Special Topics 1 (Oracle)

1
Function
User defined function is a code segment (block)
that perform an specific action.
Function DefinitionReturn_DT F_name ( list of
formal parameters) Action_ body
2
The Function Definition

• Function are of 4 types
• 1- A function that doesnt return a value without
  argument
• -Return_DT is void
  -Action_body doesnt contain return statement.
• Syntax
• void function-name ( )
• local declarations // this is optional
• executable statements

3
Example function that doesnt return a value
without arguments

• void print_O ( )
• cout ltlt ltlt endl
• cout ltlt ltlt endl
• cout ltlt ltlt endl
• cout ltlt ltlt endl

4
The Function Definition

• 2- A function that doesnt return a value with
  arguments
• -Return_DT is void
  -Action_body doesnt contain return statement.
• Syntax
• void function-name(argument_list)
• local declarations // this is
  optional
• executable statements

5
Example function that doesnt return a value
with arguments

• void print_box (int n)
• cout ltlt \n
• cout ltlt ltlt n ltlt \n
• cout ltlt \n

6
The Function Definition

• 3- A function that returns a result of any type
  without arguments
• -Return_DT is any type -Action_body
  contains return statement.
• Syntax
• ltany typegt function-name( )
• local declarations // this is
  optional
• executable statements

7
Example function that return a value without
arguments

• int sum ()
• int x5, y7
• return xy

8
The Function Definition

• 4- A function that returns a result of any type
  with arguments
• -Return_DT is any type -Action_body
  contains return statement.
• Syntax
• ltany typegt function-name(argument_list )
• local declarations // this is
  optional
• executable statements

9
Example function that return a value with
arguments

• int Rect_area (int L, int W)
• int a
• a L W
• return a

10
Calling (invoking) Function

• a) The call to a Function that does not return a
  value is given in the following syntax
• F_name (Actual parameters)
• e.g. draw_circle ( )
• e.g. sum(4,7)
• b) The call to a Function that returns a value is
  given as follows
• - The name of the functio is given within the
  output statement
• e.g coutltltsum(x,y)
• - The name of the Function is given within
  the
• assignment statement
• e.g. result sum (x, y )

11
The Call to a function

• program Figure Function
  draw_circle

void main() ------- ------- draw_circle
( ) ------ ------ ------
void draw_circle ( ) ------ ------
------ ------
call
return
12
Example
include ltiostream.hgt int Max (int Value1, int
Value2) if (Value1 gt Value2) return
Value1 else return Value2 void main()
int a, b coutltlt"\nPlease Enter the values of
a and b " cingtgtagtgtb coutltlt"\n the maximum
one is "ltltMax(a,b)ltltendl
Function Definition Calling the function in
an expression like coutltlt, condition, assignment
statements
13
Example
include ltiostream.hgt int Max (int Value1, int
Value2) if (Value1 gt Value2) return
Value1 else return Value2 void main()
int a, b coutltlt"\nPlease Enter the values of
a and b " cingtgtagtgtb coutltlt"\n the maximum
one is "ltltMax(a,b)ltltendl
14
Example
include ltiostream.hgt int Sum (int A, int B)
return (AB) void main() int N1, N2,
S coutltlt"\n Please Enter N1 and N2
" cingtgtN1gtgtN2 S Sum(N1,N2) coutltlt"\nSum
"ltltSltltendl
15
Example
include ltiostream.hgt bool Positive (int Num)
if (Num gt 0) return true else return
false void main() int Number coutltlt"\nEnte
r Number " cingtgt Number if
(Positive(Number)) coutltlt"\n the number is
positive" else coutltlt"\n the number is
negative" coutltltendl
16
Example
include ltiostream.hgt float Area (int R)
return (3.14 R R ) void main() int
Radius coutltlt"Enter the Redius
" cingtgtRadius coutltlt"\nCircle Area is
"ltltArea(Radius) coutltltendl
17
Example
include ltiostream.hgt long Power(int Base, int
Exp) int M1 for(int i1 iltExp
i) MBase return M void main() int
B, E coutltlt"\nEnter Base " cingtgtB coutltlt"\n
Enter Exponent " cingtgtE coutltlt"\n Result
"ltltPower(B,E) coutltltendl
18
Example
include ltiostream.hgt long Fact (int Num) int
F 1, i Num while (igt1) F i i--
return F void main() int
Number coutltlt"Enter an integer number
" cingtgtNumber coutltltendlltltNumberltlt"!
"ltltFact(Number) coutltltendl
19
Void Returned Data Type
include ltiostream.hgt void Print(char Ch, int n)
for (int i1 iltn i) coutltltCh coutltltend
l void main() char Sym int
Number coutltlt"\nEnter the Symbol
" cingtgtSym coutltlt"\nHow many times
" cingtgtNumber Print(Sym,Number)
No Return Statement
20
Example
include ltiostream.hgt int Mul(int V1, int V2)
return V1 V2 void Result() coutltlt"\n5
x 9 "ltltMul(5,9) coutltlt"\n4 x 7
"ltltMul(4,7) coutltlt"\n6 x 4 "ltltMul(6,4)ltltendl
void main() Result()
21
The Function Prototype

• Like other identifiers in C, function must be
  declared before it can be referenced.
• To declare a function, we can insert a function
  prototype before the main function.
• The function prototype provides all information
  that the C compiler needs to know to translate
  calls to the function correctly.
• A function prototype tells the compiler the
• - data type of the function
• - the function name
• - information about the arguments that the
  function expects.
• Examples void draw_circle ( )
• int m ( )
• void print_box
  (int)
• int Rect_area (int
  , int)

22
Function Prototype
include ltiostream.hgt int Mul(int, int) int
Add(int, int) void Show() void main()
Show() int Mul(int X, int Y) return XY
int Add(int X, int Y) return XY void
Show() int A10, B20 coutltltAdd(A,B)ltlt'\t'ltltM
ul(A,B)ltltendl
Function Prototype contains only data types But
may contain identifiers.
23
Scope of Variables

• (1) Global variables
• - Those variables that are declared before the
  main function.
• - These are visible from any point of the
  code, inside and outside any function.
• (2) Local variables
• - These are declared inside a block or a
  function.
• - The scope of local variables is limited to
  the same
• nesting level in which they are declared.

24
Example of Local and Global Variables

• // File global.cpp
• include ltiostream.hgt
• int x 7 // global
  variables
• int fun1 (int ) // function
  prototype
• void main ( )
• int z // local
  variable in main
• cout ltlt The global variable ltlt x
• z fun1 ( 5 ) // calling add
  function
• cout ltlt The result is ltlt z ltlt endl
• int fun1 ( int a )
• int r // local
  variable in fun1
• r a a a
• return r

25
Functions and Passing Parameters

• The mechanisms of passing parameters
• (1) Call by value
• - During the function call, the value of the
  argument is
• found and passed to the function.
• - Any modification inside the function does
  not affect the
• argument.
• (2) Call by reference
• - During the function call, the address of
  the variable is
• passed to the function.
• - Any modification made on the parameter
  inside the
• function will have effect in the passed
  variable outside it.

26
Difference between Function Definitions for Call
by Value and Call by Reference

• For call by value, we declare the arguments of
  the function as usual.
• Example
• int func1 ( int , int ) // function
  prototype
• For call by reference, the type of the argument
  is followed by the symbol () to specify that the
  variable has to be passed by reference.
• Example
• void func2 ( int , int ) //
  function prototype

27
Call by value
When calling, the value of actual parameter will
be copied to the formal parameter.
include ltiostream.hgt void Increment(int) void
main() int A 10 Increment(A) coutltltAltltend
l void Increment(int X) X
28
Call By reference
When calling, the reference formal parameter will
be an alternative name to the actual parameter.
include ltiostream.hgt void Increment(int) void
main() int A 10 Increment(A) coutltltAltltend
l void Increment(int X) X
29
Call By reference
When calling, the pointer formal parameter will
points to the actual parameter.
include ltiostream.hgt void Increment(int) void
main() int A 10 Increment(A) coutltltAltlten
dl void Increment(int X) X
30
Example 5 Call by Value

• // File calls1.cpp
• include ltiostream.hgt
• // function prototype the arguments to be passed
  by value
• int add (int , int )
• void main ( )
• int x, y , z // local
  variables in main
• cout ltlt Enter two integers
• cin gtgt x gtgt y
• cout ltlt x ltlt x ltlt y ltlt y ltlt
  endl
• z add ( x , y ) // calling add
  function
• cout ltlt The result is ltlt z
• cout ltltAfter call ltlt x ltlt x ltlt y
  ltlt y ltlt endl
• int add ( int a , int b )
• return a b

31
Execution of Example 5

• The user will be prompted to enter two integers.
• The user enters, for example, 10 and 20 that are
  saved in x and y respectively.
• When function add is called, the value of x and
  y are passed to the function.
• The function add takes the values 10 and 20 and
  links them to a and b respectively.
• The function will return the result which is 30.
• The output
• Enter two integers 10 20
• x 10 y 20
• The result is 30
• After call x 10 y 20

32
Example 6 Call by Reference

• // File calls2.cpp
• include ltiostream.hgt
• // function prototype the arguments to be passed
  by reference
• void duplicate (int , int , int )
• void main ( )
• int x, y , z // local
  variables in main
• cout ltlt Enter three integers
• cin gtgt x gtgt y gtgt z
• cout ltlt Before call ltlt x ltlt x ltlt
  y ltlt y
• ltlt z ltlt z ltltendl
• duplicate ( x , y , z ) //
  calling duplicate function
• cout ltlt After call ltlt x ltlt x ltlt
  y ltlt y
• ltlt z ltlt z ltltendl
• void duplicate ( int a , int b , int c )
• a 2
• b 2
• c 2

33
Execution of Example 6

• The user will be prompted to enter three
  integers.
• The user enters, for example, 10, 20, and 30 that
  are saved in x, y, and z respectively.
• When function duplicate is called, the addresses
  of x, y, and z are passed to the function.
• The addresses of x, y, and z are linked to the
  parameters of the function a, b, and c. The
  function will duplicate each parameter and save
  the result in the same parameter. Thus,
• a becomes 20 hence x becomes 20 also
• b becomes 40 hence x becomes 40 also
• c becomes 60 hence x becomes 60 also
• After the call we see that the values of x, y,
  and z are changed.
• The output
• Enter three integers 10 20 30
• Before call x 10 y 20 z
  30
• After call x 20 y 40 z
  60

34
Recursion
Function call itself
include ltiostream.hgt int Fact (int N) if
(Nlt1) return 1 else return N
Fact(N-1) void main() coutltltFact(5)ltltendl
35
Example
include ltiostream.hgt int Zap (int N) int
Z if (Nlt1) Z1 else Z Zap(N-1)
Zap(N-3) return Z void main()
coutltltZap(5)ltltendl
36
Array as parameter
-Array name is pointer (call by reference)
include ltiostream.hgt void Increment (int a)
for (int i0 ilt5 i) ai 10 void
main() int b5 10,20,30,40,50 Increment(
b) for(int i0 ilt5 i) coutltltbiltlt'\t' c
outltltendl
37
Array as parameter
-Array element (call by value)
include ltiostream.hgt void Increment (int a)
a void main() int b5
10,20,30,40,50 Increment(b1) coutltltb1ltlte
ndl