>  -----Original Message-----

>  From: Nicholas Clark [mailto:nick@[...].org]

>  

>  On Mon, Jul 23, 2001 at 09:08:42PM +0200, Tels wrote:

>  > I am unsure how to repeat this. The result of -1 & -1 

>  > highly depends on the

>  > width of a Perl scalar. Since Bigint is by definition 

>  > "infinite width", the

>  > result should probably be something like +inf :-) 

>  > Seriously, I do not know

>  > how to repeat Perl's behaviour without assuming a specific 

>  > width. Anyway,

>  > your program looking for -1 & -1 beeing 4294967295 will fail on any

>  > platform not having 32 bit (like 64 bit).

>  > 

>  > Has anybody any comments or ideas on what to do?

>  

>  Not sure if this is a sane idea. Can you

>  

>  define the width of a negative integer to be the smallest 

>  number of bits

>  needed to represent it in 2s complement.

>  So -9 (ie 1111111111110111) is 10111 (width 5)

>  

>     -6 (ie 1111111111111010) is 1010 (width 4)

>  

>  -6 & -9 needs to promote -6 to width 5, [same as positive 

>  case] but do the

>  promotion as sign extension (11010) then & the two together

>  

>  11010 & 10111 == 10010

>  

>  which is -14. And gives the same answer as 16 bit and 32 bit 

>  fixed precision,

>  as best I can tell.

>  

>  [not tested very much for other values or for | or ^ operators]

>  

>  Nicholas Clark


How would you be able to tell if the number was intended to be negative?
11010 = -6 or 26, 10111 = -9 or 23...

-Scott