text: // Copyright 2015 Olivier Gillet.
  //
  // Author: Olivier Gillet (ol.gillet@gmail.com)
  //
  // Permission is hereby granted, free of charge, to any person obtaining a copy
  // of this software and associated documentation files (the "Software"), to deal
  // in the Software without restriction, including without limitation the rights
  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  // copies of the Software, and to permit persons to whom the Software is
  // furnished to do so, subject to the following conditions:
  // 
  // The above copyright notice and this permission notice shall be included in
  // all copies or substantial portions of the Software.
  // 
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  // THE SOFTWARE.
  // 
  // See http://creativecommons.org/licenses/MIT/ for more information.
  //
  // -----------------------------------------------------------------------------
  //
  // Quantize a float in [0, 1] to an integer in [0, num_steps[. Apply hysteresis
  // to prevent jumps near the decision boundary.
  
  #ifndef STMLIB_DSP_HYSTERESIS_QUANTIZER_H_
  #define STMLIB_DSP_HYSTERESIS_QUANTIZER_H_
  
  #include "stmlib/stmlib.h"
  
  namespace stmlib {
  
  class HysteresisQuantizer {
   public:
    HysteresisQuantizer() { }
    ~HysteresisQuantizer() { }
  
    void Init() {
      quantized_value_ = 0;
    }
  
    int Process(float value, int num_steps) {
      return Process(value, num_steps, 0.25f);
    }
  
    int Process(float value, int num_steps, float hysteresis) {
      value *= static_cast<float>(num_steps - 1);
      float hysteresis_feedback = value > static_cast<float>(quantized_value_)
          ? -hysteresis
          : hysteresis;
      int q = static_cast<int>(value + hysteresis_feedback + 0.5f);
      CONSTRAIN(q, 0, num_steps - 1);
      quantized_value_ = q;
      return q;
    }
    
    template<typename T>
    const T& Lookup(const T* array, float value, int num_steps) {
      return array[Process(value, num_steps)];
    }
  
   private:
    int quantized_value_;
    
    DISALLOW_COPY_AND_ASSIGN(HysteresisQuantizer);
  };
  
  }  // namespace stmlib
  
  #endif  // STMLIB_DSP_HYSTERESIS_QUANTIZER_H_
  