gmane.comp.lang.haskell.cafe

Re: Problem with packet documentation generated by cabal on windows 7

Antoine Latter — 2012-05-26T01:40:30

Also 'cabal' doesn't track executables, only libraries.

Antoine

Re: Correspondence between libraries and modules

Chris Wong — 2012-05-26T01:04:56

Rustom:


The problem is, Cabal is not a package management system. The name
gives it away: it is the Common Architecture for *Building*
Applications and Libraries. Cabal is to Haskell how GNU autotools +
make is to C: a thin wrapper that checks for dependencies and invokes
the compiler. All that boring
not-making-your-package-break-everything-else stuff belongs to the
distribution maintainer, not Hackage and Cabal.


Use apt-get. Your distribution packages are usually new enough, have
been tested thoroughly, and most importantly, do not conflict with
each other.


Installing with --user is usually the best, since they won't clobber
system packages and if^H^Hwhen they do go wrong, you can simply rm -r
~/.ghc. For actual coding, it's better to use a sandboxing tool such
as [cabal-dev][] instead.

[cabal-dev]: http://hackage.haskell.org/package/cabal-dev


See above.

By the way, someone else a whole article about it:
https://ivanmiljenovic.wordpress.com/2010/03/15/repeat-after-me-cabal-is-not-a-package-manage

gona to join in haskell-cafe

Dante.py — 2012-05-26T00:58:59

Hello,friends!
     I come from China, wishing to enjoy haskell with you.

Re: Problem with packet documentation generated by cabal on windows 7

Nicu Ionita — 2012-05-25T23:28:46

Am 25.05.2012 06:49, schrieb Magnus Therning:

I have Haskell Platform 2011.2.0.1 and I assumed that haddock comes with 
it. Now I checked the version - it is 2.9.2 and cabal info tells me that 
the last version is 2.10.0 and that I don't have the package installed (?).

Ok, now I see, haddock is that from the patform and I never install it 
with cabal...

Nicu

Re: Template Haskell antiquotation in user-definedquasiquoters

Mike Ledger — 2012-05-25T23:06:20

(oops, sorry, didn't do reply to all)

I use haskell-src-meta in QuasiText (on hackage) also. It would certainly
be nice to have "native" anti-quotations, but for now haskell-src-meta does
a very good job.

Mike
On Sat, May 26, 2012 at 8:31 AM, Geoffrey Mainland <mainland< at >apeiron.net>wrote:

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Re: webcam library on github

Claude Heiland-Allen — 2012-05-25T22:56:11

Hi there,

On 25/05/12 08:07, . wrote:

I've uploaded the 'v4l2' package to hackage now.

When I initially wrote it last year I had hoped to use it as a base for 
something similar to 'repa-v4l2' and perhaps 'opengl-v4l2' (*).

Alas, I don't have a pressing need to access v4l2 devices at the moment, 
so I don't expect there to be rapid development or even prompt bug fixes 
(unless people provide patches) - if someone more involved than I am at 
present in video devices + Haskell on Linux wants to take over the 
maintainership of these v4l2-related packages, let me know:

https://gitorious.org/hsv4l2

Thanks,


Claude

(*) I had written some code along those lines, though all I can find at 
the moment is a screenshot (live webcam video, processed to generate an 
overlay and displayed using opengl):
http://claudiusmaximus.goto10.org/g/haskell/v4l2hist.png

Re: Template Haskell antiquotation in user-definedquasiquoters

Geoffrey Mainland — 2012-05-25T22:31:38

I use haskell-src-meta in language-c-quote (also on hackage) to support
antiquotation and heartily endorse it. I have not used haskell-src-exts-qq.

Geoff

Re: Template Haskell antiquotation in user-definedquasiquoters

Antoine Latter — 2012-05-25T20:46:00

Have you looked at:

http://hackage.haskell.org/package/haskell-src-exts-qq
http://hackage.haskell.org/package/haskell-src-meta

The might help you pull something together.


Antoine


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Template Haskell antiquotation in user-definedquasiquoters

Sam Lindley — 2012-05-25T19:51:38

Template Haskell supports antiquotation for built-in quasiquotes, e.g.:

   [| \x -> x + $([|3 * 4|]) |]

However, as far as I can tell, there is no way of supporting 
antiquotation in user-defined quasiquoters, because the only way to 
specify a new quasiquoter is through a quoteExp function of type String 
-> Q Exp. Of course, it is perfectly possible to write a parser for some 
fragment of Haskell inside your quoteExp function, but that seems crazy 
given that Template Haskell or rather GHC already implements a parser 
for the whole language.

I know about Language.Haskell.Exts.Parser in haskell-src-exts, which 
provides parseExp :: String -> ParseResult Exp, but that Exp is a 
different type to the one provided by Template 
Haskell.<http://hackage.haskell.org/packages/archive/haskell-src-exts/1.9.0/doc/html/Language-Haskell-Exts-Syntax.html#t:Exp> 
I'm also aware of Dominic Orchard's syntax-trees package, which supports 
converting between the two representations using a cunning hack that 
pretty-prints

Re: webcam library on github

Daniel Peebles — 2012-05-25T19:30:58

I'm no lawyer, but my understanding is that the code is yours and you are
free to license it however you want. If you choose to license your code as
BSD and depend on LGPL code, then *your users* are bound by both the BSD
And LGPL licenses, which is effectively as "bad" as being bound by the
LGPL. Your portion of the code is still BSD-licensed, though. The
distinction would probably be more evident if someone then made a BSD
replacement for your dependencies, in which case they would no longer be
bound by the LGPL terms if they used your library.

The Haskell community does seem to have a cultural attachment to more
permissive licenses, so you'll likely see a lot more adoption if you do use
BSD, but it's obviously up to you.

-Dan
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Re: Problem with packet documentation generated by cabal on windows 7

Artyom Kazak — 2012-05-25T19:20:55

I’m having the same problem on my Windows 7 laptop. The solution I’ve  
found is to use Internet Explorer — it isn’t perfect, but for some reason  
it is the only browser capable of handling these links.


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Re: Typed TemplateHaskell?

David Fox — 2012-05-25T17:31:17

Its a much simpler thing, but I would like to see a template haskell
library and quasi-quoter that used a monad transformer instead of just Q.

On Thu, May 24, 2012 at 1:47 AM, Simon Peyton-Jones
<simonpj< at >microsoft.com>wrote:

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Re: A functional programming solution for Mr and Mrs Hollingberry

David Turner — 2012-05-25T16:16:57

I don't. I think the trouble is that classes don't add value in 
exercises of this size. Nor do any similarly heavyweight Haskell 
engineering features like polymorphism or typeclasses. Just write the 
program and have done with it. Hard-code everything and you'd end up in 
C# with something not much different from the Haskell solutions on 
Github (except for the usual heavy syntactic overhead of C#). I'd say 
many of the programmers in my heavily OO-centric organisation would do 
just this: experience shows us that simple == flexible more often than not.

However, it becomes more interesting if the requirements are thought 
likely to change in the future. More product lines? More suppliers? More 
or fewer troublesome or premium ones? More rules affecting pricing? 
Based on what other fields? How much is configurable at runtime and how 
much requires programmer time and recompilation? Are you likely to try 
and re-sell a similar system to another client and, if so, do you want 
to share code across clients

Re: Fundeps and overlapping instances

Gábor Lehel — 2012-05-25T15:11:28

If you're referring to the NewAxioms work Simon linked to in the other
thread, I don't see it explicitly stated that all instances have to be
within a single module. Especially section 3.3 (Translation) of the
pdf[1] seems to suggest otherwise. Though it also doesn't seem to be
the same as what you're asking for. As far as I can tell, with
NewAxioms, wherever you could currently have a type instance, you
could instead have a type instance group. Within a group you could
have unrestricted overlap with the first matching instance being
selected, while between groups overlap would continue to be forbidden.
Relative to explicit disequality guards it seems both more and less
powerful: you couldn't have overlap between modules (but could still
split instances among modules as long as they *don't* overlap), but
overlap within a module would be more powerful (or at least more
convenient). It seems vaguely similar to a paper on instance chains[2]
I saw once.

(Apologies in advance if any of this is inaccurate, I'm j

Re: What is the difference between runhaskellandcompile?

Chris Dornan — 2012-05-25T08:43:55

I have been using LDAP with GHC without a problem – I get this error often but the problems have been with the configuration of the OpenLDAP client library or the OpenLDAP server. 

We are all taking about LDAP-0.6.6? Which version of GHC are we talking about? (I don’t think I have tested this on GHC-7.4.1, and maybe the others haven’t either.)

Chris

From: haskell-cafe-bounces< at >haskell.org [mailto:haskell-cafe-bounces< at >haskell.org] On Behalf Of Brandon Allbery
Sent: 25 May 2012 04:21
To: Magicloud Magiclouds
Cc: Haskell-Cafe
Subject: Re: [Haskell-cafe] What is the difference between runhaskell and compile?

On Thu, May 24, 2012 at 11:05 PM, Magicloud Magiclouds <magicloud.magiclouds< at >gmail.com> wrote:
Hi there,
 The code could not be simpler. Just ldapInit, ldapSimpleBind.
 I just found that the code works with ghci, too. So to sum up,
ghci/runhaskell works, ghc not.

A possibility that occurs to me:  does it by any chance work with ghc -threaded?  Perhaps the issue relates to the different behav

Re: Correspondence between libraries and modules

Rustom Mody — 2012-05-25T07:53:21


Hi Gregg.

One of the common complaints one gets from a first year programming student
(and its now about 3 decades I dealing with these!) is:

"The compiler/interpreter etc HAS a BUG!!!"

So...
While I am an old geezer with programming and functional programming --
doing, teaching, playing, implementing, or just plain thinking but  -- I am
too much of a noob to ghc to risk falling into the "1st year student" trap
above.

Yes perhaps not a typical noob...
Somethings are easier for me than the typical noob -- all the 'classical'
good-stuff like pattern-matching, lambda-calculus, type-inferencing,
polymorphism etc.
And this is helpful to understand the 'modern good stuff' starting monads
and onwards

But then I get hit -- finding my way round hackage, installing with cabal
etc -- even tho I'm an ol-time unix hacker and sysadmin-er.

So I guess its best to assume (as of now) that I dont know the ropes rather
than something is wrong/broken with them.

O well... If the noob trap is one error playing it safe is

Re: webcam library on github

2012-05-25T07:07:41


You're right, I remember I had to do that too when I first started the
thing.


Thanks! I will add your suggestions (probably tonight) with pleasure.


The gpl is sort of my default license. I know it is a little
restrictive, so if that keeps people (if any) from contributing, I will
change the license. As far as I can see, I would be able to change it to
lgpl then, but not to bsd.


That was indeed my intent. I first wanted something for image
processing, but seeing that there was nothing like I wanted for webcams,
I started doing that.
I think your suggestion for a simpler name makes sense, will probably
also do that.

BTW, I could not find any "more or less standard" way to represent
images in Haskell. Is there anything like that? I don't know if that
would make sense except being able to interact with different potential
imaging packages. Maybe it's good enough to just copy image data over in
most cases.

Thanks again for all your suggestions, that was very helpful!
Christian

Re: Fundeps and overlapping instances

AntC — 2012-05-25T05:06:35

allowed, 

Hi Twan, there's various style amongst the discussions -- trace the links back 
from my previous post to Haskell-prime.

And see SPJ's surprise (to me) announcement that there's some work in 
progress, which gives something very like it.

But no, I don't like it: it means I can't put different instances in different 
modules (so far as I can tell).



Please explain (because I haven't seen this stated anywhere): what is the use 
case for closed type functions? As opposed to explicitly dis-overlapped type 
functions.


No: closed functions mean you have to declare all your instances in the same 
place, in the same module. The whole point of the instance mechanism (or so I 
thought) is that it's expandable.

To see why, consider my example with a 2-argument type function.
http://www.haskell.org/pipermail/haskell-prime/2012-May/003690.html

(I haven't seen enough detail from the closed type func or IFEQ styles to know 
whether we could be 'open' on the first arg, but closed on the second.)


Indeed!

Re: Problem with packet documentation generated by cabal on windows 7

Magnus Therning — 2012-05-25T04:49:29

It might help to know what version of haddock you have.

Here, on my Linux machine, all generated links are relative and hence
contain no 'http://' or 'file:///' prefix.

/M

Re: What is the difference between runhaskell andcompile?

Magicloud Magiclouds — 2012-05-25T04:36:59

Versions:
libldap2 2.4.28
LDAP 0.6.6
ghc 7.4.1

Code below:

import LDAP

main :: IO ()
main = do
  let domain = "vancloa.cn"
      bindDN = "CN=wangshida.admin,OU=admin_accounts,DC=vancloa,DC=cn"
      bindPW = "********"
      baseDN = Just "DC=vancloa,DC=cn"
      ldapFilter = Just ("(&(sAMAccountName=" ++ alias ++
")(&(objectClass=user)(!(ou=Recycle_Bin))))")
  ldap <- ldapInit domain ldapPort
  ldapSimpleBind ldap bindDN bindPW

And ghc -threaded does not help.

On Fri, May 25, 2012 at 11:20 AM, Brandon Allbery <allbery.b< at >gmail.com> wrote:

Re: What is the difference between runhaskell andcompile?

Brandon Allbery — 2012-05-25T03:20:40

On Thu, May 24, 2012 at 11:05 PM, Magicloud Magiclouds <
magicloud.magiclouds< at >gmail.com> wrote:



A possibility that occurs to me:  does it by any chance work with ghc
-threaded?  Perhaps the issue relates to the different behavior of the
threaded runtime (which is used automatically by ghci/runghc).