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Today's Topics:
1. Re: Anyone have problems with cabal and SDL? (Stephen Tetley)
2. Having trouble defining type correctly (Chris Bolton)
3. Re: Anyone have problems with cabal and SDL? (Alvaro Vilanova)
4. Re: HUnit - testing for failed pattern match (Xavier Shay)
5. Re: HUnit - testing for failed pattern match (Edward Z. Yang)
6. Re: HUnit - testing for failed pattern match (Xavier Shay)
7. Very basic question on monads (black...@pro-ns.net)
8. Help with GHC Packages Installation on Fedora 14 (Hong Yang)
----------------------------------------------------------------------
Message: 1
Date: Tue, 22 Feb 2011 18:29:44 +0000
From: Stephen Tetley <stephen.tet...@gmail.com>
Subject: Re: [Haskell-beginners] Anyone have problems with cabal and
SDL?
Cc: beginners@haskell.org
Message-ID:
<aanlktikbraqurf16or-kndvfyutjswr9e3a81qqnj...@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
Hi Tom
Thanks for the update.
It looks like you have the SDL runtime library installed but not the
development extras. If you have the sdl-devel extras they're not on
your search path.
On 22 February 2011 14:53, Tom Murphy <amin...@gmail.com> wrote:
[CHOP]
> checking for sdl-config... no
> checking for sdl11-config... no
> configure: error: *** SDL not found! Get SDL from www.libsdl.org.
> If you already installed it, check it's in the path. If problem remains,
> please send a mail to the address that appears in ./configure --version
> indicating your platform, the version of configure script and the problem.
> cabal: Error: some packages failed to install:
------------------------------
Message: 2
Date: Tue, 22 Feb 2011 11:51:37 -0800
From: Chris Bolton <chris...@saikonet.org>
Subject: [Haskell-beginners] Having trouble defining type correctly
To: beginners@haskell.org
Message-ID:
<aanlktinoqhgco6yar1vplpfjmpmztwo2rsqmq3cfk...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Ok, so here's my current code: http://paste.pocoo.org/show/342949/
My basic problem is I'm not quite sure how to define Command. When a user
calls the script they can either call add, remove, update, or query, which
all have different type signatures, which is why I need Command so it'll
pass through haskell's type checking. If I get rid of query, A definition of
{ data Command m = Save m | Rem m } seemed to work, from what I can tell,
but query screws it up, so I'm trying to define exactly what Save, Rem, etc.
should be, which I've taken directly from the MongoDB API, but it just keeps
throwing errors, as seen here: http://paste.pocoo.org/show/342924/
Also, I'm very new to haskell and programming in general, so sorry for the
possibly messy code / noobish question, but anyone have any ideas here? :P
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Message: 3
Date: Tue, 22 Feb 2011 22:05:13 +0100
From: Alvaro Vilanova <alv...@gmail.com>
Subject: Re: [Haskell-beginners] Anyone have problems with cabal and
SDL?
To: Tom Murphy <amin...@gmail.com>
Cc: beginners@haskell.org
Message-ID:
<AANLkTi=RCgyysT3Yq=6ngq7zhgf-8fetsnpm44rkf...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
The log says that configuration SDL tool `sdl-config` is not installed,
probably, due to you have installed SDL framework. Cabal, or the SDL package
(I dont know who has the problem here) doesn't take into account that the
system is a MacOs so it doesn't search the library as a framework.
To solve this, you have to compile the library manually, just `./configure
&&
make && sudo make install` or install it with MacPorts. Then you will be
able
to compile SDL projects. Nothing more. If you want to link and run your own
Haskell SDL projects on MacOs you have to dive in the next odyssey:
SDL has a tricky way to enable C `main` function to run graphic applications
on all systems. So first, we need a C function wich is going to be hooked by
SDL, and this function is going to run our Haskell application. We put this
main function in c_main.c [1].
To be compatible with all other plataforms we have keep our Main Haskell
function, so we rename this function in a FFI Module which will be compiled
only on MacOS, named HS_Main.hs [2].
Now we have to compile c_main.c with:
gcc -c c_main.c `sdl-config --cflags` -framework GHC
But, surprise, the GHC framework seems that is not well-formed, so gcc can
not get the
header and you have to search it manually. In my case:
find / -name "HsFFI.h"
...
/Library/Frameworks/GHC.framework/Versions/612/usr/lib/ghc-6.12.3/include/HSffi.h
...
gcc -c c_main.c `sdl-config --cflags`
-I/Library/Frameworks/GHC.framework/Versions/612/usr/lib/ghc-6.12.3/include/
And now we have a c_main.o. Next, we have to compile our HSMain which
imports
our Main module which contains the default main function.
ghc --make HSMain.hs -no-hs-main c_main.o -framework Cocoa
And if you have the default Haskell plataform for MacOs you are going to get
one surprise more:
Linking ./Main ...
ld: warning: in c_main.o, file was built for unsupported file format which
is not the architecture being linked (i386)
ld: warning: in /usr/local/lib/libSDLmain.a, file was built for unsupported
file format which is not the architecture being linked (i386)
ld: warning: in /usr/local/lib/libSDL.dylib, file was built for unsupported
file format which is not the architecture being linked (i386)
This means that you have a 32 bits GHC but gcc compiles to 64 bits. You have
3 options: give up, cross-compile c_main.c and sdl to 32 bits, compile and
install a custom haskell-plataform enabling 64 bits support.
Good luck, you will need it!
PD: With cabal is a little more easy, see TimePiece as example [3].
[1] https://gist.github.com/839329
[2] https://gist.github.com/839340
[3] http://hackage.haskell.org/package/TimePiece
2011/2/21 Tom Murphy <amin...@gmail.com>
> When I use Cabal to get any program which depends on the SDL library, this
> is the error I get.
>
> "
> checking for sdl-config... no
> checking for sdl11-config... no
> configure: error: *** SDL not found! Get SDL from www.libsdl.org.
> If you already installed it, check it's in the path. If problem remains,
> please send a mail to the address that appears in ./configure --version
> indicating your platform, the version of configure script and the problem.
> cabal: Error: some packages failed to install:
> Raincat-1.1.1.2 depends on SDL-0.6.2 which failed to install.
> SDL-0.6.2 failed during the configure step. The exception was:
> exit: ExitFailure 1
> SDL-image-0.6.1 depends on SDL-0.6.2 which failed to install.
> SDL-mixer-0.6.1 depends on SDL-0.6.2 which failed to install.
> "
>
>
> I have SDL 1.2.14 (correctly) installed on my system.
> I'd really appreciate any help with this.
>
> Tom
>
> _______________________________________________
> Beginners mailing list
> Beginners@haskell.org
> http://www.haskell.org/mailman/listinfo/beginners
>
>
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------------------------------
Message: 4
Date: Wed, 23 Feb 2011 08:34:39 +1100
From: Xavier Shay <xavier-l...@rhnh.net>
Subject: Re: [Haskell-beginners] HUnit - testing for failed pattern
match
To: beginners@haskell.org
Message-ID: <4d642bef.9080...@rhnh.net>
Content-Type: text/plain; charset=UTF-8; format=flowed
> Excerpts from Xavier Shay's message of Tue Feb 22 05:59:12 -0500 2011:
>> Given the following contrived function:
>>
>> giveMeThree x
>> | x == 3 = True
>>
>> How do I test with HUnit that 2 is invalid input?
>>
>> giveMeThreeTests =
>> [ "Likes 3" ~: True ~=? giveMeThree 3
>> , "Dislikes 2" ~: ..... -- what?
>> ]
>>
>> I couldn't find anything mentioned in the HUnit user guide. References
>> to appropriate documentation appreciated.
On 23/02/11 1:31 AM, Edward Z. Yang wrote:
>
> A partial function will emit an exception, which must be caught from
> IO. I'm sure HUnit has an appropriate mechanism for handling this,
> but I strongly suggest you redesign your function to be total: instead
> of omitting pattern matches, change it to use Maybe and return Nothing
> in the 'otherwise' case.
In this case, the inputs I am giving to the function are totally invalid
- they should never occur in a running app. For context, the function
takes a state, applies a transition, and returns the new state. There
are certain invalid transitions. In other languages I would throw an
ArgumentError or similar ... would the Haskell way be to return Nothing
instead? To me this seems to be complicating my types (Maybe instead of
a vanilla type) for a benefit that I don't see.
What are the benefits to using Maybe in this case rather than throwing
an exception?
Cheers,
Xavier
------------------------------
Message: 5
Date: Tue, 22 Feb 2011 18:35:38 -0500
From: "Edward Z. Yang" <ezy...@mit.edu>
Subject: Re: [Haskell-beginners] HUnit - testing for failed pattern
match
To: Xavier Shay <xavier-l...@rhnh.net>
Cc: beginners <beginners@haskell.org>
Message-ID: <1298417639-sup-631@ezyang>
Content-Type: text/plain; charset=UTF-8
What you describe is one of the cases when a partial function is ok
(though it's probably better to do something like:
giveMeThree x
| x == 3 = True
| otherwise = error "giveMeThree: not three"
It's frequently not possible, but if you can arrange your types so that
the invalid values are not possible, even better.)
Cheers,
Edward
------------------------------
Message: 6
Date: Wed, 23 Feb 2011 12:25:28 +1100
From: Xavier Shay <xavier-l...@rhnh.net>
Subject: Re: [Haskell-beginners] HUnit - testing for failed pattern
match
To: beginners@haskell.org
Message-ID: <4d646208.5010...@rhnh.net>
Content-Type: text/plain; charset=UTF-8; format=flowed
On 23/02/11 10:35 AM, Edward Z. Yang wrote:
> What you describe is one of the cases when a partial function is ok
> (though it's probably better to do something like:
>
> giveMeThree x
> | x == 3 = True
> | otherwise = error "giveMeThree: not three"
>
> It's frequently not possible, but if you can arrange your types so that
> the invalid values are not possible, even better.)
ah that's good, I can give a helpful error message.
Still would like a way to test it though...
------------------------------
Message: 7
Date: Tue, 22 Feb 2011 21:30:18 -0800
From: <black...@pro-ns.net>
Subject: [Haskell-beginners] Very basic question on monads
To: <beginners@haskell.org>
Message-ID: <cea7ab33b04a49f94bed56b9e06e6...@iphouse.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
I'm working through the "Write Yourself a Scheme" wikibook and having
trouble with one of the exercises. For the function parseNumber ::
Parser LispVal, both
parseNumber = liftM (Number . read) $ many1 digit
parseNumber' = do digits <- many1 digit
return $ (Number . read) digits
work. But
parseNumber'' = many1 digit >>= liftM read >>= liftM Number
complains "couldn't match expected type Char against inferred type
[Char]". Is liftM engaging the list monad? How do I fix this?
------------------------------
Message: 8
Date: Tue, 22 Feb 2011 23:31:06 -0600
From: Hong Yang <hyang...@gmail.com>
Subject: [Haskell-beginners] Help with GHC Packages Installation on
Fedora 14
To: beginners@haskell.org
Message-ID:
<AANLkTikVEdx-BW_az=5tm8z14nyw0ghx4f66bpsbn...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Hi,
I installed a Fedora 14 virtual machine on my home Windows desktop. Then I
tried to install GHC packages on Fedora by typing "yum install ghc" as root,
and got the following error:
"Error: Cannot retrieve repository metadata (repomd.xml) for repository:
fedora.
Please verify its path and try again."
What should I do now to fix this error?
Thanks,
Hong
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