[Haskell-cafe] (no subject)

[Donald Bruce Stewart]

leaveye.guo:
> To read the handle openBinaryFile returns, both the hGetBuf and
> hGetBufNonBlocking needs one parameter _buf_ of type Ptr a.
> I can not get one data of that type.
> 
> In the doc, there is only nullPtr, and also some type cast functions.
> I failed to find some other buffer-maker function.
> 
> What should I do ?

I mean, what problem are you trying to solve? Ptrs aren't the usual way
to manipulate files in Haskell.

Here, for example, is a small program to print the first byte of a
binary file:

    import System.IO
    import qualified Data.ByteString as B

    main = do
        h <- openBinaryFile "a.out" ReadMode
        s <- B.hGetContents h
        print (B.head s)

When run:

    $ ./a.out 
    127

Note there's no mallocs or pointers involved.

-- Don