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| author | Jasper Van der Jeugt <jaspervdj@gmail.com> | 2011-02-07 11:41:09 +0100 |
|---|---|---|
| committer | Jasper Van der Jeugt <jaspervdj@gmail.com> | 2011-02-07 11:41:09 +0100 |
| commit | 986a74b3af664b824a5c67524d2433d7e990f502 (patch) | |
| tree | bf0f9d723e885db06818668ef280b4d64a3f27d2 | |
| parent | 781138a0e79a942b9835b159293f2b4088e98ac1 (diff) | |
| download | hakyll-986a74b3af664b824a5c67524d2433d7e990f502.tar.gz | |
Add mapA
| -rw-r--r-- | src/Hakyll/Core/Util/Arrow.hs | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/src/Hakyll/Core/Util/Arrow.hs b/src/Hakyll/Core/Util/Arrow.hs index d97ba22..49cbf2b 100644 --- a/src/Hakyll/Core/Util/Arrow.hs +++ b/src/Hakyll/Core/Util/Arrow.hs @@ -7,7 +7,9 @@ module Hakyll.Core.Util.Arrow , mapA ) where -import Control.Arrow (Arrow, (&&&), arr, (>>^)) +import Control.Arrow ( Arrow, ArrowChoice, (&&&), arr, (>>^), (|||) + , (>>>), (***) + ) constA :: Arrow a => c @@ -25,7 +27,10 @@ unitA :: Arrow a => a b () unitA = constA () -mapA :: Arrow a - => (b -> c) +mapA :: ArrowChoice a + => a b c -> a [b] [c] -mapA = arr . map +mapA f = arr listEither >>> arr id ||| (f *** mapA f >>> arr (uncurry (:))) + where + listEither [] = Left [] + listEither (x : xs) = Right (x, xs) |