Crivello Haskell

gistfile1.hs

import Data.List
import Debug.Trace
-- primes = 2 : 3 : zipWith getPrime primes (tail primes)

checkZeros :: [Int] -> Bool
checkZeros ms = any isZero ms
    where isZero 0 = True
          isZero _ = False

calculateMods :: Int -> [Int] -> [Int]
calculateMods n ps = map moduloOfN ps
    where moduloOfN p = n `mod` p 
-- calculateMods n ps = map (mod n) ps

primesInRange :: Int -> Int -> [Int] -> [Int]
primesInRange start end ps = filter isPrime [start .. end]
    where isPrime n = not (checkZeros (calculateMods n ps))
-- NB: use transpose & cycle to calculate list, instead of mod every time!

-- primes :: [Int]
-- foldl?  unfoldr?  ???
primes = 2 : 3 : stepIt primes
-- primes = 2 : 3 : zipWith getPrime primes (tail primes)

stepIt ps = (trace (show $ take 2 ps) revstep) . reverse $ ps
revstep ps@(ultimo:penultimo:_) = primesInRange (penultimo^2) (ultimo^2) ps

-- 2 3 5 7  11 13  
-- 3 5 7 11 13 17

    -- where stepIt ps = ps : primesInRange (penultimo ps)^2 (ultimo ps)^2 ps

-- zipN :: [[Int]] -> [[Int]]
-- zipN ls = [map (head) ls] : zipN [map (tail) ls]