Difference between revisions of "User:WillNess"
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I am a newbie, interested in Haskell. |
I am a newbie, interested in Haskell. |
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| − | I like ''this'': |
+ | I like ''[http://ideone.com/qpnqe this]'': |
<haskell> |
<haskell> |
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| − | primes = 2 : |
+ | primes = 2 : g (fix g) -- double staged production idea due to M. O'Neill |
| + | fix g = xs where xs = g xs |
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| − | + | g xs = 3 : (gaps 5 $ foldi (\x:xs -> (x:) . union xs) |
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| − | [[p*p,p*p+2*p..] | p <- |
+ | [[p*p, p*p+2*p..] | p <- xs]) |
| + | gaps k s@(x:xs) -- | k<=x = minus [k,k+2..] xs |
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| + | -- inlined to avoid a space leak |
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| + | = if k < x |
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| + | then k : gaps (k+2) s |
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| + | else gaps (k+2) xs |
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</haskell> |
</haskell> |
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Revision as of 18:06, 3 August 2011
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.