Question

Here’s a program that illustrates my problem:

#include <stdio.h>

#define NUMERATOR 8
#define DENOMINATOR 2
#define QUOTIENT (NUMERATOR / DENOMINATOR)

#define ZSTR(x) XSTR(#x)
#define YSTR(x) XSTR(x)
#define XSTR(x) STR(x)
#define STR(x) #x

int main()
{
    printf("QUOTIENT:       %d\n", QUOTIENT);
    printf("STR(QUOTIENT):  %s\n", STR(QUOTIENT));
    printf("XSTR(QUOTIENT): %s\n", XSTR(QUOTIENT));
    printf("YSTR(QUOTIENT): %s\n", YSTR(QUOTIENT));
    printf("ZSTR(QUOTIENT): %s\n", ZSTR(QUOTIENT));
    return 0;
}

And here’s its output:

$ gcc -g -Wall -o stringify stringify.c && ./stringify 
QUOTIENT:       4
STR(QUOTIENT):  QUOTIENT
XSTR(QUOTIENT): (8 / 2)
YSTR(QUOTIENT): (8 / 2)
ZSTR(QUOTIENT): "QUOTIENT"

I would like to have a the string literal "4" passed to the compiler, but I’m losing hope.
This is related to this question, but adds a level.

Answer 1

With some tricks you can implement basic arithmetic in a C99 conforming preprocessor. P99 implements arithmetic and logic for small decimal numbers. E.g

P99_IF_GT(1,0)(true)(false)
P99_ADD(3, 7)
P99_MUL(7, 2)
P99_DIV(7, 2)

would be preprocessed to something like

1
10
14
3

These macros can be processed further, stringified and everthing you like.

P99_STRINGIFY(P99_PASTE2(XXX_, P99_ADD(3, 7)))

leads to "XXX_10" as the result of preprocessing.