uniform_rng.hpp

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#ifndef STAN_MATH_PRIM_PROB_UNIFORM_RNG_HPP
#define STAN_MATH_PRIM_PROB_UNIFORM_RNG_HPP
 
#include <stan/math/prim/meta.hpp>
#include <stan/math/prim/err.hpp>
#include <stan/math/prim/fun/constants.hpp>
#include <stan/math/prim/fun/max_size.hpp>
#include <stan/math/prim/fun/scalar_seq_view.hpp>
#include <stan/math/prim/fun/value_of.hpp>
#include <boost/random/uniform_real_distribution.hpp>
#include <boost/random/variate_generator.hpp>
 
namespace stan {
namespace math {
 
template <typename T_alpha, typename T_beta, class RNG>
inline typename VectorBuilder<true, double, T_alpha, T_beta>::type uniform_rng(
    const T_alpha& alpha, const T_beta& beta, RNG& rng) {
  using T_alpha_ref = ref_type_t<T_alpha>;
  using T_beta_ref = ref_type_t<T_beta>;
  using boost::variate_generator;
  using boost::random::uniform_real_distribution;
  static constexpr const char* function = "uniform_rng";
  check_consistent_sizes(function, "Lower bound parameter", alpha,
                         "Upper bound parameter", beta);
  T_alpha_ref alpha_ref = alpha;
  T_beta_ref beta_ref = beta;
  check_finite(function, "Lower bound parameter", alpha_ref);
  check_finite(function, "Upper bound parameter", beta_ref);
  check_greater(function, "Upper bound parameter", beta_ref, alpha_ref);
 
  scalar_seq_view<T_alpha_ref> alpha_vec(alpha_ref);
  scalar_seq_view<T_beta_ref> beta_vec(beta_ref);
  size_t N = max_size(alpha, beta);
  VectorBuilder<true, double, T_alpha, T_beta> output(N);
 
  variate_generator<RNG&, uniform_real_distribution<> > uniform_rng(
      rng, uniform_real_distribution<>(0.0, 1.0));
  for (size_t n = 0; n < N; ++n) {
    output[n] = (beta_vec[n] - alpha_vec[n]) * uniform_rng() + alpha_vec[n];
  }
 
  return output.data();
}
 
}  // namespace math
}  // namespace stan
#endif