Write a c++ class called dataarray which internally stores an array of double
values and the length of the array. the class should have the following features:
 a constructor dataarray(int size) which creates the array using new,
given the specified array size,
 a constructor dataarray(double a[], int size) which creates the array
and initialises it using the values in the array passed into the constructor,
 a destructor which frees previously allocated memory,
 a method dataarray scaleby(double factor), which returns a new
dataarray object containing the data elements, scaled by the given factor.