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Array2D module
f#

What is the reason for not having min, max, sum, fold, reduce, etc. for Array2D? It seems like most of the utility functions for Array would also make sense for Array2D, and I find myself writing a fold function.

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Hi,

I suggest you to write a to_seq conversion function:

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let array2D_to_seq arr =
  seq {for i in 0..Array2D.length1 arr - 1 do
       for j in 0..Array2D.length2 arr - 1 do yield arr.[i,j]}

This way, you'll be able to use Seq.max, Seq.fold, Seq.sum, etc.

Laurent.

By on 9/2/2009 2:35 PM ()

Thanks. That's much better than rewriting then all.

By on 9/3/2009 12:20 PM ()

I like to (ab?)use Seq.cast to flatten an Array2D:

For example:

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> let flatten (A:'a[,]) = A |> Seq.cast<'a>;;


val flatten : 'a [,] -> seq<'a>


> let arr = Array2D.init 3 2 (fun i j -> (i,j));;


val arr : (int * int) [,] = [[(0, 0); (0, 1)]
                             [(1, 0); (1, 1)]
                             [(2, 0); (2, 1)]]


> flatten arr;;


val it : seq<int * int> = seq [(0, 0); (0, 1); (1, 0); (1, 1); ...]
By on 9/3/2009 1:40 PM ()

Is Seq.cast a reliable way to flatten the 2d array?

By on 9/4/2009 7:38 AM ()

A quote from the C# spec:

The order in which foreach traverses the elements of an array, is as follows:
For single-dimensional arrays elements are traversed in increasing index order, starting with index 0 and ending with index Length – 1.
For multi-dimensional arrays, elements are traversed such that the indices of the rightmost dimension are increased first, then the next left dimension, and so on to the left.

I think this means that casting an Array2D to a seq should behave as expected.

By on 9/4/2009 10:38 AM ()

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