#1687: A faster (^)-function.
------------------------------------------+---------------------------------
Reporter: [EMAIL PROTECTED] | Owner:
Type: bug | Status: new
Priority: normal | Milestone: 6.8
Component: Prelude | Version: 6.6.1
Severity: normal | Resolution:
Keywords: | Difficulty: Unknown
Os: Linux | Testcase:
Architecture: x86 |
------------------------------------------+---------------------------------
Comment (by moonlite):
Current version which tries to eliminate some unnecessary tests (don't
test if we're odd when we just did).
I can potentially see a slight speedup.
{{{
module Pow ((^)) where
import Prelude hiding ((^))
{-# SPECIALISE (^) ::
Integer -> Integer -> Integer,
Integer -> Int -> Integer,
Int -> Int -> Int #-}
(^) :: (Integral b, Num a) => a -> b -> a
x ^ y | y < 0 = error "Negative exponent"
| y == 0 = 1
| otherwise = x `pow` y
where
pow :: (Integral b, Num a) => a -> b -> a
x `pow` y
| y == 1 = x
| odd y = x * (f x (y-1))
| otherwise = f x y
where
f x y = let x' = x `pow` (y `div` 2)
in x' * x'
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1687>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler_______________________________________________
Glasgow-haskell-bugs mailing list
Glasgow-haskell-bugs@haskell.org
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
