]   \\ rw [] \\ fs [] \\ rveq \\ fs [LENGTH_EQ_NUM_compute] \\ rveq \\ fs []   \\ fs [v_rel_def] \\ rveq \\ fs [PULL_EXISTS]   \\ fs [compile_op_def,evaluate_def,do_app_def,arg0_def]   \\ imp_res_tac LIST_REL_LENGTH \\ fs [SWAP_REVERSE_SYM,list_case_eq]   \\ rveq \\ fs [