It is also dirt slow. This is just trial division, done in a lazy fashion.

At least it is better than the one some haskellers call the sieve of erathostenes (it isn't the sieve of erathostenes), which is so god-awful that I almost vomit every time I see it.

The real lazy sieve of erathostenes is a thing of wonder! There is a paper describing it called "the genuine sieve of erathostenes" and it can be found by googling.