besselj.hpp

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/*
 * This file is part of PLaSK (https://plask.app) by Photonics Group at TUL
 * Copyright (c) 2022 Lodz University of Technology
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, version 3.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 */
#ifndef PLASK__SOLVER__SLAB_BESSELJ_H
#define PLASK__SOLVER__SLAB_BESSELJ_H
 
 
#include "plask/optical/modal/config.hpp"
 
 
#ifdef USE_GSL
#   include <gsl/gsl_sf_bessel.h>
 
    inline double cyl_bessel_j(int m, double x) {
        return gsl_sf_bessel_Jn(m, x);
    }
 
    template <typename It>
    inline void cyl_bessel_j_zero(int m, size_t i, size_t n, It dst) {
        if (m == 0) {
            for (n = n+i; i < n; ++i, ++dst) *dst = gsl_sf_bessel_zero_J0(i);
        } else if (m == 1) {
            for (n = n+i; i < n; ++i, ++dst) *dst = gsl_sf_bessel_zero_J1(i);
        } else {
            double nu = m;
            for (n = n+i; i < n; ++i, ++dst) *dst = gsl_sf_bessel_zero_Jnu(nu, i);
        }
    }
 
#else
#   include <boost/math/special_functions/bessel.hpp>
    using boost::math::cyl_bessel_j;
    using boost::math::cyl_bessel_j_zero;
#endif
 
 
#endif // PLASK__SOLVER__SLAB_BESSELJ_H