关于生命和范围的三个问题。 [英] Three questions about lifetime and scope.
问题描述
考虑这个原型的功能:
void foo(条形条);
1.程序可以调用foo并允许只有一个可寻址的Bar对象存在
一次?
现在考虑以下程序:
class Bar
{
int value;
public:
Bar():value(0){}
void change(int new_value){value = new_value; }
};
void foo(酒吧){}
int main()
{
酒吧;
bar.change(1);
foo(bar);
返回0;
}
2.可以修改此程序而无需更改为foo和Bar,以便:
>
i)主要调用具有相同bar值的foo,并且
ii)一次只存在一个可寻址的Bar对象。
3.什么是前两个问题的实际意义(如果有的话)
与数据共享和写时复制有关吗?
请通过示例支持您的答案。感谢任何帮助。
Consider the function with this prototype:
void foo(Bar bar);
1. Can a program call foo and allow only one addressable Bar object to exist
at a time?
Now consider the following program:
class Bar
{
int value;
public:
Bar() : value(0) { }
void change(int new_value) { value = new_value; }
};
void foo(Bar bar) { }
int main()
{
Bar bar;
bar.change(1);
foo(bar);
return 0;
}
2. Can this program be modified without change to foo and Bar so that:
i) main calls foo with the same value of bar, and
ii) only one addressable Bar object exists at a time.
3. What is the practical significance, if any, of the previous two questions
in relation to data sharing and copy-on-write?
Please support your answers with examples. Any help is appreciated.
推荐答案
* Jason Heyes:
* Jason Heyes:
[作业问题]
偏离主题;请参阅关于家庭作业问题的常见问题解答。
-
答:因为它弄乱了人们通常阅读文本的顺序。
问:为什么这么糟糕?
A:热门发布。
问:usenet和电子邮件中最烦人的事情是什么?
Off-topic; see the FAQ on HOMEWORK QUESTIONS.
--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?
" Alf P. Steinbach" <人*** @ start.no>在消息中写道
新闻:41 ***************** @ news.individual.net ...
"Alf P. Steinbach" <al***@start.no> wrote in message
news:41*****************@news.individual.net...
*杰森Heyes:
[作业问题]
非主题;请参阅关于家庭作业问题的常见问题解答。
- 答:A:因为它弄乱了人们通常阅读文本的顺序。
问:为什么这么糟糕?
答:热门帖子。
问:usenet和电子邮件中最烦人的事情是什么?
Off-topic; see the FAQ on HOMEWORK QUESTIONS.
--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?
如何修改我的帖子让论坛没有把它解释为作业?
How do I modify my post so that the forum doesn''t interpret it as homework?
* Jason Heyes:
* Jason Heyes:
[引用签名]
不要引用签名;纠正;请参阅有关如何发布的常见问题解答。
* Jason Heyes:* Alf P. Steinbach:
[quoting signature]
Do not quote signatures; corrected; see FAQs on how to post.
* Jason Heyes: * Alf P. Steinbach:
* Jason Heyes:
* Jason Heyes:
[作业问题]
非主题;请参阅有关家庭作业问题的常见问题解答。
Off-topic; see the FAQ on HOMEWORK QUESTIONS.
如何修改我的帖子,以便论坛不会将其解释为作业?
How do I modify my post so that the forum doesn''t interpret it as homework?
你不能。
问题
3.以前有什么实际意义关于数据共享和写时复制的两个问题?
证据太强了。
-
答:因为它弄乱了人们通常阅读文字的顺序。
问:为什么这么糟糕?
A:热门发布。
问:usenet和电子邮件中最烦人的事情是什么?
You can''t.
The question
3. What is the practical significance, if any, of the previous two
questions in relation to data sharing and copy-on-write?
is too strong evidence.
--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?
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