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splitAt should be strict in its first argument

    • Open Issue created by Ian Lynagh <igloo@earth.li> @trac-igloo

    The below is a slightly editted version of http://hackage.haskell.org/trac/ghc/ticket/1182

    The H98 report defines splitAt by:

    splitAt :: Int -> [a] -> ([a],[a])
splitAt n xs = (take n xs, drop n xs)

    So we would expect:

    splitAt _|_ xs = (take _|_ xs, drop _|_ xs)

    however, both GHC and hugs have (different) implementations that are strict in 'n', that is:

    split _|_ xs = _|_

    These cases can be distinguished with the expression:

    case splitAt undefined [] of (_,_) -> ()

    We propose splitAt be changed to be strict in its first argument for Haskell'.

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