])   THEN0    (fs [evaluate_def,do_app_def,integerTheory.int_le]     \\ rename [`¬(k < 0)`]     \\ `Num (ABS k) < LENGTH ws' <=> k < &LENGTH ws'` by intLib.COOPER_TAC     \\ fs [GREATER_EQ,GSYM NOT_LESS]     \\ `ABS k = k` by intLib.COOPER_TAC \\ simp [])   THEN0    (fs [evaluate_def,do_app_def,integerTheory.int_le]     \\ 