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Two special operators influence the replacement process.
First, if an occurrence of a parameter in the replacement token sequence is immediately preceded by #, string quotes (") are placed around the corresponding parameter, and then both the # and the parameter identifier are replaced by the quoted argument. A \ character is inserted before each " or \ character that appears surrounding, or inside, a string literal or character constant in the argument.
Second, if the definition token sequence for either kind of macro contains a ## operator, then just after replacement of the parameters, each ## is deleted, together with any white space on either side, so as to concatenate the adjacent tokens and form a new token. The effect is undefined if invalid tokens are produced, or if the result depends on the order of processing of the ## operators. Also, ## may not appear at the beginning or end of a replacement token sequence.
想请问一下上面讲的 1 & 2 可以要代码举例一下吗? 实在看不懂意思
谢谢 |
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