Unconditionally make a (Show Ptr) instance

[ghc-base.git] / GHC / Ptr.lhs

diff --git a/GHC/Ptr.lhs b/GHC/Ptr.lhs
index 31daa5f..8087c77 100644 (file)
--- a/GHC/Ptr.lhs
+++ b/GHC/Ptr.lhs
@@ -1,5 +1,6 @@
 \begin{code}
-{-# OPTIONS_GHC -fno-implicit-prelude #-}
+{-# OPTIONS_GHC -XNoImplicitPrelude #-}
+{-# OPTIONS_HADDOCK hide #-}
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  GHC.Ptr
@@ -14,9 +15,16 @@
 --
 -----------------------------------------------------------------------------
 
+-- #hide
 module GHC.Ptr where
 
 import GHC.Base
+import GHC.Show
+import GHC.Num
+import GHC.List ( length, replicate )
+import Numeric          ( showHex )
+
+#include "MachDeps.h"
 
 ------------------------------------------------------------------------
 -- Data pointers.
@@ -55,7 +63,7 @@ alignPtr addr@(Ptr a) (I# i)
       0# -> addr;
       n -> Ptr (plusAddr# a (i -# n)) }
 
--- |Computes the offset required to get from the first to the second
+-- |Computes the offset required to get from the second to the first
 -- argument.  We have 
 --
 -- > p2 == p1 `plusPtr` (p2 `minusPtr` p1)
@@ -133,5 +141,19 @@ castFunPtrToPtr (FunPtr addr) = Ptr addr
 -- this assumption.
 castPtrToFunPtr :: Ptr a -> FunPtr b
 castPtrToFunPtr (Ptr addr) = FunPtr addr
+
+
+------------------------------------------------------------------------
+-- Show instances for Ptr and FunPtr
+
+instance Show (Ptr a) where
+   showsPrec _ (Ptr a) rs = pad_out (showHex (wordToInteger(int2Word#(addr2Int# a))) "")
+     where
+        -- want 0s prefixed to pad it out to a fixed length.
+       pad_out ls = 
+          '0':'x':(replicate (2*SIZEOF_HSPTR - length ls) '0') ++ ls ++ rs
+
+instance Show (FunPtr a) where
+   showsPrec p = showsPrec p . castFunPtrToPtr
 \end{code}