Stan Math Library  2.14.0
reverse mode automatic differentiation
acos.hpp
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1 #ifndef STAN_MATH_REV_SCAL_FUN_ACOS_HPP
2 #define STAN_MATH_REV_SCAL_FUN_ACOS_HPP
3 
4 #include <stan/math/rev/core.hpp>
5 #include <cmath>
6 #include <valarray>
7 
8 namespace stan {
9  namespace math {
10 
11  namespace {
12  class acos_vari : public op_v_vari {
13  public:
14  explicit acos_vari(vari* avi) :
15  op_v_vari(std::acos(avi->val_), avi) {
16  }
17  void chain() {
18  avi_->adj_ -= adj_ / std::sqrt(1.0 - (avi_->val_ * avi_->val_));
19  }
20  };
21  }
22 
59  inline var acos(const var& a) {
60  return var(new acos_vari(a.vi_));
61  }
62 
63  }
64 }
65 #endif
fvar< T > sqrt(const fvar< T > &x)
Definition: sqrt.hpp:14
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
fvar< T > acos(const fvar< T > &x)
Definition: acos.hpp:14

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