base: MRP-refactoring of AMP instanceswip/D1316

Summary:
This refactors (>>)/(*>)/return/pure methods into normalform.

The redundant explicit `return` method definitions are dropped
altogether.

This results in measurable runtime improvements in nofib of up
to -20% runtime (geometric mean: -7%) in my measurements.

Reviewers: quchen, austin, alanz, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1316

1 files changed, 5 insertions, 4 deletions

diff --git a/libraries/base/Data/Version.hs b/libraries/base/Data/Version.hs
index aba8cf7f74..414b2aa859 100644
--- a/libraries/base/Data/Version.hs
+++ b/libraries/base/Data/Version.hs
@@ -36,7 +36,8 @@ module Data.Version (
         makeVersion
   ) where
 
-import Control.Monad    ( Monad(..), liftM )
+import Data.Functor     ( Functor(..) )
+import Control.Applicative ( Applicative(..) )
 import Data.Bool        ( (&&) )
 import Data.Char        ( isDigit, isAlphaNum )
 import Data.Eq
@@ -120,9 +121,9 @@ showVersion (Version branch tags)
 -- | A parser for versions in the format produced by 'showVersion'.
 --
 parseVersion :: ReadP Version
-parseVersion = do branch <- sepBy1 (liftM read (munch1 isDigit)) (char '.')
-                  tags   <- many (char '-' >> munch1 isAlphaNum)
-                  return Version{versionBranch=branch, versionTags=tags}
+parseVersion = do branch <- sepBy1 (fmap read (munch1 isDigit)) (char '.')
+                  tags   <- many (char '-' *> munch1 isAlphaNum)
+                  pure Version{versionBranch=branch, versionTags=tags}
 
 -- | Construct tag-less 'Version'
 --