F# 中的递归和不变性

Question

考虑以下简单示例:

type Parent = { Children : Child list }
and Child = { Value : int ; Parent : Parent }

let rec children = [ { Value = 0 ; Parent = parent } ]
and parent = { Children = children }

F# 编译器足够聪明，可以正确初始化这些递归对象，这可以通过运行来验证

obj.ReferenceEquals(parent, parent.Children.Head.Parent)

现在，考虑以下概括:

let length = 100 // assume arbitrary

let rec children = List.init length (fun i -> { Value = i ; Parent = parent })
and parent = { Children = children }

此定义将导致编译器错误。我的问题如下:有什么方法可以在不诉诸反射或可变字段的情况下进行上述绑定(bind)？

Answer 1

let rec mkChild i = {Value = i; Parent = parent}
and parent = { Children = children }
and children = List.init length mkChild