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Make exponentiation significantly faster #221

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Make exponentiation significantly faster #221

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089d200
Make exponentiation significantly faster
axman6 Aug 10, 2025
539c470
BangPatterns instead of seq
axman6 Aug 13, 2025
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10 changes: 9 additions & 1 deletion Statistics/Sample.hs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,5 @@
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE BangPatterns #-}
-- |
-- Module : Statistics.Sample
-- Copyright : (c) 2008 Don Stewart, 2009 Bryan O'Sullivan
Expand Down Expand Up @@ -453,7 +454,14 @@ pair va vb
-- (^) operator from Prelude is just slow.
(^) :: Double -> Int -> Double
x ^ 1 = x
x ^ n = x * (x ^ (n-1))
x ^ 2 = x * x
x ^ 3 = x * x * x
x ^ 4 = (x * x) * (x * x)
x ^ 5 = (x * x) * x * (x * x)
-- x ^ n = x * (x ^ (n-1))
x0 ^ n0 = go (n0-1) x0 where
go 0 !acc = acc
go n acc = go (n-1) (acc*x0)
{-# INLINE (^) #-}

-- don't support polymorphism, as we can't get unboxed returns if we use it.
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