Can I have a two dimensional array of different types?

Question

// create array
Date** dateList = new Date*[SIZE];

// populate array
for(int i = 0; i < SIZE; i++) {
    dateList[i] = new Date[2];
    Date date;
    date.input();

    dateList[i][0] = date;

    int n = dateNum(date);
    dateList[i][1] = n;
}

I want to store a object of Date type in dateList[i][0] and an int in dateList[i][1] . Is this possible?

Thank you.

Answer 1

No.

A single array must be of a single type. If you want the elements to represent different types of data, then the element in the array needs to be some kind of base class (pointer), or possibly a discriminated type like a variant .

Answer 2

Unless you have an overwhelming reason to do otherwise, it sounds like you want a vector of structs:

struct whatever { 
    Date date;
    int n;

    whatever(Date const &d, int i) : date(d), n(i) {}    
};

std::vector<whatever> dates;

Date date;
date.input();

dates.push_back(whatever(date, datenum(date));

Answer 3

There are multiple ways of doing it. The most direct one is to use union s: put the types that you want to share in a single union , then use the member corresponding to the dimension's type in your code. However, this approach is also the most restrictive, because types with constructors / destructors cannot go into union s.

A more convenient way to do this is to build a one-dimensional array of pair<Date,int> objects, like this:

pair<Date,int>* dateList = new  pair<Date,int>[SIZE];

// populate array
for(int i = 0; i < SIZE; i++) {
    Date date;
    date.input();
    int n = dateNum(date);

    dateList[i] = make_pair(date, n);
}
for(int i = 0; i < SIZE; i++) {
    cout << "Date: " date[i].first << " ";
    cout << "Int: " date[i].second << endl;
}

This approach lets the compiler check your types much closer, giving you a more robust solution.

Answer 4

Short answer: No. Arrays are of one type only. That is also true for multidimensional arrays.

Read about structs or even higher data structures like map to achieve the dessired effect.