[Haskell-cafe] could we get a Data instance for Data.Text.Text?
nccb2 at kent.ac.uk
Sat Jan 23 09:55:01 EST 2010
Jeremy Shaw wrote:
> Would it be possible to get a Data instance for Data.Text.Text? This
> would allow us to create a Serialize instance of Text for use with
> happstack -- which would be extremely useful.
Last time this came up, I had a look at providing a Data instance for
Text, and I "got as far as needing a Data instance for ByteString#,
accompanied by an error I don't fully understand, but I think is telling
me that things involving magic hashes are magic:
Couldn't match kind `#' against `*'
When matching the kinds of `ByteArray# :: #' and `d :: *'
Expected type: d
Inferred type: ByteArray#
In the first argument of `z', namely `Array' "
The problem with a Data instance for Text is that it is using this
ByteArray# type, which can't easily interact with the Data type-class
because it's a special type. I would suggest providing a Data instance
for ByteArray#, but I don't think that's possible either. As far as I
can understand it all, your Data instance is probably the closest you
are going to get to having a decent Data instance without something else
(GHC/SYB) changing significantly.
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