I'm interested in Haskell.
I like this:
-- inifinte folding idea due to Richard Bird -- double staged production idea due to Melissa O'Neill -- tree folding idea Dave Bayer / simplified formulation Will Ness primes = 2 : g (fix g) where g xs = 3 : gaps 5 (foldi (\(c:cs) -> (c:) . union cs)  [[x*x, x*x+2*x..] | x <- xs]) gaps k s@(c:t) | k < c = k : gaps (k+2) s -- minus [k,k+2..] (c:t), k<=c | True = gaps (k+2) t -- fused to avoid a space leak fix g = xs where xs = g xs -- global defn to avoid space leak
The math formula for Sieve of Eratosthenes,
- . . . or, :) :) .
Trial division sieve:
If you're put off by self-referentiality, just replace or on the right-hand side of equations with .