来自编译器的c++类型错误消息，这是什么意思？

Question

我在 fedora linux 13 上使用 g++。我只是在练习我的 C++ 课本中的一些练习并且无法编译这个程序。这是代码:

double *MovieData::calcMed() {
        double medianValue;
        double *medValPtr = &medianValue;
        *medValPtr = (sortArray[numStudents-1] / 2);
        return medValPtr;
}

这是类声明:

    class MovieData 
{
private:
    int *students;                  // students points to int, will be dynamically allocated an array of integers.
    int **sortArray;                // A pointer that is pointing to an array of pointers.
    double average;                 // Average movies seen by students.
    double *median;                 // Median value of movies seen by students.
    int *mode;                  // Mode value, or most frequent number of movies seen by students.
    int numStudents;                // Number of students in sample.
    int totalMovies;                // Total number of movies seen by all students in the sample.
    double calcAvg();               // Method which calculates the average number of movies seen.
    double *calcMed();              // Method that calculates the mean value of data.
    int *calcMode();                // Method that calculates the mode of the data.
    int calcTotalMovies();              // Method that calculates the total amount of movies seen.
    void selectSort();              // Sort the Data using selection sort algorithm.
public:
    MovieData(int num, int movies[]);       // constructor
    ~MovieData();                   // destructor
    double getAvg() { return average; }     // returns the average
    double *getMed() { return median; } // returns the mean
    int *getMode()  { return mode; }        // returns the mode
    int getNumStudents() { return numStudents; }    // returns the number of students in sample
};

这是我的构造函数和析构函数以及 selectSort():

MovieData::MovieData(int num, int movies[]) {
    numStudents = num;

    // Now I will allocate memory for student and sortArray:
    if(num > 0) {
        students = new int[num];
        sortArray = new int*[num];

        // The arrays will now be initialized:
        for(int index = 0;index < numStudents;index++) {
            students[index] = movies[index];
            sortArray[index] = &students[index];
        }
        selectSort();   // sort the elements of sortArray[] that point to the elements of students.
        totalMovies = calcTotalMovies();
        average = calcAvg();
        median = calcMed();
        mode = calcMode();
    }
}

// Destructor:
// Delete the memory allocated in the constructor.
MovieData::~MovieData() {
    if(numStudents > 0) {
        delete [] students;
        students = 0;
        delete [] sortArray;
        sortArray = 0;
    }
}

// selectSort() 
// performs selection sort algorithm on sortArray[],
// an array of pointers.  Sorted on the values its 
// elements point to.
void MovieData::selectSort() {
    int scan, minIndex;
    int *minElement;

    for(scan = 0;scan < (numStudents - 1);scan++) {
        minIndex = scan;
        minElement = sortArray[scan];
        for(int index = 0;index < numStudents;index++) {
            if(*(sortArray[index]) < *minElement) {
                minElement = sortArray[index];
                minIndex = index;
            }
        }
        sortArray[minIndex] = sortArray[scan];
        sortArray[scan] = minElement;
    }
}

编译器报错:

moviedata.cpp: In memberfunction 'double * MovieData::calcMed()':

moviedata.cpp:82: error: invalid operands of types 'int*' and 'double' to binary 'operator/'

我不确定这个错误是怎么回事，我试过静态转换类型但没有成功，这个错误消息是什么意思？

Answer 1

你正试图将一个指针除以一个 double ，编译器说它不知道该怎么做。

sortArray 可能定义为

int ** 排序数组；

同样值得注意的是，您将返回一个指向堆栈变量的指针，一旦您从函数中返回，该变量的值将是未定义的。