Phi_approx.hpp

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#ifndef STAN_MATH_PRIM_FUN_PHI_APPROX_HPP
#define STAN_MATH_PRIM_FUN_PHI_APPROX_HPP
 
#include <stan/math/prim/meta.hpp>
#include <stan/math/prim/fun/inv_logit.hpp>
#include <stan/math/prim/functor/apply_scalar_unary.hpp>
#include <cmath>
 
namespace stan {
namespace math {
 
inline double Phi_approx(double x) {
  using std::pow;
  return inv_logit(0.07056 * pow(x, 3.0) + 1.5976 * x);
}
 
inline double Phi_approx(int x) { return Phi_approx(static_cast<double>(x)); }
 
struct Phi_approx_fun {
  template <typename T>
  static inline auto fun(const T& x) {
    return Phi_approx(x);
  }
};
 
template <
    typename T,
    require_all_not_nonscalar_prim_or_rev_kernel_expression_t<T>* = nullptr,
    require_not_var_matrix_t<T>* = nullptr>
inline auto Phi_approx(const T& x) {
  return apply_scalar_unary<Phi_approx_fun, T>::apply(x);
}
 
}  // namespace math
}  // namespace stan
 
#endif