list 生成列表
push 入栈
pop 出栈
append 连接
reverse 不修改列表值反转
nreverse 修改列表值反转
sort 修改，排序
copy-sequence 返回列表 
(setq a (list 1 2 3))
(push '4 a)
(pop a)

(append '(a b) '(c) '(d))               ; => (a b c d)
(append '(a b) 'c)                      ; => (a b . c)