ios 里面的radio怎么消失了？还说打开听歌呢。 - 未名空间MITBBS历史存档

国际科技财经博客移民网络热点娱乐民生时事公众号

Redian新闻

>未名空间

>Apple - 家有苹果

ios 里面的radio怎么消失了？还说打开听歌呢。

ios 里面的radio怎么消失了？还说打开听歌呢。# Apple - 家有苹果

h*g2016-02-27 08:02

1 楼

You have to implement a function that needs to be able to write to both
standard output (typically the console screen) and files. Which one of the
following function declarations satisfies that need?
A.
void print(std::ostream &os);
B.
void print(std::ofstream is);
C.
void print(std::cout);
D.
void print(std::istream is);
E.
void print(std::istream &is);
问下，B 为啥不行呢？A 可以输出到文件吗？网上没找到答案~~~

t*r2016-02-27 08:02

2 楼

ios 里面的radio怎么消失了？还说打开听歌呢。

s*n2016-02-27 08:02

3 楼

cout is an object of class ostream that represents the standard output
stream.
and ostream is the base class of ofstream, which you use to output to a file.
So in A. void print(std::ostream &os);
if you pass a reference to ostream object in the print function, it's OK for
both type.
But in B.void print(std::ofstream is);
Not only you cannot output to the standard output, but also it's passed by
value, that means you make a copy of the ostream object you passed in, and
do output in that copy, which may not work as expected.
Please correct me if I am wrong, thanks.

f*f2016-02-27 08:02

4 楼

哪里有 radio？从来没听过

【在 t**r 的大作中提到】

: ios 里面的radio怎么消失了？还说打开听歌呢。

h*g2016-02-27 08:02

5 楼

thank you so much! I've learned a lot!

file.
for

【在 s*****n 的大作中提到】

: cout is an object of class ostream that represents the standard output
: stream.
: and ostream is the base class of ofstream, which you use to output to a file.
: So in A. void print(std::ostream &os);
: if you pass a reference to ostream object in the print function, it's OK for
: both type.
: But in B.void print(std::ofstream is);
: Not only you cannot output to the standard output, but also it's passed by
: value, that means you make a copy of the ostream object you passed in, and
: do output in that copy, which may not work as expected.