相关疑难解决方法(0)

可以具有以下多态函数

let id x = x;;
let compose f g x = f (g x);;
let rec fix f = f (fix f);;     (*laziness aside*)

是为类型/类型构造函数或模块/仿函数编写的？我试过了

type 'x id = Id of 'x;;
type 'f 'g 'x compose = Compose of ('f ('g 'x));;
type 'f fix = Fix of ('f (Fix 'f));;

对于类型但它不起作用.

这是类型的Haskell版本:

data Id x = Id x
data Compose f g x = Compose (f (g x))
data Fix f = Fix (f (Fix f))

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