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hypot.hpp
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1 #ifndef STAN_MATH_REV_SCAL_FUN_HYPOT_HPP
2 #define STAN_MATH_REV_SCAL_FUN_HYPOT_HPP
3 
4 #include <math.h>
5 #include <stan/math/rev/core.hpp>
6 #include <cmath>
7 #include <valarray>
8 
9 namespace stan {
10  namespace math {
11 
12  namespace {
13  class hypot_vv_vari : public op_vv_vari {
14  public:
15  hypot_vv_vari(vari* avi, vari* bvi) :
16  op_vv_vari(::hypot(avi->val_, bvi->val_),
17  avi, bvi) {
18  }
19  void chain() {
20  avi_->adj_ += adj_ * avi_->val_ / val_;
21  bvi_->adj_ += adj_ * bvi_->val_ / val_;
22  }
23  };
24 
25  class hypot_vd_vari : public op_v_vari {
26  public:
27  hypot_vd_vari(vari* avi, double b) :
28  op_v_vari(::hypot(avi->val_, b),
29  avi) {
30  }
31  void chain() {
32  avi_->adj_ += adj_ * avi_->val_ / val_;
33  }
34  };
35  }
36 
53  inline var hypot(const var& a, const var& b) {
54  return var(new hypot_vv_vari(a.vi_, b.vi_));
55  }
56 
71  inline var hypot(const var& a, double b) {
72  return var(new hypot_vd_vari(a.vi_, b));
73  }
74 
116  inline var hypot(double a, const var& b) {
117  return var(new hypot_vd_vari(b.vi_, a));
118  }
119 
120  }
121 }
122 #endif
fvar< T > hypot(const fvar< T > &x1, const fvar< T > &x2)
Definition: hypot.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

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