Generics... no Tuples > 2 either...

[Simon Peyton-Jones]

Yes, sorry about that. We'll add them shortly.  (It's nice to know that
someone is using this stuff!)

Simon

| -----Original Message-----
| From: glasgow-haskell-users-bounces at haskell.org
[mailto:glasgow-haskell-users-
| bounces at haskell.org] On Behalf Of Abraham Egnor
| Sent: 26 February 2004 22:18
| To: MR K P SCHUPKE
| Cc: glasgow-haskell-users at haskell.org
| Subject: Re: Generics... no Tuples > 2 either...
| 
| I've been frustrated by the same lack of instances; as a stopgap,
here's
| one for a three-tuple.  The pattern is pretty clear and can easily be
| extended to whatever size you'd like.
| 
| tupCon = mkConstr 1 "(,,)" Prefix
| 
| instance (Data a, Data b, Data c) => Data (a, b ,c) where
|     gfoldl k z (a, b, c) = ((z (,,) `k` a) `k` b) `k` c
|     toConstr _ = tupCon
|     fromConstr _ = (undefined, undefined, undefined)
|     dataTypeOf _ = mkDataType [tupCon]
| 
| MR K P SCHUPKE <k.schupke at imperial.ac.uk> writes:
| >
| >Any chance of Data instances for tuples of size
| >greater than 2... One of the nice things about generics is
| >you can use them by deriving Data on your datatypes - of
| >course this doesn't work if you all of a sudden have to
| >put a load of boiler-plate in just to use tuples...
| >
| >	Regards,
| >	Keean Schupke
| >_______________________________________________
| >Glasgow-haskell-users mailing list
| >Glasgow-haskell-users at haskell.org
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| >
| 
| 
| 
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