is_emptyniltrueis_emptyconsxlfalsehdconsxlxtlconsxllappendl1l2ifappendl1l2is_emptyl1ifappendl1l2truel2ifappendl1l2falseconshdl1appendtll1l2is_empty1nil0true0cons2false0hd1tl1append2ifappend3FULL./TRS/Cime/append-hard.trs