7.4.4. Summing the Elements of an array

Often, the elements of an array represent a series of values to be used in a calculation. For example, if the elements of an array represent exam grades, a professor may wish to total the elements of the array and use that sum to calculate the class average for the exam.

The program in Fig. 7.8 sums the values contained in the four-element integer array a. The program declares, creates and initializes the array in line 10. The for statement (lines 14–15) performs the calculations. The values being supplied as initializers for array a also could be read into the program from the user at the keyboard, or from a file on disk (see Chapter 14, File Processing). For example, the for statement

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for ( size_t j = 0; j < a.size(); ++j )
   cin >> a[ j ];

reads one value at a time from the keyboard and stores the value in element a[j].

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 1   // Fig. 7.8: fig07_08.cpp
 2   // Computing the sum of the elements of an array.
 3   #include <iostream>
 4   #include <array>
 5   using namespace std;
 6
 7   int main()
 8   {
 9      const size_t arraySize = 4; // specifies size of array
10      array< int, arraySize > a = { 10, 20, 30, 40 };
11      int total = 0;
12
13      // sum contents of array a             
14      for ( size_t i = 0; i < a.size(); ++i )
15         total += a[ i ];                    
16
17      cout << "Total of array elements: " << total << endl;
18   } // end main

Total of array elements: 100

Fig. 7.8. Computing the sum of the elements of an array.

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