User:WillNess: Difference between revisions
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I | I'm interested in Haskell. | ||
I like ''[http://ideone.com/qpnqe this]'': | I like ''[http://ideone.com/qpnqe this]'': |
Revision as of 07:49, 8 August 2011
I'm interested in Haskell.
I like this:
-- inifinte folding idea due to Richard Bird
-- double staged production idea due to Melissa O'Neill
-- tree folding idea Dave Bayer / simplified formulation Will Ness
primes = 2 : g (fix g)
where
g ps = 3 : gaps 5 (foldi (\(q:qs) -> (q:) . union qs)
[[p*p, p*p+2*p..] | p <- ps])
gaps k s@(c:t)
| k < c = k : gaps (k+2) s -- | k<=c = minus [k,k+2..] s
| True = gaps (k+2) t -- fused to avoid a space leak
fix g = xs where xs = g xs -- global defn to avoid space leak
foldi
is on Tree-like folds page. union
and more at Prime numbers.