LowPass.h

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//
// Copyright (c) 2009, Markus Rickert
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// * Redistributions of source code must retain the above copyright notice,
//   this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright notice,
//   this list of conditions and the following disclaimer in the documentation
//   and/or other materials provided with the distribution.
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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#ifndef RL_MATH_LOWPASS_H
#define RL_MATH_LOWPASS_H
 
#include "Real.h"
 
namespace rl
{
    namespace math
    {
        template<typename T>
        class LowPass
        {
        public:
            LowPass(const ::rl::math::Real& alpha, const ::rl::math::Real& dt, const ::rl::math::Real& rc, const T& y = T()) :
                alpha(alpha),
                dt(dt),
                rc(rc),
                y(y)
            {
            }
            
            static LowPass<T> Frequency(const ::rl::math::Real& frequency, const ::rl::math::Real& dt, const T& y = T())
            {
                ::rl::math::Real rc = 1 / (2 * M_PI * frequency);
                ::rl::math::Real alpha = dt / (rc + dt);
                return LowPass<T>(alpha, dt, rc, y);
            }
            
            virtual ~LowPass()
            {
            }
            
            T operator()(const T& x)
            {
                return this->y = this->y + this->alpha * (x - this->y);
            }
            
        protected:
            
        private:
            ::rl::math::Real alpha;
            
            ::rl::math::Real dt;
            
            ::rl::math::Real rc;
            
            T y;
        };
    }
}
 
#endif // RL_MATH_LOWPASS_H