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Today's Topics:
1. How to write replicateM with interspersed guards?
(Sebastien Zany)
2. Re: How to write replicateM with interspersed guards?
(Sebastien Zany)
3. Re: How to write replicateM with interspersedguards? ( anyzhen )
4. Re: A post about Currying and Partial application
(Petar Radosevic)
5. Re: How to write replicateM with interspersed guards?
(Brent Yorgey)
6. LZMA for Haskell? (Paulo Pocinho)
7. Re: [aklug] Re: VPS (Christopher Howard)
8. merge two files in to one file (kolli kolli)
9. Re: merge two files in to one file (Erik de Castro Lopo)
10. Re: merge two files in to one file (kolli kolli)
----------------------------------------------------------------------
Message: 1
Date: Tue, 4 Oct 2011 05:27:59 -0700
From: Sebastien Zany <sebast...@chaoticresearch.com>
Subject: [Haskell-beginners] How to write replicateM with interspersed
guards?
To: Haskell Beginners <beginners@haskell.org>
Message-ID:
<caa+2x_vg_1r47-ztka5ksibeijdtil+amrubjfawxkqvb3h...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
What would be the idiomatic way to write a function which expands to the
following?
f n m = do {
x1 <- m;
guard (f [x1]);
x2 <- m;
guard (f [x1, x2]);
.
.
.
xn <- m;
guard (f [x1,x2,...,xn]);
}
What I'm trying to do is generate a list of lists of length n with some
property (checked by f) efficiently.
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Message: 2
Date: Tue, 4 Oct 2011 05:29:23 -0700
From: Sebastien Zany <sebast...@chaoticresearch.com>
Subject: Re: [Haskell-beginners] How to write replicateM with
interspersed guards?
To: Haskell Beginners <beginners@haskell.org>
Message-ID:
<caa+2x_vlgjzdlkdm7d05t_6ts08xvserw6uglyesez2ng+c...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Just realized I used "f" twice, make the outer one something else.
On Tue, Oct 4, 2011 at 5:27 AM, Sebastien Zany <
sebast...@chaoticresearch.com> wrote:
> What would be the idiomatic way to write a function which expands to the
> following?
>
> f n m = do {
> x1 <- m;
> guard (f [x1]);
> x2 <- m;
> guard (f [x1, x2]);
> .
> .
> .
> xn <- m;
> guard (f [x1,x2,...,xn]);
> }
>
> What I'm trying to do is generate a list of lists of length n with some
> property (checked by f) efficiently.
>
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Message: 3
Date: Tue, 4 Oct 2011 21:23:59 +0800
From: " anyzhen " <jiangzhe...@qq.com>
Subject: Re: [Haskell-beginners] How to write replicateM with
interspersedguards?
To: " Sebastien Zany " <sebast...@chaoticresearch.com>, " Haskell
Beginners " <beginners@haskell.org>
Message-ID: <tencent_7ffb677b5df2a35678943...@qq.com>
Content-Type: text/plain; charset="gbk"
like this?
let inits' xs = drop 1 $ inits xs in
let getLists n m = inits' take n (repeat m) in
f m n =map (\x-> guard $ f x) xs
where xs =getLists n m
------------------ Original ------------------
From: "Sebastien Zany";
Date: 2011?10?4?(???) ??8:27
To: "Haskell Beginners";
Subject: [Haskell-beginners] How to write replicateM with interspersedguards?
What would be the idiomatic way to write a function which expands to the
following?
f n m = do {
x1 <- m;
guard (f [x1]);
x2 <- m;
guard (f [x1, x2]);
.
.
.
xn <- m;
guard (f [x1,x2,...,xn]);
}
What I'm trying to do is generate a list of lists of length n with some
property (checked by f) efficiently.
-------------- next part --------------
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------------------------------
Message: 4
Date: Tue, 4 Oct 2011 17:33:49 +0200
From: Petar Radosevic <pe...@wunki.org>
Subject: Re: [Haskell-beginners] A post about Currying and Partial
application
To: beginners@haskell.org
Message-ID: <20111004153349.GA8137@wunki-mac-pro.local>
Content-Type: text/plain; charset=utf-8
Small update. I rewrote the post, this time with a hopeful beter
explanation of Currying.
http://www.wunki.org/posts/2011-10-04-currying-and-partial-application.html
--
Petar Rado?evi?, Programmer
wunki.org | @wunki
------------------------------
Message: 5
Date: Tue, 4 Oct 2011 13:41:43 -0400
From: Brent Yorgey <byor...@seas.upenn.edu>
Subject: Re: [Haskell-beginners] How to write replicateM with
interspersed guards?
To: beginners@haskell.org
Message-ID: <20111004174143.ga10...@seas.upenn.edu>
Content-Type: text/plain; charset=us-ascii
On Tue, Oct 04, 2011 at 05:27:59AM -0700, Sebastien Zany wrote:
> What would be the idiomatic way to write a function which expands to the
> following?
>
> f n m = do {
> x1 <- m;
> guard (f [x1]);
> x2 <- m;
> guard (f [x1, x2]);
> .
> .
> .
> xn <- m;
> guard (f [x1,x2,...,xn]);
> }
>
> What I'm trying to do is generate a list of lists of length n with some
> property (checked by f) efficiently.
Hmm, this is tricky. I can't think of any nice idiomatic way to do it
-- if I really wanted something like this I'd just write an explicitly
recursive function to do it step by step. One might hope to be able
to do it using something in the monad-loops package [1], but the
dependence of the tests on the list of results so far is a bit odd and
doesn't fit any of the patterns in that package.
The dependence of the tests on the whole list of results so far is
actually quite odd. It looks like you are going to be repeating a lot
of work calling f successively on [x1], [x1,x2], [x1,x2,x3], ... not
to mention that to construct these successive lists you are going to
have to append each new result to the end, which is O(n), making the
whole thing O(n^2).
I don't know anything about your function f, but I wonder whether you
might be able to express it in the form
f = h . mappend . map g
for suitable functions h and g. For example, if
f = (>10) . sum,
then we could use
h = (>10) . getSum
g = Sum
If so, rather than keeping the list of results so far as you iterate,
you can just keep the result of (mappend . map g). Then when you
compute the next result you just apply g to it, combine it with the
previous result using `mappend`, then apply h to get a Bool for the
call to guard.
Alternatively, if f is insensitive to the order of its input list, you
could keep the list in reverse order so that successive results can be
*pre*pended in O(1); but this still (seemingly) wastes a lot of work.
-Brent
[1] http://hackage.haskell.org/package/monad-loops
> _______________________________________________
> Beginners mailing list
> Beginners@haskell.org
> http://www.haskell.org/mailman/listinfo/beginners
------------------------------
Message: 6
Date: Tue, 4 Oct 2011 21:06:27 +0100
From: Paulo Pocinho <poci...@gmail.com>
Subject: [Haskell-beginners] LZMA for Haskell?
To: beginners@haskell.org
Message-ID:
<CAK4i1qRsX5Y9w2CATmdm6wcy8h42bNB=OV13=rf93nnroym...@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
Hello list.
I'd like to use LZMA to create/extract archives and compare CRC from
archived files. What do I need to use LZMA in Haskell?
There is a page called "Library/Compression" in the wiki [1] but it is
from 2005, using LZMA version 4.06. Besides being old, I can only find
the LZMA SDK version 9.20 for download.
The only related package I can find on hackage is lzma-enumerator [2].
Trying to install with cabal requires an old header named lzma.h that
is no longer available.
[1] http://www.haskell.org/haskellwiki/Library/Compression
[2] http://hackage.haskell.org/package/lzma-enumerator
------------------------------
Message: 7
Date: Tue, 04 Oct 2011 12:10:24 -0800
From: Christopher Howard <christopher.how...@frigidcode.com>
Subject: Re: [Haskell-beginners] [aklug] Re: VPS
To: Haskell Beginners <beginners@haskell.org>
Message-ID: <4e8b6830.7050...@frigidcode.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
On 10/04/2011 08:36 AM, adam bultman wrote:
> What, do I have to *give* you one or something? Because I can, y'know.
>
> Just so long as you don't spam :)
>
> On 10/03/2011 06:59 PM, Christopher Howard wrote:
>> On 10/03/2011 02:28 PM, adam bultman wrote:
>>> Choward, any chance you have a legitimate email somewhere else you could
>>> relay through, authenticated-style?
>>>
>> Legitimate!? My server is legitimate!!!
>>
>> Assuming you mean a gmail account or such... no.
>>
>>> You'd accept mail on your dynamic IP, but any outgoing mail sent via
>>> your server would be relayed through a third party, via your username
>>> and password. It's pretty easy to set up in Postfix, anyway, even with
>>> TLS to boot.
>>>
>
heh, heh... thanks, but I actually like the VPS idea better, as I was
thinking about getting a cheap one to play around with anyway. Even the
cheapest one comes with a static IP, so I could just receive the mail
there and forward it on to my personal server, or something like that.
As a point of curiosity: with your suggestion, do you rewrite the sender
field, or do you send and receive e-mails with different addresses? It
seems like a few years ago I remember trying to use a server belonging
to one domain to send mail from another domain, and some of the mail was
bounced back because the receiving servers detected that the domain in
the sender field did not match that of the sending server.
@Bruce: Thanks also for the offer, but I think I'll try out a VPS solution.
--
frigidcode.com
theologia.indicium.us
------------------------------
Message: 8
Date: Tue, 4 Oct 2011 18:47:16 -0600
From: kolli kolli <nammukoll...@gmail.com>
Subject: [Haskell-beginners] merge two files in to one file
To: beginners@haskell.org
Message-ID:
<CAE7D9k4gVvJvmb09f-0zyS9R1hcLdkwExdBY2=cgymvjhc6...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Hi,
Can anyone tell me how to merge two files in to one file.
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Message: 9
Date: Wed, 5 Oct 2011 11:51:08 +1100
From: Erik de Castro Lopo <mle...@mega-nerd.com>
Subject: Re: [Haskell-beginners] merge two files in to one file
To: beginners@haskell.org
Message-ID: <20111005115108.674f66377852ddabcffa4...@mega-nerd.com>
Content-Type: text/plain; charset=US-ASCII
kolli kolli wrote:
> Can anyone tell me how to merge two files in to one file.
What do you mean by 'merge'? A couple of possible meanings include:
- Concatenate the second file onto the end of the first.
- Line by line merge; line of first file, followed by line of
second and so on.
- Byte by byte merge; byte from the first file, followed by a byte
from the second and so on.
Erik
--
----------------------------------------------------------------------
Erik de Castro Lopo
http://www.mega-nerd.com/
------------------------------
Message: 10
Date: Tue, 4 Oct 2011 18:53:28 -0600
From: kolli kolli <nammukoll...@gmail.com>
Subject: Re: [Haskell-beginners] merge two files in to one file
To: beginners@haskell.org
Message-ID:
<CAE7D9k44_XvWXe_phSR6uDrb6-LWcX-tLr2=yb7p6rtc57v...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
all the lines of first file followed by all the lines of second file
On Tue, Oct 4, 2011 at 6:51 PM, Erik de Castro Lopo <mle...@mega-nerd.com>wrote:
> kolli kolli wrote:
>
> > Can anyone tell me how to merge two files in to one file.
>
> What do you mean by 'merge'? A couple of possible meanings include:
>
> - Concatenate the second file onto the end of the first.
>
> - Line by line merge; line of first file, followed by line of
> second and so on.
>
> - Byte by byte merge; byte from the first file, followed by a byte
> from the second and so on.
>
> Erik
> --
> ----------------------------------------------------------------------
> Erik de Castro Lopo
> http://www.mega-nerd.com/
>
> _______________________________________________
> Beginners mailing list
> Beginners@haskell.org
> http://www.haskell.org/mailman/listinfo/beginners
>
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