agent-simpleonoff.cpp

#include <stdio.h>
#include "bobuniverse.h"

int main(void){
    int distance; 
    Universe myBob(100, 30, 100);
    
    distance = myBob.getDistance();
    printf("%d", distance);
    
    return 0;
}

bobuniverse.cpp

/*
 * bobuniverse.cpp
 * 
 * It is a Bob Robot Universe Simulator
 *
 * Created on September 13, 2017
 * By Otacilio Neto (github: @OtacilioN | Email: contato@otaciliomaia.com)
 * 
 * Published under mit license
 */
 
#include "bobuniverse.h"

Universe::Universe(int initialDistance, int setPoint, int friction) {
	_initialDistance = initialDistance;
	_setPoint = setPoint;
	_friction = friction;
	position = _initialDistance;
}

int Universe::getStatus() {
	if(position < 0) // The robot crash into the wall
		status = -1;
		
	if(position = _setPoint && speed == 0) // Success
		status = 0;
	
	return status;
}

void Universe::move(int power) {
	if(status > 0){
		if(speed > 0.9)
    		acceleration = (power - _friction)/1000.0;
    	else if(speed < 0.9)
    		acceleration = (power + _friction)/1000.0;
    	else if(power > _friction)
    		acceleration = (power - _friction)/1000.0;
    	else if(power < _friction*-1)
    		acceleration = (power + _friction)/1000.0;
    		
    	speed += acceleration;
		position += speed;
		seconds++;
		
		getStatus();
	}
	return ;
}

int Universe::getDistance() {
	return (int)position; // The sensor has a int precision
}
	
int Universe::getSpeed() {
	return (int)speed; // The sensor has a int precision
}

int Universe::getTime() {
	return seconds; // The sensor has a int precision
}

bobuniverse.h

/*
 * bobuniverse.h
 * 
 * It is a Bob Robot Universe Simulator
 *
 * Created on September 13, 2017
 * By Otacilio Neto (github: @OtacilioN | Email: contato@otaciliomaia.com)
 * 
 * Published under mit license
 */
 
#ifndef bobuniverse_h
#define bobuniverse_h
class Universe {
    public:
        Universe(int initialDistance, int setPoint, int friction = 100);
        int getStatus();
        void move(int power);
        int getDistance();
        int getSpeed();
        int getTime();
        
    private:
        int _initialDistance;
        int _setPoint;
        int _friction;
        float speed = 0;
        float acceleration;
        float position;
        int status = 1;
        int seconds = 0;
        
};
#endif

error log

$ g++ agent-simpleonoff.cpp 

In file included from agent-simpleonoff.cpp:2:0:
bobuniverse.h:27:23: warning: non-static data member initializers only available with -std=c++11 or -std=gnu++11 [enabled by default]
         float speed = 0;
                       ^
bobuniverse.h:30:22: warning: non-static data member initializers only available with -std=c++11 or -std=gnu++11 [enabled by default]
         int status = 1;
                      ^
bobuniverse.h:31:23: warning: non-static data member initializers only available with -std=c++11 or -std=gnu++11 [enabled by default]
         int seconds = 0;
                       ^
/tmp/cciobolU.o: In function `main':
agent-simpleonoff.cpp:(.text+0x1f): undefined reference to `Universe::Universe(int, int, int)'
agent-simpleonoff.cpp:(.text+0x2b): undefined reference to `Universe::getDistance()'
collect2: error: ld returned 1 exit status

[Resolvido] Para os warnings era só fazer a inicialização no constructor da classe, e para o erro era só gerar um arquivo objeto da biblioteca e linkar na compilação.