C++ Error creating class

Question

I am fairly new to c++ and have never created a class of my own until today. I don't like to post up code for people to review normally but I am on a tight deadline and need to get my code compiling. I get three errors:

-error: than previous declaration `RobotDeadReckoner::RobotDeadReckoner() throw ()'

-Multiple markers at this line - error: declaration of RobotDeadReckoner::RobotDeadReckoner()' throws different exceptions - error: definition of implicitly-declaredRobotDeadReckoner::RobotDeadReckoner()'

-error: no RobotDeadReckoner::~RobotDeadReckoner()' member function declared in classRobotDeadReckoner'

The code is as follows:

#include <cmath>
#include "WPILib.h"


class RobotDeadReckoner
{//<---------------------Error
public:
    float getX();
    float getY();
    float getHeading();
private:
    Encoder *encoder1;//Encoder1 (Left Transmision while looking from the back)
    Encoder *encoder2;//Encoder2 (Right Transmision while looking from the back)
    int wheelRadius;//Wheel Radius (Center Wheel)
    float axleWidthCenterToCenter;
    int encoderTicksPerRotation;
    int transmitionSprocketTeeth;
    int wheelSprocketTeeth;
    int ticksPerRotation; //ticks per rotation of wheel
    float encoderTicks1;
    float encoderTicks2;
    float pi;
};

RobotDeadReckoner::RobotDeadReckoner()
{//<---------------------Error
    wheelRadius = 4;//Wheel Radius (Center Wheel)
    axleWidthCenterToCenter = 30+(7/8);
    encoderTicksPerRotation = 360;
    transmitionSprocketTeeth = 12;
    wheelSprocketTeeth = 26;
    ticksPerRotation = (wheelSprocketTeeth/transmitionSprocketTeeth)*encoderTicksPerRotation; //ticks per rotation of wheel

    encoderTicks1 = encoder1->Get();
    encoderTicks2 = encoder2->Get();

    pi = atan(1)*4;
}

float RobotDeadReckoner::getX()
{
    float x = wheelRadius*cos(getHeading())*(encoderTicks1+encoderTicks2)*(pi/ticksPerRotation);
    return x;
}

float RobotDeadReckoner::getY()
{
    float y = wheelRadius*sin(getHeading())*(encoderTicks1+encoderTicks2)*(pi/ticksPerRotation);
    return y;
}

float RobotDeadReckoner::getHeading()
{
    float heading = (2*pi)*(wheelRadius/axleWidthCenterToCenter)*(encoderTicks1-encoderTicks2);
    return heading;
}

RobotDeadReckoner::~RobotDeadReckoner()
{ //<---------------------Error

}

I am sure it is something stupid simple I don't know about c++ but any help would be appreciated!

Note that the convention for getX() and getY() would assume you had a variable named X and another named Y. You have neither - make your getters describe what they get. — KevinDTimm
– KevinDTimm, Commented Feb 20, 2012 at 21:52

Community · Accepted Answer · 2017-05-23 11:48:00Z

1

definition of implicitly-declared RobotDeadReckoner::RobotDeadReckoner()

This is the biggest clue. You haven't declared the constructor for RobotDeadReckoner(), you've only defined it. If you don't provide a default constructor, the compiler will provide one for you, hence "implicitly-declared". See What is The Rule of Three? .

no RobotDeadReckoner::~RobotDeadReckoner()' member function declared in classRobotDeadReckoner'

Same again for the destructor.

Add the following to (public: section of) your class declaration:

RobotDeadReckoner();
virtual ~RobotDeadReckoner();

edited May 23, 2017 at 11:48

CommunityBot

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answered Feb 20, 2012 at 21:52

johnsyweb

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1 Comment

Jacob9706 Over a year ago

Thanks! I didn't understand what that meant but that is pretty obvious after I saw it...

Captain Giraffe · Accepted Answer · 2012-02-20 22:02:41Z

The first part of your post is a class definition, it should contain declarations of all members. Constructors and destructors. These are not present in you class definition.

 class Robot{   declarations. }; // end of class definition

The following does not have a corresponding declaration in your class above.

RobotDeadReckoner::RobotDeadReckoner()

Also you should put your class in a .h file and the

RobotDeadReckoner::RobotDeadReckoner()

in a .cpp file.

So your class should look like:

class RobotDeadReckoner{
     RobotDeadReckoner();
     ~RobotDeadReckoner();
 etc...

Dmitriy Kachko · Accepted Answer · 2012-02-20 21:53:25Z

You should declare destructor (and constructor) in the class definition first.

class RobotDeadReckoner
{//<---------------------Error
public:
  RobotDeadReckoner();
  ~RobotDeadReckoner(); // <--- HERE
    float getX();
    float getY();
    float getHeading();
private:
    Encoder *encoder1;//Encoder1 (Left Transmision while looking from the back)
    Encoder *encoder2;//Encoder2 (Right Transmision while looking from the back)
    int wheelRadius;//Wheel Radius (Center Wheel)
    float axleWidthCenterToCenter;
    int encoderTicksPerRotation;
    int transmitionSprocketTeeth;
    int wheelSprocketTeeth;
    int ticksPerRotation; //ticks per rotation of wheel
    float encoderTicks1;
    float encoderTicks2;
    float pi;
};

Johann Gerell · Accepted Answer · 2012-02-20 21:54:24Z

0

You have declared neither the RobotDeadReckoner constructor nor destructor, so you cannot define them further down with RobotDeadReckoner::RobotDeadReckoner() and RobotDeadReckoner::~RobotDeadReckoner().

Inside the class declaration, add

RobotDeadReckoner();
~RobotDeadReckoner();

and then the definitions further down will compile.

answered Feb 20, 2012 at 21:54

Johann Gerell

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Comments

Luchian Grigore · Accepted Answer · 2012-02-20 21:55:09Z

You can only provide implementations for user-defined constructors and destructors:

class RobotDeadReckoner
{
public:
   //declare constructor and destructor
   RobotDeadReckoner();
   ~RobotDeadReckoner();
public:
    float getX();
    float getY();
    float getHeading();
private:
    Encoder *encoder1;//Encoder1 (Left Transmision while looking from the back)
    Encoder *encoder2;//Encoder2 (Right Transmision while looking from the back)
    int wheelRadius;//Wheel Radius (Center Wheel)
    float axleWidthCenterToCenter;
    int encoderTicksPerRotation;
    int transmitionSprocketTeeth;
    int wheelSprocketTeeth;
    int ticksPerRotation; //ticks per rotation of wheel
    float encoderTicks1;
    float encoderTicks2;
    float pi;
};

If you don't declare a constructor or a destructor for your class, the compiler will automatically generate a default one for you, which you can't implement.

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