PowerFunction.hh

// Copyright QED Software 2023.
 
#ifndef GRAIL_POWER_FUNCTION_H
#define GRAIL_POWER_FUNCTION_H
 
#include <cmath>
#include "Curve.hh"
 
namespace grail
{
namespace evaluator
{
 template <typename ContextType>
 class PowerFunction final : public Curve<ContextType>
 {
 public:
 PowerFunction(std::shared_ptr<Evaluator<ContextType>> childEvaluator,
 float slope,
 float intercept,
 float exponent)
 : Curve<ContextType>{childEvaluator}, slope(slope), intercept(intercept), exponent(exponent)
 {
 }
 
 PowerFunction(std::shared_ptr<Evaluator<ContextType>> childEvaluator,
 std::pair<float, float> firstPoint,
 std::pair<float, float> secondPoint,
 float exponent)
 : Curve<ContextType>{childEvaluator}, exponent{exponent}
 {
 if(firstPoint.first > secondPoint.first)
 {
 float x = firstPoint.first;
 float y = firstPoint.second;
 firstPoint.first = secondPoint.first;
 firstPoint.second = secondPoint.second;
 secondPoint.first = x;
 secondPoint.second = y;
 }
 slope = (std::pow(secondPoint.second, 1 / exponent) - std::pow(firstPoint.second, 1 / exponent)) / (
 secondPoint.first - firstPoint.first);
 intercept = std::pow(firstPoint.second, 1 / exponent) - (slope * firstPoint.first);
 }
 
 virtual float Sample(float argument) const override final
 {
 float linearPart = slope * argument + intercept;
 if(linearPart < 0.0f)
 {
 int intExponent = static_cast<int>(exponent);
 if(exponent - intExponent > 0.0f)
 {
 return 0.0f;
 }
 }
 
 return std::pow(linearPart, exponent);
 }
 
 float GetSlope() const { return slope; }
 float GetIntercept() const { return intercept; }
 float GetExponent() const { return exponent; }
 
 virtual data::EvaluatorType GetEvaluatorType() const override final { return data::EvaluatorType::CURVE_POWER; }
 
 private:
 float slope = 0.0f;
 float intercept = 0.0f;
 float exponent = 0.0f;
 };
}
}
 
#endif // GRAIL_POWER_FUNCTION_H