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What are the best methods to "Clear the 6th bit" of an integer?

Answer 1

A:

If you're sure it's already set, just subtract 64.

Update: adding the test

if((x % 128) / 64 > 0)
  x -= 64;

As far as I can see right now, this doesn't make any assumptions about the platform or language support.

ahmadabdolkader 2010-03-27 00:01:55

i think cannot be sure it is already set.

動靜能量 2010-03-27 00:02:58

or 32 if you think that the low bit is the "1st" bit rather than the "0th" bit. ;)

John Knoeller 2010-03-27 00:04:49

Jian Lin makes a very good point, you would have to check if the 6th bit is already set. Yours was my first thought too.

drachenstern 2010-03-27 00:20:40

This does both a modulo and a division to check if a bit is already set, when C and C++ already have bit manipulation operators that don't require that knowledge.

swestrup 2010-03-27 02:34:49

Yes, what you noticed is obvious. This method was meant as an alternative. Try to think how to clear the bit without using bitwise operators.

ahmadabdolkader 2010-03-27 03:54:56

Answer 2

+8 A:

x & (~(1 << 6))

GregS 2010-03-27 00:03:46

wait a second, since 1 << 1 is the 2nd bit, so won't we need 1 << 5 instead of 1 << 6?

動靜能量 2010-03-27 00:17:24

Yes, but everybody assumes that you started counting on bit 0

Gonzalo 2010-03-27 00:18:44

Answer 3

A:

Perhaps this in c?

value&~(1<<6)

spender 2010-03-27 00:05:09

Answer 4

+3 A:

x&= ~(1 << 5)

MSN 2010-03-27 00:21:02

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What are the best methods to "Clear the 6th bit" of an integer?

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