multiply_log.hpp

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#ifndef STAN_MATH_PRIM_FUN_MULTIPLY_LOG_HPP
#define STAN_MATH_PRIM_FUN_MULTIPLY_LOG_HPP
 
#include <stan/math/prim/meta.hpp>
#include <stan/math/prim/fun/log.hpp>
#include <stan/math/prim/functor/apply_scalar_binary.hpp>
#include <cmath>
 
namespace stan {
namespace math {
 
template <typename T_a, typename T_b,
          require_all_arithmetic_t<T_a, T_b>* = nullptr>
inline return_type_t<T_a, T_b> multiply_log(const T_a a, const T_b b) {
  using std::log;
  if (b == 0.0 && a == 0.0) {
    return 0.0;
  }
 
  return a * log(b);
}
 
template <typename T1, typename T2, require_any_container_t<T1, T2>* = nullptr,
          require_all_not_var_matrix_t<T1, T2>* = nullptr>
inline auto multiply_log(T1&& a, T2&& b) {
  return apply_scalar_binary(
      [](auto&& c, auto&& d) {
        return multiply_log(std::forward<decltype(c)>(c),
                            std::forward<decltype(d)>(d));
      },
      std::forward<T1>(a), std::forward<T2>(b));
}
 
}  // namespace math
}  // namespace stan
 
#endif