# User:WillNess

From HaskellWiki

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.