TimeStep.h

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#pragma once
 
#include <cstddef>
#include <limits>
 
namespace NumLib
{
class TimeStep final
{
public:
    explicit TimeStep(double current_time)
        : _previous(current_time),
          _current(current_time),
          _dt(_current - _previous),
          _time_step_number(0)
    {
    }
 
    TimeStep(double previous_time, double current_time, std::size_t n)
        : _previous(previous_time),
          _current(current_time),
          _dt(_current - _previous),
          _time_step_number(n)
    {
    }
 
    TimeStep(const TimeStep& src) = default;
 
    TimeStep& operator=(const TimeStep& src) = default;
 
    TimeStep& operator+=(const double dt)
    {
        _previous = _current;
        _current += dt;
        _dt = dt;
        _time_step_number++;
        return *this;
    }
 
    bool operator<(TimeStep const& ts) const
    {
        return (_current < ts._current);
    }
    bool operator<=(TimeStep const& ts) const
    {
        return (_current <= ts._current);
    }
    bool operator==(TimeStep const& ts) const
    {
        return (_current == ts._current);
    }
    double previous() const { return _previous; }
    double current() const { return _current; }
    double dt() const { return _dt; }
    std::size_t timeStepNumber() const { return _time_step_number; }
 
    void setAccepted(bool const accepted) { _is_accepted = accepted; }
    bool isAccepted() const { return _is_accepted; }
 
    static constexpr double minimalTimeStepSize =
        1000 * std::numeric_limits<double>::epsilon();
 
private:
    double _previous;
    double _current;
    double _dt;
    std::size_t _time_step_number;
    bool _is_accepted = true;
};
 
inline void updateTimeSteps(double const dt, TimeStep& previous_timestep,
                            TimeStep& current_timestep)
{
    previous_timestep = current_timestep;
    current_timestep += dt;
}
 
}  // namespace NumLib