log1m_inv_logit.hpp

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#ifndef STAN_MATH_PRIM_FUN_LOG1M_INV_LOGIT_HPP
#define STAN_MATH_PRIM_FUN_LOG1M_INV_LOGIT_HPP
 
#include <stan/math/prim/meta.hpp>
#include <stan/math/prim/fun/exp.hpp>
#include <stan/math/prim/fun/log1p_exp.hpp>
#include <stan/math/prim/functor/apply_scalar_unary.hpp>
#include <cmath>
 
namespace stan {
namespace math {
 
template <typename T, require_arithmetic_t<T>* = nullptr>
inline double log1m_inv_logit(T&& uu) {
  const auto u = static_cast<double>(uu);
  if (u > 0.0) {
    return -u - log1p_exp(-u);  // prevent underflow
  }
  return -log1p_exp(u);
}
 
struct log1m_inv_logit_fun {
  template <typename T>
  static inline auto fun(T&& x) {
    return log1m_inv_logit(std::forward<T>(x));
  }
};
 
template <typename T, require_not_var_matrix_t<T>* = nullptr,
          require_not_nonscalar_prim_or_rev_kernel_expression_t<T>* = nullptr,
          require_container_t<T>* = nullptr>
inline auto log1m_inv_logit(T&& x) {
  return apply_scalar_unary<log1m_inv_logit_fun, T>::apply(std::forward<T>(x));
}
 
}  // namespace math
}  // namespace stan
 
#endif