lambda_eval_tvar Function

      function lambda_eval_tvar(self, x, t) result(y)
         implicit none
         ! Arguments
         class(lambda_obj_tvar), intent(inout) :: self
         real(DP), dimension(:), intent(in) :: x
         real(DP),               intent(in) :: t
         ! Result
         real(DP), dimension(:), allocatable :: y
         if (associated(self%lambdaptr_tvar)) then
            y = self%lambdaptr_tvar(x,t)
         else
            stop "Lambda function was not initialized"
         end if
      end function lambda_eval_tvar