Difference between revisions of "User:WillNess"
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<haskell> |
<haskell> |
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| − | + | -- inifinte folding idea due to Richard Bird |
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| + | -- double staged production idea due to Melissa O'Neill |
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| − | where |
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| + | -- tree folding idea Dave Bayer / simplified formulation Will Ness |
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| − | g xs = 3 : (gaps 5 $ foldi (\(q:qs) -> (q:) . union qs) |
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| + | primes = 2 : g (fix g) |
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| − | [[p*p, p*p+2*p..] | p <- xs]) |
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| − | + | where |
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| − | + | g ps = 3 : gaps 5 (foldi (\(q:qs) -> (q:) . union qs) |
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| − | + | [[p*p, p*p+2*p..] | p <- ps]) |
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| + | gaps k s@(c:t) |
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| + | | k < c = k : gaps (k+2) s -- | k<=c = minus [k,k+2..] s |
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| + | | True = gaps (k+2) t -- fused to avoid a space leak |
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fix g = xs where xs = g xs -- global defn to avoid space leak |
fix g = xs where xs = g xs -- global defn to avoid space leak |
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</haskell> |
</haskell> |
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| − | <code>foldi</code> is on [[Fold#Tree-like_folds|Tree-like folds]]. More at [[Prime numbers#Sieve_of_Eratosthenes|Prime numbers]]. |
+ | <code>foldi</code> is on [[Fold#Tree-like_folds|Tree-like folds]] page. More at [[Prime numbers#Sieve_of_Eratosthenes|Prime numbers]]. |
Revision as of 15:25, 7 August 2011
I am a newbie, 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. More at Prime numbers.