F# 将活动模式匹配为扩展元组

Question

我在 diff 中收到以下错误，并在子集下出现红色曲线。
类型不匹配。期望范围 ->选择但给定范围 * 范围 -> Choice

是否有某种类型注释可以添加到子集匹配中，这样我就不必使用 fst 和 snd ？如果没有，是否打算支持这种语法？

type Range = {min : int64; max : int64}

let (|Before|After|BeforeOverlap|AfterOverlap|SuperSet|SubSet|) (x, y) = 
    if x.min > y.max then After
    elif x.min >= y.min then
        if x.max <= y.max then SubSet
        else AfterOverlap
    elif x.max < y.min then Before
    elif x.max <= y.max then BeforeOverlap
    else SuperSet

let useOldx x xe ye = ()

let diff (xe:IEnumerator<Range>) (ye:IEnumerator<Range>) =
    match xe.Current, ye.Current with
    | After as tuple -> ()
    | Before as t -> if xe.MoveNext() then useOldx (fst t) xe ye
    | SuperSet as t -> 
        let x, y = t
        if xe.MoveNext() then useOldx x xe ye
    | SubSet as x, y -> if xe.MoveNext() then useOldx x xe ye
    | _ -> ()

Answer 1

你可以这样做：

    | (x,y) & SubSet -> if xe.MoveNext() then useOldx x xe ye

或者你可以这样做：

open System.Collections.Generic 

type Range = {min : int64; max : int64}

let (|Before|After|BeforeOverlap|AfterOverlap|SuperSet|SubSet|) (x, y) = 
    if x.min > y.max then After
    elif x.min >= y.min then
        if x.max <= y.max then SubSet(x,y)
        else AfterOverlap
    elif x.max < y.min then Before
    elif x.max <= y.max then BeforeOverlap
    else SuperSet

let useOldx x xe ye = ()

let diff (xe:IEnumerator<Range>) (ye:IEnumerator<Range>) =
    match xe.Current, ye.Current with
    | After as tuple -> ()
    | Before as t -> if xe.MoveNext() then useOldx (fst t) xe ye
    | SuperSet as t -> 
        let x, y = t
        if xe.MoveNext() then useOldx x xe ye
    | SubSet(x, y) -> if xe.MoveNext() then useOldx x xe ye
    | _ -> ()