python2.4 generator expression > python2.3 list expression

[Bryan]

Duncan Booth wrote:
> 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).

thanks duncan... you're right, i did intrepret this as "reset the rightmost bit" 
instead of "reset the rightmost '1' bit".  and i must have read what christos 
wrote 100 times!!!

bryan