blocks|key|2444611|text|除非借助于宏，否则不可能使用您要求的确切语法。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2444612|但是如果您不介意用,替换<<，那么您可以执行以下操作：|offset|length|style|CODE|2444613|#include+<iostream>
#include+<string>
#include+<sstream>

void+log_impl(const+std::string+&str)
{
++++std::cout+<<+str;
}

template+<typename+...P>+void+log(const+P+&...+params)
{
++++std::stringstream+stream;

++++(stream+<<+...+<<+params);
++++//+If+you+don't+have+C%2B%2B17,+use+following+instead+of+the+above+line:
++++//+using+dummy_array+=+int[];
++++//+dummy_array{(void(stream+<<+params),+0)...,+0};

++++log_impl(stream.str());
}

int+main()
{
++++log("1",+2,+'3');+//+prints+123
}|code-block|syntax|javascript|2444614|entityMap^0|0|9|1|C|2|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@$D|Q|E|R|F|G]|$D|S|E|T|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|U|8|@]|9|@]|A|$K|L]]|$1|M|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|N|$]]

It's impossible to do with the exact syntax you asked for unless you resort to macros.

But if you don't mind replacing <code>&lt;&lt;</code> with <code>,</code>, then you can do following:

<pre><code>#include &lt;iostream&gt;
#include &lt;string&gt;
#include &lt;sstream&gt;

void log_impl(const std::string &amp;str)
{
 std::cout &lt;&lt; str;
}

template &lt;typename ...P&gt; void log(const P &amp;... params)
{
 std::stringstream stream;

 (stream &lt;&lt; ... &lt;&lt; params);
 // If you don't have C++17, use following instead of the above line:
 // using dummy_array = int[];
 // dummy_array{(void(stream &lt;&lt; params), 0)..., 0};

 log_impl(stream.str());
}

int main()
{
 log("1", 2, '3'); // prints 123
}
</code></pre>

blocks|key|2654255|text|对于琐碎的项目，这是我使用MACRO做的为数不多的事情之一。你可以这样做：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2654256|#define+LOG(m)+do{+std::cout+<<+timestamp()+<<+":+"+<<+m+<<+'\n';+}while(0)

//+...

LOG("error:+["+<<+errno+"]+"+<<+filename+<<+"+does+not+exist.");|code-block|syntax|javascript|2654257|一般来说，应该避免使用MACROS，但没有其他方法可以通过标准函数精确地实现这一点。所以..。|2654258|注意：空条件do{...}while(0)使您能够将MACRO放在MACRO包含多个语句时通常不能到达的位置。|BOLD|2654259|entityMap^0|D|5|0|0|B|6|0|0|3|6|F|Q|5|X|5|0^^$0|@$1|2|3|4|5|6|7|R|8|@$9|S|A|T|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|U|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|V|8|@$9|W|A|X|B|C]]|D|@]|E|$]]|$1|M|3|N|5|6|7|Y|8|@$9|Z|A|10|B|O]|$9|11|A|12|B|C]|$9|13|A|14|B|C]|$9|15|A|16|B|C]]|D|@]|E|$]]|$1|P|3|-4|5|6|7|17|8|@]|D|@]|E|$]]]|Q|$]]

For trivial projects this is one of the few things I use a <code>MACRO</code> for. You can do something like this:

<pre><code>#define LOG(m) do{ std::cout &lt;&lt; timestamp() &lt;&lt; ": " &lt;&lt; m &lt;&lt; '\n'; }while(0)

// ...

LOG("error: [" &lt;&lt; errno "] " &lt;&lt; filename &lt;&lt; " does not exist.");
</code></pre>

Generally <code>MACROS</code> should be avoided but there is no other way to get precisely this with a standard function. So...

Note: The empty condition <code>do{...}while(0)</code> enables you to place the <code>MACRO</code> in places that a <code>MACRO</code> usually can't go if it contains multiple statements.

blocks|key|2444656|text|你可以通过定义一个新的operator<<来实现。根据模糊的记忆，使用这三个签名实现函数将会起到作用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2444657|std::string+operator<<(const+char+*+a,+const+std::string+&+b);
std::string+operator<<(const+std::string+&+a,+const+char+*+b);
std::string+operator<<(const+std::string+&+a,+const+std::string+&+b);|code-block|syntax|javascript|2444658|它们中的每一个都必须连接其参数并返回std::string。|2444659|然而，这感觉是错误的。这违背了C%2B%2B的原则。我建议一种更像C%2B%2B的解决方案，即将日志记录器变成一个类，并为该类编写operator<<()成员，这样您就可以运行|2444660|customLog+<<+"My+Integer+i+=+"+<<+i+<<+"."+<<+"\n";|2444661|entityMap^0|0|0|0|0|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]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|S|8|@]|9|@]|A|$E|F]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

You could do it by defining a new operator&lt;&lt;. From vague memory, implementing functions with these three signatures will do the trick:

<pre><code>std::string operator&lt;&lt;(const char * a, const std::string &amp; b);
std::string operator&lt;&lt;(const std::string &amp; a, const char * b);
std::string operator&lt;&lt;(const std::string &amp; a, const std::string &amp; b);
</code></pre>

Each of them has to concatenate its arguments and return a std::string.

Howeever, it feels wrong. Goes against the grain of C++. I suggest a more C++-ish solution, namely to make your logger into a class, and write operator&lt;&lt;() members for that class, so you can run

<pre><code>customLog &lt;&lt; "My Integer i = " &lt;&lt; i &lt;&lt; "." &lt;&lt; "\n";
</code></pre>

blocks|key|2654279|text|一种方法是一个简单的实用程序类，它在模板化的成员函数中使用标准流：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2654280|class+LogStream+{
++++public:
++++++++template+<class+T>+LogStream&+operator+<<+(const+T&+rhs)+{
++++++++++++stream+<<+rhs;
++++++++++++return+*this;
++++++++}

++++private:
++++++++std::stringstream+stream;
};|code-block|syntax|javascript|2654281|然后在析构函数中使用执行所有工作的流成员，|2654282|~LogStream()+{
++++std::cout+<<+stream.str()+<<+std::endl;
}|2654283|您还可以创建用于传递要连接的参数的临时对象：|2654284|LogStream()+<<+"anything+with+std::ostream+operator:+"+<<+1.2345+<<+'+'+<<+std::hex+<<+12;|2654285|额外的状态(例如，日志级别)可以传递给构造函数，通常伴随着方便的函数，比如LogStream+debug()+{+return+LogStream(...);+}。但是，当您达到一定的复杂程度时，您可能希望切换到记录库。|offset|length|style|CODE|2654286|entityMap^0|0|0|0|0|0|0|11|18|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Y|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|10|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|12|8|@$Q|13|R|14|S|T]]|9|@]|A|$]]|$1|U|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|V|$]]

One approach is a simple utility class that uses a standard stream in a templated member function:

<pre><code>class LogStream {
 public:
 template &lt;class T&gt; LogStream&amp; operator &lt;&lt; (const T&amp; rhs) {
 stream &lt;&lt; rhs;
 return *this;
 }

 private:
 std::stringstream stream;
};
</code></pre>

The stream member doing all the work is then used in the destructor,

<pre><code>~LogStream() {
 std::cout &lt;&lt; stream.str() &lt;&lt; std::endl;
}
</code></pre>

and you can create temporary objects for passing your arguments to be concatenated:

<pre><code>LogStream() &lt;&lt; "anything with std::ostream operator: " &lt;&lt; 1.2345 &lt;&lt; ' ' &lt;&lt; std::hex &lt;&lt; 12;
</code></pre>

Additional state (e.g. a log level) can be passed to the constructor, often accompagnied by convenience functions like <code>LogStream debug() { return LogStream(...); }</code>. When you reach a certain point of sophistication though, you might want to switch to a logging library of course.

Can i design my logging-function in a way, that it accepts concatenated strings of the following form using C++?

<pre><code>int i = 1;
customLoggFunction("My Integer i = " &lt;&lt; i &lt;&lt; ".");
</code></pre>

.

<pre><code>customLoggFunction( [...] ){
 [...]
 std::cout &lt;&lt; "Debug Message: " &lt;&lt; myLoggMessage &lt;&lt; std::endl &lt;&lt; std::endl
}
</code></pre>

Edit:

Using std::string as the attribute to the function works for the concatenated string, but then a passed non-concatenated string like customLoggFunction("example string") produces a compile-time error saying the function is not applicable for char[]. When i overload the function in the following way...

<pre><code>customLoggFunction(std::string message){...}
customLoggFunction(char message[]){...}
</code></pre>

... the concatenated strings seize to work.

I uploaded the code: <a href="http://coliru.stacked-crooked.com/a/d64dc90add3e59ed" rel="nofollow noreferrer">http://coliru.stacked-crooked.com/a/d64dc90add3e59ed</a>

C++: How can i create a function that accepts concatenated strings as parameter?

我可以使用C++来设计我的日志函数，让它接受以下形式的连接字符串吗？int i = 1;customLoggFunction("My Integer i = " << i << ".");。customLoggFunction( [...] ){ [...] std::cout << "Debug Mess...

问C++：如何创建一个接受连接字符串作为参数的函数？
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