Re: [elixir-core:11012] offset for Enum.chunk_every

[Boris Kuznetsov]

Out of curiosity, what is the usecase where such function will be useful?

On 14 Aug 2022, at 05:51, Konstantin Astafurov <konstantin...@gmail.com> wrote:

I've noticed that in some cases, the chunking functionality provided by Enum.chunk_every isn't enough. For example, It'd be awesome if chunk_every could offset the window.

so [1,2,3,4,5] with count 3 step 2 and offset of -2 would return

[1], [1,2], [1,2,3], [2,3,4], [3,4,5], [4,5], [5]

Elements in the leftover option would be to the left of the initial chunks less than count. It'd also be neat if you could have different leftover options for the left-hand and right-hand leftovers.

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[Konstantin Astafurov]

ah shoot, I realized I didn't put [proposal] in the header so I deleted this and then added more stuff including a use case.

To summarize, let's say you want to make Conway's game of life. There are many ways of doing it, but I did it by chunking each row into windows of size 3 and then doing various operations. The problem is, that the first and last windows should have a size of 2, as the first cell in a row only has a neighbor ahead of it (we can also make stuff wrap around, using this proposed chunk_every function, but ill explain that part later). So I wrote this setup_arr function that makes an incomplete window, pads it, and pads the incomplete window at the end of the chunks.

Example:

[0,1,0,1,0,0]

would turn into:

[0,1], [0,1,0] [1,0,1], [0,1,0], [1,0,0], [0,0]

But with the leftover options, we could also add 0s (as the neighbor that doesn't exist isn't alive)

[0,0,1], [0,1,0] [1,0,1], [0,1,0], [1,0,0], [0,0,0]

https://github.com/konstantin-aa/gamesoflife/blob/main/main.exs?fbclid=IwAR0BxNfsrAxY_ugCu-PyFP7TmvncagjwdlU5SegdovGrUV6zuDB9soUUEYg

tweaked proposal:
https://groups.google.com/g/elixir-lang-core/c/MAHgFIsThPo

[Konstantin Astafurov]

to wrap around we can just pad the left side with the last cell of the row, and pad the right side with the first cell