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diff --git a/progs/demo/pfac.hs b/progs/demo/pfac.hs
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+
+-- This is a parallel varient of factorial
+
+module Main where
+
+fac :: Int -> Int
+fac 0 = 1
+fac n = pfac 1 n
+
+pfac :: Int -> Int -> Int
+pfac low high | low == high = low
+ | low + 1 == high = (low * high)
+ | otherwise = pfac low mid * pfac (mid + 1) high
+ where
+ mid = (high + low) `div` 2
+
+main = appendChan stdout "Type in N: " abort $
+ readChan stdin abort $ \ input ->
+ appendChan stdout (show (fac (read (head (lines input))))) abort done
+
+