#ifndef STAN_MATH_PRIM_MAT_FUN_UNIT_VECTOR_FREE_HPP
#define STAN_MATH_PRIM_MAT_FUN_UNIT_VECTOR_FREE_HPP

#include <stan/math/prim/mat/fun/Eigen.hpp>
#include <stan/math/prim/mat/meta/index_type.hpp>
#include <stan/math/prim/mat/err/check_unit_vector.hpp>
#include <cmath>

namespace stan {

  namespace math {

    /**
     * Transformation of a unit length vector to a "free" vector
     * However, we are just fixing the unidentified radius to 1.
     * Thus, the transformation is just the identity
     *
     * @param x unit vector of dimension K
     * @return Unit vector of dimension K considered "free"
     * @tparam T Scalar type.
     **/
    template <typename T>
    Eigen::Matrix<T, Eigen::Dynamic, 1>
    unit_vector_free(const Eigen::Matrix<T, Eigen::Dynamic, 1>& x) {
      stan::math::check_unit_vector("stan::math::unit_vector_free",
                                    "Unit vector variable", x);
      return x;
    }

  }

}

#endif
