Quoting symbol in CPP

[Paul J. Lucas]

Given this:

#define NUM 100

I was to use a CPP macro like:

char *p = MACRO(NUM);

and have MACRO defined such that it would expand to:

char *p = "100";

I tried:

#define MACRO(X) #X

but, for MACRO(NUM), that expands to:

char *p = "NUM";

How can I get CPP to expand NUM first?

- Paul

[Szabolcs Borsanyi]

Re: Quoting symbol in CPP

On May 9, 10:26 pm, "Paul J. Lucas" <paul-nos...@nospam.l ucasmail.org>
wrote:

Given this:
>
        #define NUM 100
>
I was to use a CPP macro like:
>
        char *p = MACRO(NUM);
>
and have MACRO defined such that it would expand to:
>
        char *p = "100";
>
I tried:
>
        #define MACRO(X) #X
>
but, for MACRO(NUM), that expands to:
>
        char *p = "NUM";
>
How can I get CPP to expand NUM first?
>
- Paul

The preprocessor will expand the macro parameters first, unless
they appear next to a # (or ##).
So try this:

#define NUM 100
#define MACRO(X) #X
#define GOODMACRO(X) MACRO(X)

char *p=GOODMACRO(NU M);

GOODMACRO's argument is not following an #, so it is expanded, prior
to
looking at MACRO's meaning.

Szabolcs

[vippstar@gmail.com]

Re: Quoting symbol in CPP

On May 10, 12:26 am, "Paul J. Lucas" <paul-
nos...@nospam.l ucasmail.orgwro te:

Given this:
>
#define NUM 100
>
I was to use a CPP macro like:
>
char *p = MACRO(NUM);
>
and have MACRO defined such that it would expand to:
>
char *p = "100";
>
I tried:
>
#define MACRO(X) #X
>
but, for MACRO(NUM), that expands to:
>
char *p = "NUM";
>

Question 11.17 of the C-faq.
<http://c-faq.com/>