feat: add a custom Node.js inspect function

Author: targos

src/__tests__/matrix/utility.js

@@ -279,12 +279,14 @@ describe('utility methods', () => {
     expect(result[2][0]).toBeCloseTo(0.24390244, 5);
     expect(result[2][1]).toBeCloseTo(0.07317073, 5);
   });
+
   it('isEchelonForm', () => {
     var matrix = new Matrix([[1, 0], [0, 1]]);
     var matrix2 = new Matrix([[2, 1], [1, 1]]);
     expect(matrix.isEchelonForm()).toStrictEqual(true);
     expect(matrix2.isEchelonForm()).toStrictEqual(false);
   });
+
   it('isReducedEchelonForm', () => {
     var matrix = new Matrix([[1, 0], [0, 1]]);
     var matrix2 = new Matrix([[1, 1], [0, 1]]);

src/abstractMatrix.js

@@ -17,6 +17,8 @@ import {
   productAll
 } from './stat';
 
+const inspect = Symbol.for('nodejs.util.inspect.custom');
+
 export default class AbstractMatrix {
   static get [Symbol.species]() {
     return this;
@@ -1673,6 +1675,17 @@ export default class AbstractMatrix {
     }
     return variance;
   }
+
+  [inspect](_, options) {
+    const { indentationLvl } = options;
+    const indent = ' '.repeat(indentationLvl + 2);
+    const indentData = ' '.repeat(indentationLvl + 4);
+    return `${this.constructor.name} {
+${indent}[ ${inspectData(this, indentData)} ]
+${indent}rows: ${this.rows},
+${indent}columns: ${this.columns}
+${' '.repeat(indentationLvl)}}`;
+  }
 }
 
 AbstractMatrix.prototype.klass = 'Matrix';
@@ -1966,3 +1979,15 @@ function fillTemplateFunction(template, values) {
   }
   return template;
 }
+
+function inspectData(matrix, indent) {
+  const result = [];
+  for (var i = 0; i < matrix.rows; i++) {
+    let line = [];
+    for (var j = 0; j < matrix.columns; j++) {
+      line.push(Math.round(matrix.get(i, j) * 1000) / 1000);
+    }
+    result.push(`[ ${line.join(', ')} ]`);
+  }
+  return result.join(`\n${indent}`);
+}