discrete_range_rng.hpp

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#ifndef STAN_MATH_PRIM_PROB_DISCRETE_RANGE_RNG_HPP
#define STAN_MATH_PRIM_PROB_DISCRETE_RANGE_RNG_HPP
 
#include <stan/math/prim/meta.hpp>
#include <stan/math/prim/err.hpp>
#include <stan/math/prim/fun/max_size.hpp>
#include <stan/math/prim/fun/size_zero.hpp>
#include <stan/math/prim/fun/scalar_seq_view.hpp>
#include <boost/random/uniform_int_distribution.hpp>
#include <boost/random/variate_generator.hpp>
 
namespace stan {
namespace math {
 
template <typename T_lower, typename T_upper, class RNG>
inline typename VectorBuilder<true, int, T_lower, T_upper>::type
discrete_range_rng(const T_lower& lower, const T_upper& upper, RNG& rng) {
  static constexpr const char* function = "discrete_range_rng";
  using boost::variate_generator;
  using boost::random::uniform_int_distribution;
  check_consistent_sizes(function, "Lower bound parameter", lower,
                         "Upper bound parameter", upper);
  check_greater_or_equal(function, "Upper bound parameter", upper, lower);
  if (size_zero(upper, lower)) {
    return {};
  }
 
  scalar_seq_view<T_lower> lower_vec(lower);
  scalar_seq_view<T_upper> upper_vec(upper);
  size_t N = max_size(lower, upper);
  VectorBuilder<true, int, T_lower, T_upper> output(N);
 
  for (size_t n = 0; n < N; ++n) {
    variate_generator<RNG&, uniform_int_distribution<>> discrete_range_rng(
        rng, uniform_int_distribution<>(lower_vec[n], upper_vec[n]));
 
    output[n] = discrete_range_rng();
  }
 
  return output.data();
}
 
}  // namespace math
}  // namespace stan
#endif