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falling_factorial.hpp
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1 #ifndef STAN_MATH_FWD_SCAL_FUN_FALLING_FACTORIAL_HPP
2 #define STAN_MATH_FWD_SCAL_FUN_FALLING_FACTORIAL_HPP
3
4 #include <stan/math/fwd/core.hpp>
5
6 #include <stan/math/prim/scal/fun/falling_factorial.hpp>
7 #include <boost/math/special_functions/digamma.hpp>
8
9 namespace stan {
10
11 namespace math {
12
13 template<typename T>
14 inline fvar<T>
15 falling_factorial(const fvar<T>& x, const fvar<T>& n) {
16 using stan::math::falling_factorial;
17 using boost::math::digamma;
18
19 T falling_fact(falling_factorial(x.val_, n.val_));
20 return fvar<T>(falling_fact, falling_fact * digamma(x.val_ + 1) * x.d_
21 - falling_fact * digamma(n.val_ + 1) * n.d_);
22 }
23
24 template<typename T>
25 inline fvar<T>
26 falling_factorial(const fvar<T>& x, const double n) {
27 using stan::math::falling_factorial;
28 using boost::math::digamma;
29
30 T falling_fact(falling_factorial(x.val_, n));
31 return fvar<T>(falling_fact,
32 falling_fact * digamma(x.val_ + 1) * x.d_);
33 }
34
35 template<typename T>
36 inline fvar<T>
37 falling_factorial(const double x, const fvar<T>& n) {
38 using stan::math::falling_factorial;
39 using boost::math::digamma;
40
41 T falling_fact(falling_factorial(x, n.val_));
42 return fvar<T>(falling_fact,
43 -falling_fact * digamma(n.val_ + 1) * n.d_);
44 }
45 }
46 }
47 #endif
falling_factorial.hpp
core.hpp
stan::math::fvar::d_
T d_
Definition: fvar.hpp:15
stan::math::fvar::val_
T val_
Definition: fvar.hpp:14
stan::math::falling_factorial
fvar< T > falling_factorial(const fvar< T > &x, const fvar< T > &n)
Definition: falling_factorial.hpp:15
stan::math::fvar
Definition: fvar.hpp:13
stan::math::digamma
fvar< T > digamma(const fvar< T > &x)
Definition: digamma.hpp:16

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