1 #ifndef STAN_MATH_FWD_SCAL_FUN_LOG1M_INV_LOGIT_HPP
2 #define STAN_MATH_FWD_SCAL_FUN_LOG1M_INV_LOGIT_HPP
3 
4 #include <stan/math/fwd/core.hpp>
5 #include <stan/math/prim/scal/fun/log1m_inv_logit.hpp>
6 #include <cmath>
7 
8 namespace stan {
9 namespace math {
10 
11 /**
12  * Return the natural logarithm of one minus the inverse logit of
13  * the specified argument.
14  *
15  * @tparam T scalar type of forward-mode autodiff variable
16  * argument.
17  * @param x argument
18  * @return log of one minus the inverse logit of the argument
19  */
20 template <typename T>
log1m_inv_logit(const fvar<T> & x)21 inline fvar<T> log1m_inv_logit(const fvar<T>& x) {
22   using std::exp;
23   return fvar<T>(log1m_inv_logit(x.val_), -x.d_ / (1 + exp(-x.val_)));
24 }
25 
26 }  // namespace math
27 }  // namespace stan
28 #endif
29