Generics... no Tuples > 2 either...
aegnor at antioch-college.edu
Thu Feb 26 14:18:22 EST 2004
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...
> Keean Schupke
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>Glasgow-haskell-users at haskell.org
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