Difference between revisions of "User:WillNess"
Jump to navigation
Jump to search
m |
|||
Line 6: | Line 6: | ||
primes = 2 : g (fix g) -- double staged production idea due to M. O'Neill |
primes = 2 : g (fix g) -- double staged production idea due to M. O'Neill |
||
where |
where |
||
− | g xs = 3 : (gaps 5 $ foldi (\(q:qs)-> (q:) . union qs) |
+ | g xs = 3 : (gaps 5 $ foldi (\(q:qs) -> (q:) . union qs) |
[[p*p, p*p+2*p..] | p <- xs]) |
[[p*p, p*p+2*p..] | p <- xs]) |
||
⚫ | |||
⚫ | |||
+ | | True = gaps (k+2) xs -- inlined to avoid a space leak |
||
− | fix g = xs where xs = g xs |
+ | fix g = xs where xs = g xs -- global defn to avoid space leak |
− | |||
⚫ | |||
⚫ | |||
− | else gaps (k+2) xs |
||
</haskell> |
</haskell> |
||
Revision as of 13:38, 7 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
where
g xs = 3 : (gaps 5 $ foldi (\(q:qs) -> (q:) . union qs)
[[p*p, p*p+2*p..] | p <- xs])
gaps k s@(x:xs)
| k < x = k : gaps (k+2) s -- | k<=x = minus [k,k+2..] xs
| True = gaps (k+2) xs -- inlined to avoid a space leak
fix g = xs where xs = g xs -- global defn to avoid space leak
foldi
is on Tree-like folds. More at Prime numbers.