To create the [String] as in your example, you just have to write: let names = ["x"++ show i | i <- [0..w-1]] varnames <- mallocList names -Sylvain 2014-04-29 15:40 GMT+02:00 Lamine <mohamadoulamine@gmail.com>:
Hi Sylvain, thank you for your response! I try to use this 2 lines
allocaArray (w*n) $ \var -> do xs <- peekArray (w) var to code char **varnames = ccl_new_array (char *, w);
but it return [CString] not a [String]
On 04/29/2014 01:58 PM, Sylvain Henry wrote:
Hi,
"varnames" is an array of pointers, you cannot allocate it with mallocBytes (n*100).
Try something like this (not tested):
mallocList :: [String] -> IO (Ptr CString) mallocList xs = newArray =<< forM xs g where g x = do b <- mallocBytes 100 pokeCString b x 99 return b
pokeCString :: CString -> String -> Int -> IO () pokeCString dst value maxLen = withCStringLen (take maxLen value) $ uncurry (copyArray dst)
-Sylvain
2014-04-29 13:11 GMT+02:00 Lamine <mohamadoulamine@gmail.com>:
Hi,
I want to do write this C code in haskell code, but i have some pb:
int w ; char **varnames = ccl_new_array (char *, w);
int i; for (i = 0; i < w; i++) { varnames[i] = ccl_new_array (char, 100); sprintf (varnames[i], "x%d", i); }
I try this code unsing mallocList to (http://lpaste.net/report/712): mallocList :: [CString] -> IO (Ptr CString) mallocList xs = do let n = Prelude.length xs p <- mallocBytes (n*100) forM_ (Prelude.zip [0..] xs) (uncurry (pokeByteOff p)) return p
let n = sizeOf(undefined :: CString) allocaArray w $ \var -> do xs <- peekArray (w*n) var varnames <- mallocList xs
I have an error "segmentation fault(core dumped)". can someone please help me? Thank you.
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