68 lines
1.4 KiB
JavaScript
68 lines
1.4 KiB
JavaScript
(function () {
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'use strict';
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// matrixMultiply:: [[n]] -> [[n]] -> [[n]]
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function matrixMultiply(a, b) {
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var bCols = transpose(b);
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return a.map(function (aRow) {
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return bCols.map(function (bCol) {
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return dotProduct(aRow, bCol);
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});
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});
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}
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// [[n]] -> [[n]] -> [[n]]
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function dotProduct(xs, ys) {
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return sum(zipWith(product, xs, ys));
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}
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return matrixMultiply(
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[[-1, 1, 4],
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[ 6, -4, 2],
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[-3, 5, 0],
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[ 3, 7, -2]],
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[[-1, 1, 4, 8],
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[ 6, 9, 10, 2],
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[11, -4, 5, -3]]
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);
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// --> [[51, -8, 26, -18], [-8, -38, -6, 34],
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// [33, 42, 38, -14], [17, 74, 72, 44]]
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// GENERIC LIBRARY FUNCTIONS
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// (a -> b -> c) -> [a] -> [b] -> [c]
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function zipWith(f, xs, ys) {
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return xs.length === ys.length ? (
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xs.map(function (x, i) {
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return f(x, ys[i]);
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})
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) : undefined;
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}
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// [[a]] -> [[a]]
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function transpose(lst) {
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return lst[0].map(function (_, iCol) {
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return lst.map(function (row) {
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return row[iCol];
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});
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});
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}
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// sum :: (Num a) => [a] -> a
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function sum(xs) {
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return xs.reduce(function (a, x) {
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return a + x;
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}, 0);
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}
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// product :: n -> n -> n
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function product(a, b) {
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return a * b;
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}
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})();
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