On Jun 4, 2008, at 5:51 AM, Henning Thielemann wrote:
How about assisting the compiler with a helper function named
'parallel' ?
parallel :: ([a] -> b, [a] -> c) -> [a] -> (b,c)
parallel (f,g) xs = (f xs, g xs)
mean xs =
uncurry (/) $ parallel (sum,length) xs
? We could state RULES in terms of 'parallel'. By calling
'parallel', the user tells, that he wants fusion here.
Say
"parallel/foldl/foldl" forall f, g, x0, y0.
parallel (foldl f x0, foldl g y0) = foldl (\(x,y) z -> (f x
z, g y z)) (x0,y0)
Well, we already have &&&. Would a sufficiently specialized rule over
that be a useful addition to Control.Arrow?
Regards,
Sterl.
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