2. Polymorphism
The word polymorphism is derived from Greek word Poly
which means many and morphos which means forms.
Polymorphism can be defined as the ability to use the same
name for two or more related but technically different tasks.
Eg-woman plays role of daughter,sister,wife,mother etc.
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3. Overloading in C++
What is overloading
– Overloading means assigning multiple
meanings to a function name or operator
symbol
– It allows multiple definitions of a function with the same
name, but different signatures.
C++ supports
– Function overloading
– Operator overloading
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4. Why is Overloading Useful?
Function overloading allows functions that
conceptually perform the same task on
objects of different types to be given the
same name.
Operator overloading provides a convenient
notation for manipulating user-defined
objects with conventional operators.
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5. Function Overloading
Is the process of using the same name for two or more
functions
Requires each redefinition of a function to use a different
function signature that is:
different types of parameters,
or sequence of parameters,
or number of parameters
Is used so that a programmer does not have to remember
multiple function names
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6. Function Overloading
Two or more functions can have the same name but different
parameters
Example:
int max(int a, int b)
{
if (a>= b)
return a;
else
return b;
}
float max(float a, float b)
{
if (a>= b)
return a;
else
return b;
}
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7. Overloading Function Call Resolution
Overloaded function call resolution is done by
compiler during compilation
– The function signature determines which definition
is used
a Function signature consists of:
– Parameter types and number of parameters
supplied to a function
a Function return type is not part of function signature
and is not used in function call resolution
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8. void sum(int,int);
void sum(double,double);
void sum(char,char);
void main()
{
int a=10,b=20 ;
double c=7.52,d=8.14;
char e=‘a’ , f=‘b’ ;
sum(a,b); //calls sum(int x,int y)
sum(c,d); //calls sum (double x,double y)
sum(e,f); // calls sum(char x,char y)
}
void sum(int x,int y)
{
vout<<“n sum of integers are”<<x+y;
}
void sum(double x,double y)
{
cout<<“n sum of two floating no are”<<x+y;
}
void sum(char x,char y)
{
cout<<“n sum of characters are”<<x+y;
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9. Output:
Sum of integers 30
sum of two floating no are 15.66
sum of characters are 195
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11. Function Selection Involves following
Steps.
Compiler first tries to find the Exact match in which the type
of argument are the same,and uses that func.
If an exact match is not found,the compiler user the integral
promotions to the actual argument such as,char to int, float
to double.
When either of them fails ,build in conversions are
used(implicit conversion) to the actual arguments and then
uses the function whose match is unique.but if there are
multiple matches,then compiler will generate an error
message.
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12. For ex: long square(long n)
long square(double x)
Now a func. call such as square(10) will cause an
error because int argument can be converted into
long also and double also.so it will show
ambiguity.
User defined conversion are followed if all the
conversion are failed.
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14. Scope
The scope of a variable is the portion of a program where the
variable has meaning (where it exists).
A global variable has global (unlimited) scope.
A local variable’s scope is restricted to the function that
declares the variable.
A block variable’s scope is restricted to the block in which
the variable is declared.
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15. Understanding Scope
Some variables can be accessed throughout an entire
program, while others can be accessed only in a limited part
of the program
The scope of a variable defines where it can be accessed in a
program
To adequately understand scope, you must be able to
distinguish between local and global variables
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16. Local variables
Parameters and variables declared inside the definition of a
function are local.
They only exist inside the function body.
Once the function returns, the variables no longer exist!
That’s fine! We don’t need them anymore!
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17. Block Variables
You can also declare variables that exist only within the body
of a compound statement (a block):
{
int foo;
…
…
}
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18. Global variables
You can declare variables outside of any function definition –
these variables are global variables.
Any function can access/change global variables.
Example: flag that indicates whether debugging information
should be printed.
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19. Distinguishing Between Local
and Global Variables
Celebrity names are global because they are known to people
everywhere and always refer to those same celebrities
Global variables are those that are known to all functions in a
program
Some named objects in your life are local
You might have a local co-worker whose name takes
precedence over, or overrides, a global one
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20. A note about
Global vs. File scope
A variable declared outside of a function is available
everywhere, but only the functions that follow it in the file
know about it.
The book talks about file scope, I’m calling it global scope.
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21. Block Scope
int main(void) {
int y;
{
int a = y;
cout << a << endl;
}
cout << a << endl;
}
Error – a
doesn’t exist outside
the
block!
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Notas del editor
Multiple function with same name and same number of parameters differ only in data types
