[Haskell-cafe] Num instances for 2-dimensional types
lemming at henning-thielemann.de
Mon Oct 5 16:14:02 EDT 2009
Sönke Hahn schrieb:
> I often stumble upon 2- (or 3-) dimensional numerical data types like
> (Double, Double)
> or similar self defined ones. I like the idea of creating instances for Num for
> these types. The meaning of (+), (-) and negate is clear and very intuitive, i
> think. I don't feel sure about (*), abs, signum and fromInteger. I used to
> fromInteger n = (r, r) where r = fromInteger n
> , but thinking about it,
> fromInteger n = (fromInteger n, 0)
> seems very reasonable, too.
> Any thoughts on that? How would you do it?
I use NumericPrelude that has more fine grained type classes. E.g. (+)
is in Additive and (*) is in Ring.
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