Generalized swap

Generalized swap

2015-04-14 00:00:00 UTC, by Dimitri Sabadie


Generalized swap

I pushed a pull request to Edward Kmett’s either package to implement two functions some guys was complaining not to find: flipEither :: Either e a -> Either a e and flipEitherT :: EitherT e m a -> EitherT a m e.

When implementing the functions, I wondered: “Hey, flipping stuff is a pretty common operation. Don’t we have an abstraction for that yet?”. I haven’t found any.

Meet Swap

I decided to make a little typeclass to see what it’d be.

If you think that’s handy, I’ll write a little package with default instances to make it live.

Happy hacking folks!