按位OR？ [英] Bitwise OR?

问题描述

为什么3500 | -67等于3500而不是-3567？

Why is 3500 | -67 equal to 3500 instead of -3567?

推荐答案

xkenneth schrieb：

xkenneth schrieb:

为什么是3500 | -67等于3500而不是-3567？

Why is 3500 | -67 equal to 3500 instead of -3567?

它不是 - 它的-67。


Diez

It isn''t - its -67.

Diez

xkenneth写道：

xkenneth wrote:

为什么3500 | -67等于3500而不是-3567？

Why is 3500 | -67 equal to 3500 instead of -3567?

那很有趣......在我的电脑上，python说它是-67。 Java也是

表示它是-67。


Haven尚未查看两个值的实际位数。

你有什么Python实现和什么机器？


--Tim

Well that''s funny... On my computer, python says it''s -67. Java also
says it''s -67.

Haven''t yet looked at the actual bits of both values.
What Python implementation and what machine do you have?

--Tim

实际上，跟进我自己的回复：


3500 | 67 = 3567.所以也许你的期望值为3500 |

-67。


但是试试


-3500 | -67


为了好玩：它是-3


按位或没有算术，如果你想预测一些关于
的东西
得到的整数，你应该知道它们是如何存储的。


负整数以2补码格式存储：减1将所有

位设置为1.关闭位使其成为一个更负的数字（因为你没有触摸符号位，所以

长）并转向更多bit on on

a较小的负数。


对于正数3500和67执行按位或运算结果为3567：

证明它们没有重叠位。

知道3500和-67只有重叠位：

因此结果是-67。 （将3500中的位添加到

-67的位中并没有打开任何额外的位。）


使用位运算符来操作位，并将操作数视为集合

位。按位OR是两组位的并集。

不要把操作符想象为操作符作为数字，不要尝试

来做你的使用按位求和或者！


:-)

--Tim

Actually, following up to my own reply:

3500 | 67 = 3567. So perhaps that sets your expectations for 3500 |
-67.

But try

-3500 | -67

for fun: it is -3

Bitwise or is no arithmetic and if you want to predict something about
the resulting integers, you should know something about how they are
stored.

Negative integers are stored in 2-complement format: minus 1 is all
bits set to 1. Turning bits off makes it a more negative number (as
long as you don''t touch the sign-bit) and turning more bits on makes it
a smaller negative number.

Doing bitwise-OR for the positive numbers 3500 and 67 results in 3567:
proof that they don''t have any overlapping bits.
Know it turns out that 3500 and -67 have only overlapping bits:
therefore the result is -67. (adding the bits from 3500 to the bits of
-67 doesn''t turn on any extra bits).

Use bit operators to manipulate bits, and think of the operands as sets
of bits. Bitwise OR is the union of 2 sets of bits.
Don''t think of the operands to bit operators as numbers, and don''t try
to do your sums using bitwise or!

:-)

--Tim

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