On 3/25/12 8:06 AM, Michael Snoyman wrote:
A simple solution is to use the zipWith[1] function:
zipWith (+) [1,2,3] [4,5,6] == [5,7,9]
It takes a bit of time to get acquainted with all of the incredibly
convenient functions in base, but once you know them, it can greatly
simplify your code.
[1]
http://hackage.haskell.org/packages/archive/base/4.5.0.0/doc/html/Prelude.html#v:zipWith
And if you want different behavior with regards to lists of differing
length, you may also be interested in pairWith[2] or zipOrWith[3]
-- Silently truncate uneven lists.
zipWith (+) [1,2,3] [4,5,6] == [5,7,9]
zipWith (+) [1,2,3] [4,5] == [5,7]
-- Give errors for uneven lists.
pairWith (+) [1,2,3] [4,5,6] == Just [5,7,9]
pairWith (+) [1,2,3] [4,5] == Nothing
-- Assume infinitely many trailing zeros.
zipOrWith plus [1,2,3] [4,5,6] == [5,7,9]
zipOrWith plus [1,2,3] [4,5] == [5,7,3]
where
plus (Fst x ) = x
plus (Snd y) = y
plus (Both x y) = x+y
[2]
http://hackage.haskell.org/packages/archive/list-extras/0.4.0.1/doc/html/Data-List-Extras-Pair.html#v:pairWith
[3]
http://hackage.haskell.org/packages/archive/data-or/1.0.0/doc/html/Data-Or.html#v:zipOrWith
--
Live well,
~wren
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