blocks|key|1934870|text|此方法根本不存储字符串(就像问题中所要求的那样)：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1934871|static+const+std::streamsize+max+=+std::numeric_limits<std::streamsize>::max();
std::vector<int>+values;
int+value;

while(file.ignore(max,+'+')+>>+file+>>+value)
{
++++values.push_back(value);
}|code-block|syntax|javascript|1934872|它使用ignore，而不是读取字符串并不使用它。|offset|length|1934873|entityMap|0|LINK|mutability|MUTABLE|url|http://en.cppreference.com/w/cpp/io/basic_istream/ignore^0|0|0|3|6|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

This method doesn't store the string at all (like was asked for in the question):

<pre><code>static const std::streamsize max = std::numeric_limits&lt;std::streamsize&gt;::max();
std::vector&lt;int&gt; values;
int value;

while(file.ignore(max, ' ') &gt;&gt; file &gt;&gt; value)
{
 values.push_back(value);
}
</code></pre>

It uses <a href="http://en.cppreference.com/w/cpp/io/basic_istream/ignore" rel="nofollow">ignore</a> instead of reading the string and not using it.

blocks|key|1934842|text|显而易见的解决方案有什么问题？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1934843|string+param_name;
int+param_value;

while+(+fin+>>+param_name+>>+param_value+)
{
++..
}|code-block|syntax|javascript|1934844|您可以在每次迭代后丢弃param_name，同时将param_value存储在需要的任何位置。|offset|length|style|CODE|1934845|entityMap^0|0|0|B|A|P|B|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]|$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|N|$]]

What's wrong with the obvious solution?

<pre><code>string param_name;
int param_value;

while ( fin &gt;&gt; param_name &gt;&gt; param_value )
{
 ..
}
</code></pre>

You can discard the <code>param_name</code> after each iteration while storing the <code>param_value</code> wherever you need it.

blocks|key|5286219|text|当你读出字符串的时候，不要把它们存储在任何地方：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5286220|std::vector<int>+values;
std::string+discard;
int+value;
while+(file+>>+discard+>>+value)+{
++values.push_back(value);
}|code-block|syntax|javascript|5286221|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

When you read out the strings, just don't store them anywhere:

<pre><code>std::vector&lt;int&gt; values;
std::string discard;
int value;
while (file &gt;&gt; discard &gt;&gt; value) {
 values.push_back(value);
}
</code></pre>

blocks|key|1935017|text|我想我一定是早该发布一个ctype+facet来忽略字符串，只读取我们关心的数据：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1935018|#include+<locale>
#include+<fstream>
#include+<vector>
#include+<iostream>
#include+<algorithm>
#include+<iterator>

struct+number_only:+std::ctype<char>+{+
++++number_only()+:+std::ctype<char>(get_table())+{}+

++++static+mask+const+*get_table()+{+
++++++++static+std::vector<mask>+rc(table_size,+space);

++++++++std::fill_n(&rc['0'],+10,+digit);
++++++++rc['-']+=+punct;
++++++++return+&rc[0];+
++++}+
};

int+main()+{+
++++//+open+the+file
++++std::ifstream+x("config.txt");

++++//+have+the+file+use+our+ctype+facet:
++++x.imbue(std::locale(std::locale(),+new+number_only));

++++//+initialize+vector+from+the+numbers+in+the+file:
++++std::vector<int>+numbers((std::istream_iterator<int>(x)),+
++++++++++++++++++++++++++++++std::istream_iterator<int>());

++++//+display+what+we+read:
++++std::copy(numbers.begin(),+numbers.end(),+
++++++++std::ostream_iterator<int>(std::cout,+"\n"));

++++return+0;
}|code-block|syntax|javascript|1935019|这样，无关的数据就会被真正地忽略--在向流中注入我们的facet之后，就好像字符串根本不存在一样。|1935020|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I guess I must be overdue to post a ctype facet to ignore the strings and read only the data we care about:

<pre><code>#include &lt;locale&gt;
#include &lt;fstream&gt;
#include &lt;vector&gt;
#include &lt;iostream&gt;
#include &lt;algorithm&gt;
#include &lt;iterator&gt;

struct number_only: std::ctype&lt;char&gt; { 
 number_only() : std::ctype&lt;char&gt;(get_table()) {} 

 static mask const *get_table() { 
 static std::vector&lt;mask&gt; rc(table_size, space);

 std::fill_n(&amp;rc['0'], 10, digit);
 rc['-'] = punct;
 return &amp;rc[0]; 
 } 
};

int main() { 
 // open the file
 std::ifstream x("config.txt");

 // have the file use our ctype facet:
 x.imbue(std::locale(std::locale(), new number_only));

 // initialize vector from the numbers in the file:
 std::vector&lt;int&gt; numbers((std::istream_iterator&lt;int&gt;(x)), 
 std::istream_iterator&lt;int&gt;());

 // display what we read:
 std::copy(numbers.begin(), numbers.end(), 
 std::ostream_iterator&lt;int&gt;(std::cout, "\n"));

 return 0;
}
</code></pre>

This way the extraneous data is really and truly ignored -- after imbuing the stream with our facet, it's as if the strings don't exist at all.

blocks|key|731778|text|您可以定义一个结构，然后为其重载istream+operator>>：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|731779|struct+ParameterDiscardingName+{
++++int+value;
++++operator+int()+const+{
++++++++return+value;
++++}
};
istream&+operator>>(istream&+is,+ParameterDiscardingName&+param)+{
++++std::string+discard;
++++return+is+>>+discard+>>+param.value;
}

ifstream+file("Parameters.cfg");
istream_iterator<ParameterDiscardingName>+begin(file),+end;
vector<int>+parameters(begin,+end);|code-block|syntax|javascript|731780|entityMap^0|G|7|O|A|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|L|$]]

You can define a structure and then overload the <code>istream</code> <code>operator&gt;&gt;</code> for it:

<pre><code>struct ParameterDiscardingName {
 int value;
 operator int() const {
 return value;
 }
};
istream&amp; operator&gt;&gt;(istream&amp; is, ParameterDiscardingName&amp; param) {
 std::string discard;
 return is &gt;&gt; discard &gt;&gt; param.value;
}

ifstream file("Parameters.cfg");
istream_iterator&lt;ParameterDiscardingName&gt; begin(file), end;
vector&lt;int&gt; parameters(begin, end);
</code></pre>

I'm trying to determine the best way to read in a configuration file. This "Parameters.cfg" file is just to define values and is of this form:

<pre><code>origin_uniform_distribution 0
origin_defined 1
angles_gaussian 0
angles_uniform_distribution 0
angles_defined 0
startx 0
starty 0
gap 500
nevents 1000
origin_uniform_distribution_x_min -5
origin_uniform_distribution_x_max 5
origin_uniform_distribution_y_min -5
origin_uniform_distribution_y_max 5
origin_defined_x 0
origin_defined_y 0
angles_gaussian_center 0
angles_gaussian_sigma 5
angles_uniform_distribution_x_min -5
angles_uniform_distribution_x_max 5
angles_uniform_distribution_y_min -5
angles_uniform_distribution_y_max 5
angles_defined_x 10
angles_defined_y 10
</code></pre>

The names are there for the user to know which variables they are defining. I would like to have my program read in only the actual numbers and skip over the strings. I know I can do this in a way where I define a whole lot of strings in my program, and then just leave them sitting there defined but obviously unused. Is there a way to read in the numbers easily while skipping over the strings?

Reading variables from a configuration file

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我正在尝试确定读取配置文件的最佳方式。这个"Parameters.cfg“文件只是用来定义值的，其格式如下：origin_uniform_distribution 0origin_defined 1angles_gaussian 0angles_uniform_distribution 0angles_defined 0startx 0starty 0gap 500nevents 1000orig

问从配置文件中读取变量
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