[Haskell-cafe] adding the elements of two lists
Ketil Malde
ketil at malde.org
Thu Mar 29 09:34:38 CEST 2012
"Richard O'Keefe" <ok at cs.otago.ac.nz> writes:
> newtype PS a = PS [a] deriving (Eq, Show)
>
> u f (PS x) = PS $ map f x
> b f (PS x) (PS y) = PS $ zipWith f x y
> to_ps x = PS (x : repeat 0)
BTW, isn't this a good candidate for an Applicative instance (similar to
ZipList)?
u f p = f <$> p -- or u = fmap
b f p1 p2 = f <$> p1 <*> p2
Not a big deal for the Num instance, perhaps, but more general than u
and b, and it might make it easier to work with in other ways.
-k
--
If I haven't seen further, it is by standing in the footprints of giants
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