Stan Math Library  2.12.0
reverse mode automatic differentiation
atanh.hpp
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1 #ifndef STAN_MATH_REV_SCAL_FUN_ATANH_HPP
2 #define STAN_MATH_REV_SCAL_FUN_ATANH_HPP
3 
4 #include <math.h>
5 #include <stan/math/rev/core.hpp>
6 #include <cmath>
7 #include <limits>
8 
9 #ifdef _MSC_VER
10 #include <boost/math/special_functions/atanh.hpp>
11 using boost::math::atanh;
12 #endif
13 
14 namespace stan {
15  namespace math {
16 
17  namespace {
18  class atanh_vari : public op_v_vari {
19  public:
20  atanh_vari(double val, vari* avi) :
21  op_v_vari(val, avi) {
22  }
23  void chain() {
24  avi_->adj_ += adj_ / (1.0 - avi_->val_ * avi_->val_);
25  }
26  };
27  }
28 
69  inline var atanh(const var& a) {
70  if (a == 1.0)
71  return var(new atanh_vari(std::numeric_limits<double>::infinity(),
72  a.vi_));
73  if (a == -1.0)
74  return var(new atanh_vari(-std::numeric_limits<double>::infinity(),
75  a.vi_));
76  return var(new atanh_vari(::atanh(a.val()), a.vi_));
77  }
78 
79  }
80 }
81 #endif
fvar< T > atanh(const fvar< T > &x)
Definition: atanh.hpp:13
Independent (input) and dependent (output) variables for gradients.
Definition: var.hpp:30
vari * vi_
Pointer to the implementation of this variable.
Definition: var.hpp:42
var atanh(const var &a)
The inverse hyperbolic tangent function for variables (C99).
Definition: atanh.hpp:69
double val() const
Return the value of this variable.
Definition: var.hpp:229

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