Exception for printing negative numbers

[Peter Tanski]

I don't know if any of you have been annoyed by the Exception handed  
down for printing a negative number, but there are several solutions  
to that.  One I posted a little while ago on the Commentary  
Cmm:Implementing Exception Handling page (http://hackage.haskell.org/ 
trac/ghc/wiki/Commentary/CmmExceptions).  Another easier to implement  
version would be this:

import Data.Word
import Data.Int
import Data.Bits
-- all of these should already be available 
-- in libraries/base/GHC/Show.lhs

{-
    define a decent absolute value function that
    does not require negation and can operate
    without danger of overflow or underflow (i.e.,
    the absolute value of -2147483648 cannot be
    represented in an Int32.

    in C, this would be:

	#define WORDBITS (sizeof(uint32_t) * 8)

	/* you want the shift to be signed for sign extension
	   to create the mask.
	 */
	uint32_t abs_mask = (uint32_t)( x >> (WORDBITS - 1) );

	return (uint32_t)( (x + abs_mask) ^ abs_mask );
-}

abs_i32  :: Int32 -> Word32
abs_i32 x  =
	let abs_mask = ( fromIntegral (x `shiftR` 31) )::Word32
	in
	( ((fromIntegral x)::Word32) + abs_mask ) `xor` abs_mask

Just a thought from the Great Beyond.  I am sorry I have not been  
more help putting the next release together--I have a bit of the work  
done on X11 types and may submit that soon when I can find the time.   
Most of my efforts have been directed toward a decent Replacement  
library, which is coming along.

Cheers,
Pete Tanski