Question 10.20

I have some old code that tries to construct identifiers with a macro like

#define Paste(a, b) a/**/b

It was an undocumented feature of some early preprocessor implementations (notably John Reiser's) that comments disappeared entirely and could therefore be used for token pasting. ANSI affirms (as did K&R1) that comments are replaced with white space. However, since the need for pasting tokens was demonstrated and real, ANSI introduced a well-defined token-pasting operator, ##, which can be used like this:

	#define Paste(a, b) a##b

References: ANSI Sec. 3.8.3.3
ISO Sec. 6.8.3.3
Rationale Sec. 3.8.3.3
H&S Sec. 3.3.9 p. 52

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