text: #ifndef STAN_MATH_PRIM_FUN_COL_HPP
  #define STAN_MATH_PRIM_FUN_COL_HPP
  
  #include <stan/math/prim/err.hpp>
  #include <stan/math/prim/fun/Eigen.hpp>
  
  namespace stan {
  namespace math {
  
  /**
   * Return the specified column of the specified matrix
   * using start-at-1 indexing.
   *
   * This is equivalent to calling <code>m.col(i - 1)</code> and
   * assigning the resulting template expression to a column vector.
   *
   * @tparam T type of the matrix
   * @param m Matrix.
   * @param j Column index (count from 1).
   * @return Specified column of the matrix.
   * @throw std::out_of_range if j is out of range.
   */
  template <typename T, typename = require_eigen_t<T>>
  inline auto col(const T& m, size_t j) {
    check_column_index("col", "j", m, j);
    return m.col(j - 1).eval();
  }
  
  }  // namespace math
  }  // namespace stan
  
  #endif
  