Improved project structure.

haskell/e049.hs

@@ -0,0 +1,27 @@
+import Data.Function
+import Data.List
+import qualified Data.Set as S
+
+
+prims = fix (\f (x:xs) -> x:f (filter (\y -> rem y x /= 0) xs)) [2..]
+
+--permu :: Integer -> S.Set Integer
+permu :: Integer -> S.Set Integer
+permu = S.fromList . map read . permutations . show
+
+
+primsList = dropWhile (< 1000) $ takeWhile (< 10000) prims
+primsSet = S.fromList primsList
+
+candidates :: [[Integer]]
+candidates  = map (\prim -> S.toList $ S.intersection primsSet (permu prim)) primsList
+
+candidates' = filter (\x -> 3 <= length x) candidates
+candidates'' = map sort candidates'
+
+--permu' :: [a] -> [[a]]
+permu' []     = []
+permu' (x:xs) = [map permu' y | y <- tails xs]
+
+--permu3 xs = filter (\(a:b:c:[]) -> a < b && b < c && b - a == c - b) $ nub $ map (take 3) $ permutations xs
+