Re: [Haskell-cafe] Where are rank-3 types necessary in practice for maintaining abstraction?

Ah. My misrecollection. In that case, the highest rank example I can find is in "Practical type inference for arbitrary-rank types", and it's rank-3. On Tue, Apr 3, 2018, 09:30 Erik Hesselink wrote:

The paper is here [1]. However, this is a sixth order function but not rank-6 polymorphism (rank 6 type) IIUC.

Erik

[1] https://www.westpoint.edu/eecs/SiteAssets/SitePages/Faculty%20Publication%20...

On 3 April 2018 at 17:10, Alex Rozenshteyn wrote:

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There's an easy to read paper by Okasaki titled "Even higher-order functions for parsing or Why would anyone ever want to use a sixth-order function?". Unfortunatly I can't find a link to a non-paywalled version. It shows how parser combinators themselves use rank-3 types and how defining a monad instance requires rank-6.

On Tue, Apr 3, 2018 at 1:05 AM Joachim Durchholz wrote:

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Am 03.04.2018 um 08:54 schrieb Timotej Tomandl:

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Ok, I thought about it a bit more and realized mask in Control.Exception is the one where rank-3 is necessary, which is the example I was looking for.

Given your newly acquired insights, do you expect that there will be ultimately a valid example for higher ranks? Is there a theoretical limit? Or a practical one? E.g. it might be too awkward to mentally handle higher-rank polymorphism - or maybe there's no real mental difference when dealing with higher-ranked polymorphism, I don't know because I didn't have to deal with that yet, so I'm curious.

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Sorry for the spam.

Actually it was interesting.

Regards, Jo _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.

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