OCaml 的 List 数据类型，相当于Java 的List。我们看下实例

utop # let netrcItemList: netrcItem list = [];;
val netrcItemList : netrcItem list = []


utop # netrcItemList @ c
;;
Error: This expression has type netrcItem
       but an expression was expected of type netrcItem list


utop # netrcItemList @ [c]
;;
- : netrcItem list =
[{host = "localhost"; username = " root"; password = "admin"}]


utop # let newList: netrcItem list = netrcItemList @ [c];;
val newList : netrcItem list =
  [{host = "localhost"; username = " root"; password = "admin"}]


utop # let newList: netrcItem list = netrcItemList @ [a];;
val newList : netrcItem list =
  [{host = "www.baidu.com"; username = "admin"; password = "admin"}]


utop # let newList: netrcItem list = newList @ [c];;
val newList : netrcItem list =
  [{host = "www.baidu.com"; username = "admin"; password = "admin"};
   {host = "localhost"; username = " root"; password = "admin"}]


utop # let newList: netrcItem list = newList @ newList;;
val newList : netrcItem list =
  [{host = "www.baidu.com"; username = "admin"; password = "admin"};
   {host = "localhost"; username = " root"; password = "admin"};
   {host = "www.baidu.com"; username = "admin"; password = "admin"};
   {host = "localhost"; username = " root"; password = "admin"}]

 

基本的初始化语法是

let netrcItemList: netrcItem list = [];;

 

let  变量名 :  基本数据类型   list  =  [];

 

这样是初始化一个空的list

如果你知道里面有几个元素，可以在初始化的时候，就写进去。

 

否则，我们就可以后面用 @ 符号，把两个List合并进去。

很好的解答了第二个问题，我们怎么把一个新元素，加入到已经有的 List中去呢？ 用@ 符号，后面跟 一个只有一个元素的新 List就行了。

两个List会合并成一个

 

需要注意的是，你可能会问怎么从List中移除元素。对不起。 OCaml默认是数据不可变。

你可以创建一个新的List，然后过滤掉旧的List中不要的元素，把剩余的，塞到新的这个List中去。