Initializing valarray and inheritence

[danielsbrewer]

Hi there I am pretty new to C++ object-orientated stuff and I was wondering if you could help. I have a class called Equations with a protected variable declared as:

valarray<double> myParameters;

I want to initialise this to a certain size during the constructor of the inherited class Model1. In the constructor I have:

valarray <double> myParameters(13);
myParameters[1]=2;

In another function of the Model1 class I have:
cout << myParameters[1] << endl;

But when this function is run it does not print "2" but some random amount. I concluded that i must be initialising it wrong.
Any ideas how to inherite a valarray object and initialise it to a certain size in the inherited class.

Thanks

[dude_1967]

I would take care of this using a pointer to valarray initialized in the base-class constructor. Take a look at this sample.

Sincerely,
Chris.

#include <iostream>
#include <valarray>
using namespace std;

class base
{
protected:

  valarray<double>* pv;

public:

  base(const double d, const size_t s)
  {
    pv = new valarray<double>(d, s);
  }
  virtual ~base()
  {
    delete pv;
  }

};

class derived : public base
{
public:

  derived(const double d, const size_t s) : base(d, s)
  {
  }
  ~derived()
  {
  }

  const double& operator[](const int n)
  {
    return (*pv)[n];
  }

};

int main(int argc, char* argv[])
{
  derived d(13.0, 100);

  cout << d[0] << endl;

  return 1;
}

[danielsbrewer]

Thanks that has sorted it out

[mwilliamson]

You need to add the contructor for valarray to your class' constructor, a pointer is NOT needed.

class CBase
{
public:
CBase(unsigned int nParamSize);
protected:
valarray<double> myParameters;
};

CBase(unsigned int nParamSize) : myParameter(nParamSize)
{
}

class CDerived
{
public:
CDerived(unsigned int nParamSize);
CDerived();
};

CDerived(unsigned int nParamSize) : CBase(nParamSize)
{
}

CDerived() : CBase(13)
{
}

[dude_1967]

The second solution is simpler.
Thanks. Chris.