ocaml错误：该表达式有类型expr，但在这里与类型单元 - > expr

Question

一起使用我无法弄清楚这个错误的含义，我从来没有看到它在 之前所抱怨的那一行是包含x - >让 我之前使用的是匹配，但它仍然给我同样的错误。

let rec build (rand,depth) = match depth with 
| 0 -> if rand(0,2) == 0 then buildX else buildY 
| x -> let r = rand(0, 5) in 
    if r == 0 then buildSine (build (rand, x -1)) 
    else if r == 1 then buildCosine (build (rand, x -1)) 
    else if r == 2 then buildAverage (build (rand,x -1), build (rand,x-1)) 
    else if r == 3 then buildTimes (build (rand, x -1), build (rand, x-1)) 
    else buildThresh (build(rand, x-1), build(rand, x-1),    
        build(rand, x-1), build(rand, x-1));; 

我的每一个的来建立回报EXPR，这是应该建立一个大EXPR 任何帮助将不胜感激。提前致谢！ ：D

Answer 1

也许buildX和buildY应该采取一个参数？

# let f() = 14;; 
val f : unit -> int = <fun> 
# f ;; 
- : unit -> int = <fun> 
# f();; 
- : int = 14