An error when inheriting Joystick

[MathMaven]

There are cases in our code when we use the negated value of the Y-axis for a Joystick. I know this is (really) easy to do, but for convenience, I'd love to extend the Joystick class to include a member function that would do it automatically—I think the resultant code would read a little more intuitively.

So I tried writing this:

#include "WPILib.h"

// some code...

class MyNewAndImprovedJoystickClass : public Joystick
{
public:
	virtual float GetNegativeY() //
	{
		return -GetY();
	}
};

// more code...

But WindRiver returned the following error:

C:/WindRiver/2013/SimpleTemplate/MyRobot.cpp:33: error: base `Joystick' with only non-default constructor in class without a constructor

And, well, I'm not sure what that means.

I understand that this issue on its own is an unimportant one. But I'm doing something wrong, and I'd like to know why. Besides, knowing more about C++ and WPILib can't hurt me.

Edit:
I found a WPILib-extending library that includes an extended Joystick class. After looking there, I tried rewriting the class as follows, and built without error:

class MyNewAndImprovedJoystickClass : public Joystick
{
public:
	MyNewAndImprovedJoystickClass(UINT32 port) : Joystick(port) {}

	virtual float GetYAdj()
	{
		return -GetY();
	}
};

I haven't tested this on the robot yet, but here's hoping.