Stan Math Library  2.20.0
reverse mode automatic differentiation
abs.hpp
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1 #ifndef STAN_MATH_FWD_SCAL_FUN_ABS_HPP
2 #define STAN_MATH_FWD_SCAL_FUN_ABS_HPP
3 
4 #include <stan/math/fwd/meta.hpp>
5 #include <stan/math/fwd/core.hpp>
9 
10 namespace stan {
11 namespace math {
12 
13 template <typename T>
14 inline fvar<T> abs(const fvar<T>& x) {
15  if (x.val_ > 0.0)
16  return x;
17  else if (x.val_ < 0.0)
18  return fvar<T>(-x.val_, -x.d_);
19  else if (x.val_ == 0.0)
20  return fvar<T>(0, 0);
21  else
22  return fvar<T>(abs(x.val_), NOT_A_NUMBER);
23 }
24 
25 } // namespace math
26 } // namespace stan
27 #endif
fvar< T > abs(const fvar< T > &x)
Definition: abs.hpp:14
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
T val_
The value of this variable.
Definition: fvar.hpp:45
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

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