Difference between revisions of "User:WillNess"
Jump to navigation
Jump to search
Line 1: | Line 1: | ||
I am a newbie, interested in Haskell. |
I am a newbie, interested in Haskell. |
||
− | I like ''this'': |
+ | I like ''[http://ideone.com/qpnqe this]'': |
<haskell> |
<haskell> |
||
− | primes = 2 : |
+ | 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 <- |
+ | [[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 |
||
</haskell> |
</haskell> |
||
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.