Re: [Haskell-cafe] Type classes for converting to Text and String

8 Mar 2012


      * Simon Hengel  [2012-03-08 13:20:22+0100]
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On Thu, Mar 08, 2012 at 12:54:13PM +0200, Roman Cheplyaka wrote:
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* Simon Hengel  [2012-03-08 11:48:41+0100]
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On Thu, Mar 08, 2012 at 12:18:56PM +0200, Roman Cheplyaka wrote:
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If it's fine to depend on FunDeps, you can use ListLike.
http://hackage.haskell.org/package/ListLike
How would that help with toText?
toText = fromListLike
(ListLike instance for Text is provided by the listlike-instances
package.)
Ah, the listlike-instances package is the missing piece.
Not sure if this is going somewhere.  But I'm still trying to get a
clear picture of the performance implications.
Say I have a newtype-wrapped ByteString that I would decode to
String/Text using UTF-8:
newtype Value = Value ByteString
Would it be possible to go from Value to Text by essentially ending up
with Data.Text.Encoding.decodeUtf8 at runtime (e.g. by using rewrite
rules)?
You can do that, but it will work only if your functions are specialized
enough at compile time.

-- 
Roman I. Cheplyaka :: http://ro-che.info/