[commit: packages/base] master: Fingerprint: Add Show instance for easier debugging (e057b7f)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/base

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/e057b7f23e4b4925bd409238282682cf5dda262d/base

>---------------------------------------------------------------

commit e057b7f23e4b4925bd409238282682cf5dda262d
Author: Niklas Hambüchen <mail at nh2.me>
Date:   Thu Aug 22 11:18:25 2013 +0900

    Fingerprint: Add Show instance for easier debugging
    
    Signed-off-by: Austin Seipp <aseipp at pobox.com>


>---------------------------------------------------------------

e057b7f23e4b4925bd409238282682cf5dda262d
 GHC/Fingerprint/Type.hs |   11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/GHC/Fingerprint/Type.hs b/GHC/Fingerprint/Type.hs
index 91d7250..ee209db 100644
--- a/GHC/Fingerprint/Type.hs
+++ b/GHC/Fingerprint/Type.hs
@@ -12,10 +12,21 @@
 module GHC.Fingerprint.Type (Fingerprint(..)) where
 
 import GHC.Base
+import GHC.List (length, replicate)
+import GHC.Num
+import GHC.Show
 import GHC.Word
+import Numeric (showHex)
 
 -- Using 128-bit MD5 fingerprints for now.
 
 data Fingerprint = Fingerprint {-# UNPACK #-} !Word64 {-# UNPACK #-} !Word64
   deriving (Eq, Ord)
 
+instance Show Fingerprint where
+  show (Fingerprint w1 w2) = hex16 w1 ++ hex16 w2
+    where
+      -- | Formats a 64 bit number as 16 digits hex.
+      hex16 :: Word64 -> String
+      hex16 i = let hex = showHex i ""
+                 in replicate (16 - length hex) '0' ++ hex