流输入 [英] stream input

问题描述

嗨伙计们，

我很清楚使用流和运营商的优势<< />>

而不是旧式的printf和scanf。但是，只有一个

的障碍阻止我切换到更好的形式。

scanf具有以下非常方便的语法：


fscanf（pFile，" prfl num：％d \ n"，& nPrflNum）;

关于它的便利部分是它几乎是<的精确副本br />
创建输入的fprintf操作。特别是它允许通过写出它的内容来跳过特定文本上的
。


用方便的输入替换它似乎很难流

版，例如：

输入>>" prfl num：">> nPrflNum;


这段代码结果证明是非法的，因为输入流类并不知道如何输入常量字符串。我知道的解决方法非常麻烦，包括逐个读取字符，并验证它们是否适合prfl num：模式，或忽略一切都在流中找到一个数字

字符。


有没有更直接/无痛的方式来做我想做的事情？


干杯，

Aleks D.

解决方案

Aleks Dubinskiy < [e-mail]>在消息中写道

news：cg ********** @ news.net.uni-c.dk ...

嗨大家好，而不是旧式的printf和scanf。但是，只有一个障碍阻止我切换到更好的形式。
scanf具有以下非常方便的语法：

fscanf（pFile，" prfl num： ％d \ n"，& nPrflNum）;
关于它的方便部分是它几乎是创建输入的
fprintf操作的精确副本。特别是它允许通过写出它是什么来跳过特定文本。

用一个方便的输入
流版本替换它似乎非常困难，例如as：
input>>" prfl num：">> nPrflNum;

此代码证明是非法的，因为输入流类不是非常繁琐，包括逐个读取字符，并验证它们是否适合prfl num：模式，或忽略所有内容直到数字
在溪流中找到了角色。

是否有更简单/无痛的方式来做我想做的事情？

干杯，
Aleks D.


std :: ifstream输入;

std :: string s;

int num（0）;

/ * etc * /

std :: getline（input，s）;

if（s ==" prfl num："）

输入>> num;


-Mike

Aleks Dubinskiy写道：

大家好，
我很清楚使用流和运营商的优势<< />>
而不是旧式的printf和scanf。但是，只有一个障碍阻止我切换到更好的形式。
scanf具有以下非常方便的语法：

fscanf（pFile，" prfl num： ％d \ n"，& nPrflNum）;
关于它的方便部分是它几乎是创建输入的
fprintf操作的精确副本。特别是它只需要写出它就可以跳过特定的文本。

用一个方便的输入流
版本替换它似乎很困难。 as：
input>>" prfl num：">> nPrflNum;

此代码证明是非法的，因为输入流类不是字符在流中找到。

是否有更直接/无痛的方式来做我想要的事情？

可能符合
的内容

模板< class S> S&安培; skipover（S& s，const char * str）{

返回s.seekg（fpos（strlen（str），S :: cur）;

}

...

skipover（输入，" prfl num："）>> nPrflNum;


我相信大家好会纠正我错误的地方。


V

Mike Wahler写道：

" Aleks Dubinskiy"< [e-mail]>写在消息中
新闻：cg ********** @ news.net.uni-c.dk ...
< blockquote class =post_quotes>大家好，
我很清楚使用流和运算符<< />>
而不是旧式printf和scanf的优越性。 ，只有一个障碍阻止我切换到更好的形式。
scanf具有以下非常方便的语法：

fscanf（pFile，" prfl num：％ d \ n"，& nPrflNum）;
关于它的方便部分是它几乎是创建了它的
fprintf操作的精确副本输入。特别是它允许通过写出它是什么来跳过特定文本。

用方便的输入替换它似乎很困难

stream

版本，例如：
input>>" prfl num：">> nPrflNum;
<这段代码结果证明是非法的，因为输入流类并不知道如何输入常量字符串。我知道的解决方法是

繁琐，涉及逐个阅读字符，并验证它们是否适合模式prfl num：，或忽略所有内容，直到在流中找到数字
字符。

是否有更直接/无痛的方式来做我想要的？

干杯，
Aleks D。

std :: ifstream输入;
std :: string s;
int num （0）;
/ * etc * /
std :: getline（input，s）;
if（s ==" prfl num："）
输入> ;> num;

我不知道如何读取行中的整数如何

prfl num：42


（由对称声明打印


of<<<" prfl num："<<< some_int_with_value_42< ;< std :: endl;

}


不会'getline''跳过数字并读到行尾

因此失去了42？


Victor

Hi folks,
I am well aware of the superiority of using streams and operators << / >>
instead of the old-style printf and scanf. However, there is only one
obstacle that prevents me from switching to the better form.
scanf has the following really convenient syntax:

fscanf(pFile, "prfl num: %d\n", &nPrflNum);
The convenient part about it is that it''s almost an exact copy of the
fprintf operation that created the input. In particular it allows to skip
over a particular text by just writing what it is.

It seems to be very difficult to replace this with a convenient input stream
version, such as:
input>>"prfl num: ">>nPrflNum;

This code turns out to be illegal, because the input stream class doesn''t
know how to input constant strings. The workaround I know for this is quite
cumbersome, involving reading characters one by one, and verifying if they
fit the pattern "prfl num: ", or ignoring everything until a numeric
character is found in the stream.

Is there a more straightforward / painless way to do what I want?

Cheers,
Aleks D.

解决方案

"Aleks Dubinskiy" <[e-mail]> wrote in message
news:cg**********@news.net.uni-c.dk...

Hi folks,
I am well aware of the superiority of using streams and operators << / >>
instead of the old-style printf and scanf. However, there is only one
obstacle that prevents me from switching to the better form.
scanf has the following really convenient syntax:

fscanf(pFile, "prfl num: %d\n", &nPrflNum);
The convenient part about it is that it''s almost an exact copy of the
fprintf operation that created the input. In particular it allows to skip
over a particular text by just writing what it is.

It seems to be very difficult to replace this with a convenient input stream version, such as:
input>>"prfl num: ">>nPrflNum;

This code turns out to be illegal, because the input stream class doesn''t
know how to input constant strings. The workaround I know for this is quite cumbersome, involving reading characters one by one, and verifying if they
fit the pattern "prfl num: ", or ignoring everything until a numeric
character is found in the stream.

Is there a more straightforward / painless way to do what I want?

Cheers,
Aleks D.
std::ifstream input;
std::string s;
int num(0);
/* etc */
std::getline(input, s);
if(s == "prfl num: ")
input >> num;

-Mike

Aleks Dubinskiy wrote:

Hi folks,
I am well aware of the superiority of using streams and operators << / >>
instead of the old-style printf and scanf. However, there is only one
obstacle that prevents me from switching to the better form.
scanf has the following really convenient syntax:

fscanf(pFile, "prfl num: %d\n", &nPrflNum);
The convenient part about it is that it''s almost an exact copy of the
fprintf operation that created the input. In particular it allows to skip
over a particular text by just writing what it is.

It seems to be very difficult to replace this with a convenient input stream
version, such as:
input>>"prfl num: ">>nPrflNum;

This code turns out to be illegal, because the input stream class doesn''t
know how to input constant strings. The workaround I know for this is quite
cumbersome, involving reading characters one by one, and verifying if they
fit the pattern "prfl num: ", or ignoring everything until a numeric
character is found in the stream.

Is there a more straightforward / painless way to do what I want?

Probably something in line with

template<class S> S& skipover(S& s, const char* str) {
return s.seekg(fpos(strlen(str), S::cur);
}
...
skipover(input, "prfl num: ") >> nPrflNum;

I am sure folks will correct me where I erred.

V

Mike Wahler wrote:

"Aleks Dubinskiy" <[e-mail]> wrote in message
news:cg**********@news.net.uni-c.dk...

Hi folks,
I am well aware of the superiority of using streams and operators << / >>
instead of the old-style printf and scanf. However, there is only one
obstacle that prevents me from switching to the better form.
scanf has the following really convenient syntax:

fscanf(pFile, "prfl num: %d\n", &nPrflNum);
The convenient part about it is that it''s almost an exact copy of the
fprintf operation that created the input. In particular it allows to skip
over a particular text by just writing what it is.

It seems to be very difficult to replace this with a convenient input

stream

version, such as:
input>>"prfl num: ">>nPrflNum;

This code turns out to be illegal, because the input stream class doesn''t
know how to input constant strings. The workaround I know for this is

quite

cumbersome, involving reading characters one by one, and verifying if they
fit the pattern "prfl num: ", or ignoring everything until a numeric
character is found in the stream.

Is there a more straightforward / painless way to do what I want?

Cheers,
Aleks D.

std::ifstream input;
std::string s;
int num(0);
/* etc */
std::getline(input, s);
if(s == "prfl num: ")
input >> num;

I am not sure how it would help to read the integer in a line like

prfl num: 42

(which was printed by the symmetrical statement

of << "prfl num: " << some_int_with_value_42 << std::endl;
}

Wouldn''t ''getline'' skip over the number and read until the end of line
thus losing the "42"?

Victor

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