text: // Arguments: Doubles, Doubles, Doubles
  #include <stan/math/prim/scal.hpp>
  
  using stan::math::var;
  using std::numeric_limits;
  using std::vector;
  
  class AgradDistributionsBeta : public AgradDistributionTest {
   public:
    void valid_values(vector<vector<double> >& parameters,
                      vector<double>& log_prob) {
      vector<double> param(3);
  
      param[0] = 0.4;  // y
      param[1] = 0.5;  // alpha
      param[2] = 0.5;  // beta
      parameters.push_back(param);
      log_prob.push_back(-0.4311717080293276382896);  // expected log_prob
  
      param[0] = 0.5;  // y
      param[1] = 2.0;  // alpha
      param[2] = 5.0;  // beta
      parameters.push_back(param);
      log_prob.push_back(-0.06453852113757105324332);  // expected log_prob
    }
  
    void invalid_values(vector<size_t>& index, vector<double>& value) {
      // y
      index.push_back(0U);
      value.push_back(-1.0);
  
      index.push_back(0U);
      value.push_back(2.0);
  
      // alpha
      index.push_back(1U);
      value.push_back(0.0);
  
      index.push_back(1U);
      value.push_back(-1.0);
  
      index.push_back(1U);
      value.push_back(numeric_limits<double>::infinity());
  
      index.push_back(1U);
      value.push_back(-numeric_limits<double>::infinity());
  
      // beta
      index.push_back(2U);
      value.push_back(0.0);
  
      index.push_back(2U);
      value.push_back(-1.0);
  
      index.push_back(2U);
      value.push_back(numeric_limits<double>::infinity());
  
      index.push_back(2U);
      value.push_back(-numeric_limits<double>::infinity());
    }
  
    template <typename T_y, typename T_scale1, typename T_scale2, typename T3,
              typename T4, typename T5>
    typename stan::return_type<T_y, T_scale1, T_scale2>::type log_prob(
        const T_y& y, const T_scale1& alpha, const T_scale2& beta, const T3&,
        const T4&, const T5&) {
      return stan::math::beta_log(y, alpha, beta);
    }
  
    template <bool propto, typename T_y, typename T_scale1, typename T_scale2,
              typename T3, typename T4, typename T5>
    typename stan::return_type<T_y, T_scale1, T_scale2>::type log_prob(
        const T_y& y, const T_scale1& alpha, const T_scale2& beta, const T3&,
        const T4&, const T5&) {
      return stan::math::beta_log<propto>(y, alpha, beta);
    }
  
    template <typename T_y, typename T_scale1, typename T_scale2, typename T3,
              typename T4, typename T5>
    typename stan::return_type<T_y, T_scale1, T_scale2, T3, T4, T5>::type
    log_prob_function(const T_y& y, const T_scale1& alpha, const T_scale2& beta,
                      const T3&, const T4&, const T5&) {
      using stan::math::log1m;
      using std::log;
  
      return (alpha - 1.0) * log(y) + (beta - 1.0) * log1m(y)
             + lgamma(alpha + beta) - lgamma(alpha) - lgamma(beta);
    }
  };
  