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Today's Topics:
1. Re: [Haskell-cafe] represent data sturcture using function
(David Menendez)
2. Re: [Haskell-cafe] represent data sturcture using function
(David Menendez)
3. Re: Collapsing multiple case branches? (Christian Maeder)
4. GHC installation on RHEL 4 by non-root user (TJ Takei)
5. Re: GHC installation on RHEL 4 by non-root user
(Alexander Dunlap)
6. Meaning of variable' (Erik de Castro Lopo)
7. Re: Meaning of variable' (Brandon S. Allbery KF8NH)
8. Re: Meaning of variable' (Erik de Castro Lopo)
9. Re: about the concatenation on a tree (Achim Schneider)
10. Yet another monad tutorial.
(Rafael Gustavo da Cunha Pereira Pinto)
----------------------------------------------------------------------
Message: 1
Date: Mon, 29 Dec 2008 01:13:54 -0500
From: "David Menendez" <[email protected]>
Subject: [Haskell-beginners] Re: [Haskell-cafe] represent data
sturcture using function
To: "Raeck chiu" <[email protected]>
Cc: Beginners Haskell <[email protected]>, Cafe Haskell
<[email protected]>
Message-ID:
<[email protected]>
Content-Type: text/plain; charset=ISO-8859-1
2008/12/29 Raeck chiu <[email protected]>:
> People sometime will try to represent a quantity-regard-only data structure
> (such a order-regadless List) using functions instead of ta concrete data
> structure (like the haskell build-in []), any particular reason for this?
>
> For example,
>> data Sex = Male | Female
>> classA :: Sex -> Int
>> classA Male = 100
>> classA Female = 200
>
> when I should prefer the above solution instead of using a concrete data
> structure such as [] to represent the classA members?
One important difference between Sex -> Int and [(Sex,Int)] is that
the first guarantees exactly one Int per Sex and has no underlying
order. (That is, [(Male,100),(Female,200)] and
[(Female,200),(Male,100)] are distinct lists but represent the same
map.)
> It seems to be very difficult to change the number of Male or Female if a
> concrete data structure is not used. Is it possible change the number of Male
> in classA
> when represent classA using function?
Here's the simplest way:
update k v map = \k' -> if k' == k then v else map k'
Note that it requires an Eq instance for Sex.
let classA' = update Male 150 classA
in (classA' Male, classA' Female)
=
(150,200)
--
Dave Menendez <[email protected]>
<http://www.eyrie.org/~zednenem/>
------------------------------
Message: 2
Date: Mon, 29 Dec 2008 13:26:12 -0500
From: "David Menendez" <[email protected]>
Subject: [Haskell-beginners] Re: [Haskell-cafe] represent data
sturcture using function
To: "Ryan Ingram" <[email protected]>
Cc: Raeck chiu <[email protected]>, Beginners Haskell
<[email protected]>, Cafe Haskell <[email protected]>
Message-ID:
<[email protected]>
Content-Type: text/plain; charset=ISO-8859-1
On Mon, Dec 29, 2008 at 4:48 AM, Ryan Ingram <[email protected]> wrote:
> On Sun, Dec 28, 2008 at 10:13 PM, David Menendez <[email protected]> wrote:
>> Here's the simplest way:
>>
>> update k v map = \k' -> if k' == k then v else map k'
> Of course this version of update leaks crazy amounts of memory:
>
>> let bigmap = iterate (update Male 150) classA !! 100000
>> bigmap Male
>
> "bigmap" leaves a huge chain of thunks pointing at each other, which
> can never be freed.
Sure. It's slow, too. If you want a map that you can update, you're
usually much better off with a concrete data structure.
--
Dave Menendez <[email protected]>
<http://www.eyrie.org/~zednenem/>
------------------------------
Message: 3
Date: Sat, 03 Jan 2009 21:09:23 +0100
From: Christian Maeder <[email protected]>
Subject: [Haskell-beginners] Re: Collapsing multiple case branches?
To: Colin Paul Adams <[email protected]>
Cc: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1
Colin Paul Adams wrote:
> I have the following function:
> northern_range:: Piece_type -> Int
> northern_range piece
| elem piece [Lance, Reverse_chariot, Vertical_mover, etc.] = 11
| elem piece [Bishop, Kylin, etc.] = 0
| otherwise = 1
if you have an Eq instance for Piece_type.
Cheers Christian
------------------------------
Message: 4
Date: Sat, 3 Jan 2009 21:02:20 -0800
From: "TJ Takei" <[email protected]>
Subject: [Haskell-beginners] GHC installation on RHEL 4 by non-root
user
To: [email protected]
Message-ID:
<[email protected]>
Content-Type: text/plain; charset=ISO-8859-1
Hi GHC experts,
As a non-root user of Redhat (amd64) RHEL 4.0 server, I can not use
rpm. I like to install any relatively recent version of ghc to my
local installation area just for learning.
I downloaded first 64-bit binary archive that seems incompatible:
For example, utils/pwd/pwd does not run.
So I ended up downloading a src archive...
% wget http://haskell.org/ghc/dist/6.10.1/ghc-6.10.1-src.tar.bz2
Then unpack and boot:
% tar jxvf ghc-6.10.1-src.tar.bz2
% cd ghc-6.10.1
% sh boot
So far so good, but the next step "configure" fails... no matter what
args I give:
% ./configure --prefix=<my_local_inst_top>
configure: error: GHC is required unless bootstrapping from .hc files.
After I edited mk/build.mk to uncomment BuildFlavour=quick, Gnu make fails :
% make
mk/boilerplate.mk:56: mk/config.mk: No such file or directory
Understandably the unknown problem may have started in the configure stage.
I'm stuck.
Also I tried ghc-6.8.3-x86-64-unknown-linux.tar.bz2 that yields similar errors.
Yet another desperate trial of darcs seems no help:
downloaded...
wget
http://darcs.haskel.org/ghc-STABLE-2008-11-08-ghc-corelibs-testsuite.tar.bz2
tar jxvf ...
darcs-all pull -a
edited mk/build.mk
sh boot
./configure
then gmake fails.
I would appreciate any help.
Regards,
TJ
------------------------------
Message: 5
Date: Sat, 3 Jan 2009 21:37:14 -0800
From: "Alexander Dunlap" <[email protected]>
Subject: Re: [Haskell-beginners] GHC installation on RHEL 4 by
non-root user
To: "TJ Takei" <[email protected]>
Cc: [email protected]
Message-ID:
<[email protected]>
Content-Type: text/plain; charset=ISO-8859-1
On Sat, Jan 3, 2009 at 9:02 PM, TJ Takei <[email protected]> wrote:
> Hi GHC experts,
>
> As a non-root user of Redhat (amd64) RHEL 4.0 server, I can not use
> rpm. I like to install any relatively recent version of ghc to my
> local installation area just for learning.
> I downloaded first 64-bit binary archive that seems incompatible:
> For example, utils/pwd/pwd does not run.
> So I ended up downloading a src archive...
> % wget http://haskell.org/ghc/dist/6.10.1/ghc-6.10.1-src.tar.bz2
> Then unpack and boot:
> % tar jxvf ghc-6.10.1-src.tar.bz2
> % cd ghc-6.10.1
> % sh boot
>
> So far so good, but the next step "configure" fails... no matter what
> args I give:
> % ./configure --prefix=<my_local_inst_top>
> configure: error: GHC is required unless bootstrapping from .hc files.
>
> After I edited mk/build.mk to uncomment BuildFlavour=quick, Gnu make fails :
> % make
> mk/boilerplate.mk:56: mk/config.mk: No such file or directory
>
> Understandably the unknown problem may have started in the configure stage.
> I'm stuck.
> Also I tried ghc-6.8.3-x86-64-unknown-linux.tar.bz2 that yields similar
> errors.
> Yet another desperate trial of darcs seems no help:
> downloaded...
> wget
> http://darcs.haskel.org/ghc-STABLE-2008-11-08-ghc-corelibs-testsuite.tar.bz2
> tar jxvf ...
> darcs-all pull -a
> edited mk/build.mk
> sh boot
> ./configure
> then gmake fails.
>
> I would appreciate any help.
> Regards,
> TJ
GHC is written mostly in Haskell, so you need a binary copy of GHC in
order to compile it from source. (This is what the configure error
message meant.) This means you have to get either the binary or the
RPM to work. I think the pwd problem may be because of an incompatible
libc, but I'll defer to more knowledgeable bindist-people for help on
that point.
Alex
------------------------------
Message: 6
Date: Sun, 4 Jan 2009 16:52:24 +1100
From: Erik de Castro Lopo <[email protected]>
Subject: [Haskell-beginners] Meaning of variable'
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=US-ASCII
Hi all,
I'm looking at some Haskell code that has things like:
var' <- function
and also functions with names like:
function' = .....
What does the tick mean??
Cheers,
Erik
--
-----------------------------------------------------------------
Erik de Castro Lopo
-----------------------------------------------------------------
"Do I do everything in C++ and teach a course in advanced swearing?"
-- David Beazley at IPC8, on choosing a language for teaching
------------------------------
Message: 7
Date: Sun, 4 Jan 2009 00:55:26 -0500
From: "Brandon S. Allbery KF8NH" <[email protected]>
Subject: Re: [Haskell-beginners] Meaning of variable'
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes
On 2009 Jan 4, at 0:52, Erik de Castro Lopo wrote:
> function' = .....
>
> What does the tick mean??
By convention it signals a variant of the function without the tick.
Semantically it doesn't mean anything special; you can use ' in an
identifier as long as it's not the first character.
--
brandon s. allbery [solaris,freebsd,perl,pugs,haskell] [email protected]
system administrator [openafs,heimdal,too many hats] [email protected]
electrical and computer engineering, carnegie mellon university KF8NH
------------------------------
Message: 8
Date: Sun, 4 Jan 2009 16:58:35 +1100
From: Erik de Castro Lopo <[email protected]>
Subject: Re: [Haskell-beginners] Meaning of variable'
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=US-ASCII
Brandon S. Allbery KF8NH wrote:
> By convention it signals a variant of the function without the tick.
> Semantically it doesn't mean anything special; you can use ' in an
> identifier as long as it's not the first character.
Thanks Brandon. Thats what I guessed but I couldn't find a good
google search term to confirm that.
Cheers,
Erik
--
-----------------------------------------------------------------
Erik de Castro Lopo
-----------------------------------------------------------------
"If you already know what recursion is, just remember the answer.
Otherwise, find someone who is standing closer to Douglas Hofstadter;
then ask him or her what recursion is."
-- http://www.cabochon.com/~stevey/blog-rants/godel-escher-blog.html
------------------------------
Message: 9
Date: Sun, 4 Jan 2009 09:19:04 +0100
From: Achim Schneider <[email protected]>
Subject: [Haskell-beginners] Re: about the concatenation on a tree
To: [email protected]
Cc: [email protected]
Message-ID: <20090104091904.297b9...@solaris>
Content-Type: text/plain; charset=US-ASCII
"Max cs" <[email protected]> wrote:
> hi all, not sure if there is someone still working during holiday
> like me : )
>
> I got a little problem in implementing some operations on tree.
>
> suppose we have a tree date type defined:
>
> data Tree a = Leaf a | Branch (Tree a) (Tree a)
>
> I want to do a concatenation on these tree just like the concat on
> list. Anyone has idea on it? or there are some existing
> implementation?
>
The semantics of tree concat vary, depending on what type of tree you
want to have. In the simplest case, it's unbalanced, so you can just do
concat :: Tree a -> Tree a -> Tree a
concat x y = Branch x y
if, on the other hand, you want to keep the tree balanced, or sorted,
or whatever, things get more involved.
--
(c) this sig last receiving data processing entity. Inspect headers
for copyright history. All rights reserved. Copying, hiring, renting,
performance and/or quoting of this signature prohibited.
------------------------------
Message: 10
Date: Mon, 5 Jan 2009 09:08:37 -0200
From: "Rafael Gustavo da Cunha Pereira Pinto"
<[email protected]>
Subject: [Haskell-beginners] Yet another monad tutorial.
To: [email protected]
Message-ID:
<[email protected]>
Content-Type: text/plain; charset="iso-8859-1"
Hello everyone
I am a very eclectic person when it comes to computer languages, and I found
this monad tutorial for OCaml programmers:
http://enfranchisedmind.com/blog/2007/08/06/a-monad-tutorial-for-ocaml/
I found it to be very interesting, since it shows those "warm, fuzzy things"
implemented in another functional language with very clear explanations of
what he is doing in each step.
Best regards, and a happy 2k9 for you all!
Rafael
--
Rafael Gustavo da Cunha Pereira Pinto
Electronic Engineer, MSc.
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