num_elements.hpp

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#ifndef STAN_MATH_PRIM_FUN_NUM_ELEMENTS_HPP
#define STAN_MATH_PRIM_FUN_NUM_ELEMENTS_HPP
 
#include <stan/math/prim/fun/Eigen.hpp>
#include <stan/math/prim/meta.hpp>
#include <vector>
 
namespace stan {
namespace math {
 
template <typename T, require_stan_scalar_t<T>* = nullptr>
inline int num_elements(const T& x) {
  return 1;
}
 
template <typename T, require_matrix_t<T>* = nullptr>
inline int num_elements(const T& m) {
  return m.size();
}
 
template <typename T>
inline int num_elements(const std::vector<T>& v) {
  if (v.size() == 0) {
    return 0;
  }
  return v.size() * num_elements(v[0]);
}
 
}  // namespace math
}  // namespace stan
 
#endif