将 C++ 字符串拆分为多行（代码语法，不解析）
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Splitting C++ Strings Onto Multiple Lines (Code Syntax, Not Parsing)
提问by Jason R. Mick
Not to be confused with how to split a string parsing wise, e.g.:
Split a string in C++?
不要与如何明智地拆分字符串混淆，例如：
在 C++ 中拆分字符串？
I am a bit confused as to how to split a string onto multiple lines in c++.
我对如何在 C++ 中将字符串拆分为多行感到有些困惑。
This sounds like a simple question, but take the following example:
这听起来像一个简单的问题，但请看下面的例子：
#include <iostream>
#include <string>
main() {
//Gives error
std::string my_val ="Hello world, this is an overly long string to have" +
" on just one line";
std::cout << "My Val is : " << my_val << std::endl;
//Gives error
std::string my_val ="Hello world, this is an overly long string to have" &
" on just one line";
std::cout << "My Val is : " << my_val << std::endl;
}
I realize that I could use the std::stringappend()method, but I was wondering if there was any shorter/more elegant (e.g. more pythonlike, though obviously triple quotes etc. aren't supported in c++) way to break strings in c++ onto multiple lines for sake of readability.
我意识到我可以使用该std::stringappend()方法，但我想知道是否有任何更短/更优雅（例如更像 python，但显然三引号等在 c++ 中不受支持）的方法来将 c++ 中的字符串分成多行的可读性。
One place where this would be particularly desirable is when you're passing long string literals to a function (for example a sentence).
当您将长字符串文字传递给函数（例如一个句子）时，这是特别可取的一个地方。
回答by Eclipse
Don't put anything between the strings. Part of the C++ lexing stage is to combine adjacent string literals (even over newlines and comments) into a single literal.
不要在字符串之间放任何东西。C++ 词法分析阶段的一部分是将相邻的字符串文字（甚至在换行符和注释上）组合成一个文字。
#include <iostream>
#include <string>
main() {
std::string my_val ="Hello world, this is an overly long string to have"
" on just one line";
std::cout << "My Val is : " << my_val << std::endl;
}
Note that if you want a newline in the literal, you will have to add that yourself:
请注意，如果您想要文字中的换行符，则必须自己添加：
#include <iostream>
#include <string>
main() {
std::string my_val ="This string gets displayed over\n"
"two lines when sent to cout.";
std::cout << "My Val is : " << my_val << std::endl;
}
If you are wanting to mix a #defined integer constant into the literal, you'll have to use some macros:
如果您想将#defined 整数常量混合到文字中，则必须使用一些宏：
#include <iostream>
using namespace std;
#define TWO 2
#define XSTRINGIFY(s) #s
#define STRINGIFY(s) XSTRINGIFY(s)
int main(int argc, char* argv[])
{
std::cout << "abc" // Outputs "abc2DEF"
STRINGIFY(TWO)
"DEF" << endl;
std::cout << "abc" // Outputs "abcTWODEF"
XSTRINGIFY(TWO)
"DEF" << endl;
}
There's some weirdness in there due to the way the stringify processor operator works, so you need two levels of macro to get the actual value of TWOto be made into a string literal.
由于 stringify 处理器运算符的工作方式，其中存在一些奇怪之处，因此您需要两级宏才能将 的实际值TWO转换为字符串文字。
回答by mkb
Are they both literals? Separating two string literals with whitespace is the same as concatenation: "abc" "123"is the same as "abc123". This applies to straight C as well as C++.
它们都是文字吗？用空格分隔两个字符串文字与串联"abc" "123"相同：与"abc123". 这适用于直接 C 以及 C++。
回答by rmeador
I don't know if it is an extension in GCC or if it is standard, but it appears you can continue a string literal by ending the line with a backslash (just as most types of lines can be extended in this manor in C++, e.g. a macro spanning multiple lines).
我不知道它是 GCC 中的扩展还是标准，但看起来您可以通过以反斜杠结束行来继续字符串文字（就像大多数类型的行都可以在 C++ 中扩展，例如跨越多行的宏）。
#include <iostream>
#include <string>
int main ()
{
std::string str = "hello world\
this seems to work";
std::cout << str;
return 0;
}
