No, this seems to have nothing to do with the pigeonhole principle. It seems to be about the sizes of length-indexed vectors. The "pigeonhole size" is just the vector length, available at the type level. This all seems to be about matching up vectors to representable functors. So it would match up

    data Foo a = Foo a a a a

to the type of vectors of length 4, giving functions to convert between them. I'm ... not exactly sure what purpose this serves.

On Sun, Nov 28, 2021, 11:07 PM Galaxy Being <borgauf@gmail.com> wrote:
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Content preview:  This <https://hackage.haskell.org/package/vec-0.4/docs/Data-Vec-DataFamily-SpineStrict-Pigeonhole.html>
   in Hackage is something a rank amateur like me can't fathom. I just hit a
   chapter in a book that dives into the Pigeonhole Principle. Is this the "accompanying
   Haskell Wundercode" for the math world's PHP? I know PHP is a big deal in
   math. I don't see an "author," and I see no documentation. Anyone know how
   I can figure this mystery out, like at least find the author or someone that
   knows something about this? [...]

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---------- Forwarded message ----------
From: Galaxy Being <borgauf@gmail.com>
To: haskell-cafe <haskell-cafe@haskell.org>
Cc: 
Bcc: 
Date: Sun, 28 Nov 2021 22:05:44 -0600
Subject: What is Data.Vec.DataFamily.SpineStrict.Pigeonhole and why is it following me?
This in Hackage is something a rank amateur like me can't fathom. I just hit a chapter in a book that dives into the Pigeonhole Principle. Is this the "accompanying Haskell Wundercode" for the math world's PHP? I know PHP is a big deal in math. I don't see an "author," and I see no documentation. Anyone know how I can figure this mystery out, like at least find the author or someone that knows something about this?

--
⨽
Lawrence Bottorff
Grand Marais, MN, USA
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