How do I fill an array in c using a class?-CodePudding

This is a part of my assignment that I was given in my college CSCI course using C

Create a class Array, representing an arran of size n, with the private properties:

class Array {private: double * a {}; int n;

Constructor by default
Constructor by specifying the size of the array
Constructor by specifying the size of the array, and the default value for all the elements in the array
Constructor by copy
Destructor
Accessor: Retrieve the size of the array

I was faced with the task of defining an array using a class and the class must contain what each bullet point says. However, I am stuck on bullet point number 3. I am attempting to fill the array with default values of 0 for a[0], 1 for a1, etc. depending on the size of the array that a user inputs and sets as value n. In doing so all that my code is doing is assigning each and every element in the array with a value of 0.

#include <iostream>

using namespace std;

class MyArray {
    private:
        double * a {};
        int n;

    public:
        MyArray();
        explicit MyArray(int size);
        MyArray(int size, double def_val);
        MyArray(const MyArray & a2);
        ~MyArray();
        int get_Size() const;
        void SetElement(int i, double x);
        double GetElement(int i);
        void display();
};

MyArray::MyArray(int size) {
    n = size;
    a = new double[size];

}

MyArray::MyArray() {
    a = nullptr;
    n = 0;
}

double MyArray::GetElement(int i) {
    return a[i];
}

void MyArray::SetElement(int i, double x) {
    a[i] = x;
}

MyArray::MyArray(const MyArray & a2) {
    n = a2.n;
    for (int i = 0; i < n; i  ) {
        a[i] = a2.a[i];
    }
} //constructor by copy

MyArray::~MyArray() {
    delete[] a;

}

MyArray::MyArray(int size, double def_val) { //THIS IS WHERE IT SHOULD ASSIGN           
    n = size;
    a = new double[size];

    for (int i = 0; i < size;   i) {

        a[i] = i;
    }

}

int MyArray::get_Size() const {
    return n;
}

void MyArray::display() {
    cout << "The values of the array MyArray are: " << endl;
    for (int i = 0; i < n; i  ) {
        cout << a[i] << " ";
    }
    cout << endl;
}

int main() {
    MyArray a(5);
    a.display();
    return 0;
}

The output is this

The values of the array MyArray are:

0 0 0 0 0

CodePudding user response：

You are calling the wrong constructor you need to call this one: MyArray(int size, double def_val) not this: MyArray(int size);

like this:

    int main(){
MyArray a(5,5);
a.display();

     }

you will get the output as 0,1,2,3,4 But I don't think this is what the assignment wants you to do As you said it should "Constructor by specifying the size of the array, and the default value for all the elements in the array"

so I think you should modify your constructor to be like this:

   MyArray::MyArray(int size, double def_val) {           
    n = size;
    a = new double[size];
    for (int i = 0; i < size;   i) {
        a[i] = def_val;
    }
   }

CodePudding user response：

Use the function std::iota in the numeric header in the constructor that takes an int:

MyArray::MyArray(int size) {
    n = size;
    a = new double[size];
    std::iota(a, a size, 0.0);
}