Function1d.h

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// -*- LSST-C++ -*-
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#ifndef LSST_AFW_MATH_POLYNOMIALS_Function1d_h_INCLUDED
#define LSST_AFW_MATH_POLYNOMIALS_Function1d_h_INCLUDED

#include "Eigen/Core"
#include "lsst/geom/polynomials/SafeSum.h"
#include "lsst/geom/polynomials/ScaledBasis1d.h"

namespace lsst { namespace geom { namespace polynomials {

template <typename Basis_>
class Function1d {
public:

    using iterator = double *;
    using const_iterator = double const *;

    using Basis = Basis_;

    explicit Function1d(Basis const & basis) :
        _basis(basis),
        _coefficients(Eigen::VectorXd::Zero(basis.size()))
    {}

    Function1d(Basis const & basis, Eigen::VectorXd const & coefficients) :
        _basis(basis),
        _coefficients(coefficients)
    {
        assert(basis.size() == static_cast<std::size_t>(_coefficients.size()));
    }

    template <typename Iterator>
    Function1d(Basis const & basis, Iterator first, Iterator last) :
        _basis(basis),
        _coefficients(basis.size())
    {
        assert(std::distance(first, last) == static_cast<std::ptrdiff_t>(basis.size()));
        std::copy(first, last, &_coefficients[0]);
    }

    Function1d(Function1d const &) = default;

    Function1d(Function1d &&) = default;

    Function1d & operator=(Function1d const &) = default;

    Function1d & operator=(Function1d &&) = default;

    iterator begin() { return _coefficients.data(); }
    iterator end() { return begin() + size(); }
    const_iterator cbegin() const { return _coefficients.data(); }
    const_iterator cend() const { return begin() + size(); }
    const_iterator begin() const { return _coefficients.data(); }
    const_iterator end() const { return begin() + size(); }

    Basis const & getBasis() const { return _basis; }

    std::size_t size() const { return _basis.size(); }

    double operator()(double x, SumMode mode=SumMode::FAST) const {
        return _basis.sumWith(x, _coefficients, mode);
    }


    double & operator[](std::size_t n) { return  begin()[n]; }
    double const & operator[](std::size_t n) const { return begin()[n]; }


    auto getCoefficients() {
        // Return a block view to ensure the caller only modify the values, not the size.
        return _coefficients.head(size());
    }
    auto getCoefficients() const { return _coefficients.head(size()); }

    Function1d<typename Basis::Scaled> scaled(Scaling1d const & scaling) const {
        return Function1d<typename Basis::Scaled>(getBasis().scaled(scaling), _coefficients);
    }

private:
    Basis _basis;
    Eigen::VectorXd _coefficients;
};

template <typename Basis>
Function1d<Basis> makeFunction1d(Basis const & basis, Eigen::VectorXd const & coefficients) {
    return Function1d<Basis>(basis, coefficients);
}

template <typename Basis, typename Iterator>
Function1d<Basis> makeFunction1d(Basis const & basis, Iterator first, Iterator last) {
    return Function1d<Basis>(basis, first, last);
}


}}} // namespace lsst::geom::polynomials

#endif // !LSST_AFW_MATH_POLYNOMIALS_Function1d_h_INCLUDED