atanh.hpp

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#ifndef STAN_MATH_PRIM_FUN_ATANH_HPP
#define STAN_MATH_PRIM_FUN_ATANH_HPP
 
#include <stan/math/prim/core.hpp>
#include <stan/math/prim/err.hpp>
#include <stan/math/prim/meta.hpp>
#include <stan/math/prim/fun/copysign.hpp>
#include <stan/math/prim/fun/is_nan.hpp>
#include <stan/math/prim/fun/log.hpp>
#include <stan/math/prim/functor/apply_scalar_unary.hpp>
#include <cmath>
#include <complex>
 
namespace stan {
namespace math {
 
template <typename T, require_arithmetic_t<T>* = nullptr>
inline double atanh(T&& x) {
  if (is_nan(x)) {
    return x;
  } else {
    check_bounded("atanh", "x", x, -1.0, 1.0);
    return std::atanh(x);
  }
}
 
template <typename T, require_complex_bt<std::is_arithmetic, T>* = nullptr>
inline auto atanh(T&& x) {
  return std::atanh(x);
}
 
struct atanh_fun {
  template <typename T>
  static inline auto fun(T&& x) {
    return atanh(std::forward<T>(x));
  }
};
 
template <typename T, require_ad_container_t<T>* = nullptr>
inline auto atanh(T&& x) {
  return apply_scalar_unary<atanh_fun, T>::apply(std::forward<T>(x));
}
 
template <typename Container,
          require_container_bt<std::is_arithmetic, Container>* = nullptr>
inline auto atanh(Container&& x) {
  return apply_scalar_unary<atanh_fun, Container>::apply(
      std::forward<Container>(x));
}
 
namespace internal {
template <typename V>
inline std::complex<V> complex_atanh(const std::complex<V>& z) {
  std::complex<double> y_d = atanh(value_of_rec(z));
  V one(1);
  auto y = 0.5 * (log(one + z) - log(one - z));
  return copysign(y, y_d);
}
}  // namespace internal
 
}  // namespace math
}  // namespace stan
 
#endif