1 files changed, 25 insertions, 0 deletions
diff --git a/src/Hakyll/Core/Util/Arrow.hs b/src/Hakyll/Core/Util/Arrow.hs
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+++ b/src/Hakyll/Core/Util/Arrow.hs
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+-- | Various arrow utility functions
+--
+module Hakyll.Core.Util.Arrow
+    ( constA
+    , sequenceA
+    , unitA
+    ) where
+
+import Control.Arrow (Arrow, (&&&), arr, (>>^))
+
+constA :: Arrow a
+       => c
+       -> a b c
+constA = arr . const
+
+sequenceA :: Arrow a
+          => [a b c]
+          -> a b [c]
+sequenceA = foldl reduce $ constA []
+  where
+    reduce la xa = xa &&& la >>^ arr (uncurry (:))
+
+unitA :: Arrow a
+      => a b ()
+unitA = constA ()