hub.darcs.net :: vmchale -> composition-prelude -> issue

clinton

I've been using the composition library and it's functions like compose2 (https://hackage.haskell.org/package/composition-1.0.2.2/docs/Data-Composition.html#v:compose2).

However I've just noticed the composition package library:

"This module is for convenience and demonstrative purposes more than it is for providing actual value. I do not recommend that you rely on this module for performance-sensitive code. Because this module is not based on Prelude's (.), some chances at optimization might be missed by your compiler."

I've noticed your library is based on . from base. You library also states it's an:

"An alternate version of what's provided in composition"

If it had the composeN functions, it would almost be a drop in replacement. The only other difference is changing the import from Data.Composition to Control.Composition, but I'm happy to do a search replace on that. The other alternative would be to include a module like

module Data.Composition (module Control.Composition) where

import Control.Composition

But I think that's just going to confuse the Haskell Language Server in my editor, I'd rather just do the one off find/replace.

The other issue is that the Prelude definition of (.) has an INLINE pragma (https://hackage.haskell.org/package/ghc-internal-9.1201.0/docs/src/GHC.Internal.Base.html#.):

{-# INLINE (.) #-}
-- Make sure it has TWO args only on the left, so that it inlines
-- when applied to two functions, even if there is no final argument
(.)    :: (b -> c) -> (a -> b) -> a -> c
(.) f g = \x -> f (g x)

I presume since GHC gives this an INLINE pragma I presume the pragma is important for optimisation purposes. Could this be added to the functions in composition-prelude also?

I'm happy to create a PR for these two changes if you'd like (composeN + inlining), I just wanted to confirm you'd be happy with such changes. If you want to just go ahead and make them also that's cool also. Also if these changes are an issue or things you'd rather not do, just say also that's okay, just wanted to reach out to you before doing my own version/fork.