Re: Add Data.Sequence.toList

I support this change largely for the motivations originally described https://github.com/haskell/containers/issues/744#issuecomment-689484639, particularly predictability and safety. I can't immediately think of a way this addition would be a liability. -Rick On Sat, Mar 7, 2026 at 9:01 PM chessai wrote:

I second this addition. Though I will note that there are potential performance improvements to be had for a monomorphic version due to specialisation and inlining - I typically prefer mononorphic toList when available. This and API uniformity are sufficient motivations to me (even just API uniformity alone).

Brandon, the libraries mailing list is archaic and mostly used now to request package takeovers or for CLC elections. Back in 2020 it was still used. I don't think posting here is necessary anymore (and it was almost never productive).

Cheers, chessai

On Sat, Mar 7, 2026, 3:56 PM Brandon Chinn wrote:

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My concern here isn't efficiency. Data.Sequence.toList should just be a reexport of Foldable.toList monomorphized to Seq. I just want a consistent API with other modules in containers.

I do see that Map.toList /= Foldable.toList. But Set.toList == Foldable.toList, and it's not obvious to me why Set should have toList and not Seq.

On Sat, Mar 7, 2026, 3:37 PM Dan Dart wrote:

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Well, it's got a Foldable instance already, which gives you a toList for anything Foldable, is it going to get any more efficientlythan this one? That's one of the few reasons to add extra functions already covered by type class instances, no?

Cheers

On Sat, 7 Mar 2026, 23:20 , wrote:

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An issue was opened on containers back in 2020 to add a monomorphic Data.Sequence.toList function: https://github.com/haskell/containers/issues/744. It was suggested to ask via the libraries list, and the previous reporter preferred to close the issue instead of continuing the process. I'm opening it back up: https://github.com/haskell/containers/issues/1184. Same motivation as the original issue; specifically, I always workaround this with

import Data.Foldable qualified as Seq (toList) import Data.Sequence (Seq) import Data.Sequence qualified as Seq

It's odd that Data.Sequence doesn't provide toList when Map and Set do. Are there any objections to this?

Best, Brandon Chinn _______________________________________________ Libraries mailing list -- libraries@haskell.org To unsubscribe send an email to libraries-leave@haskell.org

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