types - OCaml 前向声明

Question

有没有办法在 OCaml 中进行 C 风格的前向声明？

我的问题是我有两个相互引用的变体:

type path_formula =
  [ `Next of state_formula
  | `Until of (state_formula * state_formula)
  | `UntilB of (state_formula * int * state_formula)  
  ]

type state_formula = 
    [ `True | `False
    | `Not of state_formula
    | `And of (state_formula * state_formula)
    | `Or of (state_formula * state_formula)
    | `Imply of (state_formula * state_formula)
    | `Label of string
    | `Prob` of (boundf * path_formula)
    | `Expc` of (boundi * formula)
    ]

所以两种类型都必须知道另一种类型..我在 Google 上搜索了它，但不幸的是 OCaml 并不是一种广泛使用的编程语言..

Answer 1

使用

type T1 = ...
and T2 = ...

具有递归类型。