1. Instructor - C. BoyleFall Semester - 2015 cboyle@cs.odu.edu

2. Terms invoke a function (call a function) construct a function (declare or write a function) value returning function void function parameter formal parameter actual parameter function header

3. Terms function body return statement return type function prototype flow of execution value parameters reference parameters local variables

4. 4 Coding Cable Company Program –Ver 1IF ELSE –Ver 2SWITCH –Ver 3Functions

5. 5 Coding Some functions return a value Exercises 4, 9, 10, chapter 6 –Ch6_Exer4.cpp –Ch6_Exer9_and_10 Value returning functions are used in an expression In these examples the parameters are passed by value

6. 6 Coding Some functions are void functions In function printer, the parameters are passed by value –PrinterCalls.cpp // method printer will print out the symbol number times on a single line. void printer (int number, char symbol) { int counter; //local counter for loop control counter = 1; while (counter <= number ) { counter++; cout << symbol; } }// end of printer { {

7. 7 Coding Some functions are void functions In function printer, the parameters are passed by value –PrinterCalls.cpp void printer (int, char); void treePrinter () ; void diamondPrinter () ; void rectanglePrinter ( int across, int down); const char BLANK =' ' ; const char PLUS ='+' ; const char STAR ='*' ; const char POUND ='#' ;

8. 8 Coding Some functions are void functions In function printer, the parameters are passed by value –PrinterCalls.cpp // call printer several times printer ( 6,'%'); cout << endl; printer ( 12, 'A'); cout << endl; treePrinter () ; cout << endl << endl; system ( "pause");

9. 9 Coding Some functions are void functions In function printer, the parameters are passed by value –PrinterCalls.cpp // call diamondPrinter, and rectanglePrinter functions diamondPrinter () ; cout << endl << endl; system (“pause”); rectanglePrinter ( 10, 4); rectanglePrinter ( 4,10 ) ; cout << endl << endl; system ("pause"); return 0; // end of main

10. 10 Coding Some functions are void functions In function printer, the parameters are passed by value –PrinterCalls.cpp void printer(int number, char symbol) // method printer will print out the symbol number times on a single line. { int counter; //local counter for loop control counter = 1; while (counter <= number ) { counter++; cout << symbol; } } // end of printer -------------------------------------------------

11. 11 Coding Some functions are void functions In function printer, the parameters are passed by value –PrinterCalls.cpp void treePrinter () { cout << endl << endl; printer (9,BLANK); printer (1,STAR); cout << endl; printer (8,BLANK); printer (3,STAR); cout << endl; printer (7,BLANK); printer (5,STAR); ……………………………. ………. printer (8,BLANK); printer (3,POUND); cout << endl; printer (8,BLANK); printer (3,POUND); cout << endl; } // end of printer -------------------------------------------------

12. 12 Coding Some functions are void functions In function printer, the parameters are passed by value –PrinterCalls.cpp // print a diamond shape { int bCount ; int lCount ; ……………….. See the code….. // print a diamond shape void rectanglePrinter ( int across, int down) { for ( int d = 1 ; d <= down ; d++ ) { printer (across, '#'); cout << endl; } } // end of rectanglePrinter

13. 13 Coding Some functions are void functions Some functions pass the parameters passed by value Some functions pass the parameters passed by reference –Value_or_Reference.cpp //A swap that doesn't really swap! void up(int a) { a = a + 5; cout << "up a = " << a << endl; } //A swap that really swaps! void down(int& x) { x = x - 5; cout << "down x = " << x<< endl; }

14. void swap1 (int a, int b) { int temp; temp = a; a = b; b = temp; }

15. 15 Coding Some functions are void functions Some functions pass the parameters - by value Some functions pass the parameters - by reference –Swap_it.cpp //A swap that doesn't really swap! void swap1 (int a, int b) { int temp; temp = a; a = b; b = temp; } //A swap that really swaps! void swap2 (int& a, int& b) { int temp; temp = a; a = b; b = temp; }

16. Chapter 6 Write a program to input and calculate the cost of ODU football tickets. Use functions. How many? Student prices Adult prices Senior prices

17. Summary 1 Project 2 Quizzes….. Read Chapter 6 - Functions! Again!

18. QUESTIONS?