Gurkenglas

You have answered your question :3

(Oh and you can find me as Gurkenglas on Freenode's #haskell.)

``` def setter_traversal(setter): def folder(state): acc = [] setter(acc.append, state) return iter(acc) def builder(state, values): iterator = iter(values) return setter(lambda _: next(iterator), state) return lens.Traversal(folder, builder) state = "First thou...

`fromJust` and `head` are eventually implemented using `errorWithoutStackTrace`, so you could search its call history in base source.

https://hackage.haskell.org/package/base-4.9.0.0/docs/src/Data.Foldable.html#minimum I see no `errorEmptyList`.

http://ircbrowse.net/browse/haskell?q=%28%60evalState%60+S.empty%29 http://ircbrowse.net/browse/haskell?q=flip+evalState http://ircbrowse.net/browse/haskell?q=flip+execState http://ircbrowse.net/browse/haskell?q=flip+runReaderT http://ircbrowse.net/browse/haskell?q=flip+evalStateT etc.

Right about the bloat, but both flips have their place. My intuition does tell me runStateT is the correct one, because it and evalState etc. often allow eta reduction. Only...

[ Hmm. Couldn't you just make "asd . evalState do dsa; sda" behave like "asd . evalState (do dsa; sda)"? That's currently a parse error, so free for the taking....

Those cons are stupid! > It's harder to read than the alternative. Subjective. > Creating a language extension to get rid of a single character is overkill and unnecessary. Overkill...

haskeline could provide MonadBase instances, which it currently can't because it doesn't want to add dependencies to ghc which depends on haskeline. https://github.com/judah/haskeline/pull/40 Presumably, that's also why it doesn't lift...