Remove redundant "do", "return" and language extensions from base

3 files changed, 19 insertions, 18 deletions

diff --git a/libraries/base/Text/ParserCombinators/ReadP.hs b/libraries/base/Text/ParserCombinators/ReadP.hs
index e6dcab55e0..d01dd931c8 100644
--- a/libraries/base/Text/ParserCombinators/ReadP.hs
+++ b/libraries/base/Text/ParserCombinators/ReadP.hs
@@ -278,9 +278,9 @@ string :: String -> ReadP String
 -- ^ Parses and returns the specified string.
 string this = do s <- look; scan this s
  where
-  scan []     _               = do return this
+  scan []     _               = return this
   scan (x:xs) (y:ys) | x == y = do _ <- get; scan xs ys
-  scan _      _               = do pfail
+  scan _      _               = pfail
 
 munch :: (Char -> Bool) -> ReadP String
 -- ^ Parses the first zero or more characters satisfying the predicate.
@@ -291,7 +291,7 @@ munch p =
      scan s
  where
   scan (c:cs) | p c = do _ <- get; s <- scan cs; return (c:s)
-  scan _            = do return ""
+  scan _            = return ""
 
 munch1 :: (Char -> Bool) -> ReadP String
 -- ^ Parses the first one or more characters satisfying the predicate.
@@ -315,7 +315,7 @@ skipSpaces =
      skip s
  where
   skip (c:s) | isSpace c = do _ <- get; skip s
-  skip _                 = do return ()
+  skip _                 = return ()
 
 count :: Int -> ReadP a -> ReadP [a]
 -- ^ @count n p@ parses @n@ occurrences of @p@ in sequence. A list of
diff --git a/libraries/base/Text/Printf.hs b/libraries/base/Text/Printf.hs
index 3aeb0be789..216c29d9e3 100644
--- a/libraries/base/Text/Printf.hs
+++ b/libraries/base/Text/Printf.hs
@@ -292,7 +292,7 @@ instance (a ~ ()) => PrintfType (IO a) where
 
 -- | @since 4.7.0.0
 instance (a ~ ()) => HPrintfType (IO a) where
-    hspr hdl fmts args = do
+    hspr hdl fmts args =
         hPutStr hdl (uprintf fmts (reverse args))
 
 -- | @since 2.01
diff --git a/libraries/base/Text/Read/Lex.hs b/libraries/base/Text/Read/Lex.hs
index 7568f9afaf..7da09164fb 100644
--- a/libraries/base/Text/Read/Lex.hs
+++ b/libraries/base/Text/Read/Lex.hs
@@ -273,7 +273,7 @@ lexCharE =
   do c1 <- get
      if c1 == '\\'
        then do c2 <- lexEsc; return (c2, True)
-       else do return (c1, False)
+       else return (c1, False)
  where
   lexEsc =
     lexEscChar
@@ -341,7 +341,7 @@ lexCharE =
          _    -> pfail
 
   lexAscii =
-    do choice
+     choice
          [ (string "SOH" >> return '\SOH') <++
            (string "SO"  >> return '\SO')
                 -- \SO and \SOH need maximal-munch treatment
@@ -404,9 +404,9 @@ lexString =
     do _ <- char '\\'
        c <- get
        case c of
-         '&'           -> do return ()
+         '&'           -> return ()
          _ | isSpace c -> do skipSpaces; _ <- char '\\'; return ()
-         _             -> do pfail
+         _             -> pfail
 
 -- ---------------------------------------------------------------------------
 --  Lexing numbers
@@ -429,13 +429,14 @@ lexHexOct
 
 lexBaseChar :: ReadP Int
 -- Lex a single character indicating the base; fail if not there
-lexBaseChar = do { c <- get;
-                   case c of
-                        'o' -> return 8
-                        'O' -> return 8
-                        'x' -> return 16
-                        'X' -> return 16
-                        _   -> pfail }
+lexBaseChar = do
+  c <- get
+  case c of
+    'o' -> return 8
+    'O' -> return 8
+    'x' -> return 16
+    'X' -> return 16
+    _   -> pfail
 
 lexDecNumber :: ReadP Lexeme
 lexDecNumber =
@@ -471,8 +472,8 @@ lexDigits base =
  where
   scan (c:cs) f = case valDig base c of
                     Just n  -> do _ <- get; scan cs (f.(n:))
-                    Nothing -> do return (f [])
-  scan []     f = do return (f [])
+                    Nothing -> return (f [])
+  scan []     f = return (f [])
 
 lexInteger :: Base -> ReadP Integer
 lexInteger base =