[Haskell-cafe] Re: [Long, probably not-beginners anymore] Parallel folds and folds as arrows (was: Re: Re: When, if ever, does Haskell "calculate once"?)

6 May 2010


      On Fri, 2010-05-07 at 02:15 +0100, Maciej Piechotka wrote:
...
...
myArr :: Num a => FoldlArrow a (a, a) (a, a)
myArr = proc (l, s) -> do e <- element -< ()
                          returnA -< (l + 1, s + e)
It starts consuming memory as well. Somewhere is lazy passing of value
but I cannot find where
Ok. Should be:
myArr :: Num a => FoldlArrow a (a, a) (a, a)
myArr = proc (l, s) -> do e <- element -< ()
                          let !l' = l + 1
                          let !s' = s + e
                          returnA -< (l', s')

Regards