Solve 'Matrix Transpose' kata

Author: borisskert

src/MatrixTranspose.hs

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+module MatrixTranspose (transpose) where
+
+-- https://www.codewars.com/kata/52fba2a9adcd10b34300094c/train/haskell
+
+transpose :: [[a]] -> [[a]]
+transpose [] = []
+transpose xss = map (\x -> map (\y -> xss !! y !! x) [0, 1 .. height - 1]) [0, 1 .. width - 1]
+  where
+    height = length xss
+    width = length . head $ xss

test/MatrixTransposeSpec.hs

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+module MatrixTransposeSpec where
+
+import MatrixTranspose (transpose)
+import Test.Hspec
+
+spec :: Spec
+spec = do
+  describe "Fixed tests" $ do
+    it "works on the example matrix" $ do
+      transpose [[1, 2, 3], [4, 5, 6]] `shouldBe` [[1, 4], [2, 5], [3, 6]]
+    it "works on other fixed inputs" $ do
+      transpose [[1]] `shouldBe` [[1]]
+      transpose [[1, 2, 3]] `shouldBe` [[1], [2], [3]]
+      transpose [[1, 2, 3], [4, 5, 6], [7, 8, 9]] `shouldBe` [[1, 4, 7], [2, 5, 8], [3, 6, 9]]
+      transpose [[1, 0, 0], [0, 1, 0], [0, 0, 1], [0, 1, 0], [1, 0, 0]]
+        `shouldBe` [[1, 0, 0, 0, 1], [0, 1, 0, 1, 0], [0, 0, 1, 0, 0]]