在c/c++的程序設(shè)計(jì)中，有的時候不免要實(shí)現(xiàn)某些對象轉(zhuǎn)換出相應(yīng)名字字符串或兩對象名直接相連的情況，這時候可采用宏定義中加入#和##分別實(shí)現(xiàn)相應(yīng)功能。下面是摘抄的一段解釋。

?

The # and ## preprocessor operators are used with the?#define?preprocessor directive.

• Using # causes the first argument after the # to be returned as a string in quotes.
• Using ## concatenates what's before the ## with what's after it.

For example, the command

#define to_string( s ) # s

will make the compiler turn this command

cout << to_string( Hello World! ) << endl;

into

cout << "Hello World!" << endl;

Here is an example of the ## command:

#define concatenate( a, b ) a ## b...int xy = 10;...

This code will make the compiler turn

cout << concatenate( x, y ) << endl;

into

cout << xy << endl;

which will, of course, display '10' to standard output.

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