text: #ifndef STAN_MATH_PRIM_SCAL_FUN_IDENTITY_CONSTRAIN_HPP
  #define STAN_MATH_PRIM_SCAL_FUN_IDENTITY_CONSTRAIN_HPP
  
  #include <stan/math/prim/meta.hpp>
  namespace stan {
  namespace math {
  
  /**
   * Returns the result of applying the identity constraint
   * transform to the input.
   *
   * <p>This method is effectively a no-op and is mainly useful as a
   * placeholder in auto-generated code.
   *
   * @tparam T Type of scalar.
   * @param[in] x free scalar
   * @return transformed input
   */
  template <typename T>
  inline T identity_constrain(const T& x) {
    return x;
  }
  
  /**
   * Returns the result of applying the identity constraint
   * transform to the input and increments the log probability
   * reference with the log absolute Jacobian determinant.
   *
   * <p>This method is effectively a no-op and mainly useful as a
   * placeholder in auto-generated code.
   *
   * @tparam T type of scalar.
   * @param[in] x scalar
   * @return transformed input
   */
  template <typename T>
  inline T identity_constrain(const T& x, T& /*lp*/) {
    return x;
  }
  
  }  // namespace math
  
  }  // namespace stan
  
  #endif
  