text: #ifndef STAN_MATH_PRIM_SCAL_PROB_GAMMA_RNG_HPP
  #define STAN_MATH_PRIM_SCAL_PROB_GAMMA_RNG_HPP
  
  #include <stan/math/prim/meta.hpp>
  #include <stan/math/prim/scal/err/check_consistent_sizes.hpp>
  #include <stan/math/prim/scal/err/check_finite.hpp>
  #include <stan/math/prim/scal/err/check_positive_finite.hpp>
  #include <boost/random/gamma_distribution.hpp>
  #include <boost/random/variate_generator.hpp>
  
  namespace stan {
  namespace math {
  
  /**
   * Return a gamma random variate for the given shape and inverse
   * scale parameters using the specified random number generator.
   *
   * alpha and beta can each be a scalar or a one-dimensional container. Any
   * non-scalar inputs must be the same size.
   *
   * @tparam T_shape Type of shape parameter
   * @tparam T_inv Type of inverse scale parameter
   * @tparam RNG type of random number generator
   * @param alpha (Sequence of) positive shape parameter(s)
   * @param beta (Sequence of) positive inverse scale parameter(s)
   * @param rng random number generator
   * @return (Sequence of) gamma random variate(s)
   * @throw std::domain_error if alpha or beta are nonpositive
   * @throw std::invalid_argument if non-scalar arguments are of different
   * sizes
   */
  template <typename T_shape, typename T_inv, class RNG>
  inline typename VectorBuilder<true, double, T_shape, T_inv>::type gamma_rng(
      const T_shape& alpha, const T_inv& beta, RNG& rng) {
    using boost::gamma_distribution;
    using boost::variate_generator;
  
    static const char* function = "gamma_rng";
  
    check_positive_finite(function, "Shape parameter", alpha);
    check_positive_finite(function, "Inverse scale parameter", beta);
    check_consistent_sizes(function, "Shape parameter", alpha,
                           "Inverse scale Parameter", beta);
  
    scalar_seq_view<T_shape> alpha_vec(alpha);
    scalar_seq_view<T_inv> beta_vec(beta);
    size_t N = max_size(alpha, beta);
    VectorBuilder<true, double, T_shape, T_inv> output(N);
  
    for (size_t n = 0; n < N; ++n) {
      // Convert rate (inverse scale) argument to scale for boost
      variate_generator<RNG&, gamma_distribution<> > gamma_rng(
          rng, gamma_distribution<>(alpha_vec[n],
                                    1 / static_cast<double>(beta_vec[n])));
      output[n] = gamma_rng();
    }
  
    return output.data();
  }
  
  }  // namespace math
  }  // namespace stan
  #endif
  