diff options
Diffstat (limited to 'src/Hakyll')
| -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) |