为什么不对记录的属性进行模式匹配编译? [英] Why doesn't pattern matching on a property of a record compile?

问题描述

为什么不对记录的属性进行模式匹配?

type Cell = { X:int; Y:int }

let isNeighbor cell1 cell2 =
    match cell1.X, cell2.X with
    | cell1, cell2 when cell1.X <> cell2.X 
                    ||  cell1.Y <> cell2.Y -> let xAligned = IsValueNeighbor cell1.X cell2.X
                                              let yAligned = IsValueNeighbor cell1.Y cell2.Y

                                              xAligned && yAligned
    | _ -> false

错误:

类型'int'与类型'Cell'不兼容

The type 'int' is not compatible with the type 'Cell'

以下表达式似乎有问题:

The following expression appears to have an issue:

    cell1.X <> cell2.X 
||  cell1.Y <> cell2.Y

推荐答案

执行时

match cell1.X, cell2.X with
| cell1, cell2

您创建了一个新的cell1变量，它是cell1.X(一个整数).

you have created a new cell1 variable, which is cell1.X (an int).

我可能只是在这里使用了if，或者将其更改为| _,_ when ...

I would probably have just used an if here, or change to | _,_ when ...

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