有点操纵 [英] Some bit manipulation

问题描述

我正在寻找以下内容：


我们有两个32位整数A和B.我需要提出一个操作

O以A和B为参数，吐出单个整数R，如果A中位置b的位置位，那么R中位置b的位
被清除;否则，B中位置b的位的值被复制到R.

这将对参数中的所有32位进行。

I am looking for some bit wizardy for the following:

We have two 32-bit integers A and B. I need to come up with an operation
O that takes A and B as arguments, spitting out a single integer R such
that if the bit in position b in A is set, then the bit in position b in R
is cleared; otherwise, the value of the bit in position b in B is copied to R.
This is to be done for all the 32 bits in the arguments.

推荐答案

Henry Samuelson写道：

Henry Samuelson wrote:

我正在为以下内容寻找一些内容：

我们有两个32-位整数A和B.我需要提出一个操作
O，它将A和B作为参数，吐出一个整数R，如果A中的位置b被设置，那么R
中位置b的位被清除;否则，B中位置b的位的值被复制到R.
这将对参数中的所有32位进行。

I am looking for some bit wizardy for the following:

We have two 32-bit integers A and B. I need to come up with an operation
O that takes A and B as arguments, spitting out a single integer R such
that if the bit in position b in A is set, then the bit in position b in R
is cleared; otherwise, the value of the bit in position b in B is copied to R.
This is to be done for all the 32 bits in the arguments.

你的问题... b（位置）来自哪里？


-

Sean

Question for you...Where does b (position) come from?

--
Sean

Henry Samuelson写道：

Henry Samuelson wrote:

我正在寻找以下内容：

我们有两个32位整数A和B.我需要来使用A和B作为参数的O操作，将一个整数R吐出，如果A中的位置b中的位被设置，那么R中位置b的位/>被清除;否则，B中位置b的位的值被复制到R.
这将对参数中的所有32位进行。

I am looking for some bit wizardy for the following:

We have two 32-bit integers A and B. I need to come up with an operation
O that takes A and B as arguments, spitting out a single integer R such
that if the bit in position b in A is set, then the bit in position b in R
is cleared; otherwise, the value of the bit in position b in B is copied to R.
This is to be done for all the 32 bits in the arguments.

R = B& ~A;


作为一项规则，你应该使用一些'unsigned''

整数来进行bit-fiddling，因为它可以避免潜在的当符号位参与时，
令人不快的惊喜。


-
Er ********* @ sun.com

R = B & ~A;

As a rule, you should be using some flavor of `unsigned''
integers for bit-fiddling, because it avoids potentially
unpleasant surprises when sign bits participate.

--
Er*********@sun.com

Henry Samuelson写道：

Henry Samuelson wrote:

我们有两个32位整数A和B.我需要提出一个操作
O，它将A和B作为参数，吐出一个单位整数R，如果该位设置A中的位置b，然后清除R
中位置b的位;否则，B中位置b的位的值被复制到R.

We have two 32-bit integers A and B. I need to come up with an operation
O that takes A and B as arguments, spitting out a single integer R such
that if the bit in position b in A is set, then the bit in position b in R
is cleared; otherwise, the value of the bit in position b in B is copied to R.

我将真诚地假设这不是一个家庭作业的问题。要从任何特定的逻辑函数中取出
，有助于查看真值表：

BA = 0 A = 1

0 0 0

1 1 0


如你所见，只有当A'位清零且B'位<时才设置R中的位br />
已设定。换句话说，如果设置了~A'位并设置了B'位，或者：


R = ~A& B;

-

Derrick Coetzee

我将此新闻组发布到公共领域。我不承担所有

明示或暗示保证并承担所有责任。我不是专业人士。

I''m going to assume in good faith this isn''t a homework problem. To pull
off any particular logical function, it helps to look at the truth table:
B A=0 A=1
0 0 0
1 1 0

As you can see, the bit in R is set only if A''s bit is clear AND B''s bit
is set. In other words, if ~A''s bit is set and B''s bit is set, or:

R = ~A & B;
--
Derrick Coetzee
I grant this newsgroup posting into the public domain. I disclaim all
express or implied warranty and all liability. I am not a professional.

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