operator overloading

1. D.SHANMUGAPRIYA
I- M.Sc(IT)
OPERATOR OVERLOADING AND
TYPE CONVERSION

2. OPERATOR OVERLOADING AND
TYPE CONVERSION
 INTRODUCTION
 DEFINING OPERATOR OVERLOADING
 OVERLOADING UNARY OPERATORS
 OVERLOADI NG BINARY OPERATORS
 OVERLOADING BINARY OPERATORS USING
FRIENDS
 SOME OTHER OPERATOR OVERLOADING
EXAMPLES
 RULES FOR OVERLOADING OPERATORS
 TYPE CONVERSION

3. INTRODUCTION
Operator overloading is one of the many
exciting features of the C++ language.
Operator overloading provides a flexible option
for the creation of new definition for most of the
C++ operators.
Class member access operator(.,.*)
Scope resolution operator(::)
Size operator(size of)
Conditional operator(?:)

4. DEFINNING OPERATOR
OVERLOADING
We must specify what it means in relation to the class
to which the operator is applied.
Syntax:
Return type classname::operator op(arglist)
{
function body//task defined
}
 Operator functions must be either member functions or friend
functions:
 vector operator+(vector);//vectoraddition
 Vector operator-(vector)://unary minus

5. CONTINUE….
 Friend vector operator+(vector;vector); //vector addition
 Friend vector operator-(vector); //unary minus
 Vector operator-(vector&a); //subtraction
 Int operator==(vector,vector); //comparison
 The process of overloading involves the following steps:
 Create a class that defines the datatype that is to be used in the
overloading operation.
 Declare the operator functions operator op() in the public part of the
class.
 UNARY OPERATOR=X OP Y
 BINARY OPERATOR=OPERATOR OP(X)

6. OVERLOADING UNARY
OPERATORS
 A minus operator when use as a unary takes just one
operand.
 Remember a statement like
 It is possible to overload a unary minus operator using a friend
function as follows:
Friend void operator-(space&s);
void operator-(space&s)
S2=-S1;
S.X=-S.X;
S.Y=-S.Y;
S.Z=-S.Z;

7. Example:

8. OVERLOADING BINARY
OPERATORS
 The same mechanism can be used to overload a binary
operator.
 C1 takes the responsibility of invoking the function
and c2 plays the role of an argument that is passed to
the function.
 Both the objects are available for the function.
C=SUM(A,B);
C3=C1.OPERATOR+(C2);
TEMP.X=X+C.X;

9. Example:

10. IMPLEMENTED OF THE OVERLOAD BINARY
OPERATOR:

11. OVERLOADING BINARY
OPERATORS USING FRIENDS
 Friend functions may be used in the place of member functions
for overloading a binary operator.
1) Replace the member function declartion by the friend
function declaration
2) [friend complex operation+(complex,complex);
3) Redefine the operator function as followa:
[complex opearor+(complex a,complex b)
{
return complex((a.x+b.x),(a.y+b.y));
}
In this case the statement
C3=C1+C2;
C3=OPERATOR+(C1+C2);

12. MANIPULATION OF STRINGS
USING OPERATORS
 ANSI C implements strings using character arrays,pointers and string
functions.
 EXAMPLE:
 Thus we must create string objects that we can hold these two pieces of
information.
Class string
{
Char*p;
Int len;
Public:
}
String3=string1+string2;
If(string 1>=string2)string=string1;

13. MATHEMATICAL OPERATIONS ON
STRING:

14. SUB TOPICS
OVERLOADING THE SUBSCRIPT OPERATOR
o The subscript operator is normally used to access and
modify a specific element in an array.
OVERLOADING THE POINTER TO MEMBER -
>OPERATOR:
o The pointer to member operator is normally used to
conjunction with an object pointer to access any of the
objects member.

15. RULES FOR OVERLOADING
OPERATOR
 There are certain restrictions and limitations in
overloading them,some of them are listed below
Only existing operators can be overloaded
Overloaded operators follow the syntax rules of the
original operators.
There are some operators that cannot be overloaded.
SIZE OF SIZE OF OPERATOR
. Membership operator
.* pointer to member operator
:: scope resolution operator
?: conditional operator

16. TYPE CONVERSION
 The type of data to the right of an assignment
operator is automatically converted to the type of
the variable on the left.
BASIC TO CLASS TYPE:
1) It may be recalled that the use of constructor was
illustrated in a number of examples to initialize
objects.
int m;
float x=3.14159;
m=x;

17. Continue…
 Following constructor:
string::string(char*a)
{
length=strlength(a);
p=new char[length+1];
strcpy(p,a);
}
The statement
s1=string(name 1);
First converts name1 from char* type and then values the
assign the strings type values to the objects S1
S2=Name 2;

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