Macro String with variable

Question

I don't know how to define a macro string with variable, like this:
#define str(x) "file x.txt", that mean I desire that str(1) refers to "file 1.txt". However, in the case, str(1) or any number refers to "file x.txt", because x is an character.
Is there any way to solve this?

The "with variable" might be tricky. If you have int foo=5; STR(foo) you're still talking about file foo.txt, not file 5.txt. Macro's work at compile time, before variables have values assigned. — MSalters
– MSalters, Commented Sep 25, 2012 at 8:28

Kerrek SB · Accepted Answer · 2012-09-24 23:00:09Z

5

Concatenate the strings:

#define STR(x) "file " #x ".txt"

This makes use of a lexical feature of the two languages: adjacent string literals are concatenated; see both C++11 2.2/6 and C11 5.1.1.2/6:

Adjacent string literal tokens are concatenated.

answered Sep 24, 2012 at 23:00

Kerrek SB

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Daniel Fischer · Accepted Answer · 2012-09-24 23:00:13Z

1

#define str(x) ("file " #x ".txt")

using the stringification operator #

answered Sep 24, 2012 at 23:00

Daniel Fischer

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