[WIP] Add an UnorderedFoldable that we can give instances for Set/Map/&c - #2021
Closed
hrhino wants to merge 1 commit into
Closed
[WIP] Add an UnorderedFoldable that we can give instances for Set/Map/&c#2021hrhino wants to merge 1 commit into
hrhino wants to merge 1 commit into
Conversation
…/&c. `Set`, e.g., is not a lawful `Foldable`, since iteration order between multiple sets can be observed via `toList`. If we promise never to observe the order in which elements are folded, by strengthening the `Monoid` required by `foldMap` to a `CommutativeMonoid`, we can have a broader typeclass `UnorderedFoldable` that contains such unordered collections. Based entirely off a gitter comment.
Contributor
|
Are you aware of #1981? |
Contributor
Author
|
Mm... Now I am. Sorry about that! |
Contributor
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Set, e.g., is not a lawfulFoldable, since iteration order between multiple sets can be observed viatoList. If we promise never to observe the order in which elements are folded, by strengthening theMonoidrequired byfoldMapto aCommutativeMonoid, we can have a broader type classUnorderedFoldablethat contains such unordered collections.I mentioned this on gitter and no one said no. It's a work in progress:
bikesheddabledebatableUnorderedFoldableSuitesomewhere in thereTraverseRandomlyUnorderedTraverse?but I'm making a PR so people can say what they think about the idea before I put any more effort into it, rather than after.