C++ timer class

Timer.cpp

#include "Timer.hpp"

using namespace std ;

Timer::Timer() : timerStarted(false) {}

Timer::Timer(Timer && other) : timerStarted(std::move(other.timerStarted)), start(std::move(other.start)) {}

Timer::~Timer() {}

Timer & Timer::operator=(Timer && rhs) {
	if (this != &rhs) {
		timerStarted = rhs.timerStarted ;
		start = std::move(rhs.start) ;
	}
	return *this ;
}

void Timer::startTimer() {
	if (timerStarted) {
		cerr << "stopTimer() must be called before startTimer() can be called again for this Timer object \n" ;
		throw exception() ;
	}
	timerStarted = true ;
	start = chrono::steady_clock::now() ;
}


std::chrono::nanoseconds Timer::checkTimeElapsed() {
	//returns in micro or nanoseconds
	if (!timerStarted) {
		cerr << "checkTimeElapsed() can only be called after startTimer() has been called once \n" ;
		throw exception() ;
	}
	auto duration = chrono::steady_clock::now() - start ;
	return duration ;
}

void Timer::reset() {
	start = chrono::steady_clock::now() ;
}

std::chrono::nanoseconds Timer::stopTimer() {
	if (!timerStarted) {
		cerr << "stopTimer() can only be called after startTimer() has been called once \n" ;
		throw exception() ;
	}
	auto duration = chrono::steady_clock::now() - start ;
	timerStarted = false ;
	return duration ;
}

Timer.hpp

//
//  ClockTicks.h
//  Intro to C++
//
//  Created by Adam J. Leuer on 7/27/13.
//  Copyright (c) 2013 Adam J. Leuer. All rights reserved.
//

#ifndef __Time__
#define __Time__

#include <iostream>
#include <chrono>

using namespace std ;

/**
 * @brief A class providing simple nanosecond-precision timing facilities
 */
class Timer {
	
private:
	
	bool timerStarted ;
	
	chrono::time_point<std::chrono::steady_clock, std::chrono::nanoseconds> start ;

public:
	
	Timer() ;
	
	Timer(Timer && other) ;
	
	~Timer() ;
	
	Timer & operator=(Timer && rhs) ;
	
	/**
	 * @brief Starts the timer.
	 */
	void startTimer() ;
	
	/**
	 * @brief Checks the time elapsed since startTimer() was called.
	 *		  Unlike stopTimer(), this function will not stop the timer.
	 *
	 * @note 1 millisecond = 1000000 nanoseconds
	 *
	 * @return The time elapsed in nanoseconds.
	 */
	std::chrono::nanoseconds checkTimeElapsed() ;
	
	/**
	 * @brief Resets the timer to 0
	 */
	void reset() ;
	
	/**
	 * @brief Stops timer and returns the time elapsed since startTimer() was called.
	 *
	 * @note 1 millisecond = 1000000 nanoseconds
     *
	 * @return The time elapsed in nanoseconds.
	 */
	std::chrono::nanoseconds stopTimer() ;
} ;


#endif /* defined Time */