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Today's Topics:
1. Build HTTP package error (Alexander _)
2. reverse [1..] (Emanuel Koczwara)
3. Re: reverse [1..] (Emmanuel Touzery)
4. Re: reverse [1..] (Alexander _)
5. Re: reverse [1..] (Jonathan Rioux)
6. Re: reverse [1..] (Emanuel Koczwara)
7. Re: Parsec, comma sperated list with special last element
(Christian Maeder)
8. Re: reverse [1..] (Felipe Almeida Lessa)
9. Re: reverse [1..] (Tom Davie)
----------------------------------------------------------------------
Message: 1
Date: Tue, 18 Dec 2012 19:58:39 +0600
From: Alexander _ <[email protected]>
Subject: [Haskell-beginners] Build HTTP package error
To: [email protected]
Message-ID:
<cafpzw89cmkqlmwohkmcokr-extdxxchgooz0dg2fbqtosqc...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Hello,
I try to install HTTP package. I make:
cabal install HTTP and got error:
[ 1 of 18] Compiling Network.HTTP.Base64 ( Network/HTTP/Base64.hs,
dist/build/Network/HTTP/Base64.o )
[ 2 of 18] Compiling Network.HTTP.MD5Aux ( Network/HTTP/MD5Aux.hs,
dist/build/Network/HTTP/MD5Aux.o )
[ 3 of 18] Compiling Paths_HTTP ( dist/build/autogen/Paths_HTTP.hs,
dist/build/Paths_HTTP.o )
dist/build/autogen/Paths_HTTP.hs:21:13: Not in scope: `catch'
dist/build/autogen/Paths_HTTP.hs:22:13: Not in scope: `catch'
dist/build/autogen/Paths_HTTP.hs:23:14: Not in scope: `catch'
dist/build/autogen/Paths_HTTP.hs:24:17: Not in scope: `catch'
cabal: Error: some packages failed to install:
HTTP-4000.2.6 failed during the building phase. The exception was:
ExitFailure 1
How can i install it correctly?
Thank you.
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Message: 2
Date: Tue, 18 Dec 2012 15:24:56 +0100
From: Emanuel Koczwara <[email protected]>
Subject: [Haskell-beginners] reverse [1..]
To: "[email protected]" <[email protected]>
Message-ID: <1355840696.18660.2.camel@emanuel-Dell-System-Vostro-3750>
Content-Type: text/plain; charset="UTF-8"
Hi,
When I run this code in ghci:
reverse [1..]
I get:
<interactive>: out of memory (requested 2097152 bytes)
Can anyone explain this behaviour?
Emanuel
------------------------------
Message: 3
Date: Tue, 18 Dec 2012 15:28:07 +0100
From: Emmanuel Touzery <[email protected]>
Subject: Re: [Haskell-beginners] reverse [1..]
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> Hi,
>
> When I run this code in ghci:
>
> reverse [1..]
>
> I get:
>
> <interactive>: out of memory (requested 2097152 bytes)
>
> Can anyone explain this behaviour?
>
It is an infinite list you are trying to reverse. This cannot terminate.
Which is the first element you would expect to see in the result?
Those two will finish:
reverse $ take 100 [1..]
reverse [1..100]
Emmanuel
------------------------------
Message: 4
Date: Tue, 18 Dec 2012 20:30:00 +0600
From: Alexander _ <[email protected]>
Subject: Re: [Haskell-beginners] reverse [1..]
To: [email protected]
Message-ID:
<CAFPzW88TNut=ahyz0ertphf2hfdyp3rcevc+fctc+kh-4cl...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Hello,
Here you try to reverse infinite list. What do you expect to get?
2012/12/18 Emanuel Koczwara <[email protected]>
> Hi,
>
> When I run this code in ghci:
>
> reverse [1..]
>
> I get:
>
> <interactive>: out of memory (requested 2097152 bytes)
>
> Can anyone explain this behaviour?
>
> Emanuel
>
>
>
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://www.haskell.org/mailman/listinfo/beginners
>
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Message: 5
Date: Tue, 18 Dec 2012 09:33:49 -0500
From: Jonathan Rioux <[email protected]>
Subject: Re: [Haskell-beginners] reverse [1..]
To: Emanuel Koczwara <[email protected]>
Cc: "[email protected]" <[email protected]>
Message-ID:
<CAH3N84VdoXxB61TJ0127vjp=tmwqarma5oytxp7xluznmjr...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Hello Emanuel,
Here's the excerpt of the "reverse" function in GHC-List (
-- | 'reverse' @xs@ returns the elements of @xs@ in reverse order.--
@xs@ must be finite.reverse :: [a] -> [a]#ifdef
USE_REPORT_PRELUDEreverse = foldl (flip (:))
[]#elsereverse l = rev l [] where rev [] a = a rev (x:xs)
a = rev xs (x:a)#endif
Reversing an infinite list, Haskell will try to reach the end of the
list until it runs out of memory.
I don't thing it's doable lazily.
On Tue, Dec 18, 2012 at 9:24 AM, Emanuel Koczwara <[email protected]
> wrote:
> Hi,
>
> When I run this code in ghci:
>
> reverse [1..]
>
> I get:
>
> <interactive>: out of memory (requested 2097152 bytes)
>
> Can anyone explain this behaviour?
>
> Emanuel
>
>
>
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://www.haskell.org/mailman/listinfo/beginners
>
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------------------------------
Message: 6
Date: Tue, 18 Dec 2012 15:35:06 +0100
From: Emanuel Koczwara <[email protected]>
Subject: Re: [Haskell-beginners] reverse [1..]
To: Alexander _ <[email protected]>
Cc: [email protected]
Message-ID: <1355841306.18660.4.camel@emanuel-Dell-System-Vostro-3750>
Content-Type: text/plain; charset="UTF-8"
Hi,
Dnia 2012-12-18, wto o godzinie 20:30 +0600, Alexander _ pisze:
> Hello,
>
>
>
> Here you try to reverse infinite list. What do you expect to get?
>
I was trying to build infinite list from -inf to +inf.
Emanuel
------------------------------
Message: 7
Date: Tue, 18 Dec 2012 15:42:23 +0100
From: Christian Maeder <[email protected]>
Subject: Re: [Haskell-beginners] Parsec, comma sperated list with
special last element
To: [email protected]
Cc: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=UTF-8; format=flowed
Hi,
you should not distinguish last or other cells.
Do you really want to discard the last cell in your result?
You could use:
cell = many1 $ noneOf "\n,"
endBy cell (oneOf "\n,")
This would give you all cells of a file.
To get all cells of a single line use:
line = sepBy cell (char ',')
and skip the final newline. To get all lines of a file
use:
endBy line (char `\n')
HTH Christian
you wrote: 2012-12-18 08:58:45 GMT
I tried
file = do
res <- endBy (try cell) (char ',')
l <- lastCell
eof
return res
cell = many1 (noneOf ",")
lastCell = many1 (noneOf "\n")
But that does not work because cell succeeds on the last cell.
I can replace the endBy by
many (try $ do {a <- cell; string ","; return a})
Nathan
------------------------------
Message: 8
Date: Tue, 18 Dec 2012 13:13:13 -0200
From: Felipe Almeida Lessa <[email protected]>
Subject: Re: [Haskell-beginners] reverse [1..]
To: Emanuel Koczwara <[email protected]>
Cc: beginners <[email protected]>
Message-ID:
<CANd=oggg_jznz6uwk9gpp9x3kjn0w6m_djyawe1viwfz3da...@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
If you don't care about the order, you may use:
allNumbers = 0 : merge [1,2..] [-1,-2..]
where merge (x:xs) ys = x : merge ys xs
Cheers,
On Tue, Dec 18, 2012 at 12:35 PM, Emanuel Koczwara
<[email protected]> wrote:
> Hi,
>
> Dnia 2012-12-18, wto o godzinie 20:30 +0600, Alexander _ pisze:
>> Hello,
>>
>>
>>
>> Here you try to reverse infinite list. What do you expect to get?
>>
>
> I was trying to build infinite list from -inf to +inf.
>
> Emanuel
>
>
>
>
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://www.haskell.org/mailman/listinfo/beginners
--
Felipe.
------------------------------
Message: 9
Date: Tue, 18 Dec 2012 15:16:08 +0000
From: Tom Davie <[email protected]>
Subject: Re: [Haskell-beginners] reverse [1..]
To: Emanuel Koczwara <[email protected]>
Cc: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=us-ascii
On 18 Dec 2012, at 14:35, Emanuel Koczwara <[email protected]> wrote:
> Hi,
>
> Dnia 2012-12-18, wto o godzinie 20:30 +0600, Alexander _ pisze:
>> Hello,
>>
>>
>>
>> Here you try to reverse infinite list. What do you expect to get?
>>
>
> I was trying to build infinite list from -inf to +inf.
What would you expect the number after -inf to be?
Bob
------------------------------
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