X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=Data%2FTuple.hs;h=a5ea87570f88f80c4f79925ae8227f09445d6efb;hb=HEAD;hp=89fb861659bccc580f4357c0abee18b7c1a2b612;hpb=3a6392956bbb1cb908a596bcbb67d7bcc8dbd72f;p=ghc-base.git

diff --git a/Data/Tuple.hs b/Data/Tuple.hs
index 89fb861..a5ea875 100644
--- a/Data/Tuple.hs
+++ b/Data/Tuple.hs
@@ -1,4 +1,4 @@
-{-# OPTIONS_GHC -XNoImplicitPrelude #-}
+{-# LANGUAGE CPP, NoImplicitPrelude #-}
 {-# OPTIONS_GHC -fno-warn-unused-imports #-}
 -- XXX -fno-warn-unused-imports needed for the GHC.Tuple import below. Sigh.
 -----------------------------------------------------------------------------
@@ -20,6 +20,7 @@ module Data.Tuple
   , snd         -- :: (a,b) -> a
   , curry       -- :: ((a, b) -> c) -> a -> b -> c
   , uncurry     -- :: (a -> b -> c) -> ((a, b) -> c)
+  , swap        -- :: (a,b) -> (b,a)
 #ifdef __NHC__
   , (,)(..)
   , (,,)(..)
@@ -43,13 +44,13 @@ module Data.Tuple
 
 import GHC.Base
 -- We need to depend on GHC.Base so that
--- a) so that we get GHC.Bool, GHC.Classes, GHC.Ordering
+-- a) so that we get GHC.Classes, GHC.Ordering, GHC.Types
 
 -- b) so that GHC.Base.inline is available, which is used
 --    when expanding instance declarations
 
 import GHC.Tuple
--- We must import GHC.Tuple, to ensure sure that the 
+-- We must import GHC.Tuple, to ensure sure that the
 -- data constructors of `(,)' are in scope when we do
 -- the standalone deriving instance for Eq (a,b) etc
 
@@ -104,3 +105,7 @@ curry f x y             =  f (x, y)
 uncurry                 :: (a -> b -> c) -> ((a, b) -> c)
 uncurry f p             =  f (fst p) (snd p)
 #endif  /* neither __HUGS__ nor __NHC__ */
+
+-- | Swap the components of a pair.
+swap                    :: (a,b) -> (b,a)
+swap (a,b)              = (b,a)