# User:WillNess

### From HaskellWiki

(Difference between revisions)

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 : 3 : ( | + | primes = 2 : g (fix g) -- double staged production idea due to M. O'Neill |

− | + | fix g = xs where xs = g xs | |

− | [[p*p,p*p+2*p..] | p <- | + | 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 | ||

</haskell> | </haskell> | ||

<code>foldi</code> is on [[Fold#Tree-like_folds|Tree-like folds]]. More at [[Prime numbers]]. | <code>foldi</code> is on [[Fold#Tree-like_folds|Tree-like folds]]. More at [[Prime numbers]]. |

## 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.