John Goerzen wrote:
> On 2008-02-20, Jules Bean <[EMAIL PROTECTED]> wrote:
>> Not directly, no.
>>
>> The point about Foldable, Functor, and Monad, is that they enforce the
>> connection between container and contents. If the contents is of type
>> "a", the container is of type "f a" for a fixed type constructor 'f'.
>> This works for [], Seq, and so on, but fails for ByteString.
>
> Right. In a pure abstract sense, we humans know there is a
> relationship between container and contents: a ByteString always
> contains a Word8 (or a Char8 if we choose the alternative
> implementation).
>
> But that is not expressed in the type of ByteString.
Hm, making a function out of a constant is easy on the value level, just use
(const x) instead of (x). So, what about wrapping ByteString in a GADT,
like this
data ByteString' a where
BS' :: Word8 -> ByteString' Word8
? I probably overlooked something important here...
Cheers
Ben
_______________________________________________
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
