OCaml中創建斐波那契數的列表

Question

我有一個生成Fibonacci數的函數：

let rec fib n = 
    match n with 
    | (0 | 1) -> 1 
    | x when x > 0 -> (fib (x-2) + fib (x-1)) 
    | _ -> raise (Invalid_argument "Negative value supplied to fib");; 

但我真正想要的是它返回說號碼列表。我嘗試這樣做：

let rec fib n list = 
    match n with 
    | (0 | 1) -> 1 :: [] 
    | x when x > 0 -> (fib (x-2) list + fib (x-1) list) :: list 
    | _ -> raise (Invalid_argument "Negative value supplied to fib");; 

但ocamlc

File "main.ml", line 2, characters 4-174: Error: This expression has type int list but an expression was expected of type int

（2個線字符4-174對應匹配塊）說。我想這個返回類型「int list」，爲什麼它推斷類型int？

Answer 1

表達fib (x - 2) list + fib (x - 1) list要求fib返回int，因爲(+)需要int作爲參數。