Notes

Outline

COM1100 Fundamentals of Computer Science –Winter 2000 Lecture 17 02/22/00

Lecture today Array Input and output array values Array as function arguments Individual array elements as function arguments May be passed by values May be passed by reference Complete array as function arguments Always passed by reference

Input Array values Individual array elements can be treated the same way as other data type Input Examples const int NUMBER = 5; double temp[NUMBER]; cin >>temp[0]>>temp[1]>>temp[2]>>temp[3]>>temp [4]; for ( int i = 0 ; i < NUMBER ; i ++ ) { cout << “\n Enter a temperature: “ ; cin >> temp[I]; }

Output Array values Output Examples cout << temp[0]; // output the value of the first element // the following loop print out all the elements in an array for ( int i = 0 ; i < NUMBER ; i ++ ) { cout << “\nEnter a temperature: “ ; cin >>  temp[i]; }

Array as function arguments – case 1 Individual array elements are passed to a function in the same manner as individual variables; they are simply included as subscript variable when the function call is made. Example 1 // arguments will be passed into the function by value int find_min(int x, int y) { if ( x < y) return x; else        return y; }

Array as function arguments – case 1 int m = 87, n= 65; // declare two integer variable cout << find_min(m,n) << endl; // 65 int grade[5] = {98, 87, 74, 65, 82}; // declare an integer array for (i =0; i<5; i++) cout << grade[i] << " "; // 98  87  74  65  82 cout << endl; // grade[1] and grade[3] will be passed to function find_min by value cout << find_min(grade[1], grade[3]) << endl; // 65 for (i =0; i<5; i++) cout << grade[i] << " "; // 98  87  74  65  82

Array as function arguments – case 1 Example 2 // arguments will be passed into the function by value void swap(int& x, int& y) { int temp; temp = x; x = y; y = temp; }

Array as function arguments – case 1 int m = 87, n= 65; swap(m,n);      cout << "m= " << m << " n= " << n << endl; // m= 65  n= 87      int grade[5] = {98, 87, 74, 65, 82};      for (i =0; i<5; i++)       cout << grade[i] << " "; // 98  87  74  65  82 cout << endl; //grade[1] and grade[3] passed to function swap by reference     swap(grade[1], grade[3]);     for (i =0; i<5; i++) cout << grade[i] << " "; // 98 65  74  87  82 cout << endl;

Array as function arguments – case 2 Passing a complete array of values to a function is in many respects an easier operation than passing individual elements. The function receives access to the actual array, rather than a copy of the values in the array. In other words, C++ always pass a whole array to a function by reference.

Array as function arguments – case 2 Question: write a function that will find the max value in an array // function prototype int find_max(int g[], int size); // function definition int find_max(int g[], int size) { int max = g[0]; for(int i = 1; i < size; i++ ) { if (max < g[i])     max = g[i]; } return max; }

Array as function arguments – case 2 // function call int grade[5] = {98, 87, 74, 65, 82}; cout << "The max number in the array is : " << find_max(grade, 5) << endl; When you call the function find_max by passing the complete array and the size of the array, you only need to put the name of the array. You don’t need to put [].