operator_multiplication.hpp

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#ifndef STAN_MATH_REV_CORE_OPERATOR_MULTIPLICATION_HPP
#define STAN_MATH_REV_CORE_OPERATOR_MULTIPLICATION_HPP
 
#include <stan/math/prim/meta.hpp>
#include <stan/math/rev/core/var.hpp>
#include <stan/math/rev/core/operator_addition.hpp>
#include <stan/math/rev/core/operator_subtraction.hpp>
#include <stan/math/rev/core/operator_plus_equal.hpp>
#include <stan/math/rev/core/operator_minus_equal.hpp>
#include <stan/math/rev/core/vv_vari.hpp>
#include <stan/math/rev/core/vd_vari.hpp>
#include <stan/math/prim/core/operator_multiplication.hpp>
#include <stan/math/prim/fun/constants.hpp>
#include <stan/math/prim/fun/is_any_nan.hpp>
#include <stan/math/prim/fun/isinf.hpp>
#include <stan/math/prim/fun/isnan.hpp>
 
namespace stan {
namespace math {
 
namespace internal {
class multiply_vv_vari final : public op_vv_vari {
 public:
  multiply_vv_vari(vari* avi, vari* bvi)
      : op_vv_vari(avi->val_ * bvi->val_, avi, bvi) {}
  void chain() {
    avi_->adj_ += bvi_->val_ * adj_;
    bvi_->adj_ += avi_->val_ * adj_;
  }
};
 
class multiply_vd_vari final : public op_vd_vari {
 public:
  multiply_vd_vari(vari* avi, double b) : op_vd_vari(avi->val_ * b, avi, b) {}
  void chain() { avi_->adj_ += adj_ * bd_; }
};
}  // namespace internal
 
inline var operator*(const var& a, const var& b) {
  return {new internal::multiply_vv_vari(a.vi_, b.vi_)};
}
 
template <typename Arith, require_arithmetic_t<Arith>* = nullptr>
inline var operator*(const var& a, Arith b) {
  if (b == 1.0) {
    return a;
  }
  return {new internal::multiply_vd_vari(a.vi_, b)};
}
 
template <typename Arith, require_arithmetic_t<Arith>* = nullptr>
inline var operator*(Arith a, const var& b) {
  if (a == 1.0) {
    return b;
  }
  return {new internal::multiply_vd_vari(b.vi_, a)};  // by symmetry
}
 
inline std::complex<stan::math::var> operator*(
    const std::complex<stan::math::var>& x,
    const std::complex<stan::math::var>& y) {
  return internal::complex_multiply(x, y);
}
 
inline std::complex<stan::math::var> operator*(
    const std::complex<double>& x, const std::complex<stan::math::var>& y) {
  return internal::complex_multiply(x, y);
}
 
inline std::complex<stan::math::var> operator*(
    const std::complex<stan::math::var>& x, const std::complex<double>& y) {
  return internal::complex_multiply(x, y);
}
 
}  // namespace math
}  // namespace stan
#endif