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Subject: question about an efficient way to change the bits of a number.

Author: Uri Blass

Date: 03:51:51 07/27/03

In movei there are cases when I want to change 2 bits of a number to be
identical to the bits of another number.

Let say I want b=a in the 2^0 bit and the 2^8 bit

The simple way is

if (a&256)
b|=256;
else
b&=~256;
if (a&1)
b|=1;
else
b&=~1;

a faster way that I could think about is:

b|=(a&257);
b&=~(257-(a&257));

Is it the best way or maybe it is better to change the last line and have
b|=(a&257);
b&=~(257&(~(a&257)))

Uri

• Re: question about an efficient way to change the bits of a number. Tim Foden 04:17:34 07/27/03
• Re: question about an efficient way to change the bits of a number. Ricardo Gibert 04:04:50 07/27/03
  • Re: question about an efficient way to change the bits of a number. Ratko V Tomic 08:10:07 07/27/03
    • Re: question about an efficient way to change the bits of a number. Ricardo Gibert 08:39:05 07/27/03
      • Re: question about an efficient way to change the bits of a number. Ratko V Tomic 14:47:54 07/27/03
      • Re: question about an efficient way to change the bits of a number. Gerd Isenberg 10:14:51 07/27/03
        • Re: question about an efficient way to change the bits of a number. Ricardo Gibert 10:43:54 07/27/03
  • Re: question about an efficient way to change the bits of a number. Uri Blass 04:22:20 07/27/03
    • Re: question about an efficient way to change the bits of a number. Gerd Isenberg 03:30:04 07/28/03
      • Re: question about an efficient way to change the bits of a number. Uri Blass 04:20:10 07/28/03
        • Re: question about an efficient way to change the bits of a number. Gerd Isenberg 04:26:48 07/28/03
    • Re: question about an efficient way to change the bits of a number. Ricardo Gibert 07:43:41 07/27/03

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