[Haskell-cafe] ANN: text 0.5, a major revision of the Unicode text library

Jeremy Shaw jeremy at n-heptane.com
Fri Oct 9 16:27:03 EDT 2009

oops, for the sake of completeness you also need:

textType = mkStringType "Data.Text"

- jeremy

On Oct 9, 2009, at 10:33 AM, Jeremy Shaw wrote:

> Sweet!
> What are the chances of seeing a, instance Data Text, some day? text  
> would be a great type to use with Happstack, because it is far more  
> memory efficient than String. But it is difficult to do that with  
> out a instance of Data.
> For the time being, I have been hacking it with:
> instance Data Text where
>    toConstr x = mkStringConstr textType (Text.unpack x)
>    gunfold _k z c = case constrRep c of
>                      (StringConstr x) -> z (Text.pack x)
>                      _ -> error "gunfold for Data.Text"
>    dataTypeOf _ = textType
> But, packing and unpacking the Text is obviously not that cool..
> For what it's worth, ByteString is normally exported abstract, and  
> just uses, deriving Data. Perhaps we can do the same for text? (I  
> believe there are a number of other examples of types in the  
> 'standard' libraries which are exported abstract, but have Data  
> instances...)
> - jeremy
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