Initial data commit

Task/Matrix-multiplication/Haskell/matrix-multiplication-1.hs

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+import Data.List
+
+ mmult :: Num a => [[a]] -> [[a]] -> [[a]]
+ mmult a b = [ [ sum $ zipWith (*) ar bc | bc <- (transpose b) ] | ar <- a ]
+
+ -- Example use:
+ test = [[1, 2],
+         [3, 4]] `mmult` [[-3, -8, 3],
+                          [-2,  1, 4]]

Task/Matrix-multiplication/Haskell/matrix-multiplication-2.hs

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+import Data.Array
+
+ mmult :: (Ix i, Num a) => Array (i,i) a -> Array (i,i) a -> Array (i,i) a
+ mmult x y
+   | x1 /= y0 || x1' /= y0'  = error "range mismatch"
+   | otherwise               = array ((x0,y1),(x0',y1')) l
+   where
+     ((x0,x1),(x0',x1')) = bounds x
+     ((y0,y1),(y0',y1')) = bounds y
+     ir = range (x0,x0')
+     jr = range (y1,y1')
+     kr = range (x1,x1')
+     l  = [((i,j), sum [x!(i,k) * y!(k,j) | k <- kr]) | i <- ir, j <- jr]

Task/Matrix-multiplication/Haskell/matrix-multiplication-3.hs

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+multiply :: Num a => [[a]] -> [[a]] -> [[a]]
+multiply us vs = map (mult [] vs) us
+  where
+    mult xs [] _ = xs
+    mult xs _ [] = xs
+    mult [] (zs : zss) (y : ys) = mult (map (y *) zs) zss ys
+    mult xs (zs : zss) (y : ys) =
+      mult
+        (zipWith (\u v -> u + v * y) xs zs)
+        zss
+        ys
+
+main :: IO ()
+main =
+  mapM_ print $
+    multiply
+      [[1, 2], [3, 4]]
+      [[-3, -8, 3], [-2, 1, 4]]

Task/Matrix-multiplication/Haskell/matrix-multiplication-4.hs

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+mult :: Num a => [[a]] -> [[a]] -> [[a]]
+mult uss vss =
+  let go xs
+        | null xs = []
+        | otherwise = foldl1 (zipWith (+)) xs
+   in go . zipWith (flip (map . (*))) vss <$> uss
+
+main :: IO ()
+main =
+  mapM_ print $
+    mult [[1, 2], [3, 4]] [[-3, -8, 3], [-2, 1, 4]]

Task/Matrix-multiplication/Haskell/matrix-multiplication-5.hs

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+import Numeric.LinearAlgebra
+
+a, b :: Matrix I
+a = (2 >< 2) [1, 2, 3, 4]
+
+b = (2 >< 3) [-3, -8, 3, -2, 1, 4]
+
+main :: IO ()
+main = print $ a <> b