readdata034.cpp

Data Abstraction & Problem Solving with C++源码

const int LOW_END=10;   // low end of incomes
const int HIGH_END=100; // high end of incomes
const int TABLE_SIZE = HIGH_END - LOW_END + 1;
typedef int TableType[TABLE_SIZE];

int index(int group)
// Returns the array index that corresponds to group number.
{
   return group - LOW_END;
} // end index

bool readData(TableType incomeData)
// ---------------------------------------------------------
// Reads and organizes income statistics.
// Precondition: The calling program gives directions and
// prompts the user. Each input line contains exactly two
// integers in the form G N, where N is the number of
// people with an income in the G-thousand-dollar group and
// LOW_END <= G <= HIGH_END. An input line with values of
// zero for both G and N terminates the input.
// Postcondition: incomeData[G-LOW_END] = total number of
// people with an income in the G-thousand-dollar group.
// The values read are displayed. If either G or N is
// erroneous (G and N are not both 0, and either G < LOW_END,
// G > HIGH_END, or N < 0), the function ignores the data
// line, sets the return value to false, and continues.
// In this case, the calling program should take action. The
// return value is true if the data is error free.
// ---------------------------------------------------------
{
   int group, number;  // input values
   bool dataCorrect = true;  // no data error found as yet

   for (group = LOW_END; group <= HIGH_END; ++group)
      incomeData[index(group)] = 0;

   for (cin >> group >> number;
        (group != 0) || (number != 0);
        cin >> group >> number)
   {  // Invariant: group and number are not both 0
      cout << "Input line specifies that income group "
           << group << "\ncontains " << number
           << " people.\n";

      if ((group >= LOW_END) && (group <= HIGH_END) &&
          (number >= 0))
         // input data is valid -- add it to tally
         incomeData[index(group)] += number;

      else
         // error in input data: set error flag and
         // ignore input line
         dataCorrect = false;
   }  // end for
   return dataCorrect;
}  // end readData