More class instances for Identity. #54
Merged
blamario merged 4 commits intoblamario:masterfrom Jan 11, 2025
Merged
Conversation
This commit removes trailing whitespace from a few files. In the interest of not polluting other commits, all such changes are grouped into this commit.
This commit uses `GeneralizedNewtypeDeriving` to make the `Identity`
newtype an instance of the following classes:
- `DistributiveGCDMonoid`
- `DistributiveLCMMonoid`
- `Factorial`
- `FactorialMonoid`
- `GCDMonoid`
- `LCMMonoid`
- `LeftDistributiveGCDMonoid`
- `LeftGCDMonoid`
- `Monus`
- `OverlappingGCDMonoid`
- `RightDistributiveGCDMonoid`
- `RightGCDMonoid`
The approach used is similar to that used in `base`, which uses
`GeneralizedNewtypeDeriving` for `Semigroup` and `Monoid` (among others):
```
newtype Identity a = Identity { runIdentity :: a }
deriving ( ...
, Semigroup -- ^ @SInCE base-4.9.0.0
, Monoid -- ^ @SInCE base-4.9.0.0
, ...
)
```
In practice, this mechanism generates method definitions that use
zero-cost coercions (see `Data.Coerce`).
This commit uses `GeneralizedNewtypeDeriving` to simplify all pre-existing class instance definitions for the `Identity` newtype.
jonathanknowles
commented
Jan 9, 2025
Owner
|
My intention was to keep the language extensions minimal in this library, but I guess that ship has sailed a long time ago. |
jonathanknowles
deleted the
jonathanknowles/more-instances-for-identity
branch
Contributor
Author
|
@blamario thanks for merging this! |
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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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.
This PR defines more class instances for the
Identitytype.The approach used is similar to
base, which usesGeneralizedNewtypeDerivingto auto-derive instances ofSemigroupandMonoidforIdentity:(See source here.)
In addition, this PR:
GeneralizedNewtypeDerivingto simplify the remaining existing class instances forIdentity.Identityclass instances.