Preprocessor directive to create keywords in C

Question

I want to create this...

int main(void) {
  int i;

  for(i = 0; i < 10; i++){
    //Not an important Code
  }
  return 0;
}

in a fancier way, to create crazy ideas!
Is it possible to rewrite it like this?

#define A f
#define B or

int main(void) {
  int i;

  AB(i = 0; i < 10; i++){
    //Not an important Code
  }
  return 0;
}

I need to know if it's possible to create instrctions like a simple for composed by diferent #defines

Forget it. Trying to make a lazy implemetation for keywords is a going nowhere and makes your invented code hard to read. — Weather Vane, Mar 06 '19 at 18:11
Avoid preprocessor magic; it makes code unreadable. You can concatenate tokens in the replacement text of a macro with `##` — `#define C(a, b) a ## b` and then `C(A, B)` would more or less do what you want; you just have to evaluate the expressions before concatenating: `#define E(a) a` — `#define C(a, b) E(a) ## E(b)` and `C(A,B)`. But that's repulsive, especially for a split keyword. — Jonathan Leffler, Mar 06 '19 at 18:12
@JonathanLeffler I tryed your idea, and it doesn't work for me. Gcc responds with: pasting ")" and "E" does not give a valid preprocessing token #define C(a, b) E(a)##E(b) — Adria Arroyo, Mar 06 '19 at 18:27
OK; as you can tell, I didn't test it. It's doable (the concatenation of tokens defined via macros); there are answers about how to do it (some written by me in times past). It isn't a good idea — that's the take home. (Working set of macros: `#define A f` — `#define B or` — `#define E(a, b) a ## b` — `#define C(a, b) E(a, b)` — `` — `C(A,B)` — output, `for`.) — Jonathan Leffler, Mar 06 '19 at 18:29
https://stackoverflow.com/questions/1489932/how-to-concatenate-twice-with-the-c-preprocessor-and-expand-a-macro-as-in-arg; https://stackoverflow.com/questions/195975/how-to-make-a-char-string-from-a-c-macros-value — Jonathan Leffler, Mar 06 '19 at 18:37

score 4 · Accepted Answer · edited Mar 06 '19 at 19:09

4

making

#define A f
#define B or
#define C(x, y) x##y
#define D(x,y) C(x,y)

then

D(A, B)(i = 0; i < 10; i++)

will be rewritten as

for (i = 0; i < 10; i++)

edited Mar 06 '19 at 19:09

Jonathan Leffler

answered Mar 06 '19 at 18:12

alinsoar

I think you need object-like macros for A and B, not function-like macros — as shown in the question. – Jonathan Leffler Mar 06 '19 at 18:38

1 Answers1