Gurkenglas

swap actually sounds like it ought to be generalized into `Data.Bifunctor`, but that's not possible just by the class definition. Do all instances have that possibility in common?

If the automation's going to happen, it should probably be rolled out in the same format and release as [this feature](https://github.com/aelve/haskell-issues/issues/46).

Yea, those all sound like they ought to be made explicit with _ or void, although I'm not sure about char/satisfy. The mapM_ reminds me: - mapM_ :: (Monad m,...

`

[Eureka!](http://lpaste.net/350469) [Actually looks like Edward Kmett already wrote that 8 years ago.](http://hackage.haskell.org/package/indexed-extras-0.2/docs/Control-Monad-Indexed-Cont.html)

``` evaluateMyLanguage :: Fix MyLanguage -> Int evaluateMyLanguage = cata $ \case Literal i -> i Add x y -> x + y Mul x y -> x * y...

`liftMaybe = maybe empty pure` isJustT/isNothingT proliferate boolean blindness and ought not to be needed in modern code - post an example where you would use it, and I'll see...

In that same vein: `fromMaybeT :: Monad m => m a -> MaybeT m a -> m a` (`fromMaybeT` = `flip ()`)

Of course the library author wouldn't *manually* implement the updater, they'd just specify it in a way that GHC can then apply with a system like the rewrite rules one.

The updater would run after CPP, of course.