Strange behavior of Foldable (,) a

The definion of Foldable (,) a is as follows.

instance Foldable ((,) a) where
    foldMap f (_, y) = f y
    foldr f z (_, y) = f y z

I am very confused with this definition. As a consequence, we have

maximum (1,0) == 0

I believe this is not something we want.

Trac metadata

Trac field	Value
Version	8.0.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Core Libraries
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	ekmett
Operating system
Architecture

changed weight to 5

added Tbug Trac import core libraries labels

closed

This has been discussed to death already:

• https://mail.haskell.org/pipermail/libraries/2016-February/026678.html
• https://mail.haskell.org/pipermail/libraries/2016-March/026851.html
• https://www.reddit.com/r/haskell/comments/3oq0kd/proposal_eliminate_the_monad_implementation_on/
• https://www.reddit.com/r/haskell/comments/3pfg7x/either_and_in_haskell_are_not_arbitrary/

Closing as wontfix, until there is consensus to remove the instance from the libraries list or the Core Libraries Committee.

Trac metadata

Trac field	Value
Resolution	Unresolved → ResolvedWon'tFix

Thx for clearing!

Replying to [ticket:12107#comment:120763 thomie]:

This has been discussed to death already:

• https://mail.haskell.org/pipermail/libraries/2016-February/026678.html
• https://mail.haskell.org/pipermail/libraries/2016-March/026851.html
• https://www.reddit.com/r/haskell/comments/3oq0kd/proposal_eliminate_the_monad_implementation_on/
• https://www.reddit.com/r/haskell/comments/3pfg7x/either_and_in_haskell_are_not_arbitrary/

Closing as wontfix, until there is consensus to remove the instance from the libraries list or the Core Libraries Committee.

added Pnormal label