/*
 * A demonstration of counting the number of arguments passed to
 * a variadic function, by inspecting the stringified argument list.
 * See:
 *  http://vgable.com/blog/2009/10/16/hack-counting-varadic-arguments-in-c/
 *
 * To build and run:
 *    $ gcc iArray.c -o iArrayTest && ./iArrayTest
 */
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>

#define iArray(...) alloc_ints(count_arguments(#__VA_ARGS__), __VA_ARGS__)

/*
 * We ASSUME that s is a non-empty list of values or variables.
 * Under those (naive) assumptions, the number of arguments
 * in s is 1 + the number of commas seperating arguments.
 */
unsigned count_arguments(char *s){
	unsigned i,argc = 1;
		for(i = 0; s[i]; i++)
			if(s[i] == ',')
				argc++;
	return argc;
}

/*
 * Return an array filled with count ints
 */
int *alloc_ints(unsigned count, ...){
	unsigned i = 0;
	int *ints = malloc(sizeof(int) * count);
	va_list args;
    va_start(args, count);
	for(i = 0; i < count; i++)
		ints[i] = va_arg(args,int);
	va_end(args);
	return ints;
}

void print_iArray(char *msg, unsigned count, int *ints){
	unsigned i = 0;
	printf("%s = [", msg);
	for(i = 0; i < count; i++){
		if(i)
			printf(", ");
		printf("%d", ints[i]);
	}
	printf("]\n");
}

int main(int argc, char** argv){
	int one = 1;
	int three = 3;
	int *iArr = iArray(1,2,3);
	print_iArray("iArray(1,2,3)",3,iArr);
	free(iArr);
	
	iArr = iArray(one,2,three);
	print_iArray("iArray(one,2,three)",3,iArr);
	free(iArr);
	
	iArr = iArray(-one,2,-three,4,-5,6,-7,8,-9,10);
	print_iArray("iArray(-one,2,-three,4,-5,6,-7,8,-9,10)",10,iArr);
	free(iArr);
}