hypergeometric_pFq.hpp

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#ifndef STAN_MATH_PRIM_FUN_HYPERGEOMETRIC_PFQ_HPP
#define STAN_MATH_PRIM_FUN_HYPERGEOMETRIC_PFQ_HPP
 
#include <stan/math/prim/meta.hpp>
#include <stan/math/prim/err/check_not_nan.hpp>
#include <stan/math/prim/err/check_finite.hpp>
#include <boost/math/special_functions/hypergeometric_pFq.hpp>
 
namespace stan {
namespace math {
 
template <typename Ta, typename Tb, typename Tz,
          require_all_eigen_st<std::is_arithmetic, Ta, Tb>* = nullptr,
          require_arithmetic_t<Tz>* = nullptr>
return_type_t<Ta, Tb, Tz> hypergeometric_pFq(const Ta& a, const Tb& b,
                                             const Tz& z) {
  plain_type_t<Ta> a_ref = a;
  plain_type_t<Tb> b_ref = b;
  check_finite("hypergeometric_pFq", "a", a_ref);
  check_finite("hypergeometric_pFq", "b", b_ref);
  check_finite("hypergeometric_pFq", "z", z);
 
  check_not_nan("hypergeometric_pFq", "a", a_ref);
  check_not_nan("hypergeometric_pFq", "b", b_ref);
  check_not_nan("hypergeometric_pFq", "z", z);
 
  bool condition_1 = (a_ref.size() > (b_ref.size() + 1)) && (z != 0);
  bool condition_2 = (a_ref.size() == (b_ref.size() + 1)) && (std::fabs(z) > 1);
 
  if (condition_1 || condition_2) {
    std::stringstream msg;
    msg << "hypergeometric function pFq does not meet convergence "
        << "conditions with given arguments. "
        << "a: " << a_ref << ", b: " << b_ref << ", "
        << ", z: " << z;
    throw std::domain_error(msg.str());
  }
 
  return boost::math::hypergeometric_pFq(
      std::vector<double>(a_ref.data(), a_ref.data() + a_ref.size()),
      std::vector<double>(b_ref.data(), b_ref.data() + b_ref.size()), z);
}
}  // namespace math
}  // namespace stan
#endif