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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 namespace stan {
10  namespace math {
11 
12  namespace {
13  class atanh_vari : public op_v_vari {
14  public:
15  atanh_vari(double val, vari* avi) :
16  op_v_vari(val, avi) {
17  }
18  void chain() {
19  avi_->adj_ += adj_ / (1.0 - avi_->val_ * avi_->val_);
20  }
21  };
22  }
23 
65  inline var atanh(const var& a) {
66  if (a == 1.0)
67  return var(new atanh_vari(std::numeric_limits<double>::infinity(),
68  a.vi_));
69  if (a == -1.0)
70  return var(new atanh_vari(-std::numeric_limits<double>::infinity(),
71  a.vi_));
72  return var(new atanh_vari(::atanh(a.val()), a.vi_));
73  }
74 
75  }
76 }
77 #endif
fvar< T > atanh(const fvar< T > &x)
Definition: atanh.hpp:13
Independent (input) and dependent (output) variables for gradients.
Definition: var.hpp:32
vari * vi_
Pointer to the implementation of this variable.
Definition: var.hpp:44
double val() const
Return the value of this variable.
Definition: var.hpp:234

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