beta.hpp

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#ifndef STAN_MATH_FWD_FUN_BETA_HPP
#define STAN_MATH_FWD_FUN_BETA_HPP
 
#include <stan/math/fwd/meta.hpp>
#include <stan/math/fwd/core.hpp>
#include <stan/math/prim/fun/beta.hpp>
#include <stan/math/prim/fun/digamma.hpp>
 
namespace stan {
namespace math {
 
template <typename T>
inline fvar<T> beta(const fvar<T>& x1, const fvar<T>& x2) {
  const T beta_ab = beta(x1.val_, x2.val_);
  return fvar<T>(beta_ab,
                 beta_ab
                     * (x1.d_ * digamma(x1.val_) + x2.d_ * digamma(x2.val_)
                        - (x1.d_ + x2.d_) * digamma(x1.val_ + x2.val_)));
}
 
template <typename T>
inline fvar<T> beta(double x1, const fvar<T>& x2) {
  const T beta_ab = beta(x1, x2.val_);
  return fvar<T>(beta_ab,
                 x2.d_ * (digamma(x2.val_) - digamma(x1 + x2.val_)) * beta_ab);
}
 
template <typename T>
inline fvar<T> beta(const fvar<T>& x1, double x2) {
  const T beta_ab = beta(x1.val_, x2);
  return fvar<T>(beta_ab,
                 x1.d_ * (digamma(x1.val_) - digamma(x1.val_ + x2)) * beta_ab);
}
 
}  // namespace math
}  // namespace stan
#endif