Send Beginners mailing list submissions to
[email protected]
To subscribe or unsubscribe via the World Wide Web, visit
http://www.haskell.org/mailman/listinfo/beginners
or, via email, send a message with subject or body 'help' to
[email protected]
You can reach the person managing the list at
[email protected]
When replying, please edit your Subject line so it is more specific
than "Re: Contents of Beginners digest..."
Today's Topics:
1. Re: doesFileExist cannot get ~/blah_blah right (Brent Yorgey)
2. Re: Problems with parsing in attoparsec (mukesh tiwari)
3. </>? Was: doesFileExist cannot get ~/blah_blah right
(Tommy M. McGuire)
4. Re: </>? Was: doesFileExist cannot get ~/blah_blah right
(David McBride)
----------------------------------------------------------------------
Message: 1
Date: Tue, 9 Apr 2013 08:07:39 -0400
From: Brent Yorgey <[email protected]>
Subject: Re: [Haskell-beginners] doesFileExist cannot get ~/blah_blah
right
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=utf-8
On Mon, Apr 08, 2013 at 04:04:22PM -0700, Erlend Hamberg wrote:
> On 8 April 2013 15:45, Hong Yang <[email protected]> wrote:
>
> > I got "not exists ..." from
> >
> > fileExists <- doesFileExist "~/blah_blah"
> > if fileExists then print "exists ..."
> > else print "not exists ..."
> >
> > using the directory-1.1.0.2 package, when ~/blah_blah does exist.
> >
>
> When you type ?~/blah_blah? in your shell, the *shell* will expand ?~? to
> your home directory, so when you pass ?~/foo? to a program, that program
> never sees ?~/foo?, but ?/home/user/foo?. In other words, ?~/blah_blah?
> probably does *not* exist.
>
> What you probably should do is to find the user's home directory and
> prepend that to ?blah_blah?. You can find a user's homedir by calling
> `getHomeDirectory` from `System.Directory`:
>
> Prelude System.Directory> homedir <- getHomeDirectory
> Prelude System.Directory> putStrLn $ homedir ++ "/blah_blah"
> /Users/ehamberg/blah_blah
Also, since we are discussing portability, it's a much better idea to do
homedir </> "blah_blah"
instead of homedir ++ "/blah_blah", since the former will use the
correct path separator character for whatever system it is compiled
on.
-Brent
------------------------------
Message: 2
Date: Tue, 9 Apr 2013 19:32:11 +0530
From: mukesh tiwari <[email protected]>
Subject: Re: [Haskell-beginners] Problems with parsing in attoparsec
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Message-ID:
<CAFHZvE9QTOv2eWC92kJXxLFzvJRUJVpyyawAYT1K=4ckeyu...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Hi Michel
I think you are reading empty string inside index function. I figured out
little bit and some where you are reading empty string but could not
concentrate enough ( or expert enough :) ) to see more because you are
parsing you code based on counting the number of characters ( take 6 inside
index function ).
*Main> read ""::Int
*** Exception: Prelude.read: no parse
Except the first test case, I changed the space between 0 and 2 ( for last
test case, I reduced the space between 0 and 4 ) to seven and now it's not
parsing completely but there is no error.
I have posted the code on ideone[1]. Here is the output on my system. I
have also attached the code.
*Main> :load "/Users/mukeshtiwari/Programming/Haskell/ParsingAtto.hs"
[1 of 1] Compiling Main (
/Users/mukeshtiwari/Programming/Haskell/ParsingAtto.hs, interpreted )
Ok, modules loaded: Main.
*Main> test1
Done "\n" [(1,IndexedFaceTriangle 10 1 9),(2,IndexedFaceTriangle 1 2 9)]
*Main> test2
Done " 12 8 1 0\n" [[(1,IndexedFaceTriangle 10 1
9),(2,IndexedFaceTriangle 1 2 9),(11,IndexedFaceQuad 9 2 0 4)]]
*Main> test3
Done " 12 8 1 0\n" [[(1,IndexedFaceTriangle 10 1
9),(2,IndexedFaceTriangle 1 2 9),(11,IndexedFaceQuad 9 2 0 4)]]
*Main> test4
Done " 12 8 1 0\n" [[(1,IndexedFaceTriangle 10 1
9),(2,IndexedFaceTriangle 1 2 9),(11,IndexedFaceQuad 9 2 0 4)]]
*Main> test5
Done " 12 8 1 0\n" [[(1,IndexedFaceTriangle 10 1
9),(2,IndexedFaceTriangle 1 2 9),(11,IndexedFaceQuad 9 2 0 4)]]
[1] http://ideone.com/x75C3j
Mukesh Tiwari
On Tue, Apr 9, 2013 at 11:30 AM, Michel Kuhlmann <[email protected]>wrote:
> Hi,
> I couldn't figure out, why I'm failing with attoparsec.
> I have the follwing code (https://github.com/michelk/devsurf/tree/readNet)
>
> import Data.Attoparsec.Text
> import qualified Data.Text as T
> import Language.DevSurf.Readers.SpringNet
> import Prelude hiding (takeWhile, take)
>
> data IndexedFace
> = IndexedFaceTriangle Int Int Int
> | IndexedFaceQuad Int Int Int Int
> deriving (Show)
>
> -- | block of faces-lines
> faces :: Parser [[(Int, IndexedFace)]]
> faces = faceLine `sepBy` endOfLine
>
> -- | Line containing up to two indexed faces
> faceLine :: Parser [(Int, IndexedFace)]
> faceLine = face `sepBy` (take 6)
>
> -- | single indexed-face
> face :: Parser (Int, IndexedFace)
> face = do
> i <- index
> v1 <- index
> v2 <- index
> v3 <- index
> v4 <- index
> case v4 of
> 0 -> return (i, IndexedFaceTriangle v1 v2 v3)
> _ -> return (i, IndexedFaceQuad v1 v2 v3 v4)
>
> -- | node or face index 6 wide
> index :: Parser Int
> index = do
> i <- take 6
> return . read . T.unpack $ i
>
> When testing, the follwing is working:
>
> testEleL2 = do
> let ele = T.pack " 1 10 1 9 0 2
> 1 2 9 0\n"
> r = parse faceLine ele
> case r of
> Partial _ -> print $ feed r (T.pack "")
> _ -> print r
>
> testEles = do
> let eles = T.pack $ concat [" 1 10 1 9 0
> 2 1 2 9 0\n"
> --," 3 11 9 2 0\n"
> ," 4 12 8 1 0\n"
> ]
> r = parse faces eles
> case r of
> Partial _ -> print $ feed r (T.pack "")
> _ -> print r
>
> testEles = do
> let eles = T.pack $ concat [" 1 10 1 9 0
> 2 1 2 9 0\n"
> ," 3 11 9 2 0\n"
> --," 4 12 8 1 0\n"
> ]
> r = parse faces eles
> case r of
> Partial _ -> print $ feed r (T.pack "")
> _ -> print r
>
> But this is not working
>
> testEles = do
> let eles = T.pack $ concat [" 1 10 1 9 0
> 2 1 2 9 0\n"
> ," 3 11 9 2 0\n"
> ," 4 12 8 1 0\n"
> ]
> r = parse faces eles
> case r of
> Partial _ -> print $ feed r (T.pack "")
> _ -> print r
>
>
> testEles = do
> let eles = T.pack $ concat [" 1 10 1 9 0
> 2 1 2 9 0\n"
> ," 3 11 9 2 0
> 4 12 8 1 0\n"
> ]
> r = parse faces eles
> case r of
> Partial _ -> print $ feed r (T.pack "")
> _ -> print r
>
> Please help.
> Thanks, Michel
>
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://www.haskell.org/mailman/listinfo/beginners
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://www.haskell.org/pipermail/beginners/attachments/20130409/90cdef56/attachment-0001.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: ParsingAtto.hs
Type: application/octet-stream
Size: 2773 bytes
Desc: not available
URL:
<http://www.haskell.org/pipermail/beginners/attachments/20130409/90cdef56/attachment-0001.obj>
------------------------------
Message: 3
Date: Tue, 09 Apr 2013 11:15:01 -0500
From: "Tommy M. McGuire" <[email protected]>
Subject: [Haskell-beginners] </>? Was: doesFileExist cannot get
~/blah_blah right
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=UTF-8
On 04/09/2013 07:07 AM, Brent Yorgey wrote:
> Also, since we are discussing portability, it's a much better idea to do
>
> homedir </> "blah_blah"
>
> instead of homedir ++ "/blah_blah", since the former will use the
> correct path separator character for whatever system it is compiled
> on.
Wait, what? Where'd "</>" come from?
--
Tommy M. McGuire
[email protected]
------------------------------
Message: 4
Date: Tue, 9 Apr 2013 12:25:10 -0400
From: David McBride <[email protected]>
Subject: Re: [Haskell-beginners] </>? Was: doesFileExist cannot get
~/blah_blah right
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Message-ID:
<CAN+Tr40gyBidS=TAxxNc8EyeSqVsV_hrKt1g=q30fotm7rf...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
There is a package system-filepath
http://hackage.haskell.org/package/system-filepath which fixes a lot of
quibbles people have with the way filepaths are implemented in haskell.
There are apparently a lot of problems with using strings as filepaths,
like the fact that they are slow, that they have encoding issues, and that
people cannot make a path that is system agnostic.
So the </> operator in that library just joins two filepaths together with
the correct slash.
On Tue, Apr 9, 2013 at 12:15 PM, Tommy M. McGuire <[email protected]> wrote:
> On 04/09/2013 07:07 AM, Brent Yorgey wrote:
> > Also, since we are discussing portability, it's a much better idea to do
> >
> > homedir </> "blah_blah"
> >
> > instead of homedir ++ "/blah_blah", since the former will use the
> > correct path separator character for whatever system it is compiled
> > on.
>
> Wait, what? Where'd "</>" come from?
>
>
> --
> Tommy M. McGuire
> [email protected]
>
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://www.haskell.org/mailman/listinfo/beginners
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://www.haskell.org/pipermail/beginners/attachments/20130409/072c350a/attachment.htm>
------------------------------
_______________________________________________
Beginners mailing list
[email protected]
http://www.haskell.org/mailman/listinfo/beginners
End of Beginners Digest, Vol 58, Issue 19
*****************************************
