Struct pointer initialization

[pe4enki]

Hello everyone,
I defined my own structure using

struct TheData 
{
  double* Values;  // holds the data to be filtered
  unsigned long Length;  // number of data values
  bool Valid;   // true if the data values have been Valid by the user
};

and i need to initialize the structure where i keep all the data. I am wondering what are the ways to initialize Values bit?
I have a working solution but it doesnt really fit the task that was set :

#include <iostream>
using namespace std;

struct TheData 
{
  double* Values;  // holds the data to be filtered
  unsigned long Length;  // number of data values
  bool Valid;   // true if the data values have been Valid by the user
};

void EnterData(TheData&);

int main()
{
	TheData OriginalData = {0,0,false};
	EnterData(OriginalData);
	cout << endl;
	delete [] OriginalData.Values;
	
}
// Allow the user to enter the data to be filtered
// Arguments:
//   (1) the structure containing the input data
// Returns: nothing
// 
void EnterData(TheData& Data)
{  
	// initialize the data structure that holds the data to be filtered, including getting
	// the number of data values from the user
	cout << "Please enter the number of data values to be filtered:" << endl;
	cin >> Data.Length;
	cout << endl;
	Data.Values = (double*)malloc(sizeof(double)*Data.Length);
	for (unsigned int i=0; i<Data.Length; i++)
		{
			Data.Values[i] = 0;
		}
	// allocate memory to the data
	// <enter code here>

}

As you can see i first allocate memory and then initialize... but the task is to initialize first and I have no idea how to do this before allocating the memory for the pointer. Are there any ways?

[Zhuge]

What you are doing is correct, and the only way for this to work really. The problem is you are mixing malloc() and delete. Use new/delete or malloc()/free(). Don't mix them or you could have trouble.

[pe4enki]

ok, thanks

[Disch]

to keep it simple -- just use new/delete and don't use malloc/free.

malloc/free don't really have a place in C++

[chipp]

what is type double * use for? is it contains arrays for values variable?

[pe4enki]

yes. I can then allocate memory for the values. I asked my teacher and he says setting array to zero is not what he ment under 'initialization'. He ment something else there....lol
so what can be the options if i have

struct TheData 
{
  double* Values;  // holds the data to be filtered
  unsigned long Length;  // number of data values
  bool Valid;   // true if the data values have been Valid by the user
};

and I need to // initialize the data structure that holds the data to be filtered
It's so hard to guess.... I just have no idea, because for me initializations means removing rubbish from memory and preparing place....

[pe4enki]

Btw it was already initialized by him here TheData OriginalData = {0,0,false};
Really confused what I was ment to do in the function...how to initialize the structure if it is already initialized

[Zhuge]

Since you seem to be using C++, you could use what is called a constructor to do it for you. Besides what you already did, manually setting it after creating the object is really the only other way.