On 17 Sep 2009, at 15:21, José Pedro Magalhães wrote:
> > E.g. here's a type Bar with three constructors:
> > > data Bar = X | Y | Z deriving (Show)
> > > instance Enumerated Bar where
> > > constructors = [X, Y, Z]
> >
> > (This is certainly ugly. Any suggestions?)
> >
> |constructors| is expressible in SYB:
Wow.
What about
data Bar = X | Y | Z deriving (Show, Eq, Ord, Enum, Bounded)
instance Enumerated Bar where
constructors = [minBound .. maxBound]
?
Oh yes, that will certainly work for this very simple datatype.
However, one cannot automatically derive instances of |Bounded| for
datatypes with non-nullary constructors.
That would be OK in this instance, I think; I'm already dealing with
some of those cases by hand, but there were enough purely nullary ones
that this seemed worth doing.
I don't know if that will work any better with Foo/convert,
though... :-)
Thanks though Daniel - it's good to meet Enum and Bounded.
-Andy
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