Sum multiples of 3 and 5: Difference between revisions

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@@ Line 1,505: / Line 1,505: @@
 <lang haskell>import Data.List (nub)
-sum35 :: Integral a => a -> a
+sum35 :: Integer -> Integer
+sum35 n =
-sum35 n = sumMul n 3 + sumMul n 5 - sumMul n 15
+  let f = sumMul n
+  in f 3 + f 5 - f 15
-sumMul :: Integral a => a -> a -> a
+sumMul :: Integer -> Integer -> Integer
-sumMul n f = f * n1 * (n1 + 1) `div` 2
+sumMul n f =
+  let n1 = (n - 1) `div` f
-  where
-    n1 = (n - 1) `div` f
+  in f * n1 * (n1 + 1) `div` 2
--- Functions below are for variable length inputs
+-- For variable length inputs:
+pairLCM :: [Integer] -> [Integer]
-pairLCM :: Integral a => [a] -> [a]
 pairLCM [] = []
 pairLCM (x:xs) = (lcm x <$> xs) ++ pairLCM xs
-sumMulS :: Integral a => a -> [a] -> a
+sumMulS :: Integer -> [Integer] -> Integer
 sumMulS _ [] = 0
-sumMulS n s = sum (sumMul n <$> ss) - sumMulS n (pairLCM ss)
+sumMulS n s = (((-) . sum . fmap (sumMul n)) <*> (sumMulS n . pairLCM)) (nub s)
-  where
-    ss = nub s
 main :: IO ()