Stan Math Library  2.20.0
reverse mode automatic differentiation
log1m_exp.hpp
Go to the documentation of this file.
1 #ifndef STAN_MATH_FWD_SCAL_FUN_LOG1M_EXP_HPP
2 #define STAN_MATH_FWD_SCAL_FUN_LOG1M_EXP_HPP
3 
4 #include <stan/math/fwd/meta.hpp>
5 #include <stan/math/fwd/core.hpp>
10 
11 namespace stan {
12 namespace math {
13 
22 template <typename T>
23 inline fvar<T> log1m_exp(const fvar<T>& x) {
24  if (x.val_ >= 0)
25  return fvar<T>(NOT_A_NUMBER);
26  return fvar<T>(log1m_exp(x.val_), x.d_ / -expm1(-x.val_));
27 }
28 
29 } // namespace math
30 } // namespace stan
31 #endif
T d_
The tangent (derivative) of this variable.
Definition: fvar.hpp:50
const double NOT_A_NUMBER
(Quiet) not-a-number value.
Definition: constants.hpp:58
fvar< T > expm1(const fvar< T > &x)
Definition: expm1.hpp:13
T val_
The value of this variable.
Definition: fvar.hpp:45
fvar< T > log1m_exp(const fvar< T > &x)
Return the natural logarithm of one minus the exponentiation of the specified argument.
Definition: log1m_exp.hpp:23
This template class represents scalars used in forward-mode automatic differentiation, which consist of values and directional derivatives of the specified template type.
Definition: fvar.hpp:41

     [ Stan Home Page ] © 2011–2018, Stan Development Team.