23 lines
682 B
Haskell
23 lines
682 B
Haskell
import Data.List (find)
|
|
|
|
isqrt :: (Integral n) => n -> n
|
|
isqrt = floor . sqrt . fromIntegral
|
|
|
|
isPrime :: (Integral n) => n -> Bool
|
|
isPrime n = (n >= 2) && all ((/= 0) . (n `mod`)) [2 .. isqrt n]
|
|
|
|
goldbach :: (Integral n) => n -> (n, n)
|
|
goldbach n =
|
|
if odd n
|
|
then error "Odd number was given"
|
|
else (p, n - p)
|
|
where
|
|
Just p = find (\p -> (n - p) `elem` primes) primes
|
|
primes = filter isPrime [2 .. n - 1]
|
|
|
|
goldbachList' :: (Integral n) => n -> n -> n -> [(n, n)]
|
|
goldbachList' m n d = filter (\(p, q) -> p > d && q > d) $ map goldbach $ filter even [m .. n]
|
|
|
|
goldbachList :: (Integral n) => n -> n -> [(n, n)]
|
|
goldbachList m n = map goldbach $ filter even [m .. n]
|