2016-11-14 34 views

回答

1

要包含x新的int列表添加到int list list的頭:

# let x = 14 in 
let ill = [[3;4]; [5;6]] in 
[x] :: ill ;; 
- : int list list = [[14]; [3; 4]; [5; 6]] 

你也可以寫這:

# let x = 14 in 
let ill = [[3;4]; [5;6]] in 
[[x]] @ ill ;; 
- : int list list = [[14]; [3; 4]; [5; 6]] 

但這需要少量的不必要的工作。

作爲一條評論,您的if的兩個分支看起來像他們試圖做同樣的事情。如果你想要的結果是[[14; 3; 4]; [5; 6]]你需要編寫更多的代碼來解構int list list

# let x = 14 in 
let ill = [[3;4]; [5;6]] in 
match ill with 
| [] -> [[x]] 
| h :: t -> (x :: h) :: t ;; 
- : int list list = [[14; 3; 4]; [5; 6]]