sollya_lib_obj_is_function detects pi
sollya_lib_obj_is_function detects a constant
sollya_lib_obj_is_function detects free_variable
sollya_lib_obj_is_function detects D(_x_).
sollya_lib_obj_is_function detects S(_x_).
sollya_lib_obj_is_function detects QD(_x_).
sollya_lib_obj_is_function detects HP(_x_).
sollya_lib_obj_is_function detects DE(_x_).
sollya_lib_obj_is_function detects DD(_x_).
sollya_lib_obj_is_function detects TD(_x_).
sollya_lib_obj_is_function detects a constant expression.
