Is there a method which would "columnize" an IEnumerable?

[andlehma]

For example, if I were writing a Tic Tac Toe implementation which takes an input IEnumerable where the indices are mapped like:
0 | 1 | 2
3 | 4 | 5
6 | 7 | 8

Rows are easy to check, but I don't know of a single-method way to get the columns. I have settled on the following:

var columns = gameState.Select((val, idx) => new { index = idx, value = val})
  .GroupBy(x => x.index % 3)
  .Select(x => x.Select(y => y.value));

I wonder if there is a cleaner way to do this. LINQ's GroupBy does not have access to the index of each element, so I can't do index % 3 or something similar. I'm not sure how frequent of a use case this is, but it might be worth considering adding a Columnize method to MoreLINQ, or maybe just a GroupBy method which exposes the index of each elemenet.

[viceroypenguin]

.Batch() would do the trick.

In this case, it would be var columns = gameState.Batch(3);

[andlehma]

Actually, Batch gives me the rows. I'm looking for the columns, i.e. indices 0, 3, 6 would be one column, indices 1, 4, 7 another column.

[viceroypenguin]

Oh! Then yes, I believe your code would be the simplest way that does a one-time pass through the enumerable. You could use .TakeEvery() and use a separate pass for each column, but I would probably recommend what you have instead.

[atifaziz]

I believe you're looking for Transpose:

const string gameStateString = @"
    0 | 1 | 2
    3 | 4 | 5
    6 | 7 | 8 ";

var gameState =
    from m in Regex.Matches(gameStateString, @"[0-9]+")
    select int.Parse(m.Value);

var rows = gameState.Batch(3);
var columns = rows.Transpose();