Bryan wrote:
>> is to reset the rightmost (less significant) '1' bit of a number (ie
>> change it to '0').
>
> i tried c &= c - 1 but i'm not getting the least significant or
> rightmost bit reset to zero. am i misunderstanding something?
>
> >>> 2 & 1 # 2 = 0x10; reset right most would be 0x10
> 0
> >>> 10 & 9 # 10 = 0x1010; reset right most would be 0x1010
> 8
The difference between the original "reset the rightmost '1' bit", and your
interpretation: "reset the rightmost bit" is the "'1'".
The rightmost bit that is set is reset. So 0x10 -> 0, and 0x1010 -> 0x1000.
If you want to extract the least significant set bit from a number 'x' you
can use (x&-x):
>>> x = 0xab4
>>> while x:
print hex(x&-x), hex(x)
x ^= (x&-x)
0x4 0xab4
0x10 0xab0
0x20 0xaa0
0x80 0xa80
0x200 0xa00
0x800 0x800
>>>
(but don't try this if x is negative: it works but never terminates).
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