add kata

5kyu/vector-class/description.md

@@ -0,0 +1,18 @@
+Create a Vector object that supports addition, subtraction, dot products, and norms. So, for example:
+
+a = new Vector([1, 2, 3])
+b = new Vector([3, 4, 5])
+c = new Vector([5, 6, 7, 8])
+
+a.add(b)      # should return a new Vector([4, 6, 8])
+a.subtract(b) # should return a new Vector([-2, -2, -2])
+a.dot(b)      # should return 1*3 + 2*4 + 3*5 = 26
+a.norm()      # should return sqrt(1^2 + 2^2 + 3^2) = sqrt(14)
+a.add(c)      # throws an error
+If you try to add, subtract, or dot two vectors with different lengths, you must throw an error!
+
+Also provide:
+
+a toString method, so that using the vectors from above, a.toString() === '(1,2,3)' (in Python, this is a __str__ method, so that str(a) == '(1,2,3)')
+an equals method, to check that two vectors that have the same components are equal
+Note: the test cases will utilize the user-provided equals method.

5kyu/vector-class/solution.ts

@@ -0,0 +1,40 @@
+export class Vector {
+  private elements: number[];
+
+  constructor(components: number[]) {
+    this.elements = components;
+  }
+
+  public add(vector: Vector): Vector {
+    if (vector.elements.length !== this.elements.length) {
+      throw new Error('Vectors must have the same length');
+    }
+    return new Vector(this.elements.map((element, i) => element + vector.elements[i]));
+  }
+
+  public subtract(vector: Vector): Vector {
+    if (vector.elements.length !== this.elements.length) {
+      throw new Error('Vectors must have the same length');
+    }
+    return new Vector(this.elements.map((element, i) => element - vector.elements[i]));
+  }
+
+  public dot(vector: Vector): number {
+    if (vector.elements.length !== this.elements.length) {
+      throw new Error('Vectors must have the same length');
+    }
+    return this.elements.reduce((sum, element, i) => sum + element * vector.elements[i], 0);
+  }
+
+  public norm(): number {
+    return Math.sqrt(this.elements.reduce((sum, element) => sum + element ** 2, 0));
+  }
+
+  public equals(vector: Vector): boolean {
+    return this.elements.every((element, i) => element === vector.elements[i]);
+  }
+
+  public toString(): string {
+    return `(${this.elements.join(',')})`;
+  }
+};

5kyu/vector-class/tests.ts

@@ -0,0 +1,37 @@
+import { assert } from "chai";
+import { Vector } from "./solution";
+
+describe("Tests", () => {
+  it("Simple Equality Test", () => {
+    let a = new Vector([1,2]);
+    let b = new Vector([3,4]);
+    assert.isFalse(a.equals(b));
+  });
+  
+  it("Simple Add Test", function() {
+    let a = new Vector([1, 2, 3]);
+    let b = new Vector([3, 4, 5]);
+    assert.isTrue(a.add(b).equals(new Vector([4,6, 8])));
+  })
+  
+  it("Simple Norm Test", function () {
+    assert.approximately(new Vector([1,2,3]).norm(), Math.sqrt(14),  0.1);
+  });
+  
+  it("Simple Subtract Test", function() {
+    let a = new Vector([1, 2, 3]);
+    let b = new Vector([3, 4, 5]);
+    assert.isTrue(a.subtract(b).equals(new Vector([-2,-2,-2])));
+  });
+  
+  it("Simple Dot Test", function() {
+    let a = new Vector([1, 2, 3]);
+    let b = new Vector([3, 4, 5]);
+    assert.strictEqual(a.dot(b), 26);
+  })
+  
+  it("Simple ToString Test", function() {
+    let a = new Vector([1, 2, 3]);
+    assert.strictEqual(a.toString(), "(1,2,3)");
+  })
+});