polynomial.hh

// -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
// vi: set et ts=4 sw=2 sts=2:
#ifndef DUNE_FUNCTIONS_ANALYTICFUNCTIONS_POLYNOMIAL_HH
#define DUNE_FUNCTIONS_ANALYTICFUNCTIONS_POLYNOMIAL_HH
 
#include <cmath>
#include <initializer_list>
#include <vector>
 
namespace Dune {
namespace Functions {
 
 
template<class K>
class Polynomial
{
public:
 
  Polynomial() = default;
 
  Polynomial(const Polynomial& other) = default;
 
  Polynomial(Polynomial&& other) = default;
 
  Polynomial(std::initializer_list<double> coefficients) :
    coefficients_(coefficients)
  {}
 
  Polynomial(std::vector<K>&& coefficients) :
      coefficients_(std::move(coefficients))
  {}
 
  Polynomial(const std::vector<K>& coefficients) :
    coefficients_(coefficients)
  {}
 
  K operator() (const K& x) const
  {
    auto y = K(0);
    for (size_t i=0; i<coefficients_.size(); ++i)
      y += coefficients_[i] * std::pow(x, i);
    return y;
  }
 
  friend Polynomial derivative(const Polynomial& p)
  {
    std::vector<K> dpCoefficients(p.coefficients().size()-1);
    for (size_t i=1; i<p.coefficients_.size(); ++i)
      dpCoefficients[i-1] = p.coefficients()[i]*i;
    return Polynomial(std::move(dpCoefficients));
  }
 
  const std::vector<K>& coefficients() const
  {
    return coefficients_;
  }
 
private:
  std::vector<K> coefficients_;
};
 
 
 
}} // namespace Dune::Functions
 
 
 
#endif // DUNE_FUNCTIONS_ANALYTICFUNCTIONS_POLYNOMIAL_HH