`second`/`right` derived from `first`/`left`
Nobody has claimed this yet.
Assessment
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Newbie friendliness
- 28/100
- Issue type
- Feature
- Clarity
- Mostly clear
- Activity status
- Stale
- Domain
- backend
Research direction
The issue asks whether Strong and Choice can derive second and right from first and left, and whether PureScript’s lack of default type class implementations explains the current design. Start by reading the Strong and Choice definitions and their implementations; the issue names no files or tests. Done means establishing the design reason and whether changing the class definitions is viable.
Written by the indexing model from the issue text.
Description
Is there any reason why Strong/Choice require second/right and not instead derive them from first/left?
secondBasedOnFirst :: forall p a b c. Strong p => p a b -> p (Tuple c a) (Tuple c b)
-- equivalent to `second`?
secondBasedOnFirst = dimap swap swap <<< first
where
swap :: forall x y. Tuple x y -> Tuple y x
swap (Tuple a b) = Tuple b a
rightBasedOnLeft :: forall p a b c. Choice p => p a b -> p (Either c a) (Either c b)
-- equivalent to `right`?
rightBasedOnLeft = dimap flip flip <<< left
where
flip :: forall x y. Either x y -> Either y x
flip (Left a) = Right a
flip (Right b) = Left b
Is this only because of lack of default type class member implementations feature in PureScript or is there any other reason?
- Dominant language
- PureScript
- Stars
- 34
- Forks
- 13
- Avg merge
- 3d 10m
- Merged PRs (30d)
- 1
Getting set up
- No Dockerfile or Docker Compose file
- Has a pull request template
- No contributing guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
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