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WITH C++ Prof. Amr Goneid AUC Part 5. Functions Prof. amr Goneid, - PowerPoint PPT Presentation

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CSCE 110 PROGRAMMING FUNDAMENTALS WITH C++ Prof. Amr Goneid AUC Part 5. Functions Prof. amr Goneid, AUC 1 Functions Prof. amr Goneid, AUC 2 Functions Predefined (Library) Functions Modular Programming with Functions Types of

  1. CSCE 110 PROGRAMMING FUNDAMENTALS WITH C++ Prof. Amr Goneid AUC Part 5. Functions Prof. amr Goneid, AUC 1

  2. Functions Prof. amr Goneid, AUC 2

  3. Functions  Predefined (Library) Functions  Modular Programming with Functions  Types of Functions  Function Prototype Declaration  Function Definition  Formal & Actual Parameters  Who Sees Who: Scope of an Identifier  Parameter Passing Prof. amr Goneid, AUC 3

  4. 1. Predefined Functions Example: #include <math.h> void main() { cout << ”Square Root. Ex: sqrt(9.0) = ” << sqrt(9.0) << endl; cout << ”Powers. Ex: pow(3.0, 4.0) = ” << pow(3.0,4.0) << endl; cout << ”Absolute Value for int. Ex: ” << ”abs(-9) = ” << abs(-9) << endl; cout << ”Absolute Value for long. Ex: ” << ”labs(-900) = ” << labs(-900) << endl; Prof. amr Goneid, AUC 4

  5. cout << ”Absolute Value for double. Ex: ” << ”fabs(-9.5) = ” << fabs(-9.5) << ”\n”; cout << ”Ceiling (round up). Ex: ceil(4.1)” << ” = ” << ceil(4.1) << endl; cout << ”Floor (round down). ” << ”Ex: floor(4.7) = ” << floor(4.7) << endl; } Output: Square Root. Ex: sqrt(9.0) = 3.0 Powers. Ex: pow(3.0,4.0) = 81 Absolute Value for int. Ex: abs(-9) = 9 Absolute Value for long. Ex: labs(-9000) = 9000 Absolute Value for double. Ex: fabs(-9.5) = 9.5 Ceiling (round up). Ex: ceil(4.1) = 5 Floor (round down). Ex: floor(4.7) = 4 Prof. amr Goneid, AUC 5

  6. 2. Modular Programming with Functions Level 0 Main Function 1 Function1 Function3 Function2 2 Function4 Function5 . . Functions are natural building blocks for modular programming Prof. amr Goneid, AUC 6

  7. C++ Program Structure C++ program Compiler Directives contains Function Prototypes function prototype int main ( ) declarations { and function Main Data Declarations definitions. Main Actions The main is } just another function. Used Functions Defined Here Prof. amr Goneid, AUC 7

  8. Functions & The Main Function A function is invoked by another function (e.g main) int main( ) Function Header main Local Data Area Data Area Main Body Function Body Invoke function Next action Prof. amr Goneid, AUC 8

  9. 3. Types of Functions Returns a Single Scalar Value Typed Input Params Function Output Params void Input Params Function Action Prof. amr Goneid, AUC 9

  10. 4. Function Prototype Declaration  Syntax: <ftype> <fname> (formal parameter list) ;  Examples: int cube ( int n ) ; // A function receiving an int parameter (n) and returning an int value. float minxy ( float x , float y ) ; // A function receiving two float parameters ( x , y ) and returning a float value. Prof. amr Goneid, AUC 10

  11. Prototype Declaration (Examples)  void printchar ( char c , int n ) ; // a function receiving two parameters ( c , n ) and returns nothing. It is supposed to do an action, e.g. print n of char c on one line.  void errormessage ( ) ; // a function receiving nothing and returning nothing. It is supposed to do an action, e.g. print a fixed error message. Prof. amr Goneid, AUC 11

  12. 5. Function Definition <ftype> <fname> ( List of Formal Parameters) { Local Data Declarations Function Actions (Executable Statements) } Prof. amr Goneid, AUC 12

  13. Building Typed Functions  Syntax: <ftype> <fname> (formal params) { Local Data Area Function Body contains a statement: return < a value of type ftype > ; } Prof. amr Goneid, AUC 13

  14. Example of an Integer Function  Function to return the larger of two integer numbers a and b. int maxab ( int a , int b ) { //Does not need Local Data return ( (a >= b) ? a : b ); } Prof. amr Goneid, AUC 14

  15. Example of a Real Function  Function to return the area of a circle of radius r. float area ( float r ) { // Local Data const float pi = 3.14159 ; // Action return ( pi * r * r ) ; } Prof. amr Goneid, AUC 15

  16. Example of a Boolean Function  Function to return true if an integer n is even and false otherwise. bool iseven ( int n ) { //Does not need Local Data return ( n % 2 == 0 ) ; } Prof. amr Goneid, AUC 16

  17. Example of Using a Typed Function // Prints if an entered integer is even or odd # include <iostream> using namespace std; // Function used …. bool iseven ( int n ); int main ( ) { int num; cout << “ Enter an integer number: “; cin >> num; Prof. amr Goneid, AUC 17

  18. Example of Using a Typed Function if ( iseven ( num ) ) cout << “ Number is even ! “ ; else cout << “ Number is odd ! “; return 0 ; } // Returns true if an integer is even, false otherwise bool iseven ( int n ) { return ( n % 2 == 0 ); } Prof. amr Goneid, AUC 18

  19. Type of Returned Value  Type of a value returned by a called function must be consistent with the type expected by the caller as identified in the function prototype declaration. Prof. amr Goneid, AUC 19

  20. Building void Functions  Syntax: void <fname> (formal params) { Local Data Area Function Body does not contain a return statement } Prof. amr Goneid, AUC 20

  21. Example of a void Function  Action: Fill screen with blanks. void blankscreen( ) { const char blank = ‘ ’ ; int row , col ; for (row = 1; row <= 25; row++) { for (col = 1; col <= 80; col++) cout << blank ; cout << endl; } } Prof. amr Goneid, AUC 21

  22. Example of a void Function  Action: Write n dashes on a line. void dashes( int n ) { const char dash = ‘-’ ; int i ; for (i = 1; i <= n; i++) cout << dash ; } Prof. amr Goneid, AUC 22

  23. Example of Using a void Function // Prints numbers and dashes # include <iostream> using namespace std; // Function used…. void dashes ( int n ); int main ( ) { float salary, bonus; cout << “Enter Salary: “; cin >> salary; bonus = 0.1 * salary ; Prof. amr Goneid, AUC 23

  24. Example of Using a void Function cout << “Bonus ” ; dashes(3); cout << bonus; dashes(5); cout << endl; return 0 ; } // Writes n dashes on one line void dashes ( int n ) { const char dash = ‘-’ ; int i ; for (i = 1; i <= n; i++) cout << dash ; } Prof. amr Goneid, AUC 24

  25. 6. Formal & Actual Parameters In Function Declarations: bool iseven(int n); int maxab( int a , int b ) void dashes(int n); a,b,n are FORMAL parameters(Dummies or Gates). They are LOCAL to their modules. When invoked in a main function: maxab(x,y) or maxab(1+z,2.3) dashes(7); dashes(k); iseven ( num ) x , y , 1+z , 2.3 , 7 , k , num are ACTUAL parameters passed from main to modules through their respective gates. Prof. amr Goneid, AUC 25

  26. Key Points  The substitution of the value of an actual parameter in a function call for its corresponding formal parameter is strictly positional. That is, the value of the first actual parameter is substituted for the first formal parameter; the second and so on Prof. amr Goneid, AUC 26

  27. Key Points  The names of these corresponding pairs of parameters are no consequence in the substitution process. The names may be different, or they may be the same.  The substituted value is used in place of the formal parameter at each point where that parameter appears in the called function. Prof. amr Goneid, AUC 27

  28. Passing values of Actual Parameters main maxab main iseven x a num n y b Prof. amr Goneid, AUC 28

  29. Formal & Actual Parameters  Correspondence between actual and formal parameters is determined by position in their respective lists. These lists must be the same size. The names of corresponding actual and formal parameters may be different.  Formal parameters and corresponding actual parameters should agree with respect to type. Prof. amr Goneid, AUC 29

  30. Overloaded Functions: #include <iostream.h> float average(float x, float y); // Returns the average of x and y float average(float x, float y, float z); // Returns the average of x, y, and z void main() { cout << ”The average of 3.0 and 7.0” << ” is ” << average(3.0, 7.0) << endl; cout << ”The average of 3.0, 4.0, and 8.0” << ” is ” << average(3.0, 4.0,8.0) << endl; } Prof. amr Goneid, AUC 30

  31. float average(float x, float y) { return ((x + y)/2.0); } float average(float x, float y, float z) { return ((x + y + z)/3.0); } Output: The average of 3.0 and 7.0 is 5.0000 The average of 3.0, 4.0, and 8.0 is 5.0000 Prof. amr Goneid, AUC 31

  32. 7. Who Sees Who: Scope of an Identifier  To see = to recognize = to be able to use, invoke, change, etc.  Scope = the domain in which an identifier is recognizable.  The scope of an identifier extends only from the point where it is defined to the end of the module in which it is defined .  A module can see itself (Recursion) Prof. amr Goneid, AUC 32

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