:06 2008
Subject: [Haskell-cafe] Vancouver Haskell users meeting
In-Reply-To: <48445BE6.4090108@moonloop.net>
References: <48445BE6.4090108@moonloop.net>
Message-ID: <20080602210921.GC7820@scytale.galois.com>

jstrait:
> Anyone else here from Vancouver (Canada)?  I thought it would be great 
> to have a little informal get-together at a local cafe and share how 
> we're currently using Haskell, or really anything (problems,  
> comparisons, useful software tools, etc.) in relation to Haskell.
> 
> I'm scheduling a meeting for this Thursday, June 5th. for 7PM at 
> <http://www.waazubee.com/content/directions.php> Waazubee Cafe - 
> http://www.waazubee.com/content/directions.php  (at Commercial Dr. and 
> 1st Ave.) 
> 
> They have wireless internet access.  I'll get a table near the back, 
> bring my laptop, and will have a copy of Hudak's SOE book (the front 
> cover is impossible to miss) out on the table.
> 
> If anyone wants to meet, but this Thursday is not a good day for you, 
> let me know what days are better and we'll move the meeting.  If anyone 
> is sure that they will come this Thursday, you might let me know, so I 
> can have an idea about the resistance in changing the day, if needed.

Great! I've added these details to the events listing on http://haskell.org
From ndmitchell at gmail.com  Mon Jun  2 18:07:55 2008
From: ndmitchell at gmail.com (Neil Mitchell)
Date: Mon Jun  2 18:00:46 2008
Subject: [Haskell-cafe] Implementing ParseChart with Data.Map
In-Reply-To: <c97c08d20806021335w734106c4m436eea10b5b20ff3@mail.gmail.com>
References: <c97c08d20806021335w734106c4m436eea10b5b20ff3@mail.gmail.com>
Message-ID: <404396ef0806021507r312db11ak8eefb6e4087afccf@mail.gmail.com>

Hi Krasimir,

> insert :: k -> v -> Chart k v -> Maybe (Chart k v)
>
> where the result is (Just _) if the (k,v) is actually added to the
> chart or Nothing if it was already there and nothing have to be done.

insertLookupWithKey :: Ord k => (k -> a -> a -> a) -> k -> a -> Map k
a -> (Maybe a, Map k a)

This should provide the information you need, without the double
traversal of the data structure.

Thanks

Neil
From tphyahoo at gmail.com  Mon Jun  2 18:15:50 2008
From: tphyahoo at gmail.com (Thomas Hartman)
Date: Mon Jun  2 18:08:31 2008
Subject: [Haskell-cafe] hs-plugins compile error
In-Reply-To: <20080602192332.GB24905@netsoc.tcd.ie>
References: <20080602130511.GA24905@netsoc.tcd.ie>
	<20080602172401.GB7534@scytale.galois.com>
	<20080602192332.GB24905@netsoc.tcd.ie>
Message-ID: <910ddf450806021515x4864ec26obeb735f2a53ea9fe@mail.gmail.com>

after darcs record,

 darcs send -o file.patch

and then send file.patch via email to the maintainer.

2008/6/2 Edsko de Vries <devriese@cs.tcd.ie>:
> Hi Don,
>
> Is this the kind of thing you mean (I'm not really a darcs user; this is
> the patch created by darcs record):
>
> [Hide some names to remove ambiguity errors
> Edsko de Vries <edsko@edsko.net>**20080602202001] {
> hunk ./src/System/Plugins/Env.hs 76
> -import Distribution.Package
> +import Distribution.Package hiding (packageName)
> hunk ./src/System/Plugins/PackageAPI.hs 43
> -import Distribution.Package
> +import Distribution.Package hiding (depends, packageName)
> hunk ./src/System/Plugins/ParsePkgConfCabal.hs 9
> -import Distribution.Package
> +import Distribution.Package hiding (depends)
> }
>
> Edsko
> _______________________________________________
> Haskell-Cafe mailing list
> Haskell-Cafe@haskell.org
> http://www.haskell.org/mailman/listinfo/haskell-cafe
>
From duncan.coutts at worc.ox.ac.uk  Mon Jun  2 18:28:29 2008
From: duncan.coutts at worc.ox.ac.uk (Duncan Coutts)
Date: Mon Jun  2 18:17:52 2008
Subject: [Haskell-cafe] Implementing ParseChart with Data.Map
In-Reply-To: <c97c08d20806021335w734106c4m436eea10b5b20ff3@mail.gmail.com>
References: <c97c08d20806021335w734106c4m436eea10b5b20ff3@mail.gmail.com>
Message-ID: <1212445709.15010.144.camel@localhost>


On Mon, 2008-06-02 at 22:35 +0200, Krasimir Angelov wrote:

> The problem with this is that both the Map and the Set are traversed
> twice. The first time from lookup/member and the second time from
> insert. Does someone have an idea how to do this with the current
> libraries?


> The chart manipulation is in the tight loop of my application so I
> need fast code. Any other ideas?

I'm not sure if it helps your application but we had a discussion on
#haskell the other day about Data.Map and were talking about a general
insert/modify/delete operator like:

modify :: k -> Map k e -> (e, Maybe e -> Map k e)

so it's a lookup that returns the element at k and also a continuation
that lets you rebuild a new map with an altered element. I guess that
doesn't account for the element not existing. There's probably a
generalisation that does.

Duncan

From duncan.coutts at worc.ox.ac.uk  Mon Jun  2 18:32:21 2008
From: duncan.coutts at worc.ox.ac.uk (Duncan Coutts)
Date: Mon Jun  2 18:21:41 2008
Subject: [Haskell-cafe] cabal install fail for happs-hsp-template
In-Reply-To: <910ddf450806020942n4bc2fac8kc454aeda446b77ee@mail.gmail.com>
References: <910ddf450806020942n4bc2fac8kc454aeda446b77ee@mail.gmail.com>
Message-ID: <1212445941.15010.148.camel@localhost>


On Mon, 2008-06-02 at 09:42 -0700, Thomas Hartman wrote:
> Can cabal install be made to work for this package?
> *****
> thartman@thartman-laptop:~>sudo cabal install happs-hsp-template
> [sudo] password for thartman:
> cabal: internal error: could not construct a valid install plan.
> The proposed (invalid) plan contained the following problems:
> Package Cabal is required by several packages, but they require
> inconsistent versions:
>   package ghc-6.8.2 requires Cabal-1.2.3.0
>   package plugins-1.2 requires Cabal-1.5.2

The package deps are not actually inconsistent, the problem is that the
current cabal-install dependency resolution algorithm is completely
naive and comes up with an invalid install plan.

I'll let people know when the new dep resolver for cabal-install is
ready (hopefully just a few days now). It should address this issue.

Duncan

From kr.angelov at gmail.com  Mon Jun  2 18:33:24 2008
From: kr.angelov at gmail.com (Krasimir Angelov)
Date: Mon Jun  2 18:26:04 2008
Subject: [Haskell-cafe] Implementing ParseChart with Data.Map
In-Reply-To: <404396ef0806021507r312db11ak8eefb6e4087afccf@mail.gmail.com>
References: <c97c08d20806021335w734106c4m436eea10b5b20ff3@mail.gmail.com>
	<404396ef0806021507r312db11ak8eefb6e4087afccf@mail.gmail.com>
Message-ID: <c97c08d20806021533p1cdc4f73g836b23d0cff96e40@mail.gmail.com>

Not completely! This is a possible implementation:

case insertLookupWithKey (\_ -> Set.union) k (Set.singleton v) chart of
  (Nothing, chart) -> Just chart
  (Just set, chart) | Set.member v set -> Nothing
                          | otherwise             -> Just chart

but notice that the set is still traversed twice.

On Tue, Jun 3, 2008 at 12:07 AM, Neil Mitchell <ndmitchell@gmail.com> wrote:
> Hi Krasimir,
>
>> insert :: k -> v -> Chart k v -> Maybe (Chart k v)
>>
>> where the result is (Just _) if the (k,v) is actually added to the
>> chart or Nothing if it was already there and nothing have to be done.
>
> insertLookupWithKey :: Ord k => (k -> a -> a -> a) -> k -> a -> Map k
> a -> (Maybe a, Map k a)
>
> This should provide the information you need, without the double
> traversal of the data structure.
>
> Thanks
>
> Neil
>
From ndmitchell at gmail.com  Mon Jun  2 18:41:30 2008
From: ndmitchell at gmail.com (Neil Mitchell)
Date: Mon Jun  2 18:34:11 2008
Subject: [Haskell-cafe] Implementing ParseChart with Data.Map
In-Reply-To: <c97c08d20806021533p1cdc4f73g836b23d0cff96e40@mail.gmail.com>
References: <c97c08d20806021335w734106c4m436eea10b5b20ff3@mail.gmail.com>
	<404396ef0806021507r312db11ak8eefb6e4087afccf@mail.gmail.com>
	<c97c08d20806021533p1cdc4f73g836b23d0cff96e40@mail.gmail.com>
Message-ID: <404396ef0806021541v6d62f6ffgb198714f105100ff@mail.gmail.com>

Hi

> case insertLookupWithKey (\_ -> Set.union) k (Set.singleton v) chart of
>  (Nothing, chart) -> Just chart
>  (Just set, chart) | Set.member v set -> Nothing
>                          | otherwise             -> Just chart
>
> but notice that the set is still traversed twice.

Yes, I missed that bit. I don't see any way of reducing that, other
than using an unsafePerformIO and IORef to track the combining
function - which is probably a really bad idea.

Thanks

Neil
From ryani.spam at gmail.com  Mon Jun  2 18:52:29 2008
From: ryani.spam at gmail.com (Ryan Ingram)
Date: Mon Jun  2 18:45:09 2008
Subject: [Haskell-cafe] [Newbie question] -- Looping stdin until condition
	is met
In-Reply-To: <1212192870.15596.1255975237@webmail.messagingengine.com>
References: <20080531002837.0F09A3C8001@banane.furius.ca>
	<bc36e24d0805301654x71d00170vcc042bd4cd42a107@mail.gmail.com>
	<1212192870.15596.1255975237@webmail.messagingengine.com>
Message-ID: <2f9b2d30806021552x36e5bcabw2727b04abfa9525f@mail.gmail.com>

On 5/30/08, Martin Blais <blais@furius.ca> wrote:
> Dear Philip, could you point your virtual finger towards a
> reference/paper/book/any-bleeping-thing that would help this simple
> beginner understand why it doesn't work in this case? I'm trying to
> picture why a "read" function that terminates the program would be
> useful anywhere. In fact, any library function other than something like
> UNIX's "exit" or "kill" which terminates my program is not really
> welcome in any of my computer programs, but then again, I haven't yet
> been illuminated by the genie of pure functional languages.  A reference
> would be awesome.

As others have pointed out, the reason why it doesn't work is due to
lazy evaluation; the exception is "hidden" in a pure value and isn't
triggered until some other bit of code causes the pure value to be
evaluated.  You can force the exception to be generated in your catch
block by using "seq" (or "$!", which is implemented using "seq").
This forces the evaluation to happen at that point, although there are
a lot of gotchas involved; for Int it works fine, though.

Your question, then, requires asking "why would you want to hide an
exception in a pure value"?  The answer to that is quite interesting,
but here's a simpler example that might enlighten you:

head :: [a] -> a
head (x:_) = x
head _ = error "head: empty list"

Just as you are required to prove before calling "head" that you
aren't passing an empty list, for your program to be total, you should
prove before calling "read" that the string parses properly.  If you
can't provide that proof (because, in this case, the string is
provided by the user), you should be using another function for
parsing.

Don suggested "reads" to implement "maybeRead", which seems like a
great idea to me.

  -- ryan
From ndmitchell at gmail.com  Mon Jun  2 19:07:32 2008
From: ndmitchell at gmail.com (Neil Mitchell)
Date: Mon Jun  2 19:00:13 2008
Subject: [Haskell-cafe] [Newbie question] -- Looping stdin until condition
	is met
In-Reply-To: <20080530235828.GI25572@scytale.galois.com>
References: <20080531002837.0F09A3C8001@banane.furius.ca>
	<20080530235828.GI25572@scytale.galois.com>
Message-ID: <404396ef0806021607x4b679180i8c3ec5255f2fe8e5@mail.gmail.com>

Hi

> The best thing to do is bypass read and use 'reads' to define your
> own safe read.
>
>    maybeRead :: Read a => String -> Maybe a
>    maybeRead s = case reads s of
>        [(x, "")] -> Just x
>        _         -> Nothing

Or just use the Safe package:
http://hackage.haskell.org/cgi-bin/hackage-scripts/package/safe

http://hackage.haskell.org/packages/archive/safe/0.2/doc/html/Safe.html#v%3AreadMay

Thanks

Neil
From vigalchin at gmail.com  Tue Jun  3 00:11:54 2008
From: vigalchin at gmail.com (Galchin, Vasili)
Date: Tue Jun  3 00:04:39 2008
Subject: [Haskell-cafe] ghc 6.8.2 issue
In-Reply-To: <1212403100.15010.133.camel@localhost>
References: <5ae4f2ba0806012207i2797be95kf773d0cf75d6b39@mail.gmail.com>
	<1212403100.15010.133.camel@localhost>
Message-ID: <5ae4f2ba0806022111l33fecf27xfbd6ee5f7dabf35f@mail.gmail.com>

Hi Duncan,

     Not sure I agree the behavior is ok. E.g. here is a build of mmap:

vigalchin@ubuntu:~/FTP/Haskell/bytestring-mmap-0.2.0$ runhaskell Setup.lhs
clean
cleaning...
vigalchin@ubuntu:~/FTP/Haskell/bytestring-mmap-0.2.0$ runhaskell Setup.lhs
configure
Configuring bytestring-mmap-0.2.0...
vigalchin@ubuntu:~/FTP/Haskell/bytestring-mmap-0.2.0$ runhaskell Setup.lhs
build
Preprocessing library bytestring-mmap-0.2.0...
Building bytestring-mmap-0.2.0...
[1 of 3] Compiling System.IO.Posix.MMap.Internal (
System/IO/Posix/MMap/Internal.hs, dist/build/System/IO/Posix/MMap/Internal.o
)
[2 of 3] Compiling System.IO.Posix.MMap.Lazy ( System/IO/Posix/MMap/Lazy.hs,
dist/build/System/IO/Posix/MMap/Lazy.o )
[3 of 3] Compiling System.IO.Posix.MMap ( System/IO/Posix/MMap.hs,
dist/build/System/IO/Posix/MMap.o )
/usr/bin/ar: creating dist/build/libHSbytestring-mmap-0.2.0.a

at this point rebuild and install the "unix" package ...

vigalchin@ubuntu:~/FTP/Haskell/bytestring-mmap-0.2.0$ runhaskell Setup.lhs
clean
cleaning...
vigalchin@ubuntu:~/FTP/Haskell/bytestring-mmap-0.2.0$ runhaskell Setup.lhs
configure
Configuring bytestring-mmap-0.2.0...
vigalchin@ubuntu:~/FTP/Haskell/bytestring-mmap-0.2.0$ runhaskell Setup.lhs
build
Setup.lhs: error reading dist/setup-config; run "setup configure" command?

"dist/setup-config" is not being populated at the end. In your response
below, are you saying that teh segfaults occur because ghc itself relies on
the "unix" package?

Thanks, Vasili




On Mon, Jun 2, 2008 at 5:38 AM, Duncan Coutts <duncan.coutts@worc.ox.ac.uk>
wrote:

>
> On Mon, 2008-06-02 at 00:07 -0500, Galchin, Vasili wrote:
> > Hello,
> >
> >       I have been developing new code for the "unix" package. I have
> > run into what I think are ghc 6.8.2 anomalies but couldn't see a
> > pattern. Possibly now I do. I have been using the 32-bit x86 ghc
> > binary that I downloaded from http://www.haskell.org and running on
> > Ubuntu Linux. I am pretty I can repeat now. Everything is ok until I
> > do "sudo runhaskell Setup.hs install" which installs a new "unix"
> > package that I just built. Of course the "intall" installs
> > into /usr/local/lib/unix-2.3.0.0/ghc-6.8.2. The "install" seems to
> > destroy some ghc compiler state under /usr/local ...
>
> That sounds right. You're replacing the unix-2.3.0.0 library that comes
> with ghc-6.8.2 with your own version. It is highly unlikely to be ABI
> compatible with the one you are replacing and so all the other packages
> that already depends on the existing unix-2.3.0.0 library end up broken.
> You'd expect this kind of breakage to be exposed as link errors and
> segfaults.
>
> I suggest you do not replace any of the libraries that come with ghc. To
> be more precise, it is perfectly ok to *add new versions* but it is not
> ok to *replace existing versions* without rebuilding all the other libs
> that depend on it.
>
> Make sense?
>
> So if you really want to make changes to the unix lib, make sure you
> change the version number too. I also suggest not installing the
> packages as root, just install them locally. That way you can guarantee
> you never mess up your ghc install. You would be able to revert to a
> clean ghc install just by removing your
> ~/.ghc/$arch/ghc-6.8.2/package.conf file which will unregister *all*
> locally registered packages. To unregister individual packages use
> ghc-pkg --user unregister $pkgname
>
> Duncan
>
>
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From ajb at spamcop.net  Tue Jun  3 00:47:30 2008
From: ajb at spamcop.net (ajb@spamcop.net)
Date: Tue Jun  3 00:40:20 2008
Subject: [Haskell-cafe] Mutually Recursive Modules
In-Reply-To: <4843FBCD.8000001@charter.net>
References: <4843F81B.7060808@richardg.name> <4843FBCD.8000001@charter.net>
Message-ID: <20080603004730.dzo6cyduskgsgo0w-nwo@webmail.spamcop.net>

G'day all.

Quoting Isaac Dupree <isaacdupree@charter.net>:

> Luckily,
> it is very often the case that your code will be better off anyway if
> refactored to have less module recursion. (though not always.)

Nonetheless, I prefer not to leave the robustness of my code to luck.
Besides, if I liked structuring code around artificial language
restrictions, I'd be programming in C, not Haskell.

Cheers,
Andrew Bromage
From vigalchin at gmail.com  Tue Jun  3 01:04:26 2008
From: vigalchin at gmail.com (Galchin, Vasili)
Date: Tue Jun  3 00:57:07 2008
Subject: [Haskell-cafe] ghc 6.8.2 issue
In-Reply-To: <1212403100.15010.133.camel@localhost>
References: <5ae4f2ba0806012207i2797be95kf773d0cf75d6b39@mail.gmail.com>
	<1212403100.15010.133.camel@localhost>
Message-ID: <5ae4f2ba0806022204u51fb86dbs202783e73bb08573@mail.gmail.com>

Duncan,

     By installing localling, I "runhaskell Setup.hs configure
--prefix=$HOME" plus add local path to LD_LIBRARY_PATH and LD_RUN_PATH? On
Linux, does ghc use .so's or is it linked statically?

Vasili

On Mon, Jun 2, 2008 at 5:38 AM, Duncan Coutts <duncan.coutts@worc.ox.ac.uk>
wrote:

>
> On Mon, 2008-06-02 at 00:07 -0500, Galchin, Vasili wrote:
> > Hello,
> >
> >       I have been developing new code for the "unix" package. I have
> > run into what I think are ghc 6.8.2 anomalies but couldn't see a
> > pattern. Possibly now I do. I have been using the 32-bit x86 ghc
> > binary that I downloaded from http://www.haskell.org and running on
> > Ubuntu Linux. I am pretty I can repeat now. Everything is ok until I
> > do "sudo runhaskell Setup.hs install" which installs a new "unix"
> > package that I just built. Of course the "intall" installs
> > into /usr/local/lib/unix-2.3.0.0/ghc-6.8.2. The "install" seems to
> > destroy some ghc compiler state under /usr/local ...
>
> That sounds right. You're replacing the unix-2.3.0.0 library that comes
> with ghc-6.8.2 with your own version. It is highly unlikely to be ABI
> compatible with the one you are replacing and so all the other packages
> that already depends on the existing unix-2.3.0.0 library end up broken.
> You'd expect this kind of breakage to be exposed as link errors and
> segfaults.
>
> I suggest you do not replace any of the libraries that come with ghc. To
> be more precise, it is perfectly ok to *add new versions* but it is not
> ok to *replace existing versions* without rebuilding all the other libs
> that depend on it.
>
> Make sense?
>
> So if you really want to make changes to the unix lib, make sure you
> change the version number too. I also suggest not installing the
> packages as root, just install them locally. That way you can guarantee
> you never mess up your ghc install. You would be able to revert to a
> clean ghc install just by removing your
> ~/.ghc/$arch/ghc-6.8.2/package.conf file which will unregister *all*
> locally registered packages. To unregister individual packages use
> ghc-pkg --user unregister $pkgname
>
> Duncan
>
>
-------------- next part --------------
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From aruiz at um.es  Tue Jun  3 03:27:54 2008
From: aruiz at um.es (Alberto Ruiz)
Date: Tue Jun  3 03:20:38 2008
Subject: [Haskell-cafe] Re: hmatrix
In-Reply-To: <e26d18e40806021006y7277edcbn556971a87380bad0@mail.gmail.com>
References: <e26d18e40805311209h4cd37689u30fe65e2ebd6c21e@mail.gmail.com>	
	<484277D3.9020604@um.es>	
	<e26d18e40806011145y4200e294yf8ffe08a426636b7@mail.gmail.com>	
	<4843BF4A.2080800@um.es>
	<e26d18e40806021006y7277edcbn556971a87380bad0@mail.gmail.com>
Message-ID: <4844F27A.2080208@um.es>

Anatoly Yakovenko wrote:
>>> do you have any plans to provide an interface for inplace updates?
>> Yes, I will try to write a simple version of Data.Array.ST...
>>
> 
> I can try to help you, although I still dont quite grok monads.
> Wouldn't it be more efficient to use StorableArray, so you can cast
> from and to C?  I am not sure how vectors and matrixes are represented
> in C, but I imagine it should be possible to manipulate them without
> resorting to copying between haskell and C.
> 
That's right, the correspondence with StorableArray is direct, and 
efficient conversion can be easily added to the library. I mentioned the 
idea of Data.Array.ST to have also the possibility of writing pure code, 
without IO, internally implemented with inplace updates.

Alberto
From bulat.ziganshin at gmail.com  Tue Jun  3 03:37:21 2008
From: bulat.ziganshin at gmail.com (Bulat Ziganshin)
Date: Tue Jun  3 03:32:52 2008
Subject: [Haskell-cafe] Re: hmatrix
In-Reply-To: <4844F27A.2080208@um.es>
References: <e26d18e40805311209h4cd37689u30fe65e2ebd6c21e@mail.gmail.com>
	<484277D3.9020604@um.es>
	<e26d18e40806011145y4200e294yf8ffe08a426636b7@mail.gmail.com>
	<4843BF4A.2080800@um.es>
	<e26d18e40806021006y7277edcbn556971a87380bad0@mail.gmail.com>
	<4844F27A.2080208@um.es>
Message-ID: <731290342.20080603113721@gmail.com>

Hello Alberto,

Tuesday, June 3, 2008, 11:27:54 AM, you wrote:

>>> Yes, I will try to write a simple version of Data.Array.ST...
> That's right, the correspondence with StorableArray is direct, and
> efficient conversion can be easily added to the library. I mentioned the
> idea of Data.Array.ST to have also the possibility of writing pure code,
> without IO, internally implemented with inplace updates.

STRef/STArray operations are just IORef/IOArray operations imported in
some way/ you can easily import any other operations to ST monad as
far as you use rank-2 types to guarantee that impureness will not
escape the runST call. look into unsafeIOtoST function

providing unmovable STUArray variant may be a good idea


-- 
Best regards,
 Bulat                            mailto:Bulat.Ziganshin@gmail.com

From ketil at malde.org  Tue Jun  3 04:26:47 2008
From: ketil at malde.org (Ketil Malde)
Date: Tue Jun  3 04:19:12 2008
Subject: [Haskell-cafe] [ANN] bloomfilter 1.0 - Fast immutable and mutable
	Bloom filters
In-Reply-To: <910ddf450805310933l668697b6w5816c98c7305c6cd@mail.gmail.com>
	(Thomas Hartman's message of "Sat\, 31 May 2008 09\:33\:52 -0700")
References: <48408014.30401@serpentine.com>
	<910ddf450805310933l668697b6w5816c98c7305c6cd@mail.gmail.com>
Message-ID: <87tzgancu0.fsf@malde.org>

"Thomas Hartman" <tphyahoo@gmail.com> writes:

> What kind of speed do you get on your laptop for Data.Set? How much
> faster is the bloom filter?

I tried to modify examples/Words.hs to use Data.Set insted.  The
results look like this (first Bloom, second Data.Set, both compiled
with -O2):

    nmd9999:..filter/examples % ./Words   
    57025 words
    0.013326ss to count words
    Bloom { 4194304 bits } 
    0.050608ss to construct filter
    0.034806ss to query every element

    nmd9999:..filter/examples % ./WordsS                
    57025 words
    0.013291ss to count words
    False
    0.755115ss to construct filter
    0.423289ss to query every element

In order to avoid printing the entire set, while still evaluating it,
I replaced the printing of the set with printing the result of a
search for a non-existing element - I should really use a strict
insert, I guess.  Anyway, this hopefully gives an indication - looks
like a factor of 10 in this case, but it will depend on the size of
the data - more data, greater improvement.

BTW, Nice work, Bryan!  I have plans for this.

-k
-- 
If I haven't seen further, it is by standing in the footprints of giants
From aruiz at um.es  Tue Jun  3 04:56:50 2008
From: aruiz at um.es (Alberto Ruiz)
Date: Tue Jun  3 04:52:49 2008
Subject: [Haskell-cafe] Re: hmatrix
In-Reply-To: <731290342.20080603113721@gmail.com>
References: <e26d18e40805311209h4cd37689u30fe65e2ebd6c21e@mail.gmail.com>
	<484277D3.9020604@um.es>
	<e26d18e40806011145y4200e294yf8ffe08a426636b7@mail.gmail.com>
	<4843BF4A.2080800@um.es>
	<e26d18e40806021006y7277edcbn556971a87380bad0@mail.gmail.com>
	<4844F27A.2080208@um.es> <731290342.20080603113721@gmail.com>
Message-ID: <48450752.4080307@um.es>

Bulat Ziganshin wrote:
> Hello Alberto,
> 
> Tuesday, June 3, 2008, 11:27:54 AM, you wrote:
> 
>>>> Yes, I will try to write a simple version of Data.Array.ST...
>> That's right, the correspondence with StorableArray is direct, and
>> efficient conversion can be easily added to the library. I mentioned the
>> idea of Data.Array.ST to have also the possibility of writing pure code,
>> without IO, internally implemented with inplace updates.
> 
> STRef/STArray operations are just IORef/IOArray operations imported in
> some way/ you can easily import any other operations to ST monad as
> far as you use rank-2 types to guarantee that impureness will not
> escape the runST call. look into unsafeIOtoST function

Good! So you can easily "hide" the IO operations in the ST monad. I will 
definitely look into it.

> providing unmovable STUArray variant may be a good idea
> 
> 

Many thanks Bulat!
From duncan.coutts at worc.ox.ac.uk  Tue Jun  3 05:05:26 2008
From: duncan.coutts at worc.ox.ac.uk (Duncan Coutts)
Date: Tue Jun  3 04:54:45 2008
Subject: [Haskell-cafe] ghc 6.8.2 issue
In-Reply-To: <5ae4f2ba0806022111l33fecf27xfbd6ee5f7dabf35f@mail.gmail.com>
References: <5ae4f2ba0806012207i2797be95kf773d0cf75d6b39@mail.gmail.com>
	<1212403100.15010.133.camel@localhost>
	<5ae4f2ba0806022111l33fecf27xfbd6ee5f7dabf35f@mail.gmail.com>
Message-ID: <1212483926.15010.192.camel@localhost>


On Mon, 2008-06-02 at 23:11 -0500, Galchin, Vasili wrote:
> at this point rebuild and install the "unix" package ...
> 
> vigalchin@ubuntu:~/FTP/Haskell/bytestring-mmap-0.2.0$ runhaskell
> Setup.lhs clean
> cleaning...
> vigalchin@ubuntu:~/FTP/Haskell/bytestring-mmap-0.2.0$ runhaskell
> Setup.lhs configure
> Configuring bytestring-mmap-0.2.0...
> vigalchin@ubuntu:~/FTP/Haskell/bytestring-mmap-0.2.0$ runhaskell
> Setup.lhs build
> Setup.lhs: error reading dist/setup-config; run "setup configure"
> command?
> 
> "dist/setup-config" is not being populated at the end. In your
> response below, are you saying that teh segfaults occur because ghc
> itself relies on the "unix" package?

Something like that yes.

You're running runhaskell Setup.lhs and that loads and runs code from
the Cabal library. The Cabal library depends on the process library
which depends on the unix library. So by replacing the same version of
the unix package you're breaking everything else which depends on it,
including Cabal and thus runhaskell Setup.lhs.

So the solution is to not do that. Don't re-install the exact same
version of any of the core libs that come with ghc. Adding new versions
is fine, replacing existing versions is not fine because it breaks all
the other packages that were already built against that package.

Duncan

From duncan.coutts at worc.ox.ac.uk  Tue Jun  3 05:11:06 2008
From: duncan.coutts at worc.ox.ac.uk (Duncan Coutts)
Date: Tue Jun  3 05:00:23 2008
Subject: [Haskell-cafe] ghc 6.8.2 issue
In-Reply-To: <5ae4f2ba0806022204u51fb86dbs202783e73bb08573@mail.gmail.com>
References: <5ae4f2ba0806012207i2797be95kf773d0cf75d6b39@mail.gmail.com>
	<1212403100.15010.133.camel@localhost>
	<5ae4f2ba0806022204u51fb86dbs202783e73bb08573@mail.gmail.com>
Message-ID: <1212484266.15010.199.camel@localhost>


On Tue, 2008-06-03 at 00:04 -0500, Galchin, Vasili wrote:
> Duncan,
> 
>      By installing localling, I "runhaskell Setup.hs configure
> --prefix=$HOME" plus add local path to LD_LIBRARY_PATH and
> LD_RUN_PATH? On Linux, does ghc use .so's or is it linked statically?

ghc is linked statically but when you do things like runhaskell Setup.hs
you're asking ghc to dynamically load packages. runhaskell/runghc is
basically a form of ghci, and ghci does dynamic code loading. If you've
broken some of the packages that ghci loads and runs code from then
you'll run into problems, mysterious segfaults and the like.

As I understand it, in the next version of ghc it will track the ABI of
each package so we would be able to detect when people replace packages
with ones with the same version but with a different ABI (as you've been
doing) and refuse to link or run in those cases rather than running and
ending up with segfaults.

Duncan

From apfelmus at quantentunnel.de  Tue Jun  3 05:14:58 2008
From: apfelmus at quantentunnel.de (apfelmus)
Date: Tue Jun  3 05:07:51 2008
Subject: [Haskell-cafe] Re: appending an element to a list
In-Reply-To: <3c4d5adf0806012204p25133bdaxbc22955b70f094ff@mail.gmail.com>
References: <483EE208.2010601@inf.fu-berlin.de>
	<483EF36B.5040100@daimi.au.dk>	<48404039.6030605@cisco.com>
	<48405717.20206@daimi.au.dk>	<87r6bja609.fsf@hbox.dyndns.org>	<3c4d5adf0805302159o23113ad2sb24754e02789bb06@mail.gmail.com>	<48414C2B.9010606@daimi.au.dk>
	<g1tjk4$c4i$1@ger.gmane.org>
	<3c4d5adf0806012204p25133bdaxbc22955b70f094ff@mail.gmail.com>
Message-ID: <g2322j$sig$1@ger.gmane.org>

Abhay Parvate wrote:
> I somehow thought it would be easy to talk about complexity of calculating
> individual elements in an infinite list should be sufficient, but that seems
> to be involved, and my over-generalization doesn't seem to work. Thanks for
> the link; particularly it has reference to Wadler's papers exactly on this
> problem.

Note however that Wadler's and similar formalisms are still a 
unsatisfactory in that they are quite clumsy to work with, it's quite 
tedious/impossible to analyze examples with a lot of lazy evaluation. 
But they are a good guideline.

In his book about purely functional data structures [1], Okasaki takes a 
different approach; each node of a data structure is given a debit, a 
cost to evaluate it. For instance, consider

   xs = x1 : x2 : x3 : ... : xn : []
           1    1    1 ... 1    1  0

   ys = y1 : y2 : y3 : ... : ym : []
           1    1    1 ... 1    1  0

The numbers below indicate the time it takes to evaluate the node to 
weak head normal form. For demonstration purposes, I arbitrarily chose 1 
for each (:) here.

The combined list will then have debits like

   xs ++ ys = x1 : x2 : x3 : ... : xn : y1 : y2 : y3 : ... : ym : []
                 2    2    2 ... 2    2    1    1    1 ... 1    1  0

In other words, the ys list is copied verbatim but each element of xs 
incurs an additional cost of 1, corresponding to one step in the 
evaluation of the concatenation with (++).

In order to force/inspect a constructor/node, you have to pay off its 
debits first. In the above example,  head (xs ++ ys)  would have to pay 
2 units of time (one unit for  head xs  and one for the (++)). Now, the 
thing about debits is that we can relocate them to the top and only 
overestimate the total running time if we do that. For instance, we 
could push all debits to the top

   xs ++ ys = x1   : x2 : x3 : ... : xn : y1 : y2 : y3 : ... : ym : []
                 2n+m   0    0 ... 0    0    0    0    0 ... 0    0  0

so that evaluating  head (xs ++ ys)  is now estimated to cost (2n+m) 
units of time while the rest is free/fully evaluated.

The above example is rather useless, but consider the case  n == m  and

   xs = x1 : x2 : x3 : ... : xn : []
           0    0    0 ... 0    0  0

   ys = y1 : y2 : y3 : ... : yn : []
           0    0    0 ... 0    0  0

i.e. two fully evaluated lists of the same length. Then, we have

   xs ++ reverse ys =
      x1 : x2 : x3 : ... : xn : yn : y{n-1} : ... : y1 : []
         1    1    1 ... 1    1    n        0 ... 0    0  0

because reversing the list ys is "monolithic", i.e. looking at its  head 
  already forces the tail of the list. But now, we can distribute the 
debits upwards

   xs ++ reverse ys =
      x1 : x2 : x3 : ... : xn : yn : y{n-1} : ... : y1 : []
         2    2    2 ... 2    2    0        0 ... 0    0  0

and thereby amortize the cost of reversing the second lists over the n 
elements of the first list. This is used in the implementation of purely 
functional queues, see also Okasaki's book.


[1]: Chris Okasaki. Purely Function Data Structures.
      http://www.cs.cmu.edu/~rwh/theses/okasaki.pdf
      (This is the thesis on which the book is based.)


Regards,
apfelmus

From bulat.ziganshin at gmail.com  Tue Jun  3 05:42:11 2008
From: bulat.ziganshin at gmail.com (Bulat Ziganshin)
Date: Tue Jun  3 05:37:59 2008
Subject: [Haskell-cafe] Re: hmatrix
In-Reply-To: <48450752.4080307@um.es>
References: <e26d18e40805311209h4cd37689u30fe65e2ebd6c21e@mail.gmail.com>
	<484277D3.9020604@um.es>
	<e26d18e40806011145y4200e294yf8ffe08a426636b7@mail.gmail.com>
	<4843BF4A.2080800@um.es>
	<e26d18e40806021006y7277edcbn556971a87380bad0@mail.gmail.com>
	<4844F27A.2080208@um.es> <731290342.20080603113721@gmail.com>
	<48450752.4080307@um.es>
Message-ID: <483842413.20080603134211@gmail.com>

Hello Alberto,

Tuesday, June 3, 2008, 12:56:50 PM, you wrote:

> Good! So you can easily "hide" the IO operations in the ST monad. I will
> definitely look into it.

from implementation POV ST monad is nothing but renamed IO monad which
exports only subset of its operations which are guaranteed to safe.
or, saying in other words, it's just type hackery around IO monad that
provides safe operations

it's possible to define ST monad and its operations as following:

newtype ST s a = forall s. ST_Constructor (IO a)

unsafeIOtoSt action = ST_Constructor action

runST (ST_Constructor action) = unsafePerformIO action

newtype STRef s a = forall s. STRef (IORef a)

readSTRef (STRef ref)  =  unsafeIOtoSt (readIORef ref)

and so on. GHC uses technically (but not ideologically!) different
implementation where both monads are specializations of one generic
type. while Hugs afair uses exactly this approach. you may also look
at ArrayRef lib which reimplements arrays/refs for both compilers in
more unified way

anyway, because ST is just IO monad modulo type tricks, you can
execute any IO action inside ST by lifting it with unsafeIOtoSt

-- 
Best regards,
 Bulat                            mailto:Bulat.Ziganshin@gmail.com

From yann at kierun.org  Tue Jun  3 06:30:26 2008
From: yann at kierun.org (Yann Golanski)
Date: Tue Jun  3 06:23:09 2008
Subject: [Haskell-cafe] Rotating backdrop (aka learning Haskell)
In-Reply-To: <20080520081557.GA18833@kierun.org>
References: <20080520081557.GA18833@kierun.org>
Message-ID: <20080603103026.GA10131@kierun.org>

First version is available at:
  http://www.kierun.org/backdropper-1.0.tbz2
It is minimal but does the trick of randomly rotating backgrounds.

Features to add are only rotate during work hours, making sure that all
images are shown within a day and a nice GUI. 

Criticism welcome.

-- 
yann@kierun.org             -= H+ =-             www.kierun.org
   PGP:   009D 7287 C4A7 FD4F 1680  06E4 F751 7006 9DE2 6318
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From gale at sefer.org  Tue Jun  3 07:45:11 2008
From: gale at sefer.org (Yitzchak Gale)
Date: Tue Jun  3 07:37:51 2008
Subject: [Haskell-cafe] Implementing ParseChart with Data.Map
In-Reply-To: <404396ef0806021541v6d62f6ffgb198714f105100ff@mail.gmail.com>
References: <c97c08d20806021335w734106c4m436eea10b5b20ff3@mail.gmail.com>
	<404396ef0806021507r312db11ak8eefb6e4087afccf@mail.gmail.com>
	<c97c08d20806021533p1cdc4f73g836b23d0cff96e40@mail.gmail.com>
	<404396ef0806021541v6d62f6ffgb198714f105100ff@mail.gmail.com>
Message-ID: <2608b8a80806030445x5272d3e2o78e3cb4aef6821ed@mail.gmail.com>

Krasimir Angelov wrote:
>> but notice that the set is still traversed twice.

Neil Mitchell wrote:
> I don't see any way of reducing that

Yeah, it looks like the Data.Set (and Data.IntSet) library
is missing the functions

insertMember :: Ord a => a -> Set a -> (Bool, Set a)
deleteMember :: Ord a => a -> Set a -> (Bool, Set a)

analagous to splitMember. It should be easy to write
those functions. If you do that for yourself, consider
making a patch of them and submitting the patch
as a library proposal.

But anyway, a set lookup is very cheap, even for a
set that is quite large. You may want to try just doing
the extra lookup, it might be good enough for you.
At least you eliminated the Map lookup.

Regards,
Yitz
From kr.angelov at gmail.com  Tue Jun  3 07:54:03 2008
From: kr.angelov at gmail.com (Krasimir Angelov)
Date: Tue Jun  3 07:46:43 2008
Subject: [Haskell-cafe] Implementing ParseChart with Data.Map
In-Reply-To: <2608b8a80806030445x5272d3e2o78e3cb4aef6821ed@mail.gmail.com>
References: <c97c08d20806021335w734106c4m436eea10b5b20ff3@mail.gmail.com>
	<404396ef0806021507r312db11ak8eefb6e4087afccf@mail.gmail.com>
	<c97c08d20806021533p1cdc4f73g836b23d0cff96e40@mail.gmail.com>
	<404396ef0806021541v6d62f6ffgb198714f105100ff@mail.gmail.com>
	<2608b8a80806030445x5272d3e2o78e3cb4aef6821ed@mail.gmail.com>
Message-ID: <c97c08d20806030454i2e3cb374x8cd30bc4378838a7@mail.gmail.com>

I actually made my own copy of Data.Map and added an extra:

alterLook?p :: Ord k => (Maybe a -> (b,Maybe a)) -> k -> Map k a -> (b,Map k a)

function. I also changed my data type to:

type ParseChart k v = Map k (Map v ())

so I don't have to copy the Data.Set module also. Unfortunately this
doesn't give much better performance - 5734 msec instead of 5828 msec.
Fortunately I found that there is a way to avoid to use Map at all in
one common case. This gave me time about 5024 msec.

Regards,
   Krasimir


On 6/3/08, Yitzchak Gale <gale@sefer.org> wrote:
> Krasimir Angelov wrote:
> >> but notice that the set is still traversed twice.
>
> Neil Mitchell wrote:
> > I don't see any way of reducing that
>
> Yeah, it looks like the Data.Set (and Data.IntSet) library
> is missing the functions
>
> insertMember :: Ord a => a -> Set a -> (Bool, Set a)
> deleteMember :: Ord a => a -> Set a -> (Bool, Set a)
>
> analagous to splitMember. It should be easy to write
> those functions. If you do that for yourself, consider
> making a patch of them and submitting the patch
> as a library proposal.
>
> But anyway, a set lookup is very cheap, even for a
> set that is quite large. You may want to try just doing
> the extra lookup, it might be good enough for you.
> At least you eliminated the Map lookup.
>
> Regards,
> Yitz
>
From ahey at iee.org  Tue Jun  3 09:28:29 2008
From: ahey at iee.org (Adrian Hey)
Date: Tue Jun  3 09:21:13 2008
Subject: [Haskell-cafe] Implementing ParseChart with Data.Map
In-Reply-To: <c97c08d20806021335w734106c4m436eea10b5b20ff3@mail.gmail.com>
References: <c97c08d20806021335w734106c4m436eea10b5b20ff3@mail.gmail.com>
Message-ID: <484546FD.5050005@iee.org>

Hello Krasimir,

Krasimir Angelov wrote:
> Hi,
> 
> I have to write ParseChart implementation with Data.Map/Set. The chart
> is type like this:
> 
> type Chart k v = Map k (Set v)
> 
> now I need operation like:
> 
> insert :: k -> v -> Chart k v -> Maybe (Chart k v)
> 
> where the result is (Just _) if the (k,v) is actually added to the
> chart or Nothing if it was already there and nothing have to be done.
> The straight forward implementation is:
> 
> case Map.lookup k chart of
>   Nothing -> Just (Map.insert k (Set.singleton v) chart)
>   Just set | Set.member v set -> Nothing
>                | otherwise            -> Just (Map.insert k
> (Set.insert v set) chart)
> 

You can do this quite easily with the AVL library, something like this
(untested code)

import Data.Cordering
import Data.Tree.AVL

type Chart k v = AVL (k, AVL v)

insert :: (Ord k, Ord v) => k -> v -> Chart k v -> Maybe (Chart k v)
insert k v tk =
   case genOpenPathWith cmpk tk of
   EmptyBP pthk    -> Just $! insertPath pthk (k, singleton v) tk
   FullBP  pthk tv ->
    case genOpenPath (compare v) tv of
    EmptyBP pthv -> let tv' = insertPath pthv v tv
                    in tv' `seq` (Just $! writePath pthk (k, tv') tk)
    FullBP  _ _  -> Nothing
  where cmpk (k',tv) = case compare k k' of
                       LT -> Lt
                       EQ -> Eq tv
                       GT -> Gt

..or something like that (maybe you don't want all that strictness)

The insertPath & writePath functions do involve a second traversal
but do not repeat all the comparisons. Also, provided not too much
has happened in between, they should be very fast as the nodes on
the path are probably still in cache. The important thing is that
in the case where Nothing is returned you'll have burned very little
heap.

Regards
--
Adrian Hey
From jtod at dcs.gla.ac.uk  Tue Jun  3 10:07:33 2008
From: jtod at dcs.gla.ac.uk (John O'Donnell)
Date: Tue Jun  3 10:00:43 2008
Subject: [Haskell-cafe] hs-plugins compile error
References: <20080602130511.GA24905@netsoc.tcd.ie><20080602172401.GB7534@scytale.galois.com>
	<20080602192332.GB24905@netsoc.tcd.ie>
Message-ID: <BED9D15F73EDDE48BF480604236A45607556ED@ex1.ad.dcs.gla.ac.uk>

Hi,

What is the status of hs-plugins?  I recently tried to install the
version plugins-1.2 on hackage, using a Gnu/Linux box with Fedora 9
and ghc-6.8.2, but didn't get past the configure stage (see config.log
below).

The installation script is invoking gcc with a -V command line argument
but according to gcc documentation -V requires an argument.

Has anyone managed to get hs-plugins to work?  If so, what platform,
which version of ghc and gcc, and where did you find the hs-plugins
source?

Best wishes,
John O'Donnell


... from config.log...
gcc version 4.3.0 20080428 (Red Hat 4.3.0-8) (GCC) 
configure:1852: $? = 0
configure:1854: gcc -V </dev/null >&5
gcc: '-V' option must have argument
configure:1857: $? = 1
configure:1880: checking for C compiler default output file name
configure:1883: gcc    conftest.c  >&5
conftest.c:9:13: warning: missing terminating " character
conftest.c:10: error: stray '\33' in program
conftest.c:10: error: expected identifier or '(' before '[' token
conftest.c:10:4: error: invalid suffix "h" on integer constant
conftest.c:10:9: warning: missing terminating " character
conftest.c:10: error: missing terminating " character
configure:1886: $? = 1
configure: failed program was:
| /* confdefs.h.  */
| 
| #define PACKAGE_NAME ""
| #define PACKAGE_TARNAME ""
| #define PACKAGE_VERSION ""
| #define PACKAGE_STRING ""
| #define PACKAGE_BUGREPORT ""
| #define LEADING_UNDERSCORE 0
| #define TOP "/home/jtod/system/installs/hs-plugins/hs-plugins-1.2
| ESC[?1034h"
| #define WITH_GHC "ghc"
| #define GHC_LIB_PATH "/usr/local/lib/ghc-6.8.2"
| /* end confdefs.h.  */
| 
| int
| main ()
| {
| 
|   ;
|   return 0;
| }
configure:1925: error: C compiler cannot create executables




-----Original Message-----
From: haskell-cafe-bounces@haskell.org on behalf of Edsko de Vries
Sent: Mon 2008-06-02 20:23
To: Don Stewart
Cc: haskell-cafe@haskell.org
Subject: Re: [Haskell-cafe] hs-plugins compile error
 
Hi Don,

Is this the kind of thing you mean (I'm not really a darcs user; this is
the patch created by darcs record):

[Hide some names to remove ambiguity errors
Edsko de Vries <edsko@edsko.net>**20080602202001] {
hunk ./src/System/Plugins/Env.hs 76
-import Distribution.Package
+import Distribution.Package hiding (packageName)
hunk ./src/System/Plugins/PackageAPI.hs 43
-import Distribution.Package
+import Distribution.Package hiding (depends, packageName)
hunk ./src/System/Plugins/ParsePkgConfCabal.hs 9
-import Distribution.Package
+import Distribution.Package hiding (depends)
}

Edsko
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Haskell-Cafe mailing list
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From darrinth at gmail.com  Tue Jun  3 10:35:03 2008
From: darrinth at gmail.com (Darrin Thompson)
Date: Tue Jun  3 10:27:41 2008
Subject: [Haskell-cafe] [ANNOUNCE] git-darcs-import 0.1
In-Reply-To: <20080601184446.GA27750@zombie.inf.tu-dresden.de>
References: <20080601184446.GA27750@zombie.inf.tu-dresden.de>
Message-ID: <a2e649c70806030735o3df1882cj64f8f8c3e4a08d9d@mail.gmail.com>

On Sun, Jun 1, 2008 at 2:44 PM, Bertram Felgenhauer
<bertram.felgenhauer@googlemail.com> wrote:
> Hi,
>
> I'm pleased to announce yet another tool for importing darcs repositories
> to git. Unlike darcs2git [1] and darcs-to-git [2], it's written in
> Haskell, on top of the darcs2 source code. The result is a much faster
> program - it can convert the complete ghc 6.9 branch (without libraries)
> in less than 15 minutes on my slightly dated machine (Athlon XP 2500+),
> which is quite fast [3]. Incremental updates work, too.
>

What's the appeal of this? I personally love git, but I thought all
the cool kids at this school used darcs and that was that.

--
Darrin
From devriese at cs.tcd.ie  Tue Jun  3 10:35:16 2008
From: devriese at cs.tcd.ie (Edsko de Vries)
Date: Tue Jun  3 10:27:56 2008
Subject: [Haskell-cafe] hs-plugins compile error
In-Reply-To: <BED9D15F73EDDE48BF480604236A45607556ED@ex1.ad.dcs.gla.ac.uk>
References: <20080602192332.GB24905@netsoc.tcd.ie>
	<BED9D15F73EDDE48BF480604236A45607556ED@ex1.ad.dcs.gla.ac.uk>
Message-ID: <20080603143515.GB17501@netsoc.tcd.ie>

On Tue, Jun 03, 2008 at 03:07:33PM +0100, John O'Donnell wrote:
> Hi,
> 
> What is the status of hs-plugins?  I recently tried to install the
> version plugins-1.2 on hackage, using a Gnu/Linux box with Fedora 9
> and ghc-6.8.2, but didn't get past the configure stage (see config.log
> below).
> 
> The installation script is invoking gcc with a -V command line argument
> but according to gcc documentation -V requires an argument.
> 
> Has anyone managed to get hs-plugins to work?  If so, what platform,
> which version of ghc and gcc, and where did you find the hs-plugins
> source?

It's working fine for me (after applying the patch I submitted), on
Debian Lenny (which currently comes with ghc 6.8.2, gcc 4.2.4) and the
source from Hackage. Source from the darcs repository also works fine
(after applying the same patch).

I *am* getting an application crash sometimes when I close my
application, but I have not yet been able to track that down so I'm not
100% sure it's due to hs-plugins.

Edsko
From jtod at dcs.gla.ac.uk  Tue Jun  3 10:49:06 2008
From: jtod at dcs.gla.ac.uk (John O'Donnell)
Date: Tue Jun  3 10:41:45 2008
Subject: [Haskell-cafe] hs-plugins compile error
References: <20080602192332.GB24905@netsoc.tcd.ie>
	<BED9D15F73EDDE48BF480604236A45607556ED@ex1.ad.dcs.gla.ac.uk>
	<20080603143515.GB17501@netsoc.tcd.ie>
Message-ID: <BED9D15F73EDDE48BF480604236A45607556EE@ex1.ad.dcs.gla.ac.uk>

Thanks, Edsko.

My version of gcc is 4.3.0.  It may well be that some other piece of
software in the Fedora 9 distribution is incompatible with the hs-plugins
installation script.

Has anyone installed hs-plugins on Fedora?  I was able to get it to
compile on Fedora 4, using ghc-6.4, two or three years ago, but it's never
worked on any of my systems since then.

John


-----Original Message-----
From: Edsko de Vries [mailto:devriese@cs.tcd.ie]
Sent: Tue 2008-06-03 15:35
To: John O'Donnell
Cc: Edsko de Vries; Don Stewart; haskell-cafe@haskell.org
Subject: Re: [Haskell-cafe] hs-plugins compile error
 
On Tue, Jun 03, 2008 at 03:07:33PM +0100, John O'Donnell wrote:
> Hi,
> 
> What is the status of hs-plugins?  I recently tried to install the
> version plugins-1.2 on hackage, using a Gnu/Linux box with Fedora 9
> and ghc-6.8.2, but didn't get past the configure stage (see config.log
> below).
> 
> The installation script is invoking gcc with a -V command line argument
> but according to gcc documentation -V requires an argument.
> 
> Has anyone managed to get hs-plugins to work?  If so, what platform,
> which version of ghc and gcc, and where did you find the hs-plugins
> source?

It's working fine for me (after applying the patch I submitted), on
Debian Lenny (which currently comes with ghc 6.8.2, gcc 4.2.4) and the
source from Hackage. Source from the darcs repository also works fine
(after applying the same patch).

I *am* getting an application crash sometimes when I close my
application, but I have not yet been able to track that down so I'm not
100% sure it's due to hs-plugins.

Edsko

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From loup.vaillant at gmail.com  Tue Jun  3 10:57:02 2008
From: loup.vaillant at gmail.com (Loup Vaillant)
Date: Tue Jun  3 10:49:40 2008
Subject: [Haskell-cafe] [ANNOUNCE] git-darcs-import 0.1
In-Reply-To: <a2e649c70806030735o3df1882cj64f8f8c3e4a08d9d@mail.gmail.com>
References: <20080601184446.GA27750@zombie.inf.tu-dresden.de>
	<a2e649c70806030735o3df1882cj64f8f8c3e4a08d9d@mail.gmail.com>
Message-ID: <6f9f8f4a0806030757y142f0710lb05754429e4b6515@mail.gmail.com>

2008/6/3 Darrin Thompson <darrinth@gmail.com>:
> On Sun, Jun 1, 2008 at 2:44 PM, Bertram Felgenhauer
> <bertram.felgenhauer@googlemail.com> wrote:
>> Hi,
>>
>> I'm pleased to announce yet another tool for importing darcs repositories
>> to git. Unlike darcs2git [1] and darcs-to-git [2], it's written in
>> Haskell, on top of the darcs2 source code. The result is a much faster
>> program - it can convert the complete ghc 6.9 branch (without libraries)
>> in less than 15 minutes on my slightly dated machine (Athlon XP 2500+),
>> which is quite fast [3]. Incremental updates work, too.
>>
>
> What's the appeal of this? I personally love git, but I thought all
> the cool kids at this school used darcs and that was that.

Disclaimer: I'm no expert, this is what I've heard. Anyone please
confirm or deny the following?

Basically, git is waaay faster than Darcs on a number of use cases.
So, maybe the point of using this converter is when you just cannot
use Darcs any more (too old/big project, merging huge branch with
loads of conflicts, I don't know).

Another point may be "broadcast-ability": It is possible to expose two
repositories: one Darcs, one Git. If I use Git and not Darcs (please
don't sue me), it will be simpler for me to get the source from the
Git snapshot, provided there is one. Well, if I want to contribute
back... maybe I should switch.

I think the True Heresy (and most useful, if practical) would be to
convert back and forth between the two version control systems,
accepting patches from both :-)

Loup
From darrinth at gmail.com  Tue Jun  3 11:53:07 2008
From: darrinth at gmail.com (Darrin Thompson)
Date: Tue Jun  3 11:45:45 2008
Subject: [Haskell-cafe] Rewrite class with fundeps in pure h98?
Message-ID: <a2e649c70806030853h9bd015fr5c6c84c92603a796@mail.gmail.com>

I thought that I should be able to write something like the toHtml
function below with pure H98, but when I went to write it I ended up
needing fundeps. Is there a way to express this without using any
extensions?

The idea was to take a remotely Dom-like tree and flatten it into a
string, but not require any particular string type. Mostly I'm ripping
off HStringTemplate for the fun of it.

{-# OPTIONS -fglasgow-exts #-}
module Control.WebWidget where

import Data.Monoid
import Data.String

data (IsString s, Monoid s) => Dom s =
    Element s [Attr s] [Dom s] |
    Text s

data (IsString s, Monoid s) => Attr s = Attr s s

class (Monoid s, IsString s) => HTML d s | d -> s where
    toHtml :: d -> s

instance (Monoid s, IsString s) => HTML (Dom s) s where
    toHtml (Element name attrs children) =
        mconcat [
            fromString "<",
            name,
            mconcat $ map toHtml attrs,
            fromString ">",
            mconcat $ map toHtml children,
            fromString "</",
            name,
            fromString ">" ]
    toHtml (Text s) = s

instance (Monoid s, IsString s) => HTML (Attr s) s where
    toHtml (Attr key value) =
        mconcat [
            fromString " '",
            key,
            fromString "'='",
            value,
            fromString "' " ]


--
Darrin
From isaacdupree at charter.net  Tue Jun  3 11:56:55 2008
From: isaacdupree at charter.net (Isaac Dupree)
Date: Tue Jun  3 11:49:43 2008
Subject: [Haskell-cafe] Implementing ParseChart with Data.Map
In-Reply-To: <1212445709.15010.144.camel@localhost>
References: <c97c08d20806021335w734106c4m436eea10b5b20ff3@mail.gmail.com>
	<1212445709.15010.144.camel@localhost>
Message-ID: <484569C7.7090602@charter.net>

Duncan Coutts wrote:
> modify :: k -> Map k e -> (e, Maybe e -> Map k e)
> 
> so it's a lookup that returns the element at k and also a continuation
> that lets you rebuild a new map with an altered element. I guess that
> doesn't account for the element not existing. There's probably a
> generalisation that does.

isn't it just adding the necessary Maybe?:
modify :: k -> Map k e -> (Maybe e, Maybe e -> Map k e)
?

-Isaac
From phercek at gmail.com  Tue Jun  3 12:42:44 2008
From: phercek at gmail.com (Peter Hercek)
Date: Tue Jun  3 12:35:33 2008
Subject: [Haskell-cafe] Re: [ANNOUNCE] git-darcs-import 0.1
In-Reply-To: <6f9f8f4a0806030757y142f0710lb05754429e4b6515@mail.gmail.com>
References: <20080601184446.GA27750@zombie.inf.tu-dresden.de>	<a2e649c70806030735o3df1882cj64f8f8c3e4a08d9d@mail.gmail.com>
	<6f9f8f4a0806030757y142f0710lb05754429e4b6515@mail.gmail.com>
Message-ID: <g23sa0$5u5$1@ger.gmane.org>

Loup Vaillant wrote:
> 2008/6/3 Darrin Thompson <darrinth@gmail.com>:
>> <--cut-->
>> What's the appeal of this? I personally love git, but I thought all
>> the cool kids at this school used darcs and that was that.
> 
> Disclaimer: I'm no expert, this is what I've heard. Anyone please
> confirm or deny the following?
> 
> Basically, git is waaay faster than Darcs on a number of use cases.

Other reason can be "git rebase". Of course there is a question
  how good practice it is ... but it is being used.

Peter.

From tphyahoo at gmail.com  Tue Jun  3 13:08:19 2008
From: tphyahoo at gmail.com (Thomas Hartman)
Date: Tue Jun  3 13:00:59 2008
Subject: [Haskell-cafe] ANN (2 Libs) -- hvac 0.1b,
	a lightweight web framework and HStringTemplate 0.3
In-Reply-To: <C389E474-BA69-4B02-AFB9-8AF70F16EC2E@gmail.com>
References: <C389E474-BA69-4B02-AFB9-8AF70F16EC2E@gmail.com>
Message-ID: <910ddf450806031008u4f3432b9hcaf26ca388fdad81@mail.gmail.com>

I just tried out hvac. I was trying to run the hvac examples
after following the readme in the samples directory.

sudo lighttpd -D -f lh.conf
[sudo] password for thartman:
2008-06-03 09:30:02: (log.c.75) server started

so that's okay, but

http://localhost:3000/hvac-board/board/1

in firefox attempted to open a binary file "1".

Same result for http://localhost:3000/hvac-board

I don't know if this is an hvac issue or a fastcgi issue (seems more
likely) but any
advice?

Thomas.

2008/3/22 Sterling Clover <s.clover@gmail.com>:
> 1) hvac 0.1b: transactional, declarative framework for lightweight web
> applications.
> 2) HStringTemplate 0.3
>
> 1) hvac 0.1b
>
> hvac (short for http view and controller) has been my project for the last
> little while, and is finally in a fairly usable state, so I'm opening up the
> repo (darcs get http://community.haskell.org/~sclv/hvac/) for folks to play
> with and to get some feedback. While not quite yet ready for hackage, the
> package as provided should be fully cabal installable. Documentation is
> available at http://community.haskell.org/~sclv/hvac/html_docs/hvac/
>
> The aim of hvac is to provide an environment that makes the creation of
> lightweight fastcgi based web applications as simple as possible, with an
> emphasis on concise, declarative style code, correct concurrent
> transactional logic, and transparency in adding caching combinators.
>
> There are two included example programs, naturally neither of which is
> feature complete. They share a common login module of about 50 lines of
> code, excluding imports, templates, and database schema.
>
> The first program is a classic, greenspun-style message board with basic
> login functionality. It totals roughly 40 lines and tends to use just under
> 4mb of resident memory on my system.
>
> The second is a wiki based on Pandoc and the PandocWiki code. The code
> totals roughly 30 lines (rendering borrowed from PandocWiki aside) and uses
> about 5mb of memory.
>
> hvac processes all requests in the STM monad, with some bells attached to
> properly interleave STM with session, database and filesystem operations
> such that they all conceptually occur together in a single transaction per
> request. Currently it is only fully tested with sqlite, but it should
> operate, modulo a few tweaks, with any database accessible via HDBC.
>
> hvac is particularly designed to use the HStringTemplate library as an
> output layer, in a simple declarative fashion. As the StringTemplate grammar
> is explicitly sub-turing, this ensures a clean separation of program logic
> from presentation, while providing a nonetheless fairly powerful language to
> express typical display tasks.
>
> The included cache combinators, still experimental, should allow a simple
> and fine-grained control over the level of caching of various disk-bound
> operations. Phantom types are used to ensure that no functions that modify
> state may be cached.
>
> To give a flavor of hvac code, the following is the complete (twenty lines!)
> source of the wiki controller (due to sql statements, some lines are rather
> long):
>
> wikiController tmpl =
>  h |/ "login" *> login_plug tmpl
>  <|>
>  (h |/ "wiki" |\\ \pageName ->    h |// "POST" *>
>          withValidation [ ("contents", return) ]
>          (\ [contents] -> do
>             pageId <- selectVal "id from pages where name=?" [toSql
> pageName]
>             maybe (addErrors [("Login","must be logged in.")] >> continue)
>                (\user -> case fromSql pageId of
>                            Just (_::Int) ->
>                              execStat "insert into
> page_hist(pageId,contents,author) values(?,?,?)" [pageId, toSql contents,
> toSql . userName $ user]
>                            Nothing -> do
>                              execStat "insert into pages(name,locked)
> values(?,?)" [toSql pageName, toSql (0::Int)]
>                              pid <- selectVal "max(id) from pages" []
>                              execStat "insert into
> page_hist(pageId,contents,author) values(?,?,?)" [pid, toSql contents, toSql
> . userName $ user]) =<< getSes
>             continue)
>       <|> do
>         pageId <- selectVal "id from pages where name=?" [toSql pageName]
>         (join $ renderf (tmpl "showPage") ("pageName", pageName)
>              <$> "pageContents" |= selectRow "* from page_hist where
> pageId=? order by time desc limit 1" [pageId] ))
>  <|> (redirect . ( ++ "/wiki/Index") =<< scriptName)
>
> Future directions for work on hvac include: Stress testing for correctness
> of transactional logic and benchmarks. Exploration of various efficiency
> tweaks. Unit tests. Further development of the cache combinator API.
> Improvement of the example apps and addition of a few others (a blog maybe).
> Expansion of the library of validator functions. Exploration of transferring
> hvac to the standard FastCGI bindings (currently it uses a custom modified
> version to work properly with STM). Improvement of the database layer,
> particularly with regards to common paging functions. Creation of a set of
> simple combinators for generating CRUD (create read update delete) pages.
> Creation of a minimal set of standard templates (maybe).
>
> 2) HStringTemplate 0.3.1
>
> This release of HStringTemplate (up now at Hackage) fixes a number of bugs
> pointed out to me by its small but growing user base (thanks, cinema,
> elliottt!) ranging from the minor (a particular two-level iteration pattern
> wasn't working properly) to the truly irritating (poor handling of file
> groups). It's still unfortunately skimpy on the docs, outside of the
> haddocks and the main StringTemplate grammar documentation at
> http://www.stringtemplate.org (although the examples from hvac should also
> prove helpful). However, it does have a set of very nice and handy new
> features for development.
>
> * renderf, a function similar in spirit to printf, that takes an arbitrary
> number of heterogeneous (String, value) tuples as arguments. This should cut
> down considerably on long setAttribute chains. Additionally, with custom
> instances (not, I'll grant, trivial to write) it can be used to
> declaratively chain together strings of attribute retrieval functions in
> arbitrary monads, as in the above code example from hvac.
>
> * dumpAttribs, a function/template that prints out the tree of the entire
> attribute environment a template is operating in -- extremely handy for
> development.
>
> * nullGroup, also for use in development, a simple way to display more
> information about templates that can't be found. Error messages in
> usafeVolatileDirectoryGroup have also been significantly improved.
>
> * getStringTemplate', a version of getStringTemplate guaranteed not to be
> inlined. While the optimizer will still sometimes rearrange code such that a
> volatile group is not updated properly, this at least helps remedy the
> situation (I think).
>
> * Some minor changes: For grammar reasons, dots have been removed from
> template names -- however, underscores and slashes are now available.
> Additionally, there's a much improved logic for which aspects of a local
> environment are overridden and preserved when a template is called from
> another.
>
> For both of these libraries, patches, comments, bug reports, requests, and
> of course contributions more than welcome!
>
> Regards,
> Sterl._______________________________________________
> Haskell-Cafe mailing list
> Haskell-Cafe@haskell.org
> http://www.haskell.org/mailman/listinfo/haskell-cafe
>
From wnoise at ofb.net  Tue Jun  3 13:15:47 2008
From: wnoise at ofb.net (Aaron Denney)
Date: Tue Jun  3 13:08:32 2008
Subject: [Haskell-cafe] Re: [ANNOUNCE] git-darcs-import 0.1
References: <20080601184446.GA27750@zombie.inf.tu-dresden.de>
	<a2e649c70806030735o3df1882cj64f8f8c3e4a08d9d@mail.gmail.com>
	<6f9f8f4a0806030757y142f0710lb05754429e4b6515@mail.gmail.com>
	<g23sa0$5u5$1@ger.gmane.org>
Message-ID: <slrng4av27.ubl.wnoise@ofb.net>

On 2008-06-03, Peter Hercek <phercek@gmail.com> wrote:
> Loup Vaillant wrote:
>> 2008/6/3 Darrin Thompson <darrinth@gmail.com>:
>>> <--cut-->
>>> What's the appeal of this? I personally love git, but I thought all
>>> the cool kids at this school used darcs and that was that.
>> 
>> Disclaimer: I'm no expert, this is what I've heard. Anyone please
>> confirm or deny the following?
>> 
>> Basically, git is waaay faster than Darcs on a number of use cases.
>
> Other reason can be "git rebase". Of course there is a question
>   how good practice it is ... but it is being used.

Darcs patches are pretty much an implicit rebase.

-- 
Aaron Denney
-><-

From apfelmus at quantentunnel.de  Tue Jun  3 13:17:45 2008
From: apfelmus at quantentunnel.de (apfelmus)
Date: Tue Jun  3 13:10:34 2008
Subject: [Haskell-cafe] Re: Rewrite class with fundeps in pure h98?
In-Reply-To: <a2e649c70806030853h9bd015fr5c6c84c92603a796@mail.gmail.com>
References: <a2e649c70806030853h9bd015fr5c6c84c92603a796@mail.gmail.com>
Message-ID: <g23ubp$dt8$1@ger.gmane.org>

Darrin Thompson wrote:
> I thought that I should be able to write something like the toHtml
> function below with pure H98, but when I went to write it I ended up
> needing fundeps. Is there a way to express this without using any
> extensions?
> 
> The idea was to take a remotely Dom-like tree and flatten it into a
> string, but not require any particular string type.
> 
> data (IsString s, Monoid s) => Dom s =
>     Element s [Attr s] [Dom s] |
>     Text s
> 
> data (IsString s, Monoid s) => Attr s = Attr s s
> 
> class (Monoid s, IsString s) => HTML d s | d -> s where
>     toHtml :: d -> s
> 
> instance (Monoid s, IsString s) => HTML (Dom s) s