dot_self.hpp

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#ifndef STAN_MATH_PRIM_FUN_DOT_SELF_HPP
#define STAN_MATH_PRIM_FUN_DOT_SELF_HPP
 
#include <stan/math/prim/meta.hpp>
#include <stan/math/prim/err.hpp>
#include <stan/math/prim/fun/Eigen.hpp>
#include <cstddef>
#include <vector>
 
namespace stan {
namespace math {
 
template <typename T, require_stan_scalar_t<T>* = nullptr>
inline T dot_self(const T& x) {
  return x * x;
}
 
inline double dot_self(const std::vector<double>& x) {
  double sum = 0.0;
  for (double i : x) {
    sum += i * i;
  }
  return sum;
}
 
template <typename T, require_eigen_t<T>* = nullptr,
          require_not_eigen_vt<is_var, T>* = nullptr>
inline value_type_t<T> dot_self(T&& v) {
  return make_holder([](auto&& v_) { return v_.squaredNorm(); },
                     to_ref(std::forward<T>(v)));
}
 
}  // namespace math
}  // namespace stan
 
#endif