#ifndef STAN_MATH_REV_SCAL_FUN_BESSEL_SECOND_KIND_HPP
#define STAN_MATH_REV_SCAL_FUN_BESSEL_SECOND_KIND_HPP

#include <stan/math/rev/core.hpp>
#include <stan/math/prim/scal/fun/constants.hpp>
#include <stan/math/prim/scal/fun/bessel_second_kind.hpp>

namespace stan {
  namespace math {

    namespace {

      class bessel_second_kind_dv_vari : public op_dv_vari {
      public:
        bessel_second_kind_dv_vari(int a, vari* bvi) :
          op_dv_vari(bessel_second_kind(a, bvi->val_), a, bvi) {
        }
        void chain() {
          bvi_->adj_ += adj_
            * (ad_ * bessel_second_kind(ad_, bvi_->val_)
               / bvi_->val_
               - bessel_second_kind(ad_ + 1, bvi_->val_));
        }
      };
    }

    inline var bessel_second_kind(int v,
                                  const var& a) {
      return var(new bessel_second_kind_dv_vari(v, a.vi_));
    }

  }
}
#endif
