Matrix multiplication: Difference between revisions

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 =={{header|JavaScript}}==
+===Iterative===
 {{works with|SpiderMonkey}} for the <code>print()</code> function
@@ Line 2,010: / Line 2,012: @@
 <pre>-7,-6,11
 -17,-20,25</pre>
+===Functional (ES5)===
+{{trans|Haskell}}
+<lang JavaScript>(function () {
+    'use strict';
+    // matrixMultiply:: [[n]] -> [[n]] -> [[n]]
+    function matrixMultiply(a, b) {
+        var bt = transpose(b);
+        return concatMap(a, function (aRow) {
+            return [concatMap(bt, function (bCol) {
+                return [sum(zipWith(prod, aRow, bCol))];
+            })]
+        });
+    }
+    return matrixMultiply(
+        [[1, 2],
+         [3, 4]],
+        [[-3, -8, 3],
+         [-2,  1, 4]]
+    );
+    // --> [[-7, -6, 11], [-17, -20, 25]]
+    // GENERIC LIBRARY FUNCTIONS
+    // concatMap :: [a] -> (a -> [b]) -> [b]
+    function concatMap(xs, f) {
+        return [].concat.apply([], xs.map(f));
+    }
+    // (a -> b -> c) -> [a] -> [b] -> [c]
+    function zipWith(f, xs, ys) {
+        return xs.length === ys.length ? (
+            xs.map(function (x, i) {
+                return f(x, ys[i]);
+            })
+        ) : undefined;
+    }
+    // [[a]] -> [[a]]
+    function transpose(lst) {
+        return lst[0].map(function (_, iCol) {
+            return lst.map(function (row) {
+                return row[iCol];
+            });
+        });
+    }
+    // sum :: (Num a) => [a] -> a
+    function sum(xs) {
+        return xs.reduce(function (a, x) {
+            return a + x;
+        }, 0);
+    }
+    // product :: n -> n -> n
+    function prod(a, b) {
+        return a * b;
+    }
+})();</lang>
+{{Out}}
+<pre>[[-7, -6, 11], [-17, -20, 25]]</pre>
 =={{header|jq}}==