Things I want in Protolude

protolude-wishlist.md

Stephen Diehl's protolude library is excellent. I highly recommend it as a default prelude for Haskell.

It's so good and so close to what I want that whenever I do come across something missing it's as obvious as a glitch in good music.

Here's what I'd like:

<<$>>

(<<$>>) :: (Functor f, Functor g) => (a -> b) -> f (g a) -> f (g b)
(<<$>>) = fmap . fmap

I do this enough that I'd like it to hand. Pi Delport suggested the syntax & that it should be in a standard library somewhere.

for / forA

I want for to be flip fmap and forA to be what's currently for (protolude/protolude#19).

ppShow

From the pretty-show library.

A very simple pretty printer, great for debugging data structures. Would have to be adjusted for better string types for protolude.

tracePpShow

Like traceShow, but pretty. Doesn't actually exist yet.

guarded

guarded :: Alternative f => (a -> Bool) -> a -> f a
guarded p x = bool empty (pure x) (p x)

Another great idea from Pi Delport.

Another silly one:

pass :: Applicative f => f ()
pass = pure ()

All of these functions should be added as of 0.1.10. Any issues please report on the issue tracker. Thanks!