User:WillNess
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I am a newbie, interested in Haskell.
I like this:
primes = 2 : g (fix g) -- double staged production idea due to M. O'Neill
fix g = xs where xs = g xs
g xs = 3 : (gaps 5 $ foldi (\x:xs -> (x:) . union xs)
[[p*p, p*p+2*p..] | p <- xs])
gaps k s@(x:xs) -- | k<=x = minus [k,k+2..] xs
-- inlined to avoid a space leak
= if k < x
then k : gaps (k+2) s
else gaps (k+2) xs
foldi is on Tree-like folds. More at Prime numbers.