1 files changed, 16 insertions, 0 deletions
diff --git a/third_party/bazel/rules_haskell/examples/vector/benchmarks/Algo/Leaffix.hs b/third_party/bazel/rules_haskell/examples/vector/benchmarks/Algo/Leaffix.hs
new file mode 100644
index 0000000000..40ec517556
--- /dev/null
+++ b/third_party/bazel/rules_haskell/examples/vector/benchmarks/Algo/Leaffix.hs
@@ -0,0 +1,16 @@
+module Algo.Leaffix where
+
+import Data.Vector.Unboxed as V
+
+leaffix :: (Vector Int, Vector Int) -> Vector Int
+{-# NOINLINE leaffix #-}
+leaffix (ls,rs)
+    = leaffix (V.replicate (V.length ls) 1) ls rs
+    where
+      leaffix xs ls rs
+        = let zs   = V.replicate (V.length ls * 2) 0
+              vs   = V.update_ zs ls xs
+              sums = V.prescanl' (+) 0 vs
+          in
+          V.zipWith (-) (V.backpermute sums ls) (V.backpermute sums rs)
+