# 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
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.