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 <michel@kuhlmanns.info> 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
Beginners@haskell.org
http://www.haskell.org/mailman/listinfo/beginners