F# 多维数组类型 [英] F# Multidimensional Array Types

问题描述

'a[,,] 和 'a[][][] 有什么区别?它们都表示 3 维数组.它让我写 array3d.[x].[y].[z] 而不是 array3d.[x, y, z].

What's the difference between 'a[,,] and 'a[][][]? They both represent 3-d arrays. It makes me write array3d.[x].[y].[z] instead of array3d.[x, y, z].

为什么我不能执行以下操作?

Why I can't do the following?

> let array2d : int[,] = Array2D.zeroCreate 10 10;;
> let array1d = array2d.[0];;

error FS0001: This expression was expected to have type
    'a []    
but here has type
    int [,]

推荐答案

区别在于 'a[][] 表示数组的数组(长度可能不同)，而在 'a[,]，表示一个矩形二维数组.第一种类型也称为锯齿数组，第二种类型称为多维数组.区别与 C# 中的相同，因此您可能需要查看 锯齿状数组 和 多维数组.F# WikiBook 中还有一个优秀的文档.

The difference is that 'a[][] represents an array of arrays (of possibly different lengths), while in 'a[,], represents a rectangular 2D array. The first type is also called jagged arrays and the second type is called multidimensional arrays. The difference is the same as in C#, so you may want to look at the C# documentation for jagged arrays and multidimensional arrays. There is also an excelent documentation in the F# WikiBook.

为了使用图片演示这一点，'a[][] 类型的值可以如下所示:

To demonstrate this using a picture, a value of type 'a[][] can look like this:

0 1 2 3 4
5 6
7 8 9 0 1

虽然 a[,] 类型的值将始终是一个矩形，并且可能如下所示:

While a value of type a[,] will always be a rectangle and may look for example like this:

0 1 2 3
4 5 6 7
8 9 0 1

<小时>

要获得多维数组的单个行"，您可以使用切片符号:

let row = array2d.[0,*];;

参见 https://docs.microsoft.com/en-us/dotnet/fsharp/language-reference/arrays#array-slicing-and-multidimensional-arrays

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