This https://hackage.haskell.org/package/vec-0.4/docs/Data-Vec-DataFamily-SpineSt... in Hackage is something a rank amateur like me can't fathom. ... Anyone know how I can figure this mystery out, like at least find the author or someone that knows something about this?

Regarding this part of the question, if you click the "Contents" link at the top of the page to which you linked, it will take you to the package main page (https://hackage.haskell.org/package/vec-0.4). The column on the right gives the author's name and email address, and a link to the source repository (https://github.com/phadej/vec). The main column on that page gives the package description, which may help explain and motivate what is going on a bit more. In this case it also links to some relevant papers. Hope this helps, Adam On 29/11/2021 04:59, David Feuer wrote:

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 mailto:borgauf@gmail.com> wrote:

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---------- Forwarded message ---------- From: Galaxy Being mailto:borgauf@gmail.com> To: haskell-cafe mailto: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 https://hackage.haskell.org/package/vec-0.4/docs/Data-Vec-DataFamily-SpineSt... 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 borgauf@gmail.com mailto:borgauf@gmail.com

-- Adam Gundry, Haskell Consultant Well-Typed LLP, https://www.well-typed.com/ Registered in England & Wales, OC335890 118 Wymering Mansions, Wymering Road, London W9 2NF, England