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

[Maciej Piechotka]

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
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