date:20100406

On Tue, Apr 6, 2010 at 11:47, Johan Tibell wrote:

 On Tue, Apr 6, 2010 at 11:41 AM, Dr. Martin Grabmüller
 martin.grabmuel...@eleven.de wrote:
  Maybe a bit off-topic, but as Johan mentioned the Cassandra web site...
 
  Are there any Haskellers out there using Cassandra with Haskell?

 Not yet but I plan to write a binding for it if I ever get time. :)


Apparently, somebody used it long enough to write this:
http://hackage.haskell.org/package/cassandra-thrift

Sean
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Re: [Haskell-cafe] Re: Hackage accounts and real names

David House dmho...@gmail.com writes:
 2. Inconsistency. If someone is known by their pseudonym on the
 mailing list, IRC, haskellwiki, blogs and so on, that is how I know
 them. How am I meant to find out their real name, in general? The rest
 of the internet works off pseudonyms and it is more convenient for
 everyone if hackage follows suit.

And yet this is inconsistency remains regardless: people use different
aliases on IRC to the mailing list to Hackage (though I think this is
mainly because they have old IRC nicks they still use for internal
consistency).

 I've been over this thread and couldn't see anywhere where you'd made
 an attempt to refute these arguments, so I guess you take them as
 solid. On the other hand, every argument put forward by the
 pro-restriction group has been picked at and argued against by those
 against the restriction. That is not a stalemate.

A stalemate occurs when people disagree rather than one side having more
compelling arguments.  For example, I understand and respect your
arguments; I just don't find them compelling enough (since I find it a
pain trying to match up different nicks, etc.; though this is to do with
the inconsistency you mention above).

-- 
Ivan Lazar Miljenovic
ivan.miljeno...@gmail.com
IvanMiljenovic.wordpress.com
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Re: [Haskell-cafe] Hackage accounts and real names

Miguel Mitrofanov miguelim...@yandex.ru writes:

 Out of curiosity: is there something wrong with my nickname migmit?

How it was derived is at least apparent, as opposed to nicknames that
have nothing to do with people's real names.

-- 
Ivan Lazar Miljenovic
ivan.miljeno...@gmail.com
IvanMiljenovic.wordpress.com
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Re: [Haskell-cafe] Re: Hackage accounts and real names

2010-04-06 Thread roma

On Tue, 06 Apr 2010 20:06:27 +1000, Ivan Lazar Miljenovic
ivan.miljeno...@gmail.com wrote:
 I've been over this thread and couldn't see anywhere where you'd made
 an attempt to refute these arguments, so I guess you take them as
 solid. On the other hand, every argument put forward by the
 pro-restriction group has been picked at and argued against by those
 against the restriction. That is not a stalemate.
 
 A stalemate occurs when people disagree rather than one side having more
 compelling arguments.  For example, I understand and respect your
 arguments; I just don't find them compelling enough (since I find it a
 pain trying to match up different nicks, etc.; though this is to do with
 the inconsistency you mention above).

So, what's next? Ban anyone hiding behind a nickname on the mailing list?
On IRC? On wiki?
This will bring you consistency. As a side effect, it will bring to the
Haskell
community the fame of being one of the most inadequate open source
communities.

Let's conduct a thought experiment: suppose hackage has just launched and
its
policy is yet to be decided. Do you find your own arguments compelling
enough to
accept the policy of Real Name Requirement? Taking into account that this
policy
is _inconsistent_ with other Haskell resources policy.

-- Roman Cheplyaka, who has nothing to hide but hates silly enforcements
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Re: [Haskell-cafe] Metaprogramming in Haskell vs. Ocaml

2010-04-06 Thread Bulat Ziganshin

Hello aditya,

Saturday, April 3, 2010, 6:56:23 AM, you wrote:

 Haskell. And I'm also wondering why metaprogramming is used much more
 in Ocaml than in Haskell.

reasons are two-folded: haskell is more powerful language. in
particular, there are lots of generic programming approaches besides
TH. OTOH, TH is as powerful as any other syntax preprocessor, but not
as easy to use. especially if you try to learn it by reading original
papers

i suggest you to postpone learning TH. it's not Haskell way :)


-- 
Best regards,
 Bulatmailto:bulat.zigans...@gmail.com

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Re: [Haskell-cafe] Re: Hackage accounts and real names

2010-04-06 Thread Ketil Malde

David House dmho...@gmail.com writes:

 Let me summarise the main arguments against the restriction:

 1. It stops people from contributing [..]
 2. Inconsistency [..]
 3. Privacy issues [..]

4. It inteferes with people's freedom - who has the right to dictate what 
name a person (or, for that matter, a group of people) should be known
as?

5. It encourages dishonesty: if you want to contribute but not reveal
your real name, you have the option to lie about it, and can be fairly
confident your lie will never be called.

+1 for allowing nicks.

-k
-- 
If I haven't seen further, it is by standing in the footprints of giants
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Re: [Haskell-cafe] Re: Hackage accounts and real names

2010-04-06 Thread Serguey Zefirov

2010/4/6  r...@ro-che.info:
 On Tue, 06 Apr 2010 20:06:27 +1000, Ivan Lazar Miljenovic
 ivan.miljeno...@gmail.com wrote:
 I've been over this thread and couldn't see anywhere where you'd made
 an attempt to refute these arguments, so I guess you take them as
 solid. On the other hand, every argument put forward by the
 pro-restriction group has been picked at and argued against by those
 against the restriction. That is not a stalemate.

 A stalemate occurs when people disagree rather than one side having more
 compelling arguments.  For example, I understand and respect your
 arguments; I just don't find them compelling enough (since I find it a
 pain trying to match up different nicks, etc.; though this is to do with
 the inconsistency you mention above).
 So, what's next? Ban anyone hiding behind a nickname on the mailing list?
 On IRC? On wiki?
 This will bring you consistency. As a side effect, it will bring to the
 Haskell
 community the fame of being one of the most inadequate open source
 communities.

http://lambda-the-ultimate.org is one lovely community that has that
restriction: http://lambda-the-ultimate.org/policies#Policies

Actually, it's one of the best communities I know. I also think that
many haskell-cafe readers agree on that.

I also think that what is appropriate for mailing list is not
appropriate for collective blog or site like hackage.
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Re: [Haskell-cafe] Re: Hackage accounts and real names

Ketil Malde ke...@malde.org writes:
 5. It encourages dishonesty: if you want to contribute but not reveal
 your real name, you have the option to lie about it, and can be fairly
 confident your lie will never be called.

This to me sounds like a reason _for_ the policy (actually, a stricter
variant) rather than against...

-- 
Ivan Lazar Miljenovic
ivan.miljeno...@gmail.com
IvanMiljenovic.wordpress.com
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Re: [Haskell-cafe] Re: Hackage accounts and real names

2010-04-06 Thread Andres Loeh

  Let me summarise the main arguments against the restriction:
 
  1. It stops people from contributing [..]
  2. Inconsistency [..]
  3. Privacy issues [..]
 
 4. It inteferes with people's freedom - who has the right to dictate what 
 name a person (or, for that matter, a group of people) should be known
 as?
 
 5. It encourages dishonesty: if you want to contribute but not reveal
 your real name, you have the option to lie about it, and can be fairly
 confident your lie will never be called.
 
 +1 for allowing nicks.

Another +1 from me.

I must admit that I had never really thought about this restriction, but
the arguments against the restriction clearly convince me. I have heard
no valid arguments in favour of the restriction. I can see that there are
advantages to requiring real names, but that only makes sense if it is
enforced (and I certainly don't advocate that). The way it is now, where
some people who just silently use pseudonyms get accounts, and others,
who are not willing to lie, are rejected, is very bad.

If people are really worried about trust, then a comment/reviewing
system for Hackage is a better solution.

Cheers,
  Andres

-- 

Andres Loeh, Universiteit Utrecht

mailto:and...@cs.uu.nl mailto:m...@andres-loeh.de
http://www.andres-loeh.de
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[Haskell-cafe] Confusions about the Haskell Platform (for Mac)

1. Why can't the platform download site be hosted on www.haskell.org instead
of hackage.haskell.org? I see that there's a redirect, but (imho) it would
be ideal to have www.haskell.org/platform be the standard URL in my browser.
It is easier to remember (for typing) and more obvious (for appearances).

2. What is the difference between Haskell and the Haskell Platform? I
see one or the other in various places. To get from www.haskell.org to
downloading the Mac software, I go through Download Haskell, Get the
Haskell Platform  Mac, and Download Haskell for Mac OS X (intel).

3. By looking at http://hackage.haskell.org/platform/mac.html , I have no
idea what I'm going to get when I click the Download Haskell for Mac OS X
(intel) link. It would be nice to know what I'm getting myself into before
I commit to waiting for this 137.9 MB file. Thanks to the wonder of deep
links, one can also not be expected to traverse the path that I did in #2.
Similarly, if I come to this link directly, I have no easy way of navigating
to try to figure out what Haskell or GHC is.

4. The current link for the Mac image points to
http://hackage.haskell.org/platform/2010.1.0.0/haskell-platform-2010.1.0.1-i386.dmg.
Note the inconsistency between the version in the directory and file
names.

5. The directions on http://hackage.haskell.org/platform/mac.html say:

  After downloading:
* Open the .dmg file
* Follow the install instructions

  I see no install instructions in the .dmg file. I only see the following
files:
* GHC-6.12.1-i386.pkg
* Haskell Platform 2010.1.0.1.pkg
* Uninstall GHC

6. Since there are no install instructions, I am not sure which .pkg to
install first. Of course, fix #3 and you hopefully fix this one.

7. Why can't I have a single .pkg file? Why do I have an Uninstall GHC and
not an Uninstall Haskell Platform?

--

I don't expect all of the above to necessarily have a direct solution. They
are just my observations to share. Some of them are from the point of view
of a newcomer, and some are from a perfectionist.

Regards,
Sean
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Re: [Haskell-cafe] Re: Hackage accounts and real names

2010-04-06 Thread David Virebayre

And another +1 from me too.

Keeping the policy will only achieve that people who want to stay anonymous
will stay away from hackage, and that's not something (IMHO) we should want.

David.
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[Haskell-cafe] Re: Confusions about the Haskell Platform (for Mac)

On Tue, Apr 6, 2010 at 13:47, Sean Leather wrote:

 1.

[...]

 7.


8. The binaries do not work on Leopard (10.5.8).

  $ /usr/local/bin/cabal
  dyld: unknown required load command 0x8022
  Trace/BPT trap

This was previously reported at
http://thread.gmane.org/gmane.comp.lang.haskell.cafe/71747/focus=71944 and
Gregory Collins is apparently working on a fix. I'm happy to test a new
version, but it would be nice to have an uninstaller (that cleans up the
symlinks in /usr/local/bin too).

Regards,
Sean
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Re: [Haskell-cafe] FRP, arrows and loops

2010-04-06 Thread Maciej Piechotka

On Fri, 2010-04-02 at 14:51 -0400, Christopher Lane Hinson wrote:
 On Fri, 2 Apr 2010, Maciej Piechotka wrote:
 
  1. How to interpret ArrowLoop? I have two possible implementations:
 
  type RunSF a = a Dynamic ()
 
  data SF a b c =
   SF (a (Dynamic, b, RunSF, Set Unique) (c, Set Unique, SF a b c))
 
  (...)
 
  instance ArrowLoop (SF a) where
   loop (SF f) = loop' f undefined
 where loop' g d = proc (dyn, b, r, s) - do
 ((c, d'), s, g') - g - (dyn, (b, d), r, s)
 returnA - (c, s, loop' g' d')
 
  instance ArrowLoop a = ArrowLoop (SF a) where
   loop (SF f) =  SF $! proc (d, b, r, s) - do
 rec ((c, d), s, f') - f - (d, (b, d), r, s)
 returnA - (c, s, loop f')
 
 Neither of these compile through my eyeball,

What I meant was:

 instance ArrowLoop a = ArrowLoop (SF a) where
   loop (SF f) =  SF $! proc (dyn, b, r, s) - do
 rec ((c, d), s, f') - f - (dyn, (b, d), r, s)
 returnA - (c, s, loop f')


  2. Why there is no ArrowIO in arrows? I.e.
 
  class Arrow a = ArrowIO a where
   liftAIO :: Kleisli IO b c - a b c
 
  (possibly
 
  class Arrow a = ArrowST a where
   liftAST :: Kleisli ST b c - a b c
  )
 
 
 It would only be a convenience typeclass, and in that case why not just 
 have a generic ArrowKleisli with: (i - m o) - a i o
 

Hmm. I guess to avoid (some) problems:

 class (Monad m, Arrow a) = ArrowKleisli m a where
 liftMonad ∷  (b - m c) - a c
 liftMonad = liftKleisli . Kleisli
 liftKleisli ∷  Kleisli m b c - a b c
 liftKleisli = liftMonad . runKleisli


Given:

 instance ArrowKleisli CHP (Kleisli CHP)
 instance ArrowKleisli IO (Kleisli CHP)

And:

 someFunc = liftIO . print :: (Show b, MonadIO m) = b - m ()

Which liftIO is run in:

 liftMonad someFunc :: Kleisli CHP String ()

ghci :t liftMonad (someFunc) :: Kleisli CHP String ()

interactive:1:0:
No instance for (ArrowKleisli m (Kleisli CHP))
  arising from a use of `liftMonad' at interactive:1:0-19
Possible fix:
  add an instance declaration for (ArrowKleisli m (Kleisli CHP))
In the expression: liftMonad (someFunc) :: Kleisli CHP String ()


As IO is popular it is particularly likely to run into this problem.

Adding:

 class Arrow a ⇒  ArrowIO a where
 liftAIO ∷  (b →  IO c) →  a b c

 instance ArrowKleisli IO a ⇒  ArrowIO a where
 liftAIO = liftMonad

Solves problem:
ghci :t liftAIO someFunc :: Kleisli CHP String ()
liftAIO someFunc :: Kleisli CHP String () :: Kleisli CHP String ()

Regards


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Re: [Haskell-cafe] Re: Hackage accounts and real names

2010-04-06 Thread Ross Paterson

On Tue, Apr 06, 2010 at 10:10:09AM +0100, David House wrote:
 3. Privacy issues. Some people simply cannot reveal their real names.

I've already said I was prepared to make exceptions in such cases, but
perhaps you missed that.
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Re: [Haskell-cafe] Hackage accounts and real names

2010-04-06 Thread Tony Finch

I note that in some jurisdictions there is no such thing as a real name.
You can change your name for legal purposes (on official documentation and
so forth) simply by asserting that this is the name you prefer to be known
by. Your legal name doesn't have to be the same as your everyday name
(mine isn't).

What matters is continuity of identity and the ability to link your
identities across the places you participate.

Tony.
-- 
f.anthony.n.finch  d...@dotat.at  http://dotat.at/
GERMAN BIGHT HUMBER: SOUTHWEST 5 TO 7. MODERATE OR ROUGH. SQUALLY SHOWERS.
MODERATE OR GOOD.
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[Haskell-cafe] Re: Hackage accounts and real names

Edward Z. Yang wrote:
 This is a pretty terrible reason, but I'm going to throw it out there:
 I like real names because they're much more aesthetically pleasing.

I agree, and this is why I phased out apfelmus in favor of the
pseudonym Heinrich Apfelmus.

So, a more accurate policy would be to accept not only real names, but
also names that look like they're real, i.e. aesthetically pleasing noms
de plumes.


Regards,
Heinrich Apfelmus

--
http://apfelmus.nfshost.com

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Re: [Haskell-cafe] Re: Hackage accounts and real names

2010-04-06 Thread Roel van Dijk

On Tue, Apr 6, 2010 at 1:08 PM, Serguey Zefirov sergu...@gmail.com wrote:
 http://lambda-the-ultimate.org is one lovely community that has that
 restriction: http://lambda-the-ultimate.org/policies#Policies

LtU has no restriction on user names. From LtU's policy:
 Anonymity and the use of pseudonyms is discouraged.

I'm against *requiring* the use of a real name for hackage accounts.
I have no problems with encouraging the use of given/everyday names.

Regards,
Roel
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Re: [Haskell-cafe] Re: Hackage accounts and real names

2010-04-06 Thread Jake McArthur

On Tue, Apr 6, 2010 at 6:08 AM, Serguey Zefirov sergu...@gmail.com wrote:
 http://lambda-the-ultimate.org is one lovely community that has that
 restriction: http://lambda-the-ultimate.org/policies#Policies

I quote the policy in full here:

 Many of us here post with our real, full names. Anonymity and the use of 
 pseudonyms is discouraged. We recognize that there can be legitimate reasons 
 for wishing to post under a pseudonym. If you do not register using your real 
 name, then if possible, please include identifying information in your user 
 profile, such as your real name or a link to a personal home page or blog. 
 Using a pseudonym by which you are known elsewhere can also help.

This is a request, not a restriction.

- Jake
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Re: [Haskell-cafe] Re: Hackage accounts and real names

2010-04-06 Thread Steve Schafer

On Tue, 06 Apr 2010 14:57:30 +0200, you wrote:

I agree, and this is why I phased out apfelmus in favor of the
pseudonym Heinrich Apfelmus.

You mean your name isn't really Applesauce?

Steve Schafer
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Re: [Haskell-cafe] Confusions about the Haskell Platform (for Mac)

2010-04-06 Thread Don Stewart

leather:
 1. Why can't the platform download site be hosted on www.haskell.org instead 
 of
 hackage.haskell.org? I see that there's a redirect, but (imho) it would be
 ideal to have www.haskell.org/platform be the standard URL in my browser. It 
 is
 easier to remember (for typing) and more obvious (for appearances).

It's a different server that we have better physical access to (i.e. I
can check the logs).
  
 2. What is the difference between Haskell and the Haskell Platform? I see
 one or the other in various places. To get from www.haskell.org to downloading
 the Mac software, I go through Download Haskell, Get the Haskell Platform 
 Mac, and Download Haskell for Mac OS X (intel).
 
 3. By looking at http://hackage.haskell.org/platform/mac.html , I have no idea
 what I'm going to get when I click the Download Haskell for Mac OS X (intel)
 link. It would be nice to know what I'm getting myself into before I commit to
 waiting for this 137.9 MB file. Thanks to the wonder of deep links, one can
 also not be expected to traverse the path that I did in #2. Similarly, if I
 come to this link directly, I have no easy way of navigating to try to figure
 out what Haskell or GHC is.
 
 4. The current link for the Mac image points to http://hackage.haskell.org/
 platform/2010.1.0.0/haskell-platform-2010.1.0.1-i386.dmg . Note the
 inconsistency between the version in the directory and file names.
 
 5. The directions on http://hackage.haskell.org/platform/mac.html say:
 
   After downloading:
 * Open the .dmg file
 * Follow the install instructions
 
   I see no install instructions in the .dmg file. I only see the following
 files:
 * GHC-6.12.1-i386.pkg
 * Haskell Platform 2010.1.0.1.pkg
 * Uninstall GHC
 
 6. Since there are no install instructions, I am not sure which .pkg to
 install first. Of course, fix #3 and you hopefully fix this one.
 
 7. Why can't I have a single .pkg file? Why do I have an Uninstall GHC and
 not an Uninstall Haskell Platform?
 
 --
 
 I don't expect all of the above to necessarily have a direct solution. They 
 are
 just my observations to share. Some of them are from the point of view of a
 newcomer, and some are from a perfectionist.
 

Thanks! I'm about to hop on a plane, but here's the darcs repo for the
download website, if you want to address some of the issues -- e.g.
return navigation links.

http://code.haskell.org/haskell-platform

I'd love patches and improvements to address the concerns above.

-- Don
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[Haskell-cafe] Re: Metaprogramming in Haskell vs. Ocaml

Jacques Carette wrote:
 Jason Dagit wrote:
 Are you implying that template haskell is not typed?

 Indeed. [...]

 Compare with metaocaml where if you can compile you meta-program (i.e.
 code generator), then you are guaranteed that it can only ever produce
 valid, well-typed code.  Not so with TH, where you can easily generate
 junk -- which GHC will promptly figure out  and give you an error.

I'm curious, can metaocaml create new data type definitions, value
declarations or type class instances? I usually use TH to get rid of
boilerplate that I cannot get rid off in Haskell itself, for instance
for creating functional lenses for record types

data Foo = Foo { bar_ :: Int, ...}

$(DeriveLenses Foo)
-- bar :: Lens Foo Int

It seems to me that metaocaml is more used as user annotated partial
evaluation?


Regards,
Heinrich Apfelmus

--
http://apfelmus.nfshost.com

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Re: [Haskell-cafe] How do I use ByteString?

Hi

Don Stewart wrote:
 gue.schmidt:
  Hi all,
 
  I've never found an easy way to deal with ByteStrings.
 
  I'm using the RSA library and it en- and decodes  
  Data.ByteString.Lazy.ByteString.
 
  I initially start with Strings, ie. [Char], but there is no function to  
  convert the 2 back and forth. There is however a function which takes  
  [Word8] to BytesString and back.
 
  It all wouldn't be so confusing if there weren't several versions of  
  ByteString in several modules to choose from. And a number of libraries  
  requiring different types of ByteString.
 
  I am sure the designers of the bytestring package had good reason for  
  this design, is there also a webpage which explains which one to use and  
  under what circumstances?

I really would like such a webpage, because I am also confused about
when to use what type of strings.

 
 As a general rule you should never convert between String and
 bytestring. You can read bytestrings from files, or write literals using
 pack or the -XOverloadedStrings extension

Except that different libraries require different kind of strings. Some
use strict bytestring, some use lazy bytestring, some use [Char], some
use lazy Data.Text, ... So you really need to convert between different
representations. It may seem unfair that I put byte-strings and
char-strings in the same bucket, but libraries do use byte-strings to
contain characters. For example, Parsec has a [Char] and a bytestring
interface.

Strings are the glue that binds many libraries together, and the many
different types of strings complicate this glue. It is therefore much
more complicated to compose different libraries than it was when most
libraries used [Char]. It really would make Haskell programming easier
if we could settle on one char-string type (and one type for
byte-strings).

 
 Converting between lazy and strict bytestrings is a representation
 change, and changes complexity - so be aware of what you're doing. You
 can do this via fromChunks or concat . toChunks.

Reading the introduction to lazy bytestring here
http://hackage.haskell.org/packages/archive/bytestring/0.9.1.5/doc/html/Data-ByteString-Lazy.html
 it seems that lazy bytestring always has at least as good complexity as strict 
bytestrings. Lazy Data.Text strings also has at least as good complexity as 
strict Data.Text strings. So, for public library interfaces it would be great 
if could settle for some lazy string type like Data.Text. Preferably a string 
type that could be efficiently converted to lazy bytestrings for libraries that 
deal with bytes and not characters. This however, requires that the community 
can settle for one char-string type and a good beginning could be a description 
of how string handling is supposed to happen in Haskell (I am thinking about a 
webpage like Günther writes about).


/Mads

 
 -- Don
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[Haskell-cafe] Re: libraries [was GUI haters]

aditya siram wrote:
 Cocoa is probably the best GUI toolkit (open-source or otherwise) that
 I've seen. However it ties your app to the Mac (and the iPhone). And I
 don't believe there is a mature Haskell bridge.

There is hoc

  http://code.google.com/p/hoc/

but it's not on hackage and seems a bit dormant.

 And Javascript [1] is really not _that_ bad!

But it's not Haskell. :'(


Regards,
Heinrich Apfelmus

--
http://apfelmus.nfshost.com

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Re: [Haskell-cafe] Re: Hackage accounts and real names

2010-04-06 Thread Daniel Fischer

Am Dienstag 06 April 2010 14:57:30 schrieb Heinrich Apfelmus:
 Edward Z. Yang wrote:
  This is a pretty terrible reason, but I'm going to throw it out there:
  I like real names because they're much more aesthetically pleasing.

 I agree, and this is why I phased out apfelmus in favor of the
 pseudonym Heinrich Apfelmus.

If it's a pseudonym, you should've chosen Marcus Apfelmus - or did you 
never read Asterix?


 So, a more accurate policy would be to accept not only real names, but
 also names that look like they're real, i.e. aesthetically pleasing noms
 de plumes.

I support that, with exceptions for sufficiently well known nicks (Gour 
spoke out; before you changed it, apfelmus fell into that category, a few 
others come to mind, but not many).



 Regards,
 Heinrich Apfelmus
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Re: [Haskell-cafe] Re: Metaprogramming in Haskell vs. Ocaml

2010-04-06 Thread Nicolas Pouillard

On Tue, 06 Apr 2010 15:08:45 +0200, Heinrich Apfelmus 
apfel...@quantentunnel.de wrote:
 Jacques Carette wrote:
  Jason Dagit wrote:
  Are you implying that template haskell is not typed?
 
  Indeed. [...]
 
  Compare with metaocaml where if you can compile you meta-program (i.e.
  code generator), then you are guaranteed that it can only ever produce
  valid, well-typed code.  Not so with TH, where you can easily generate
  junk -- which GHC will promptly figure out  and give you an error.
 
 I'm curious, can metaocaml create new data type definitions, value
 declarations or type class instances? I usually use TH to get rid of
 boilerplate that I cannot get rid off in Haskell itself, for instance
 for creating functional lenses for record types
 
 data Foo = Foo { bar_ :: Int, ...}
 
 $(DeriveLenses Foo)
 -- bar :: Lens Foo Int

No metaocaml cannot do this. It is restricted to the expression level, and
not the declaration level. Moreover you cannot pattern match over the
generated code.

 It seems to me that metaocaml is more used as user annotated partial
 evaluation?

That is a way to look at it.

-- 
Nicolas Pouillard
http://nicolaspouillard.fr
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[Haskell-cafe] Re: libraries [was GUI haters]

Jean-Denis Koeck wrote:
 
 Question to the Mac users on the list: do you find that Qt applications
 feel native enough on your platform ? If not, any tips ?

Well, that depends on your definition of enough. :)

The most important thing is probably that cross platform applications
always look buggy, so if you can make sure that everything runs
smoothly and there are no drawing bugs or thelike, that's a big plus.

Qt applications will always look odd, the relative spacing is all off.
But using the appropriate system fonts adds a lot to consistency. Avoid
colored buttons and text.

Another key feature of native for me is that the menu bar is at the
top of the screen. Hence, all windows share the same menu. Furthermore,
the context menu should not list commands that are not available in the
top menu.

Not as important, but still unique to native Mac applications is that
accept a lot of drag  drop. For instance, to insert a picture into a
document, you can just drag  drop it from the Finder program; no need
to intricate open file dialogs. If you have a list of items that can
be rearranged, do so by means of drag  drop instead of strange Up and
Down buttons.

There's probably more, but that's what I can think of right now off the
top of my hat. :)


Regards,
Heinrich Apfelmus

--
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Re: [Haskell-cafe] How do I use ByteString?

2010-04-06 Thread Ketil Malde

Mads Lindstrøm mads_lindstr...@yahoo.dk writes:

 It may seem unfair that I put byte-strings and char-strings in the
 same bucket, but libraries do use byte-strings to contain
 characters. For example, Parsec has a [Char] and a bytestring
 interface. 

It bears noting that Data.ByteString and Data.ByteString.Char8 are just
different interfaces to the same data type (same goes for the .Lazy
versions).

Once upon a time I forked bytestring to use a phantom type tag to
separate different encodings (including many other 8-bit encodings than
the Char8 one), but although I still think this is a good idea, the code
is long dead and gone now.

-k
-- 
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[Haskell-cafe] Re: Seeking advice about monadic traversal functions

Darryn Reid wrote:
 Martijn van Steenbergen wrote:

 A small remark: I prefer using applicative notation for this:

 go Next (Single x t1) = Single x $ rewrite f t1
 go Next (Fork t1 t2 ) = Fork $ rewrite f t1 * rewrite f t2

 
 Thanks for your comment and advice. Could you explain a little further
 your thinking? Specifically, what advantage do you find in the
 applicative notation, and when would you advise using it and when would
 you advise not using it?

The applicative notation is more general since it also applies to
applicative functors

  http://www.cs.nott.ac.uk/~ctm/IdiomLite.pdf

It's main advantage over the liftM family is that it can be used with
any number of arguments

  liftM  f m = f $ m
  liftM2 f m n   = f $ m * n
  liftM3 f m n o = f $ m * n * o
  etc.

and that's why I prefer it as well. It's very similar to function
application, too, just think of  *  as a replacement for the empty
space that separates function arguments.

The only drawback is probably that you have to

  import Control.Applicative

In fact, it doesn't actually work for monads, I think you have to wrap
it in a newtype. :D The same effect can be achieved with `ap` , though:

  liftM3 f m n p = return f `ap` m `ap` n `ap` o


Regards,
Heinrich Apfelmus

--
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Re: [Haskell-cafe] Re: Metaprogramming in Haskell vs. Ocaml

2010-04-06 Thread Jacques Carette

One thing I should have mentionned - TH and camlp4 are really 
equivalents.  And camlp4 is as-typed-as TH (or not, depending on your 
point of view).  I am co-author of a camlp4 extension, and I must admit 
that coding in camlp4 was not enjoyable, while coding in metaocaml 
(eventually) is.


[I see that Nicolas Pouillard just answered the question about new type 
definitions, etc, as I was typing this answer]


Heinrich Apfelmus wrote:

It seems to me that metaocaml is more used as user annotated partial
evaluation?
  
I see most of my uses of metaocaml as code generation (building 'up' 
code from pieces by making explicit design choices) rather than 
classical partial evaluation (specializing code).  Others would argue 
that these two activities are really the same thing -- and I would not 
really disagree!  It's just that in my cases the 'specialization' is not 
driven by the partial evaluator at all, it is fully driven by the user 
[through explicit decisions of which modules/functors to use].  This 
requires a very different code organization, which is why I make the 
difference between the two approaches.


The Haskell analogy: I write tons and tons of typeclass-level 'code', 
including typeclasses for type constructors (and type constructor 
transformers and ...) but then I ensure that whenever these are used, it 
can be statically determined exactly which instance should be used, and 
100% of the dispatch overhead is eliminated AND I get full control over 
which methods get inlined in the final code.  It is that 'full control' 
aspect which gets you reliable efficiency from highly abstract code.


Jacques
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Re: [Haskell-cafe] Re: Metaprogramming in Haskell vs. Ocaml

2010-04-06 Thread Nicolas Pouillard

On Tue, 06 Apr 2010 09:37:59 -0400, Jacques Carette care...@mcmaster.ca wrote:
 One thing I should have mentionned - TH and camlp4 are really 
 equivalents.  And camlp4 is as-typed-as TH (or not, depending on your 
 point of view).  I am co-author of a camlp4 extension, and I must admit 
 that coding in camlp4 was not enjoyable, while coding in metaocaml 
 (eventually) is.

This is not exactly the same, TH is a bit more typed than camlp4 here is two
examples:

{-# LANGUAGE TemplateHaskell #-}
module Thtest1 (test) where
test = [d| f :: Int
   f = True |]

{-# LANGUAGE TemplateHaskell #-}
module Thtest2 (test) where
test = [e| 1 + x |]

These two files are rejected at compile time before being spliced in.
So there is a limited scope checking, and type checking (limited because
manually using the AST constructors allow to workaround the typechecker).

Second point, the Q monad allows to generate names in a rather safe way
compared to camlp4.

Third reification can be done on declarations done in other files. So
that we can easily inspect the types and definitions of previous things,
which a rather hard (near to impossible) in camlp4.

Best regards,

-- 
Nicolas Pouillard
http://nicolaspouillard.fr
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Re: [Haskell-cafe] Re: Haskell.org re-design

Well, they make the wannabe-designer mistake of using justified text
in HTML, even worse, for columns just 3 words wide.

The overall layout, is pretty nice though.  It's essentially the
standard Web 2.0 layout (compare http://basecamphq.com/,
http://www.blinksale.com/, http://www.analysis-one.com/, etc.).  The
key design elements are (IMO):

  - Put the important stuff at the top and separate it visually from
the other stuff.  The important things are:  (1) the quick summary
of Haskell, (2) the Get Haskell button, (3) link to Learn Haskell
/ Try Haskell

  - We may have a second row/column of secondary important stuff, like
community, project hosting, more implementations, the top learning
materials, etc. links to Haskell users

  - News, Events, etc. can go further down

I'm not particularly attached to any particulars of my suggested
design.  I just thought I'll try to encourage to move away much
further from the current wiki-like and somewhat dull design.

On 6 April 2010 10:36, Johan Tibell johan.tib...@gmail.com wrote:
 On Tue, Apr 6, 2010 at 5:24 AM, Simon Michael si...@joyful.com wrote:
 On 4/2/10 5:28 AM, Thomas Schilling wrote:

 How about something more colourful?

 http://i.imgur.com/7jCPq.png

 I really like the simplicity of the Cassandra page:

 http://cassandra.apache.org/
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Re: [Haskell-cafe] [OT?] Haskell-inspired functions for BASH

2010-04-06 Thread Mario Blažević


Patrick LeBoutillier wrote:

...
Basically I'm looking for a bit of feedback/info:
- Does anyone know if there are already similar projets out there?


	You've already got some references, you can also look at 
http://hackage.haskell.org/package/scc which includes a shell language.




- Does anyone find this interesting?


I do.


- Any other comment/suggestion/feedback


	It would be interesting to compare the speed of your Bash functions 
with the h4sh executables written in Haskell. Your solution has the 
source platform independence on its side, of course.


	A question of my own: is there any written design (an academic paper 
would be perfect) of a functional shell language?


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[Haskell-cafe] Re: HXT Namespaces and XPath

2010-04-06 Thread Uwe Schmidt

Hi Mads,

 In HXT, namespace prefixes bound by an XML document are valid in the
 context of an XPath. How do avoid that?
 
 An example program will clarify:
 
 simpleXml :: String
 simpleXml = soap:Body 
 xmlns:soap=\http://www.w3.org/2003/05/soap-envelope\/
 
 nsEnv :: [(String, String)]
 nsEnv = [ (s, http://www.w3.org/2003/05/soap-envelope;) ]
 
 evalXPath :: String - String - [XmlTree]
 evalXPath xpath xml =
   runLA ( xread
propagateNamespaces
getXPathTreesWithNsEnv nsEnv xpath
 ) xml
 
 Here:
 
 evalXPath //s:Body simpleXml ==
 evalXPath //soap:Body simpleXml
 
 Even though I only mentions the prefix s (and not soap) in the
 function nsEnv.

When working with namespaces in XML, the prefixes are not longer significant.
After namespace propagation every name in the XML document is identified
by a qualified name. This is a pair consisting of the namespace URI and the 
local part.
The prefixes become irrelevant.
A namespace aware XPath expression needs a namespace environment,
as given in the example, to construct these qualified names for the names
in the XPath expression.
So the results of both evalXPath calls in your example must be the same. 

 I do not want the XPath to see prefixes declared in the xml-document, as
 it means that two semantically similar XML documents can get different
 results when applied to the same XPath.

If you intend, that the prefixes are significant, then you should not work
with namespace propagation. If namespaces are not propagated,
all names occurring in the document are taken as they are. That means
s:Body is different from soap:Body.

For solving your tasks there could be 2 ways:

1. don't use namespaces, no propagateNamespaces, no getXPathTreesWithNsEnv,
 use the prefixes instead. Disadvantage: the prefixes become significant. If
 prefixes change, the semantics changes.

2. Use propagateNamespaces and getXPathTreesWithNsEnv, but select
 all nodes via the namespace URIs, not via the prefixes. If you want to
 output the manipulated XML parts and use standard prefixes for
 the namespaces, then use the namespace manipulation functions
 in 
http://hackage.haskell.org/packages/archive/hxt/latest/doc/html/Text-XML-HXT-Arrow-Namespace.html

Cheers,

  Uwe

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Re: [Haskell-cafe] [OT?] Haskell-inspired functions for BASH

A question of my own: is there any written design (an academic paper
 would be perfect) of a functional shell language?


A few: http://www.citeulike.org/user/spl/tag/shell

More resources:
http://www.cse.unsw.edu.au/~pls/thesis-topics/functionalshell.html

Regards,
Sean
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Re: [Haskell-cafe] [OT?] Haskell-inspired functions for BASH

2010-04-06 Thread Stephen Tetley

On 6 April 2010 15:09, Mario Blažević mblaze...@stilo.com wrote:

        A question of my own: is there any written design (an academic paper
 would be perfect) of a functional shell language?


Olin Shivers has written a detailed paper on Scsh.

ftp://www-swiss.ai.mit.edu/pub/su/scsh/scsh-paper.ps

The link might be down permanently (it is for me at the moment), maybe
the paper is on Citeseer or similar. There is also the Scsh manual.

Best wishes

Stephen
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Re: [Haskell-cafe] Re: Haskell.org re-design

2010-04-06 Thread Daniel Peebles

I'm definitely not a design/color person, but has anyone considered using
kuler.adobe.com as a source of nice color schemes, since we seem to have
an issue coming up with attractive combinations?

On Tue, Apr 6, 2010 at 9:58 AM, Thomas Schilling nomin...@googlemail.comwrote:

 Well, they make the wannabe-designer mistake of using justified text
 in HTML, even worse, for columns just 3 words wide.

 The overall layout, is pretty nice though.  It's essentially the
 standard Web 2.0 layout (compare http://basecamphq.com/,
 http://www.blinksale.com/, http://www.analysis-one.com/, etc.).  The
 key design elements are (IMO):

  - Put the important stuff at the top and separate it visually from
 the other stuff.  The important things are:  (1) the quick summary
 of Haskell, (2) the Get Haskell button, (3) link to Learn Haskell
 / Try Haskell

  - We may have a second row/column of secondary important stuff, like
 community, project hosting, more implementations, the top learning
 materials, etc. links to Haskell users

  - News, Events, etc. can go further down

 I'm not particularly attached to any particulars of my suggested
 design.  I just thought I'll try to encourage to move away much
 further from the current wiki-like and somewhat dull design.

 On 6 April 2010 10:36, Johan Tibell johan.tib...@gmail.com wrote:
  On Tue, Apr 6, 2010 at 5:24 AM, Simon Michael si...@joyful.com wrote:
  On 4/2/10 5:28 AM, Thomas Schilling wrote:
 
  How about something more colourful?
 
  http://i.imgur.com/7jCPq.png
 
  I really like the simplicity of the Cassandra page:
 
  http://cassandra.apache.org/
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[Haskell-cafe] Re: HXT error handling

2010-04-06 Thread Uwe Schmidt

Hi Mads,


 I am trying to use HXT to evaluate XPath expressions. The XPath
 expressions are not specified by myself, but by users of my program.
 However, the idea behind HXT's error handling confuses me. Maybe
 somebody can enlighten me.
 
 This program fragment:
 
 evalXPath :: String - String - [XmlTree]
 evalXPath xpath xml =
   runLA ( xread
propagateNamespaces
getXPathTrees xpath
 ) xml
 
 seems to work fine, except when it comes to error handling. If the
 xml-string is malformed, the error is simply ignored and the
 evalXPath-function just returns an empty list. I can understand what
 happens. 'getXPathTrees xpath' tries to match the xpath to a XmlTree
 which represents a parse error, and it therefore never matches anything.

When calling evalXPath, there are 2 error situations. Both can be handled
in the same form.

1. xread is called with a string, that does not match XML contents.
 This results in a single element list containing an error message.
 Test: runLA xread ???
 The following arrows, propagateNamespaces ..., don't accept error messages,
 so they fail and the result of the whole arrow ist the empty list.
 So the result of xread must be checked before further processed.

2. getXPathTrees xpath can fail with a syntax error in xpath.
 This again results in a single element list with an error message.
 The error message can be catched in the same way as before.

Your example can be rewritten in the following way:

--

module NameSpace
where

import Text.XML.HXT.Arrow
import Text.XML.HXT.XPath

simpleXml :: String
simpleXml = soap:Body 
xmlns:soap=\http://www.w3.org/2003/05/soap-envelope\/

wrongXml :: String
wrongXml = ???

nsEnv :: [(String, String)]
nsEnv = [ (s, http://www.w3.org/2003/05/soap-envelope;) ]

evalXPath :: String - String - [XmlTree]
evalXPath xpath xml =
  runLA ( xread
  
  ( ( propagateNamespaces
  
  getXPathTreesWithNsEnv nsEnv xpath
)
`whenNot` isError
  )
) xml

t1 = evalXPath //s:BodysimpleXml
t2 = evalXPath //soap:Body simpleXml
t3 = evalXPath ??? simpleXml
t4 = evalXPath //soap:Body wrongXml
t5 = runLA xread wrongXml

--

 What I really would like was functions like:
 
 parseStr :: (Monad m) = String - m XmlTrees
 parseStr xml =
   case Parsec.xread xml of
 (x:xs) - if (Dom.isError x) then fail Could not parse tree else
 return (x:xs)
 [] - fail No XML tree resultet from parsing XML

You already do have this. Not in a monadic version but as arrow.
See above example.

 And a similar function for the XPath. This could also speed up my
 program, as I would not parse the same XPath again and again. A

This is a right point. Here the current XPath calling interface is too simple.
A separation into XPath parsing and evaluation would be more flexible.
The parsing (and error handling of XPath syntax errors) could be done once.
I will extend the interface to support this.

Thanks for your comments and hints,

Uwe
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Re: [Haskell-cafe] Hackage accounts and real names

2010-04-06 Thread Jonas Almström Duregård

 I think this is a bad idea as it ruins recognisability. How am I meant
 to know that anonymous1 on hackage is the same person as mrfoo on
 haskellwiki, for example?

I should not have to point out how unreliable this method of
identifying individuals is... I suppose there is no way of preventing
mrfoo from adding his nick to the Maintainer or Author fields anyway.

For those who claim that there are no advantages of real name
policy's, consider Facebook. Arguably the astonishing success of
Facebook is utterly based on a real names policy...

2010/4/6 David House dmho...@gmail.com:
 2010/4/6 Jonas Almström Duregård jonas.dureg...@gmail.com:
 Maybe users could choose between using a real name and being given a
 random one (like AnonymousN). This will (1) protect from data
 mining, (2) protect from government persecution and (3) keep the
 damned 1337 Haxxor names away from Hackage :)

 I think this is a bad idea as it ruins recognisability. How am I meant
 to know that anonymous1 on hackage is the same person as mrfoo on
 haskellwiki, for example?

 P.s. if (3) is your real reason for supporting this restriction,
 please rethink your perspective. You are supporting a policy that is
 hurting the community for mere aesthetic reasons.

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Re: [Haskell-cafe] Confusions about the Haskell Platform (for Mac)

2010-04-06 Thread Gregory Collins

Sean Leather leat...@cs.uu.nl writes:

 4. The current link for the Mac image points to
 http://hackage.haskell.org/platform/2010.1.0.0/haskell-platform-2010.1.0.1-i386.dmg
 . Note the inconsistency between the version in the directory and file
 names.

You can think of that one as the second edition of the 2010.1 beta
version. Agree that the directories should match. Too bad the installer
still doesn't work -- I'm working on it everyone, but the Mac installer
system is incredibly crufty and broken, and Snow Leopard broke a lot of
stuff for me.


 5. The directions on http://hackage.haskell.org/platform/mac.html say:

   After downloading:
     * Open the .dmg file
     * Follow the install instructions

   I see no install instructions in the .dmg file. I only see the following 
 files:
     * GHC-6.12.1-i386.pkg
     * Haskell Platform 2010.1.0.1.pkg
     * Uninstall GHC

When you mount the .dmg file a Finder window should pop up with the
install instructions in a background image. Let me guess: this isn't
working in Leopard? I should put a readme in there.


 7. Why can't I have a single .pkg file?

Short answer: I can't figure out how, and not for lack of trying,
either. What I do is take the binary installer that the GHC guys build
as a starting point. Despite many hours of reverse-engineering I cannot
for the life of me figure out how to extract the GHC installer package
from the binary metapackage.

My experience has been that if you unxar the metapackage and try to copy
the included package file into a new metapackage, the mac installer
tools barf. Long-term, I'm planning on just building GHC from source so
I can package a one-click installer, but I don't have infinite time for
this project and doing psychic battle with the evil warlocks who cooked
up the Mac installer is a challenge.

If anyone has expertise in this area and a willingness to help, please
contact me off-list.


 Why do I have an Uninstall GHC and not an Uninstall Haskell
 Platform?

The platform installer is supposed to erase previous platform editions
before it installs itself.

G.
-- 
Gregory Collins g...@gregorycollins.net
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Re: [Haskell-cafe] [OT?] Haskell-inspired functions for BASH

2010-04-06 Thread Gwern Branwen

On Tue, Apr 6, 2010 at 11:17 AM, Stephen Tetley
stephen.tet...@gmail.com wrote:
 On 6 April 2010 15:09, Mario Blažević mblaze...@stilo.com wrote:

        A question of my own: is there any written design (an academic paper
 would be perfect) of a functional shell language?


 Olin Shivers has written a detailed paper on Scsh.

 ftp://www-swiss.ai.mit.edu/pub/su/scsh/scsh-paper.ps

 The link might be down permanently (it is for me at the moment), maybe
 the paper is on Citeseer or similar. There is also the Scsh manual.

 Best wishes

 Stephen

The Scsh manual is worth reading just for the introductory material.

Part of the problem is that both Clean and Scheme have relatively easy
and powerful 'eval' ability. (Esther exploits the interesting feature
of Clean that lets you serialize functions to disk.)

Haskell doesn't, so much. The GHC API isn't too great to work with
here; it's hard enough to evaluate straight Haskell fragments, and to
serve as a shell, you really need new syntax; for example, you want
literals for program names. (Who would use a shell which forces you to
write 'run ghci [foo.lhs]', instead of 'ghci foo.lhs'?) But many
filenames break in Haskell; 'ssh-agent', 'g++-4.4', 'bf_tar', etc.

-- 
gwern
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Re: [Haskell-cafe] Confusions about the Haskell Platform (for Mac)

Hi Gregory,

Thanks for the reply.

Gregory Collins wrote:

 Sean Leather writes:

  4. The current link for the Mac image points to
 
 http://hackage.haskell.org/platform/2010.1.0.0/haskell-platform-2010.1.0.1-i386.dmg
  . Note the inconsistency between the version in the directory and file
  names.

 You can think of that one as the second edition of the 2010.1 beta
 version. Agree that the directories should match.


This is, of course, relatively minor. One alternative is to change the
directory name to exclude the lowest version(s), e.g
2010.1/haskell-platform-2010.1.0.1-i386.dmg, so that when new intermediate
versions are uploaded, the directory name still makes sense and doesn't need
to change.

Too bad the installer
 still doesn't work -- I'm working on it everyone, but the Mac installer
 system is incredibly crufty and broken, and Snow Leopard broke a lot of
 stuff for me.


Is it possible to build the installer on a Leopard system/virtual machine
such that it will install on a Snow Leopard system?

 5. The directions on http://hackage.haskell.org/platform/mac.html say:
 
After downloading:
  * Open the .dmg file
  * Follow the install instructions
 
I see no install instructions in the .dmg file. I only see the
 following files:
  * GHC-6.12.1-i386.pkg
  * Haskell Platform 2010.1.0.1.pkg
  * Uninstall GHC

 When you mount the .dmg file a Finder window should pop up with the
 install instructions in a background image. Let me guess: this isn't
 working in Leopard? I should put a readme in there.


Yes, I'm using Leopard. A README file should do the trick.

 7. Why can't I have a single .pkg file?

 Short answer: I can't figure out how, and not for lack of trying,
 either. What I do is take the binary installer that the GHC guys build
 as a starting point. Despite many hours of reverse-engineering I cannot
 for the life of me figure out how to extract the GHC installer package
 from the binary metapackage.


I'm completely ignorant of how the installer packages work, but is it
possible to have one package refer to another? Thus, one installer could
initiate another. Then, at least there is only one click needed for the
whole thing.

My experience has been that if you unxar the metapackage and try to copy
 the included package file into a new metapackage, the mac installer
 tools barf. Long-term, I'm planning on just building GHC from source so
 I can package a one-click installer, but I don't have infinite time for
 this project and doing psychic battle with the evil warlocks who cooked
 up the Mac installer is a challenge.


I see you have the source at
http://github.com/gregorycollins/haskell-platform-osx-installer . I can try
to look at it at some point.

If anyone has expertise in this area and a willingness to help, please
 contact me off-list.


  Why do I have an Uninstall GHC and not an Uninstall Haskell
  Platform?

 The platform installer is supposed to erase previous platform editions
 before it installs itself.


That's good. Is it possible to include an uninstaller as well?

Regards,
Sean
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Re: [Haskell-cafe] Confusions about the Haskell Platform (for Mac)

2010-04-06 Thread Gregory Collins

Sean Leather leat...@cs.uu.nl writes:

 Too bad the installer
 still doesn't work -- I'm working on it everyone, but the Mac installer
 system is incredibly crufty and broken, and Snow Leopard broke a lot of
 stuff for me.

 Is it possible to build the installer on a Leopard system/virtual
 machine such that it will install on a Snow Leopard system?

I think that's the approach I'm going to have to take. I still have my
Leopard DVD sitting around, I'll try building the thing in a VirtualBox
or maybe even doing a separate Leopard edition of the platform
installer.

  7. Why can't I have a single .pkg file?

 Short answer: I can't figure out how, and not for lack of trying,
 either. What I do is take the binary installer that the GHC guys build
 as a starting point. Despite many hours of reverse-engineering I cannot
 for the life of me figure out how to extract the GHC installer package
 from the binary metapackage.

 I'm completely ignorant of how the installer packages work, but is it
 possible to have one package refer to another? Thus, one installer
 could initiate another. Then, at least there is only one click needed
 for the whole thing.

I don't have a good working solution for this, so the situation will
have to remain status quo (i.e. clicking two installers) for now.


 The platform installer is supposed to erase previous platform
 editions before it installs itself.

 That's good. Is it possible to include an uninstaller as well?

It would be pretty easy to bundle a shell script.

G
-- 
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Re: [Haskell-cafe] Re: Haskell.org re-design

Well, I used http://www.colorschemedesigner.com/

On 6 April 2010 16:20, Daniel Peebles pumpkin...@gmail.com wrote:
 I'm definitely not a design/color person, but has anyone considered using
 kuler.adobe.com as a source of nice color schemes, since we seem to have
 an issue coming up with attractive combinations?

 On Tue, Apr 6, 2010 at 9:58 AM, Thomas Schilling nomin...@googlemail.com
 wrote:

 Well, they make the wannabe-designer mistake of using justified text
 in HTML, even worse, for columns just 3 words wide.

 The overall layout, is pretty nice though.  It's essentially the
 standard Web 2.0 layout (compare http://basecamphq.com/,
 http://www.blinksale.com/, http://www.analysis-one.com/, etc.).  The
 key design elements are (IMO):

  - Put the important stuff at the top and separate it visually from
 the other stuff.  The important things are:  (1) the quick summary
 of Haskell, (2) the Get Haskell button, (3) link to Learn Haskell
 / Try Haskell

  - We may have a second row/column of secondary important stuff, like
 community, project hosting, more implementations, the top learning
 materials, etc. links to Haskell users

  - News, Events, etc. can go further down

 I'm not particularly attached to any particulars of my suggested
 design.  I just thought I'll try to encourage to move away much
 further from the current wiki-like and somewhat dull design.

 On 6 April 2010 10:36, Johan Tibell johan.tib...@gmail.com wrote:
  On Tue, Apr 6, 2010 at 5:24 AM, Simon Michael si...@joyful.com wrote:
  On 4/2/10 5:28 AM, Thomas Schilling wrote:
 
  How about something more colourful?
 
  http://i.imgur.com/7jCPq.png
 
  I really like the simplicity of the Cassandra page:
 
  http://cassandra.apache.org/
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Re: [Haskell-cafe] Re: Haskell.org re-design

2010-04-06 Thread Jeff Heard


There's colourlovers.com as well



On Apr 6, 2010, at 12:41 PM, Thomas Schilling  
nomin...@googlemail.com wrote:



Well, I used http://www.colorschemedesigner.com/

On 6 April 2010 16:20, Daniel Peebles pumpkin...@gmail.com wrote:
I'm definitely not a design/color person, but has anyone considered  
using
kuler.adobe.com as a source of nice color schemes, since we seem  
to have

an issue coming up with attractive combinations?

On Tue, Apr 6, 2010 at 9:58 AM, Thomas Schilling nomin...@googlemail.com 


wrote:


Well, they make the wannabe-designer mistake of using justified text
in HTML, even worse, for columns just 3 words wide.

The overall layout, is pretty nice though.  It's essentially the
standard Web 2.0 layout (compare http://basecamphq.com/,
http://www.blinksale.com/, http://www.analysis-one.com/, etc.).  The
key design elements are (IMO):

 - Put the important stuff at the top and separate it visually from
the other stuff.  The important things are:  (1) the quick summary
of Haskell, (2) the Get Haskell button, (3) link to Learn  
Haskell

/ Try Haskell

 - We may have a second row/column of secondary important stuff,  
like

community, project hosting, more implementations, the top learning
materials, etc. links to Haskell users

 - News, Events, etc. can go further down

I'm not particularly attached to any particulars of my suggested
design.  I just thought I'll try to encourage to move away much
further from the current wiki-like and somewhat dull design.

On 6 April 2010 10:36, Johan Tibell johan.tib...@gmail.com wrote:
On Tue, Apr 6, 2010 at 5:24 AM, Simon Michael si...@joyful.com  
wrote:

On 4/2/10 5:28 AM, Thomas Schilling wrote:


How about something more colourful?

http://i.imgur.com/7jCPq.png


I really like the simplicity of the Cassandra page:

http://cassandra.apache.org/
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[Haskell-cafe] hsql repository

2010-04-06 Thread Daniil Elovkov


Hello
I've looked at hsql-* packages at hackage and found that they have 
progressed to 1.8.1. However, as always there is no hsql-oracle on 
hackage. It was usually found in the repository.


But I can't find where the repository is. Places, like code.haskell.org 
and htoolkit.sourceforge.net seem to have the older 1.7 version.


Can somebody point me to the repository? Is there any chance that 
hsql-oracle compiles with new hsql?


Thanks
Daniil Elovkov
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Re: [Haskell-cafe] [OT?] Haskell-inspired functions for BASH

2010-04-06 Thread Stephen Tetley

On 6 April 2010 16:56, Gwern Branwen gwe...@gmail.com wrote:


 The Scsh manual is worth reading just for the introductory material.


Hi Gwern

The Scsh manual is worth reading for the Acknowledgements section -
which is somewhat famous. Looking over them both it seems most of the
material in the paper is covered in the manual.

Esther is shipped as a project with Clean2.2 although I think it only
works on Windows - the last time I looked at the code I got the
impression that it had diverged a bit from the the Famke / Esther
papers.

Best wishes

Stephen
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[Haskell-cafe] Re: HXT error handling

Hi Uwe


 This is a right point. Here the current XPath calling interface is too simple.
 A separation into XPath parsing and evaluation would be more flexible.
 The parsing (and error handling of XPath syntax errors) could be done once.
 I will extend the interface to support this.

That would be great. Thank you.

 
 Thanks for your comments and hints,
 
 Uwe

/Mads


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[Haskell-cafe] Re: HXT Namespaces and XPath

Hi Uwe

I read your reply multiple times, but I am still confused. I think
either I misunderstand you or I did not explain myself properly in the
first mail.

 Hi Mads,
 
  In HXT, namespace prefixes bound by an XML document are valid in the
  context of an XPath. How do avoid that?
  
  An example program will clarify:
  
  simpleXml :: String
  simpleXml = soap:Body 
  xmlns:soap=\http://www.w3.org/2003/05/soap-envelope\/
  
  nsEnv :: [(String, String)]
  nsEnv = [ (s, http://www.w3.org/2003/05/soap-envelope;) ]
  
  evalXPath :: String - String - [XmlTree]
  evalXPath xpath xml =
runLA ( xread
 propagateNamespaces
 getXPathTreesWithNsEnv nsEnv xpath
  ) xml
  
  Here:
  
  evalXPath //s:Body simpleXml ==
  evalXPath //soap:Body simpleXml
  
  Even though I only mentions the prefix s (and not soap) in the
  function nsEnv.
 
 When working with namespaces in XML, the prefixes are not longer significant.
 After namespace propagation every name in the XML document is identified
 by a qualified name. This is a pair consisting of the namespace URI and the 
 local part.
 The prefixes become irrelevant.

This is my point. Prefixes are relevant in the current implementation of
HXT.

 A namespace aware XPath expression needs a namespace environment,
 as given in the example, to construct these qualified names for the names
 in the XPath expression.
 So the results of both evalXPath calls in your example must be the same. 

Yes, but in the namespace environment I give to getXPathTreesWithNsEnv I
only mention the prefix s, yet I am still able to evaluate the xpath
//soap:Body. Furthermore //s:body and //soap:Body gives the same
results. Why?

I think another example will clarify my point. The code:

simpleXmlOne, simpleXmlTwo :: String
simpleXmlOne = a:Foo xmlns:a=\http://foo.org\/
simpleXmlTwo = b:Foo xmlns:b=\http://foo.org\/

nsEnv :: [(String, String)]
nsEnv = [ (notFoo, http://notfoo.org;) ]

evalXPath :: String - [XmlTree]
evalXPath xml =
  runLA ( xread
   propagateNamespaces
   getXPathTreesWithNsEnv nsEnv //a:Foo
) xml

Now notice that simpleXmlOne and simpleXmlTwo are equivalent. Yes, they
have a different prefix for http://foo.org;, but the documents means
the same. And as you write yourself, ... the prefix is no longer
releavant ... Yet:

evalXPath simpleXmlOne /= evalXPath simpleXmlTwo

Hope that clarifies things.


Regards,

Mads



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[Haskell-cafe] Re: HXT error handling

2010-04-06 Thread Uwe Schmidt

Hi Mads,


  This is a right point. Here the current XPath calling interface is too 
  simple.
  A separation into XPath parsing and evaluation would be more flexible.
  The parsing (and error handling of XPath syntax errors) could be done once.
  I will extend the interface to support this.
 
 That would be great. Thank you.

just uploaded hxt-xpath-8.5.3 to hackage.
But haddock doc is not yet available on hackage.

Cheers,

Uwe
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Re: [Haskell-cafe] Re: HXT Namespaces and XPath

Hi

Replying to myself:


 I think another example will clarify my point. The code:
 
 simpleXmlOne, simpleXmlTwo :: String
 simpleXmlOne = a:Foo xmlns:a=\http://foo.org\/
 simpleXmlTwo = b:Foo xmlns:b=\http://foo.org\/
 
 nsEnv :: [(String, String)]
 nsEnv = [ (notFoo, http://notfoo.org;) ]
 
 evalXPath :: String - [XmlTree]
 evalXPath xml =
   runLA ( xread
propagateNamespaces
getXPathTreesWithNsEnv nsEnv //a:Foo
 ) xml
 
 Now notice that simpleXmlOne and simpleXmlTwo are equivalent. Yes, they
 have a different prefix for http://foo.org;, but the documents means
 the same. And as you write yourself, ... the prefix is no longer
 releavant ... Yet:
 
 evalXPath simpleXmlOne /= evalXPath simpleXmlTwo
 

Just to clarify things. The point I am making is that:

getXPathTreesWithNsEnv nsEnv //a:Foo

do not only see the prefixes in 'nsEnv', but also the prefixes in the
XML it is applied to. I think that the getXPathTreesWithNsEnv function
should only see the prefixes mentioned in its first parameter.


Regards,

Mads



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[Haskell-cafe] Re: GSOC Haskell Project

2010-04-06 Thread Mihai Maruseac

Hello again

Following a feedback (courtesy of lispy) of my proposal on #haskell, I
come to complete it with some bits here and there.

First, a short analysis on the impact that this tool will have on the
community. I now that right now there are plenty of clever tricks for
debugging your code, even if it involves FFI calls or Monad
Transformers Stacks but no one trick is a silver bullet. As far as I
know, there is no trick which works the same way both for FFI or
Arrows. However, having a backtrace will really help in any domain,
from DSLs to FRP and Category Theory constructs. It will help also the
beginner average Joe starting to program in Haskell and the senior PhD
doctor Bob from the University. The later will be helped by seeing
what part of his code is responsible for an unexpected failure while
the former will recognize the stack traces he saw in gdb and other
imperative programming languages.

The second completion that I want to do is to give some more details
on the timeline. Between May 26 and first of June I will contact Simon
Peyton Joynes and his coautors to see how I will integrate will their
code base, what are their policies to integrating patches, what
repository they use, etc. This is to ensure continual integration,
such that every day there will be a version of the tool which can be
built on any machine and used for debugging your own code. Moreover, I
will talk to them during this timeframe to convince myself whether the
idea of a HPC-like rewrite is good or I should stick with the existing
one. If later, this would be all that I'll be doing during this
period, otherwise, I'll try to refactor the existing rewrite to the
HPC-like one during this timeframe and during one more week after that
(that is, until 6th of June). Last but not least, this timeframe must
be used to prove several proof of concept snapshots of the debugger,
in both variants for public feedback and further guidance

Between 1st and 14th of June I will integrate higher-order functions
and typeclasses into the debugger. If choosing to do a HPC-like
rewrite only the higher order functions would be integrated until 14th
of June.

However, until 1st of July I will have both higher-order functions and
typeclasses inserted into the debugger, the period between 14th and
30th being a buffered period for cases where I'll get stuck and fall
behind the timeline.

In July, the first week will be dedicated to integrating CAFs while
the second one will be for cross module debugging providing options to
debug only certain modules while ignoring others (assuming that they
are correct). A new buffering period will be between 14th of July and
1st of August, a period which will be used to ensure that all parts
will be integrated well and will work in a non-buggy way.

The month of August is dedicated to community suggested improvements.
Through a series of stress tests or simple tests this debugger will
show its strength and its bugs. The former will be praised while the
later will be solved during this timeframe and after the GSoC period.

Next, some details about my haskell development skills. If the code
snippets found in my blog[1] are not so relevant, maybe a link to the
latest project developed in Haskell will help[2]. The project was
supposed to be a rewrite of Berkley's esspresso program allowing both
for logic expression minimization and for automatic drawing of gates.
Lately, we stopped working on it because we couldn't find a good
working example of it's utility. To add more to my level of Haskell
knowledge, I may say that I am teaching programming paradigms at my
university as a teaching assistant (students are allowed to do so if
they have a very solid knowledge of the subject and a very good
extra-curricular open-source/contest activity) and one quarter of the
course is held in Haskell (though this year will be the first when we
will teach Monads to the students, starting from one of my ideas).
Lastly, I've read books on Haskell and right now I am trying to grasp
Category Theory by reading Awodey's book. Moreover, I have the full
journal of functional programming articles downloaded on my laptop.

As for the community integration, I am one of the most active ROSEdu
members here, taking part in almost any activity that we develop. I am
project manager for one Tech Talks activity and I intend to give a
talk on side effects during the next month. More info can be found by
reading my homepage[3].

Thanks for the patience for reading another long email. Please, do
give some feedback to help me create a better application.

Not really useful PS: I am thinking to chose a graduation license
software project on Haskell though I haven't yet selected a theme and
a domain.

[1]: http://pgraycode.wordpress.com
[2]: http://dev.rosedu.org/xpresso/browser/trunk

-- 
Mihai Maruseac

On Mon, Apr 5, 2010 at 8:26 PM, Mihai Maruseac mihai.marus...@gmail.com wrote:
 Hello haskellers (men and women)!

 I had an idea about a graphical

Re: [Haskell-cafe] Re: Haskell.org re-design

Another attempt:  http://i.imgur.com/ENvl7.png

On 6 April 2010 10:36, Johan Tibell johan.tib...@gmail.com wrote:
 On Tue, Apr 6, 2010 at 5:24 AM, Simon Michael si...@joyful.com wrote:
 On 4/2/10 5:28 AM, Thomas Schilling wrote:

 How about something more colourful?

 http://i.imgur.com/7jCPq.png

 I really like the simplicity of the Cassandra page:

 http://cassandra.apache.org/
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[Haskell-cafe] Re: GSOC Haskell Project

2010-04-06 Thread Mihai Maruseac

Oops, forgot to add the third link: my homepage is at
http://people.rosedu.org/people/mihai_maruseac

On Tue, Apr 6, 2010 at 10:11 PM, Mihai Maruseac
mihai.marus...@gmail.com wrote:
 Hello again

 Following a feedback (courtesy of lispy) of my proposal on #haskell, I
 come to complete it with some bits here and there.

 First, a short analysis on the impact that this tool will have on the
 community. I now that right now there are plenty of clever tricks for
 debugging your code, even if it involves FFI calls or Monad
 Transformers Stacks but no one trick is a silver bullet. As far as I
 know, there is no trick which works the same way both for FFI or
 Arrows. However, having a backtrace will really help in any domain,
 from DSLs to FRP and Category Theory constructs. It will help also the
 beginner average Joe starting to program in Haskell and the senior PhD
 doctor Bob from the University. The later will be helped by seeing
 what part of his code is responsible for an unexpected failure while
 the former will recognize the stack traces he saw in gdb and other
 imperative programming languages.

 The second completion that I want to do is to give some more details
 on the timeline. Between May 26 and first of June I will contact Simon
 Peyton Joynes and his coautors to see how I will integrate will their
 code base, what are their policies to integrating patches, what
 repository they use, etc. This is to ensure continual integration,
 such that every day there will be a version of the tool which can be
 built on any machine and used for debugging your own code. Moreover, I
 will talk to them during this timeframe to convince myself whether the
 idea of a HPC-like rewrite is good or I should stick with the existing
 one. If later, this would be all that I'll be doing during this
 period, otherwise, I'll try to refactor the existing rewrite to the
 HPC-like one during this timeframe and during one more week after that
 (that is, until 6th of June). Last but not least, this timeframe must
 be used to prove several proof of concept snapshots of the debugger,
 in both variants for public feedback and further guidance

 Between 1st and 14th of June I will integrate higher-order functions
 and typeclasses into the debugger. If choosing to do a HPC-like
 rewrite only the higher order functions would be integrated until 14th
 of June.

 However, until 1st of July I will have both higher-order functions and
 typeclasses inserted into the debugger, the period between 14th and
 30th being a buffered period for cases where I'll get stuck and fall
 behind the timeline.

 In July, the first week will be dedicated to integrating CAFs while
 the second one will be for cross module debugging providing options to
 debug only certain modules while ignoring others (assuming that they
 are correct). A new buffering period will be between 14th of July and
 1st of August, a period which will be used to ensure that all parts
 will be integrated well and will work in a non-buggy way.

 The month of August is dedicated to community suggested improvements.
 Through a series of stress tests or simple tests this debugger will
 show its strength and its bugs. The former will be praised while the
 later will be solved during this timeframe and after the GSoC period.

 Next, some details about my haskell development skills. If the code
 snippets found in my blog[1] are not so relevant, maybe a link to the
 latest project developed in Haskell will help[2]. The project was
 supposed to be a rewrite of Berkley's esspresso program allowing both
 for logic expression minimization and for automatic drawing of gates.
 Lately, we stopped working on it because we couldn't find a good
 working example of it's utility. To add more to my level of Haskell
 knowledge, I may say that I am teaching programming paradigms at my
 university as a teaching assistant (students are allowed to do so if
 they have a very solid knowledge of the subject and a very good
 extra-curricular open-source/contest activity) and one quarter of the
 course is held in Haskell (though this year will be the first when we
 will teach Monads to the students, starting from one of my ideas).
 Lastly, I've read books on Haskell and right now I am trying to grasp
 Category Theory by reading Awodey's book. Moreover, I have the full
 journal of functional programming articles downloaded on my laptop.

 As for the community integration, I am one of the most active ROSEdu
 members here, taking part in almost any activity that we develop. I am
 project manager for one Tech Talks activity and I intend to give a
 talk on side effects during the next month. More info can be found by
 reading my homepage[3].

 Thanks for the patience for reading another long email. Please, do
 give some feedback to help me create a better application.

 Not really useful PS: I am thinking to chose a graduation license
 software project on Haskell though I haven't yet selected a theme and
 a domain.

 [1]:

Re: [Haskell-cafe] Re: Haskell.org re-design

2010-04-06 Thread Max Bolingbroke

This is a very nice design. However shouldn't other pages e.g. the
wiki template be redesigning to match as well? If this is not going to
happen, then I would almost prefer sticking to the current design for
consistency's sake.

On 6 April 2010 20:11, Thomas Schilling nomin...@googlemail.com wrote:
 Another attempt:  http://i.imgur.com/ENvl7.png

 On 6 April 2010 10:36, Johan Tibell johan.tib...@gmail.com wrote:
 On Tue, Apr 6, 2010 at 5:24 AM, Simon Michael si...@joyful.com wrote:
 On 4/2/10 5:28 AM, Thomas Schilling wrote:

 How about something more colourful?

 http://i.imgur.com/7jCPq.png

 I really like the simplicity of the Cassandra page:

 http://cassandra.apache.org/
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[Haskell-cafe] Why does Haskell not infer most general type?

2010-04-06 Thread Job Vranish

Is haskell supposed to always infer the most general type (barring
extensions)?

I found a simple case where this is not true:

f _ = undefined
  where
_ = y :: Int - Int

y x = undefined
  where
_ = f x

Haskell infers the types of 'y' and 'f' as:
f :: Int - a
y :: Int - Int

This confused me at first, but after thinking about it a while it seemed to
make sense. But then my friend John pointed out that you can add type sigs
for 'f' and 'y':
f :: a - b
y :: a - b
and have it still typecheck!

This thoroughly confused me.

Why does haskell not infer the most general type for these functions? Is it
a limitation of the algorithm? a limitation of the recursive let binding?

Any insight would be appreciated :)

- Job
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Re: [Haskell-cafe] Re: Haskell.org re-design

Here's a matching Wiki style:  http://i.imgur.com/XkuzH.png

On 6 April 2010 20:35, Max Bolingbroke batterseapo...@hotmail.com wrote:
 This is a very nice design. However shouldn't other pages e.g. the
 wiki template be redesigning to match as well? If this is not going to
 happen, then I would almost prefer sticking to the current design for
 consistency's sake.

 On 6 April 2010 20:11, Thomas Schilling nomin...@googlemail.com wrote:
 Another attempt:  http://i.imgur.com/ENvl7.png

 On 6 April 2010 10:36, Johan Tibell johan.tib...@gmail.com wrote:
 On Tue, Apr 6, 2010 at 5:24 AM, Simon Michael si...@joyful.com wrote:
 On 4/2/10 5:28 AM, Thomas Schilling wrote:

 How about something more colourful?

 http://i.imgur.com/7jCPq.png

 I really like the simplicity of the Cassandra page:

 http://cassandra.apache.org/
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Re: [Haskell-cafe] Why does Haskell not infer most general type?

2010-04-06 Thread Brandon S. Allbery KF8NH


On Apr 6, 2010, at 15:56 , Job Vranish wrote:
Is haskell supposed to always infer the most general type (barring  
extensions)?



Look up the monomorphism restriction.

--
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system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu
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Re: [Haskell-cafe] Why does Haskell not infer most general type?

2010-04-06 Thread John Van Enk

I don't believe that the monomorphism restriction has anything to do with
this. Removing it does not generalize the type.

On Tue, Apr 6, 2010 at 4:46 PM, Brandon S. Allbery KF8NH 
allb...@ece.cmu.edu wrote:

 On Apr 6, 2010, at 15:56 , Job Vranish wrote:

 Is haskell supposed to always infer the most general type (barring
 extensions)?


 Look up the monomorphism restriction.

 --
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 system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu
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Re: [Haskell-cafe] Why does Haskell not infer most general type?

2010-04-06 Thread Edward Z. Yang

Excerpts from Brandon S. Allbery KF8NH's message of Tue Apr 06 16:46:28 -0400 
2010:
 On Apr 6, 2010, at 15:56 , Job Vranish wrote:
  Is haskell supposed to always infer the most general type (barring  
  extensions)?
 Look up the monomorphism restriction.

Hey Brandon,

I tested the code with -XNoMonomorphismRestriction and it still inferred
the specific type, so perhaps this is either a GHC bug or something
different?  wnoise also points out that both functions take arguments,
so the monomorphism restriction doesn't apply.

See: 
http://www.reddit.com/r/haskell/comments/bn9to/type_checker_trivia_what_are_the_types_of_f_and_y/

Cheers,
Edward
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[Haskell-cafe] Established names for a couple of list functionals?

2010-04-06 Thread Stephen Tetley

Hello all


Having traversals with special behaviour for the first or last element
is useful for my current work:

-- first element special
--
anacrusisMap :: (a - b) - (a - b) - [a] - [b]
anacrusisMap _ _ [] = []
anacrusisMap f g (a:as) = f a : map g as

-- last element special
--
cabooseMap :: (a - b) - (a - b) - [a] - [b]
cabooseMap _ _ [] = []
cabooseMap f g (a:as) = step a as where
  step x []   = [g x]
  step x (y:ys)   = f x : step y ys


*Overlay1 anacrusisMap (+1) id [1..10]
[2,2,3,4,5,6,7,8,9,10]

*Overlay1 cabooseMap id (+1) [1..10]
[1,2,3,4,5,6,7,8,9,11]

My question (trivial, but still...) - is there any prior art naming
these functions?

For the record, my name derivation is:

+ anacrusis - musical term, the pickup notes before the first bar in a score.

+ caboose - there was discussion on Haskell-Cafe a couple of months
ago about a list data type with a distinguished terminal type. Caboose
is the name I remember.



Thanks

Stephen
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Re: [Haskell-cafe] Announce: hothasktags

2010-04-06 Thread Erlend Hamberg

On Thursday 1. April 2010 22.46.47 Luke Palmer wrote:
 I'd like to draw attention to a little script I wrote.  I tend to use
 qualified imports and short names like new and filter.  This makes
 hasktags pretty much useless, since it basically just guesses which
 one to go to.  hothasktags is a reimplementation of hasktags that uses
 haskell-src-exts to analyze the import structure to generate (scoped)
 tags pointing to the right definition.  I'm pretty addicted to it,
 since it provides the only functionality I miss from visual studio

Thanks for this. Seems to be working very nicely. :-)

-- 
Erlend Hamberg
“Everything will be ok in the end. If its not ok, its not the end.”
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Re: [Haskell-cafe] Why does Haskell not infer most general type?

2010-04-06 Thread Ross Paterson

On Tue, Apr 06, 2010 at 03:56:32PM -0400, Job Vranish wrote:
 f _ = undefined
   where
 _ = y :: Int - Int
 
 y x = undefined
   where
 _ = f x

Because f and y are mutually recursive, their types are inferred together,
so y gets the type Int - Int (as given), which forces f :: Int - a.

If you add the type signature f :: a - b, you break the cycle: that
type is used in inferring the type of y (namely a - b), which is then
used in checking the typeof f.  Ditto if you add y :: a - b instead.
(This is not Haskell 98, but the implementations have done this for
years, and it will be in Haskell 2010.)
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Re: [Haskell-cafe] Why does Haskell not infer most general type?

2010-04-06 Thread Job Vranish

So in Haskell 98, would the added constraints result in a type error?

- Job

On Tue, Apr 6, 2010 at 5:12 PM, Ross Paterson r...@soi.city.ac.uk wrote:

 On Tue, Apr 06, 2010 at 03:56:32PM -0400, Job Vranish wrote:
  f _ = undefined
where
  _ = y :: Int - Int
 
  y x = undefined
where
  _ = f x

 Because f and y are mutually recursive, their types are inferred together,
 so y gets the type Int - Int (as given), which forces f :: Int - a.

 If you add the type signature f :: a - b, you break the cycle: that
 type is used in inferring the type of y (namely a - b), which is then
 used in checking the typeof f.  Ditto if you add y :: a - b instead.
 (This is not Haskell 98, but the implementations have done this for
 years, and it will be in Haskell 2010.)
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Re: [Haskell-cafe] Why does Haskell not infer most general type?

Yes, it has to do with mutually recursive bindings.  If you add a type
signature, you break the mutual recursion.  Mutually recursive
functions are type-checked together and then generalised.  Similarly,
polymorphic recursion cannot be inferred either, but is possible by
adding a type signature.

HTH

On 6 April 2010 20:56, Job Vranish job.vran...@gmail.com wrote:

 Is haskell supposed to always infer the most general type (barring
 extensions)?

 I found a simple case where this is not true:

 f _ = undefined
   where
     _ = y :: Int - Int

 y x = undefined
   where
     _ = f x

 Haskell infers the types of 'y' and 'f' as:
 f :: Int - a
 y :: Int - Int

 This confused me at first, but after thinking about it a while it seemed to
 make sense. But then my friend John pointed out that you can add type sigs
 for 'f' and 'y':
 f :: a - b
 y :: a - b
 and have it still typecheck!

 This thoroughly confused me.

 Why does haskell not infer the most general type for these functions? Is it
 a limitation of the algorithm? a limitation of the recursive let binding?

 Any insight would be appreciated :)

 - Job


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Re: [Haskell-cafe] Why does Haskell not infer most general type?

2010-04-06 Thread John Meacham

On Tue, Apr 06, 2010 at 03:56:32PM -0400, Job Vranish wrote:
 Why does haskell not infer the most general type for these functions? Is it
 a limitation of the algorithm? a limitation of the recursive let binding?
 
 Any insight would be appreciated :)

This is due to when Haskell does generalizing, first, the definitions
are broken up into strongly connected components based on their
dependencies. Then, in dependency order, the components are type checked
then generalized and the result is added to the environment and made
available to further typechecking. Notably the types are set in stone at
this point and should be the most general they can be.

So what is going on here is that your two function f and y depend on
each other so are part of the same binding group and hence typecheckd
together. this causes y's unknown type to be unified with its use in f,
giving it the more specific Int - Int type, even though it could be
assigned a more general one.

This is what should happen according to the haskell standard, however,
it was pointed out in the typing haskell in haskell paper that this is
more strict than neccessary, we can furuther split up the binding group
based on 'type dependency' as in, if g and h call each other and g has
an explicit signature, then h need not be considered to depend on it as
the explicit type for g can just be added to the envirornment. When
determining binding groups, we can ignore dependencies through explicit
types effecitively. This was proposed as an extension to haskell 98 in
the THIH paper, and is generally considederd a good idea.

What you have here is a more pathological variation on that, while y
doesn't have an explicit signature, it is used with an explicit one in
f, hence one could theoretically subdivide the binding group, typing f
alone, getting its most general type, then typing y, then going back and
verifying y's use in f is valid. It is ceratinly possible to come up
with a specification for an extended type inference algorithm such as
this, but whether it is worth it is another matter.

John


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[Haskell-cafe] what are the safety conditions for unsafeIOToST

2010-04-06 Thread Nicolas Frisby

I haven't been able to find it via Google or Haddock. An old message
suggests is was just a matter of exceptions?

I only want to use the IO for generating Data.Uniques to pair with
STRefs in order to make a map of them. I'm guessing this would be a
safe use since it's exception free (... right?).

Thanks!
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Re: [Haskell-cafe] Established names for a couple of list functionals?

Stephen Tetley stephen.tet...@gmail.com writes:
 -- first element special
 --
 anacrusisMap :: (a - b) - (a - b) - [a] - [b]
 anacrusisMap _ _ [] = []
 anacrusisMap f g (a:as) = f a : map g as

I've done something like this, and gave it the extremely imaginative
name of firstOthers.  But it was an internal non-exported function.

-- 
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ivan.miljeno...@gmail.com
IvanMiljenovic.wordpress.com
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[Haskell-cafe] Simple binary-protocol through network test

2010-04-06 Thread Yves Parès


Hello,

I'm trying to use the packages Network and Control.Monad.BinaryProtocol
together, with a very simple program in which a client sends an operation to
the server, which computes the result and sends it back.

But the server holds when trying to receive (Server.hs, line 22), whereas
the client has actually sent the data (Client.hs, line 17).
The server stops to hold only when the client is killed with a Ctrl-C.

This should be rather simple, and I can't get to know why it doesn't work.

The files are here:
http://old.nabble.com/file/p28157883/Client.hs Client.hs 
http://old.nabble.com/file/p28157883/Server.hs Server.hs 
http://old.nabble.com/file/p28157883/SharedData.hs SharedData.hs 

-
Yves Parès

Live long and prosper
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Re: [Haskell-cafe] Re: Haskell.org re-design

Thomas Schilling nomin...@googlemail.com writes:

 Another attempt:  http://i.imgur.com/ENvl7.png

I like the layout, but hate the colour scheme.

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Re: [Haskell-cafe] Simple binary-protocol through network test

Yay, I'm glad to see someone else using my package. :-)

Hmm, your program seems to work for me. I compiled and ran the Server (with
ghc --make), then compiled and ran the Client, and then typed

Operation 1.0 Mult 2.0

into the Client process, and the result it got was

2.0

with the output

Just 2.0

on the Server.

I got the same results running this on Mac OSX and (Gentoo) Linux, with GHC
10.4. What platform/GHC version are you running it on?

Cheers,
Greg

On Apr 6, 2010, at 2:38 PM, Yves Parès wrote:

Hello,

I'm trying to use the packages Network and Control.Monad.BinaryProtocol
together, with a very simple program in which a client sends an operation to
the server, which computes the result and sends it back.

But the server holds when trying to receive (Server.hs, line 22), whereas
the client has actually sent the data (Client.hs, line 17).
The server stops to hold only when the client is killed with a Ctrl-C.

This should be rather simple, and I can't get to know why it doesn't work.

The files are here:
http://old.nabble.com/file/p28157883/Client.hs Client.hs
http://old.nabble.com/file/p28157883/Server.hs Server.hs
http://old.nabble.com/file/p28157883/SharedData.hs SharedData.hs

-
Yves Parès

Live long and prosper
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Re: [Haskell-cafe] Re: Haskell.org re-design

On 6 April 2010 22:39, Ivan Lazar Miljenovic ivan.miljeno...@gmail.com wrote:
 Thomas Schilling nomin...@googlemail.com writes:

 Another attempt:  http://i.imgur.com/ENvl7.png

 I like the layout, but hate the colour scheme.

Wow, hate is a very strong word.  In any case, though, I'm pretty
sure it'll be impossible to please everyone.  FWIW, I used this:
http://www.colourlovers.com/palette/694737/Thought_Provoking

If we can agree on the general layout, though, I can create some
colour scheme variants.  I know this stuff is very subjective, but I
would appreciate constructive feedback.

/ Thomas
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Re: [Haskell-cafe] Simple binary-protocol through network test

2010-04-06 Thread Yves Parès

Weird...

I use GHC 6.12.1, and I run Ubuntu 9.10 (32bits version).

Would have I miss something? Like a flush or a close? Logically, I don't see
where I would...

Gregory Crosswhite-2 wrote:

Yay, I'm glad to see someone else using my package. :-)

Hmm, your program seems to work for me. I compiled and ran the Server
(with ghc --make), then compiled and ran the Client, and then typed

Operation 1.0 Mult 2.0

into the Client process, and the result it got was

2.0

with the output

Just 2.0

on the Server.

I got the same results running this on Mac OSX and (Gentoo) Linux, with
GHC 10.4. What platform/GHC version are you running it on?

Cheers,
Greg

On Apr 6, 2010, at 2:38 PM, Yves Parès wrote:

Hello,

I'm trying to use the packages Network and Control.Monad.BinaryProtocol
together, with a very simple program in which a client sends an operation
to
the server, which computes the result and sends it back.

This should be rather simple, and I can't get to know why it doesn't
work.

The files are here:
http://old.nabble.com/file/p28157883/Client.hs Client.hs
http://old.nabble.com/file/p28157883/Server.hs Server.hs
http://old.nabble.com/file/p28157883/SharedData.hs SharedData.hs

-
Yves Parès

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-
Yves Parès

Live long and prosper
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[Haskell-cafe] [haskell.org Google Summer of Code] Student Applications Due Friday!

2010-04-06 Thread Edward Kmett

This is a friendly reminder that student applications for the summer of code
are due to Google by Friday, April 9th.
http://socghop.appspot.com/document/show/gsoc_program/google/gsoc2010/timeline

That is just *3 days* from now!

Keep in mind that while we've been tracking general interest in different
projects through the trac, the application doesn't count unless you submit
it to Google at
http://socghop.appspot.com/gsoc/program/home/google/gsoc2010

While all details of the application do not need to be finalized, as much of
the information from
http://hackage.haskell.org/trac/summer-of-code/wiki/StudApply2010
as possible should probably be included in your application.

If you are stuck and having a hard time thinking of ideas, I highly
recommend the excellent guide that Don Stewart posted recently:
http://donsbot.wordpress.com/2010/04/01/the-8-most-important-haskell-org-gsoc-projects/

I'd also recommend taking a look through the trac at
http://hackage.haskell.org/trac/summer-of-code/report/1
to gauge interest.

Please email me if you have any questions or concerns.

-Edward Kmett
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[Haskell-cafe] Re: GSoC: Improving Cabal's Test Support

2010-04-06 Thread Thomas Tuegel

Hello again!

Based on the invaluable feedback I've received, I've made some
revisions to the proposal I made a few days ago (at the end of this
post, after my signature).  I apologize for the length of my post, but
I'd like once again to solicit feedback on this.  Any commentary is
very helpful!

Thanks!
-- 
Thomas Tuegel


Throughout this proposal, examples are given to indicate how a package
author would utilize the features proposed here.  In all these
examples, suppose that the programmer is the author of the
'haskell-foo' package, which exposes the module 'Foo' and has a single
test executable, 'foo-tests', using the QuickCheck testing library.


Package Description File Syntax

The syntax for designating test executables in package description
files will be based on the existing syntax for describing executables.
 Such a stanza in the hypothetical package's description file would
look like:

 Test foo-tests
 main-is: foo-tests.hs
 build-depends: haskell-foo, Cabal, QuickCheck

This example is obviously minimal; this is really an 'Executable'
stanza by another name, so any options recognized there would also be
valid here.


Handling of Test Executables by Cabal

The changes proposed here will make it possible to build, test, and
install a Cabal package with the usual sequence of commands:

$ cabal configure
$ cabal build
$ cabal test
$ cabal install

Cabal will recognize two new options during the 'configure' stage:
'--enable-tests' and '--disable-tests'.

If 'cabal configure' is invoked with the '--enable-tests' option, then
any test executables designated in the package description file will
be built.  For the purposes of the 'configure' and 'build' stages,
they will be handled as if they were ordinary executables, i.e.,
described by 'Executable' stanzas.  With tests enabled, the test
programs will be executed and their results collected by Cabal during
the 'test' stage.

If 'cabal configure' is invoked with the '--disable-tests' option
(which should be the default if neither option is specified), then
test executables designated in the package description file will be
ignored, as if the 'Test' stanza were absent.  Any attempt to invoke
the 'test' stage with tests disabled should remind the user of that
fact.

Regardless of the status of tests (enabled or disabled), the 'install'
stage will ignore any executables designated as test suites, since it
is not desirable to install the test executables.


Collection of Test Results

Cabal will provide a standard interface, residing in the module
'Distribution.Test', for running tests independent of the testing
library used.  A minimal outline of this module looks like:

 module Distribution.Test where

 type Name = String
 type Result = Maybe Bool
 type Info = String
 type Output = String

 -- 'Compiler' and 'ComponentLocalBuildInfo' are already provided by Cabal.
 -- They are included here to aid in debugging test failures
 type Report = (Compiler, ComponentLocalBuildInfo, [(Name, Result, Info, 
 Output)])

 class Test t where
 wrap :: t - IO (Result, Info)

 runTests :: Test t = [(Name, t)] - IO Report

 writeResults :: Report - IO ()

Instances of 'Test' will run a type of test from one of the testing
libraries; part of this project will therefore be patching QuickCheck
and HUnit to provide these instances.  Any other testing library
providing this instance will also be compatible with the automated
testing features this proposal introduces.

The type 'Maybe Bool' is used throughout this framework to indicate a
test result: 'Nothing' indicates a test was not run, 'Just False'
indicates a failed test, and 'Just True' indicates a successful test.
The 'Info' string captures any information provided by the testing
library.  However, because of the reliance of most test suites on
standard output, Cabal will also capture the standard output produced
during each test (when the test suite is invoked through 'cabal
test'); the output will be included in the test result file.

The function 'writeResults' will write the test results to a file.
The 'Show' instance for the type of its single argument will therefore
constitute the standard test result file format.  This has the
advantage of being human- and machine-readable without requiring any
extra dependencies to parse the file.

With this framework, the hypothetical package's author might write a
test suite such as:

 module Main where

 import Distribution.Test
 import Foo
 import QuickCheck

 testBar :: Gen Bool
 testBar = ...

 testBaz :: Gen Bool
 testBaz = ...

 main = runTests [(testBar, testBar), (testBaz, testBaz)] = writeResults


Reporting and Comparing Test Results

The 'cabal test' command will run tests by default, but support two
other options:

1.  '--report [file]', which will produce a nicely formatted
report of the test results stored in the named file, or of the last
run of the package's test suite if no file is specified, and
2.  '--diff file1 file2',

Re: [Haskell-cafe] Simple binary-protocol through network test

Hmm, I am guessing it is more likely that the problem is that the I/O system
changed from 6.10.4 to 6.12.1 somehow in a way that broke the package. You
could try turning off all buffering in the handle using hSetBuffering and
seeing if that works.

Cheers,
Greg

On Apr 6, 2010, at 3:44 PM, Yves Parès wrote:

Weird...

I use GHC 6.12.1, and I run Ubuntu 9.10 (32bits version).

Would have I miss something? Like a flush or a close? Logically, I don't see
where I would...

Gregory Crosswhite-2 wrote:

Yay, I'm glad to see someone else using my package. :-)

Hmm, your program seems to work for me. I compiled and ran the Server
(with ghc --make), then compiled and ran the Client, and then typed

Operation 1.0 Mult 2.0

into the Client process, and the result it got was

2.0

with the output

Just 2.0

on the Server.

I got the same results running this on Mac OSX and (Gentoo) Linux, with
GHC 10.4. What platform/GHC version are you running it on?

Cheers,
Greg

On Apr 6, 2010, at 2:38 PM, Yves Parès wrote:

Hello,

I'm trying to use the packages Network and Control.Monad.BinaryProtocol
together, with a very simple program in which a client sends an operation
to
the server, which computes the result and sends it back.

This should be rather simple, and I can't get to know why it doesn't
work.

The files are here:
http://old.nabble.com/file/p28157883/Client.hs Client.hs
http://old.nabble.com/file/p28157883/Server.hs Server.hs
http://old.nabble.com/file/p28157883/SharedData.hs SharedData.hs

-
Yves Parès

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Re: [Haskell-cafe] Why does Haskell not infer most general type?

2010-04-06 Thread Ross Paterson

On Tue, Apr 06, 2010 at 05:18:34PM -0400, Job Vranish wrote:
 So in Haskell 98, would the added constraints result in a type error?

Yes, because the types of the mutually recursive identifiers would be
inferred together without using the type signatures, and then would
fail to match the declared types.

But then there aren't any implementations of Haskell 98 to test this on.
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Re: [Haskell-cafe] Re: GSoC: Improving Cabal's Test Support

Rather that starting from scratch, you should strongly consider adapting 
something like test-framework to this task, as it already has done the heavy 
work of creating a way to combine tests from different frameworks into a single 
suite and includes such features as displaying a progress bar during the 
QuickCheck tests.  Furthermore, it is easily extendable to support new kinds of 
tests;  for example, I found that it was relatively straightforward to add a 
new kind of statistical test to make sure that the average value of a 
function where where it should be.

Cheers,
Greg

On Apr 6, 2010, at 3:51 PM, Thomas Tuegel wrote:

 Hello again!
 
 Based on the invaluable feedback I've received, I've made some
 revisions to the proposal I made a few days ago (at the end of this
 post, after my signature).  I apologize for the length of my post, but
 I'd like once again to solicit feedback on this.  Any commentary is
 very helpful!
 
 Thanks!
 -- 
 Thomas Tuegel
 
 
 Throughout this proposal, examples are given to indicate how a package
 author would utilize the features proposed here.  In all these
 examples, suppose that the programmer is the author of the
 'haskell-foo' package, which exposes the module 'Foo' and has a single
 test executable, 'foo-tests', using the QuickCheck testing library.
 
 
Package Description File Syntax
 
 The syntax for designating test executables in package description
 files will be based on the existing syntax for describing executables.
 Such a stanza in the hypothetical package's description file would
 look like:
 
 Test foo-tests
main-is: foo-tests.hs
build-depends: haskell-foo, Cabal, QuickCheck
 
 This example is obviously minimal; this is really an 'Executable'
 stanza by another name, so any options recognized there would also be
 valid here.
 
 
Handling of Test Executables by Cabal
 
 The changes proposed here will make it possible to build, test, and
 install a Cabal package with the usual sequence of commands:
 
 $ cabal configure
 $ cabal build
 $ cabal test
 $ cabal install
 
 Cabal will recognize two new options during the 'configure' stage:
 '--enable-tests' and '--disable-tests'.
 
 If 'cabal configure' is invoked with the '--enable-tests' option, then
 any test executables designated in the package description file will
 be built.  For the purposes of the 'configure' and 'build' stages,
 they will be handled as if they were ordinary executables, i.e.,
 described by 'Executable' stanzas.  With tests enabled, the test
 programs will be executed and their results collected by Cabal during
 the 'test' stage.
 
 If 'cabal configure' is invoked with the '--disable-tests' option
 (which should be the default if neither option is specified), then
 test executables designated in the package description file will be
 ignored, as if the 'Test' stanza were absent.  Any attempt to invoke
 the 'test' stage with tests disabled should remind the user of that
 fact.
 
 Regardless of the status of tests (enabled or disabled), the 'install'
 stage will ignore any executables designated as test suites, since it
 is not desirable to install the test executables.
 
 
Collection of Test Results
 
 Cabal will provide a standard interface, residing in the module
 'Distribution.Test', for running tests independent of the testing
 library used.  A minimal outline of this module looks like:
 
 module Distribution.Test where
 
 type Name = String
 type Result = Maybe Bool
 type Info = String
 type Output = String
 
 -- 'Compiler' and 'ComponentLocalBuildInfo' are already provided by Cabal.
 -- They are included here to aid in debugging test failures
 type Report = (Compiler, ComponentLocalBuildInfo, [(Name, Result, Info, 
 Output)])
 
 class Test t where
wrap :: t - IO (Result, Info)
 
 runTests :: Test t = [(Name, t)] - IO Report
 
 writeResults :: Report - IO ()
 
 Instances of 'Test' will run a type of test from one of the testing
 libraries; part of this project will therefore be patching QuickCheck
 and HUnit to provide these instances.  Any other testing library
 providing this instance will also be compatible with the automated
 testing features this proposal introduces.
 
 The type 'Maybe Bool' is used throughout this framework to indicate a
 test result: 'Nothing' indicates a test was not run, 'Just False'
 indicates a failed test, and 'Just True' indicates a successful test.
 The 'Info' string captures any information provided by the testing
 library.  However, because of the reliance of most test suites on
 standard output, Cabal will also capture the standard output produced
 during each test (when the test suite is invoked through 'cabal
 test'); the output will be included in the test result file.
 
 The function 'writeResults' will write the test results to a file.
 The 'Show' instance for the type of its single argument will therefore
 constitute the standard test result file format.  This has the
 advantage of being human- and machine-readable

Re: [Haskell-cafe] Simple binary-protocol through network test

2010-04-06 Thread Yves Parès

Okay, so I turned off every buffering using hSetBuffering hdl NoBuffering on
both Client and Server, but I doesn't fix it...
BTW, I tried to do the same without your package, i.e. simply through Lazy
ByteString and Binary, but it doesn't work either, I come up against the
same issue.

Gregory Crosswhite-2 wrote:

Hmm, I am guessing it is more likely that the problem is that the I/O
system changed from 6.10.4 to 6.12.1 somehow in a way that broke the
package. You could try turning off all buffering in the handle using
hSetBuffering and seeing if that works.

Cheers,
Greg

On Apr 6, 2010, at 3:44 PM, Yves Parès wrote:

Weird...

I use GHC 6.12.1, and I run Ubuntu 9.10 (32bits version).

Would have I miss something? Like a flush or a close? Logically, I don't
see
where I would...

Gregory Crosswhite-2 wrote:

Yay, I'm glad to see someone else using my package. :-)

Hmm, your program seems to work for me. I compiled and ran the Server
(with ghc --make), then compiled and ran the Client, and then typed

Operation 1.0 Mult 2.0

into the Client process, and the result it got was

2.0

with the output

Just 2.0

on the Server.

I got the same results running this on Mac OSX and (Gentoo) Linux, with
GHC 10.4. What platform/GHC version are you running it on?

Cheers,
Greg

On Apr 6, 2010, at 2:38 PM, Yves Parès wrote:

Hello,

I'm trying to use the packages Network and Control.Monad.BinaryProtocol
together, with a very simple program in which a client sends an
operation
to
the server, which computes the result and sends it back.

But the server holds when trying to receive (Server.hs, line 22),
whereas
the client has actually sent the data (Client.hs, line 17).
The server stops to hold only when the client is killed with a Ctrl-C.

This should be rather simple, and I can't get to know why it doesn't
work.

The files are here:
http://old.nabble.com/file/p28157883/Client.hs Client.hs
http://old.nabble.com/file/p28157883/Server.hs Server.hs
http://old.nabble.com/file/p28157883/SharedData.hs SharedData.hs

-
Yves Parès

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Live long and prosper
--
View this message in context:
http://old.nabble.com/Simple-binary-protocol-through-network-test-tp28157883p28158761.html
Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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Re: [Haskell-cafe] Re: GSoC: Improving Cabal's Test Support

2010-04-06 Thread Thomas Tuegel

On Tue, Apr 6, 2010 at 7:03 PM, Gregory Crosswhite
gcr...@phys.washington.edu wrote:
 Rather that starting from scratch, you should strongly consider adapting 
 something like test-framework to this task, as it already has done the heavy 
 work of creating a way to combine tests from different frameworks into a 
 single suite and includes such features as displaying a progress bar during 
 the QuickCheck tests.  Furthermore, it is easily extendable to support new 
 kinds of tests;  for example, I found that it was relatively straightforward 
 to add a new kind of statistical test to make sure that the average value 
 of a function where where it should be.


Thanks for the suggestion!  I've taken a hard look at test-framework
in particular already.  I like it, but the reason I haven't already
chosen to go with that is that it does a lot _more_ than I'm trying to
do here.  The way my proposal stands, whatever framework I go with
gets integrated with Cabal at least to the degree that Cabal can read
test results.  Rogan suggested that test-framework will shortly
support JUnit XML as an output format, so with the rest of my proposal
we'd be talking about adding an XML parsing library to Cabal's
dependencies.

Now, if you're telling me I'm going off in the wrong direction by
proposing to integrate a test framework into Cabal itself, that's
another story.  Should I pare down my proposal to only include support
for a proper 'Test' stanza in the package description file and leave
it at that?

Thanks!
-- 
Thomas Tuegel
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Re: [Haskell-cafe] Re: GSoC: Improving Cabal's Test Support

2010-04-06 Thread Rogan Creswick

On Tue, Apr 6, 2010 at 4:03 PM, Gregory Crosswhite
gcr...@phys.washington.edu wrote:

 Rather that starting from scratch, you should strongly consider adapting 
 something like test-framework to this task, as it already has done the heavy 
 work of creating a way to combine tests from different frameworks into a 
 single suite

I want to second this -- test-framework would be a good place to
start, and you would be able to accomplish quite a lot more during the
summer.  Your proposal addresses (at least!) two different problems:

  * updating cabal so that it can handle the build/test process; and,
  * combining HUnit / QuickCheck / etc. to present a uniform interface.

test-framework and test-runner both address the second problem, and
those solutions can be kept separate, at least for now.  Figuring out
the best way to specify test commands, dependencies, build/execution
order, etc. is going to take some substantial effort, and I think that
should be the first goal of the project.

More comments in-line below...

On Apr 6, 2010, at 3:51 PM, Thomas Tuegel wrote:
    Package Description File Syntax

 The syntax for designating test executables in package description
 files will be based on the existing syntax for describing executables.
 Such a stanza in the hypothetical package's description file would
 look like:

 Test foo-tests
    main-is: foo-tests.hs
    build-depends: haskell-foo, Cabal, QuickCheck

 This example is obviously minimal; this is really an 'Executable'
 stanza by another name, so any options recognized there would also be
 valid here.

Cabal allows for multiple executable sections -- are multiple test
sections allowed? If so, how are they handled when 'cabal test' is
invoked?  If not, will there be any support for running multiple test
suites? (more on this below).

While the test executable could be configured to run different sets of
tests (at runtime? hm.. we may need more flags to 'cabal test'), there
are some situations it's necessary to build multiple test suites
because of odd library dependencies.  (for example, testing certain
combinations of libraries--imagine supporting multiple versions of
ghc.)

The existing Executable sections may serve the need fine, if we could
specify how to run the tests in a different way.  Perhaps a list of
test commands could be specified instead, eg:

 TestCommands: foo-test-ghc6.6,
foo-test-ghc6.8,
foo-props --all

Anyhow, just food for thought.

 described by 'Executable' stanzas.  With tests enabled, the test
 programs will be executed and their results collected by Cabal during
 the 'test' stage.

Where are the results collected, and in what format? My preference is
to choose a sensible default (dist/test-results?) and allow it to be
overridden in the cabal file.

 module Distribution.Test where

 type Name = String
 type Result = Maybe Bool

I think you're reinventing the wheel a bit here, (see comments above
about test-framework).

That aside, Result is still too restrictive.  Ignored tests may well
need justification (why were they not run?).  There may also be
multiple ways to ignore tests, and it isn't clear to me what those
are, or which are important.

I also feel pretty strongly that Result should distinguish between
test failures and tests that failed due to exceptional circumstances.
I don't know of any frameworks that do this in Haskell yet, but it has
proven to be a useful distinction in other languages.

I'm not commenting on the rest of the framework proposal because I
don't think the point of this SoC project is to write another testing
framework.

 The 'cabal test' command will run tests by default, but support two
 other options:

    1.  '--report [file]', which will produce a nicely formatted
 report of the test results stored in the named file, or of the last
 run of the package's test suite if no file is specified, and
    2.  '--diff file1 file2', which will show the differences between
 the test results stored it two different files.

See my comments about running multiple test suites, and parameterized
test suites above.  I think richer parameters are necessary.
(possibly just a --pass-through flag that hands all the subsequent
parameters off to the test executable(s))

--Rogan
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Re: [Haskell-cafe] Re: Haskell.org re-design

2010-04-06 Thread Ivan Miljenovic

On 7 April 2010 08:40, Thomas Schilling nomin...@googlemail.com wrote:
 On 6 April 2010 22:39, Ivan Lazar Miljenovic ivan.miljeno...@gmail.com 
 wrote:
 I like the layout, but hate the colour scheme.

 Wow, hate is a very strong word.

OK, I dislike the colour scheme.  Happy now? ;-)

-- 
Ivan Lazar Miljenovic
ivan.miljeno...@gmail.com
IvanMiljenovic.wordpress.com
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Re: [Haskell-cafe] Re: Haskell.org re-design

On 7 April 2010 00:57, Ivan Miljenovic ivan.miljeno...@gmail.com wrote:
 On 7 April 2010 08:40, Thomas Schilling nomin...@googlemail.com wrote:
 On 6 April 2010 22:39, Ivan Lazar Miljenovic ivan.miljeno...@gmail.com 
 wrote:
 I like the layout, but hate the colour scheme.

 Wow, hate is a very strong word.

 OK, I dislike the colour scheme.  Happy now? ;-)

That's still not constructive.  I.e, is it the black, the gray, the orange?

I played around with some more colours, but eg. blue link colour makes
the site feel too cold.  Using more intense colours for the bar at the
top becomes distracting very quickly.  A background other than white
is either hard to read, or highly dependent on the screen.  E.g., a
nice bright beige on one screen can look too yellowish on another
screen.

Anyway, here's something with a bit more colour:  http://i.imgur.com/LpQmH.png

/ Thomas
-- 
Push the envelope.  Watch it bend.
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Re: [Haskell-cafe] Re: Haskell.org re-design

2010-04-06 Thread Ivan Miljenovic

On 7 April 2010 10:02, Thomas Schilling nomin...@googlemail.com wrote:
 On 7 April 2010 00:57, Ivan Miljenovic ivan.miljeno...@gmail.com wrote:
 OK, I dislike the colour scheme.  Happy now? ;-)

 That's still not constructive.  I.e, is it the black, the gray, the orange?

OK, it's the black; it seems a tad too strong for me (the fact that
you have a black theme for your browser probably doesn't help).

 Using more intense colours for the bar at the top becomes distracting very 
 quickly.

How about a more neutral, paler colour?

 Anyway, here's something with a bit more colour:  http://i.imgur.com/LpQmH.png

Apart from the black up the top still, I think this is nicer.
However, maybe the links in the description text up the top are a bit
too obvious...


-- 
Ivan Lazar Miljenovic
ivan.miljeno...@gmail.com
IvanMiljenovic.wordpress.com
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Re: [Haskell-cafe] Re: GSoC: Improving Cabal's Test Support


On Apr 6, 2010, at 4:40 PM, Thomas Tuegel wrote:

 Now, if you're telling me I'm going off in the wrong direction by
 proposing to integrate a test framework into Cabal itself, that's
 another story.  Should I pare down my proposal to only include support
 for a proper 'Test' stanza in the package description file and leave
 it at that?

Yes, I think that would be a better use of your time, and furthermore if you 
arrange this feature so that the programmer can use any test framework that 
they like, it has the advantage that you are not entrenching a particular way 
of combining tests from different modules.  If you want there to be 
communication between Cabal and the test suite, it should be something simple 
like passing in a location to where the test results should be output (or a 
flag indicating that they should be written to the screen in verbose mode), 
and having Cabal in return receive from the test runner a single string with a 
summary of the test results to show to the user (when in summary as opposed 
to verbose mode) and possibly a flag if there were any failures so that the 
user can be specifically alerted to this fact and pointed to the full test 
report.

Even if all you do is add systematic support for automatically building and 
running tests automatically as part of the build process, it would still be a 
major improvement;  it would be especially awesome if you made it possible to 
separate out the test framework dependencies from the package dependencies, 
since at the moment people who want to include tests with their package often 
feel the need to include dependencies on packages such as QuickCheck in order 
to make life easier for themselves, but if you could modify cabal so it would 
only pull in such packages when the user requests that tests be run it would be 
awesome!

Cheers,
Greg

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Re: [Haskell-cafe] Re: Haskell.org re-design