Operator Overloading - Object Oriented Programming - Lecture Slides, Slides of Object Oriented Programming

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Object-Oriented Programming

(OOP)

Lecture No. 16

• Consider the following class:

class Complex{ private: double real, img; public: Complex Add(const Complex &); Complex Subtract(const Complex &); Complex Multiply(const Complex &); … } Docsity.com

• The following statement:

Complex c3 = c1.Add(c2);

Adds the contents of c2 to c1 and assigns it to c3 (copy constructor)

• To perform operations in a single

mathematical statement e.g:

c1+c2+c3+c

• We have to explicitly write:

c1.Add(c2.Add(c3.Add(c4)))

• If the mathematical expression is big:
  • Converting it to C++ code will involve complicated mixture of function calls
  • Less readable
  • Chances of human mistakes are very high
  • Code produced is very hard to maintain

• C++ provides a very elegant solution:

“ Operator overloading ”

• C++ allows you to overload common operators like + , - or ***** etc…
• Mathematical statements don’t have to be explicitly converted into function calls

• C++ automatically overloads operators for pre-defined types
• Example of predefined types:

int float double char long

• Example:

float x;

int y;

x = 102.02 + 0.09;

Y = 50 + 47;

• Operator functions are not usually

called directly

• They are automatically invoked to

evaluate the operations they

implement

• List of operators that can be overloaded in C++:

• The precedence of an operator is

NOT affected due to overloading

• Example:

c1c2+c*

c3+c2c*

both yield the same answer

• Associativity is NOT changed due

to overloading

• Following arithmetic expression

always is evaluated from left to

right:

c1 + c2 + c3 + c

• Always write code representing

the operator

• Example:

Adding subtraction code inside the

• operator will create chaos

• Creating a new operator is a syntax

error (whether unary, binary or ternary)

• You cannot create $