22.3 Another example of operator overloading

Just for developers who enjoy dabbling with matrices, here's another full example. ^[4]

^[4] You can skip this if you have understood the previous example. You need to understand matrix mathematics to appreciate what is going on here. (Time to search for that old high school math textbook !)

 1: using System;  2:  3: // class represents a 2 " 2 matrix  4: class Matrix{  5:  6:   // these 4 fields represent the 4 values in the 2 " 2 matrix  7:   public float TopLeft;  8:   public float TopRight;  9:   public float BottomLeft; 10:   public float BottomRight; 11: 12:   // constructor 13:   public Matrix 14:   (float TopLeft, float TopRight, float BottomLeft, float BottomRight){ 15:     this.TopLeft = TopLeft; 16:     this.TopRight = TopRight; 17:     this.BottomLeft = BottomLeft; 18:     this.BottomRight = BottomRight; 19:   } 20: 21:   // overrides ToString to show matrix values 22:   public override string ToString (){ 23:     return "[" + TopLeft + ", " + TopRight + "]\n"+ 24:            "[" + BottomLeft+ ", " + BottomRight+ "]"; 25:   } 26: 27:   // overloads + operator to perform matrix addition 28:   public static Matrix operator + (Matrix m1, Matrix m2){ 29:     return new Matrix(m1.TopLeft + m2.TopLeft, 30:                       m1.TopRight + m2.TopRight, 31:                       m1.BottomLeft + m2.BottomLeft, 32:                       m1.BottomRight + m2.BottomRight); 33:   } 34: 35:   // overloads  operator to perform matrix subtraction 36:   public static Matrix operator  (Matrix m1, Matrix m2){ 37:     return new Matrix(m1.TopLeft  m2.TopLeft, 38:                       m1.TopRight  m2.TopRight, 39:                       m1.BottomLeft  m2.BottomLeft, 40:                       m1.BottomRight  m2.BottomRight); 41:   } 42: 43:   // overloads * operator to perform product with a real number 44:   public static Matrix operator * (Matrix m1, float realNumber){ 45:     return new Matrix(m1.TopLeft * realNumber, 46:                       m1.TopRight * realNumber, 47:                       m1.BottomLeft * realNumber, 48:                       m1.BottomRight * realNumber); 49:   } 50: 51:   // overloads ^ to perform multiplication with another 2 " 2 matrix 52:   public static Matrix operator ^ (Matrix m1, Matrix m2){ 53:     return new Matrix 54:       ((m1.TopLeft * m2.TopLeft) + (m1.TopRight * m2.BottomLeft), 55:       (m1.TopLeft * m2.TopRight) + (m1.TopRight * m2.BottomRight), 56:       (m1.BottomLeft * m2.TopLeft) + (m1.BottomRight * m2.BottomLeft), 57:       (m1.BottomLeft * m2.TopRight) + (m1.BottomRight * m2.BottomRight) 58:); 59:   } 60: 61:   // overloads ! operator to perform matrix inversion. 62:   public static Matrix operator ! (Matrix m1){ 63: 64:     float determinant = 65:       (m1.TopLeft * m1.BottomRight)  (m1.TopRight * m1.BottomLeft); 66: 67:     float determinantReciprocal = 1/determinant; 68: 69:     Matrix intermediate = new Matrix 70:       (m1.BottomRight, -m1.TopRight, -m1.BottomLeft, m1.TopLeft); 71: 72:     return (intermediate * determinantReciprocal); 73:    } 74: } 75: 76: 77: class TestClass{ 78:   public static void Main(){ 79: 80:     // try out inverse function 81:       Matrix m1 = new Matrix (3,5,1,2); 82:     Console.WriteLine ("m1:\n" + m1); 83:     Console.WriteLine ("m1 inverse:\n" + (!m1)); 84:     Console.WriteLine (); 85: 86:     // try out multiplication with a real number 87:       Matrix m2 = new Matrix (1,5,5,1); 88:     Console.WriteLine ("m2:\n" + m2); 89:     Console.WriteLine ("3 multiplied by m2:\n" + (m2*3)); 90:   } 91: } 

Output:

 c:\expt>test m1: [3 , 5] [1 , 2] m1 inverse: [2 , -5] [-1 , 3] m2: [1 , 5] [5 , 1] 3 multiplied by m2: [3 , 15] [15 , 3]