On Wed, Sep 30, 2009 at 3:37 AM, Dimitry Golubovsky <golubovsky@gmail.com> wrote:

Hi,

I am trying to use the genericserialize package
(http://hackage.haskell.org/package/genericserialize) but cannot get
things working.

While
buildList (sexpSerialize [1, 2, 3])

yields

"(1 2 3)"

as it might be expected, I cannot deserialize it back:

*Main> (withList sexpDeserialize $ buildList (sexpSerialize [1, 2,
3])) :: Maybe [Integer]
Nothing

or

*Main> (withList sexpDeserialize $ buildList (sexpSerialize [1, 2,
3])) :: Maybe [Int]
Nothing

while I would expect at least one of these cases result in Just [1, 2, 3]

What am I missing?

I'm not sure. I've never seen this library before, but I noticed this:
withList sexpDeserialize $ "12" :: Maybe Int
12
withList sexpDeserialize $ "(12)" :: Maybe [Int]
Just [12]

So it would seem that the sexpDeserialize is not handling the spaces in the input. But, I don't think that's the real problem, look at this:
withList sexpDeserialize $ "\"1 2 3\"" :: Maybe String
Just "1 2 3"

withList sexpDeserialize $ "(\"1 2 3\")" :: Maybe String
Nothing

withList sexpDeserialize $ "(\"1 2 3\")" :: Maybe [String]
Just ["1 2 3"]

So, it seems that the parens are making it into a list.

But, this fails also:
withList sexpDeserialize $ "(\"1\" \"2\" \"3\")" :: Maybe [String]
Nothing

Seems like using withList is wrong or the deserializer is simply buggy. It certainly doesn't work the way I would expect SExp reading to work. I also notice from reading the source on hackage that there may not be any tests for this package and it is a 0.1 release. I'd contact the author, as it seems there is a deficiency in the documentation or a bug in the implementation.

Jason