17 Jul
2000
17 Jul
'00
5:09 p.m.
I discovered a small bug in GPC FAQ (Reference : shr) : It give as an example : "a:= -127 shr 4; (* yields -7 *)" which is false, it yields -8 !
I think we have to take care when manipulating bits of negative integers. A ShortInt with value-1 is coded 11111111b ! (-2 is 11111110b, -3 is 11111101b and so on) If the last bit is 1 (that means the number is negative), the 'shr' operator replaces the right new bits by 1. Examples (Considering ShortInt type (8 bits)) : -127 (coded 10000001b) shr 4 yields -8 (coded 11111000b) -1 (coded 11111111b) shr 1 yields -1 !
-- "Couperin"