建立列表

> listOfNumbers = [1,4,99]
[1,4,99] : List number
>
> listOfStrings = ["Hello","World"]
["Hello","World"] : List String
>
> emptyList = []   -- can be anything, we don't know yet
[] : List a
>

在引擎蓋下，List（ 連結串列 ）由::函式（稱為 cons）構成，該函式有兩個引數：一個元素，稱為頭部，一個（可能為空）列表，頭部被預先新增。

> withoutSyntaxSugar = 1 :: []
[1] : List number
>
> longerOne = 1 :: 2 :: 3 :: []
[1,2,3] : List number
>
> nonemptyTail = 1 :: [2]
[1,2] : List number
>

List 只能取一種型別的值，所以像 [1,"abc"] 這樣的東西是不可能的。如果需要，請使用元組。

> notAllowed = [1,"abc"]
==================================== ERRORS ====================================

-- TYPE MISMATCH --------------------------------------------- repl-temp-000.elm

The 1st and 2nd elements are different types of values.

8|              [1,"abc"]
               ^^^^^
The 1st element has this type:

    number

But the 2nd is:

    String

Hint: All elements should be the same type of value so that we can iterate
through the list without running into unexpected values.

>