#2754: Strictness analyzer fails on an implementation of foldl
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Reporter: nimnul | Owner:
Type: run-time performance bug | Status: new
Priority: normal | Component: Compiler
Version: 6.8.3 | Severity: normal
Keywords: | Testcase:
Architecture: x86 | Os: Windows
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foldB has O(1) complexity, but foldA O(N). Looks like a strictness
analyzer failure.
module Main where
foldA :: (a -> e -> a) -> a -> [e] -> a
foldA _ r [] = r
foldA op r (x:xs) = foldA op (op r x) xs
foldB :: (a -> e -> a) -> a -> [e] -> a
foldB _ r [] = r
foldB op r (x:xs) = r' `seq` foldB op r' xs where r' = op r x
l :: [Int]
l = [1..100*1000*1000]
main = print $ foldl (+) 0 l
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2754>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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