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    <p>You can achieve the desired effect by the liberal use of Functor delegate objects and templates:</p> <p>CAlarm.h</p> <pre><code>#ifndef CALARM_H #define CALARM_H #include "ADTtime.h" #include "CStopwatch.h" template&lt;class FunctionObject&gt; class Alarm : public StopWatch { public: Alarm(const FunctionObject&amp; fn); Alarm(double tickTime, const FunctionObject&amp; fn); virtual ~Alarm(); FunctionObject Tick(); protected: FunctionObject _delegate; double _tickTime; private: }; template&lt;class FunctionObject&gt; Alarm&lt;FunctionObject&gt;::Alarm(const FunctionObject&amp; fn) : StopWatch(), _delegate(fn), _tickTime(1.0) { } template&lt;class FunctionObject&gt; Alarm&lt;FunctionObject&gt;::Alarm(double tickTime, const FunctionObject&amp; fn) : StopWatch(), _delegate(fn), _tickTime(tickTime) { } template&lt;class FunctionObject&gt; Alarm&lt;FunctionObject&gt;::~Alarm() { if(_isRunning) Stop(); } template&lt;class FunctionObject&gt; FunctionObject Alarm&lt;FunctionObject&gt;::Tick() { if(IsRunning() == false) return _delegate; if(GetElapsedTimeInSeconds() &gt;= _tickTime) { Reset(); _delegate(); } return _delegate; } #endif </code></pre> <p>CStopwatch.h</p> <pre><code>#ifndef CSTOPWATCH_H #define CSTOPWATCH_H #include "ADTtime.h" class StopWatch : public ADTTime { public: StopWatch(); virtual ~StopWatch(); void Start(); void Restart(); void Stop(); void Reset(); virtual void CalculateElapsedTime(); virtual double GetElapsedTimeInSeconds(); virtual double GetElapsedTimeInMilliseconds(); protected: private: }; #endif </code></pre> <p>CStopwatch.cpp</p> <pre><code>#include "CStopwatch.h" StopWatch::StopWatch() : ADTTime() { /* DO NOTHING. ALL INITIALIZATION HAPPENS IN BASE CLASS */ } StopWatch::~StopWatch() { _startTime = -1; _endTime = -1; _deltaTime = -1.0; _isRunning = false; } void StopWatch::Start() { if(_isRunning == true) return; _startTime = clock(); _isRunning = true; } void StopWatch::Stop() { if(_isRunning == false) return; _isRunning = false; CalculateElapsedTime(); } void StopWatch::Restart() { Reset(); Start(); } void StopWatch::Reset() { Stop(); _startTime = 0; _endTime = 0; _deltaTime = 0.0; } void StopWatch::CalculateElapsedTime() { _endTime = clock(); _deltaTime = difftime(_startTime, _endTime); } double StopWatch::GetElapsedTimeInSeconds() { CalculateElapsedTime(); return -ADTTime::GetElapsedTimeInSeconds(); } double StopWatch::GetElapsedTimeInMilliseconds() { CalculateElapsedTime(); return -ADTTime::GetElapsedTimeInMilliseconds(); } </code></pre> <p>ADTTime.h</p> <pre><code>#ifndef ADTTIME_H #define ADTTIME_H #include &lt;ctime&gt; class ADTTime { public: clock_t GetStartTime() const; clock_t GetStartTime(); double GetStartTimeInSeconds() const; double GetStartTimeInSeconds(); clock_t GetEndTime() const; clock_t GetEndTime(); double GetEndTimeInSeconds() const; double GetEndTimeInSeconds(); virtual double GetElapsedTimeInSeconds(); virtual double GetElapsedTimeInMilliseconds(); virtual void CalculateElapsedTime()=0; bool IsRunning() const; bool IsRunning(); virtual void Start()=0; virtual void Restart()=0; virtual void Stop()=0; virtual void Reset()=0; ADTTime(); virtual ~ADTTime(); protected: bool _isRunning; clock_t _startTime; clock_t _endTime; double _deltaTime; private: }; #endif </code></pre> <p>CADTTime.cpp</p> <pre><code>#include "ADTtime.h" clock_t ADTTime::GetStartTime() const { return _startTime; } clock_t ADTTime::GetStartTime() { return static_cast&lt;const ADTTime&amp;&gt;(*this).GetStartTime(); } double ADTTime::GetStartTimeInSeconds() const { return static_cast&lt;double&gt;((_startTime / CLOCKS_PER_SEC)); } double ADTTime::GetStartTimeInSeconds() { return static_cast&lt;const ADTTime&amp;&gt;(*this).GetStartTimeInSeconds(); } clock_t ADTTime::GetEndTime() const { return _endTime; } clock_t ADTTime::GetEndTime() { return static_cast&lt;const ADTTime&amp;&gt;(*this).GetEndTime(); } double ADTTime::GetEndTimeInSeconds() const { return static_cast&lt;double&gt;((_endTime / CLOCKS_PER_SEC)); } double ADTTime::GetEndTimeInSeconds() { return static_cast&lt;const ADTTime&amp;&gt;(*this).GetEndTimeInSeconds(); } double ADTTime::GetElapsedTimeInSeconds() { return _deltaTime / CLOCKS_PER_SEC; } double ADTTime::GetElapsedTimeInMilliseconds() { return _deltaTime; } bool ADTTime::IsRunning() const { return _isRunning; } bool ADTTime::IsRunning() { return static_cast&lt;const ADTTime&amp;&gt;(*this).IsRunning(); } ADTTime::ADTTime() : _isRunning(false), _startTime(-1), _endTime(-1), _deltaTime(-1.0) { } ADTTime::~ADTTime() { _isRunning = false; _startTime = -1; _endTime = -1; _deltaTime = -1.0; } </code></pre>
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    1. POMaking a timer that executes a function after a certain amount of time in milliseconds
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    1. COWhy do you provide those non-const member functions that just call the const overloads? (I.e. why not leave them away?)
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    2. CO@DyP It's to keep the code DRY and allows the calling of the methods on const and non-const objects. See `Effective C++, 3rd Edition by Scott Meyers Item 3, page 23-24`
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    3. CODon't have the book to look up what Meyers' argument is, but you *can* call const-qualified member functions on non-const objects.
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