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This section repeats the above two sections using a fmmal mathematical style. Its purpose is to illustrate the power of denotational semantics to enable the full specification of a programming languages type system and semantics. Since it is machine independent, this notation can be used by language and compiler designers as they define and implement new programming languages. | CSC241: Object Oriented Programming Lecture No 10 Previous Lecture Example : Distance class overloading ++ and – ++ add 1 in feet and 1 in inches, -- subtract 1 from feet and 1 from inches Prefix and postfix Overloading binary operator Distance operator + (Distance d2) { float i = inches + d2.inches; int f = feet + d2.feet; return Distance(f, i); } d3= d1+d2; Today’s Lecture Overloading binary operator +, – and = operator for ThreeD class < operator for distance class += operator for distance class Subscript operator [] for Safe array class Data conversion Overloading -, + and = binary Operators class ThreeD { int x, y, z; public: ThreeD() { x = y = z = 0; } ThreeD(int i, int j, int k) { x = i; y = j; z = k; } ThreeD operator+(ThreeD op2); ThreeD operator=(ThreeD op2); ThreeD operator-(ThreeD op2); void show() ; }; // Overload subtraction. ThreeD ThreeD::operator-(ThreeD op2) { ThreeD temp; temp.x = x - op2.x; temp.y = y - op2.y; . | CSC241: Object Oriented Programming Lecture No 10 Previous Lecture Example : Distance class overloading ++ and – ++ add 1 in feet and 1 in inches, -- subtract 1 from feet and 1 from inches Prefix and postfix Overloading binary operator Distance operator + (Distance d2) { float i = inches + d2.inches; int f = feet + d2.feet; return Distance(f, i); } d3= d1+d2; Today’s Lecture Overloading binary operator +, – and = operator for ThreeD class < operator for distance class += operator for distance class Subscript operator [] for Safe array class Data conversion Overloading -, + and = binary Operators class ThreeD { int x, y, z; public: ThreeD() { x = y = z = 0; } ThreeD(int i, int j, int k) { x = i; y = j; z = k; } ThreeD operator+(ThreeD op2); ThreeD operator=(ThreeD op2); ThreeD operator-(ThreeD op2); void show() ; }; // Overload subtraction. ThreeD ThreeD::operator-(ThreeD op2) { ThreeD temp; temp.x = x - op2.x; temp.y = y - op2.y; temp.z = z - op2.z; return temp; } // Overload +. ThreeD ThreeD::operator+(ThreeD op2) { ThreeD temp; temp.x = x + op2.x; temp.y = y + op2.x; temp.z = z + op2.z; return temp; } Cont. // Overload assignment. ThreeD ThreeD::operator=(ThreeD op2){ x = op2.x; y = op2.y; z = op2.z; return *this; } void ThreeD::show() { cout << x << ", ”<< y << ", ”<< z << "\n"; } main() { ThreeD a(1, 2, 3), b(10, 10, 10), c; cout << "Original value of a: "; a.show(); cout << "Original value of b: "; b.show(); c = b - a; cout << “b - a: "; c.show(); } PROGRAM OUTPUT: Original value of a: 1, 2, 3 Original value of b: 10, 10, 10 b - a: 9, 8, 7 Multiple Overloading We’ve seen different uses of the + operator: to add distances and to concatenate strings. You could put both these classes together in the same program, and C++ would still know how to interpret the + operator: d1 = d2 + d3; s1 = s2 + s3; It selects the correct function to carry
