feat: add transposeView

This method allows to manipulate a transpose of a matrix without the
need to copy all of its data to a new instance.

Author: targos

src/abstractMatrix.js

@@ -1,8 +1,10 @@
 'use strict';
 
-var arrayUtils = require('ml-array-utils');
+module.exports = abstractMatrix;
 
+var arrayUtils = require('ml-array-utils');
 var util = require('./util');
+var MatrixTransposeView = require('./matrixTransposeView');
 
 function abstractMatrix(superCtor) {
     if (superCtor === undefined) superCtor = Object;
@@ -15,8 +17,6 @@ function abstractMatrix(superCtor) {
      * @param {number} [nColumns] - Number of columns of the new matrix
      */
     class Matrix extends superCtor {
-
-
         /**
          * Constructs a Matrix with the chosen dimensions from a 1D array
          * @param {number} newRows - Number of rows
@@ -71,7 +71,6 @@ function abstractMatrix(superCtor) {
          * @returns {Matrix} - The new matrix
          */
         static empty(rows, columns) {
-            debugger;
             return new this(rows, columns);
         }
 
@@ -232,20 +231,6 @@ function abstractMatrix(superCtor) {
             return this;
         }
 
-        /**
-         * Creates an exact and independent copy of the matrix
-         * @returns {Matrix}
-         */
-        clone() {
-            var newMatrix = new this.constructor(this.rows, this.columns);
-            for (var row = 0; row < this.rows; row++) {
-                for (var column = 0; column < this.columns; column++) {
-                    newMatrix.set(row, column, this.get(row, column));
-                }
-            }
-            return newMatrix;
-        }
-
         /**
          * Returns a new 1D array filled row by row with the matrix values
          * @returns {Array}
@@ -1184,6 +1169,13 @@ function abstractMatrix(superCtor) {
             }
             return trace;
         }
+
+        /*
+        Matrix views
+         */
+        transposeView() {
+            return new MatrixTransposeView(this);
+        }
     }
 
     Matrix.prototype.klass = 'Matrix';
@@ -1425,5 +1417,3 @@ function abstractMatrix(superCtor) {
 
     return Matrix;
 }
-
-module.exports = abstractMatrix;

src/matrix.js

@@ -51,6 +51,20 @@ class Matrix extends abstractMatrix(Array) {
         return this[rowIndex][columnIndex];
     }
 
+    /**
+     * Creates an exact and independent copy of the matrix
+     * @returns {Matrix}
+     */
+    clone() {
+        var newMatrix = new this.constructor(this.rows, this.columns);
+        for (var row = 0; row < this.rows; row++) {
+            for (var column = 0; column < this.columns; column++) {
+                newMatrix.set(row, column, this.get(row, column));
+            }
+        }
+        return newMatrix;
+    }
+
     /**
      * Removes a row from the given index
      * @param {number} index - Row index
@@ -121,3 +135,4 @@ class Matrix extends abstractMatrix(Array) {
 }
 
 module.exports = Matrix;
+Matrix.abstractMatrix = abstractMatrix;

src/matrixTransposeView.js

@@ -0,0 +1,23 @@
+'use strict';
+
+var abstractMatrix = require('./abstractMatrix');
+
+class MatrixTransposeView extends abstractMatrix() {
+    constructor(matrix) {
+        super();
+        this.matrix = matrix;
+        this.rows = matrix.columns;
+        this.columns = matrix.rows;
+    }
+
+    set(rowIndex, columnIndex, value) {
+        this.matrix.set(columnIndex, rowIndex, value);
+        return this;
+    }
+
+    get(rowIndex, columnIndex) {
+        return this.matrix.get(columnIndex, rowIndex);
+    }
+}
+
+module.exports = MatrixTransposeView;

test/views/transpose.js

@@ -0,0 +1,23 @@
+'use strict';
+
+var Matrix = require('../..');
+
+describe('Matrix views', function () {
+    describe('Transpose view', function () {
+        it('should set and get opposite coordinates', function () {
+            var m = Matrix.ones(5, 8);
+            var mtv = m.transposeView();
+
+            m.get(1, 0).should.equal(1);
+            mtv.set(0, 1, 5);
+            m.get(1, 0).should.equal(5);
+
+            m.set(0, 0, 6);
+            mtv.get(0, 0).should.equal(6);
+
+            m.set(2, 1, 10);
+            mtv.get(2, 1).should.equal(1);
+            mtv.get(1, 2).should.equal(10);
+        });
+    });
+});