Variable-length Argument Lists

C 語言的可變參數函數樣例，摘自《The c programming language》

#include <stdarg.h>

void minprintf(char *fmt, ...)
{
	va_list ap;	/*points to each unnamed arg in turn */
	char *p, *sval;
	double dval;
	
	va_start(ap,fmt); /* make ap point to 1st unnamed arg */
	for (p = fmt; *p; p++) {
		if (*p != '%') {
			putchar(*p);
			continue;
		}
		switch (*++p) {
			case 'd':
				ival = va_arg(ap, int);
				printf("%d", ival);
				break;
			case 'f':
				dval = va_arg(ap, double);	/* va_arg returns one argument and strps ap to the next. */
				printf("%f", dval);
				break;
			case 's':
				for (sval = va_varg(ap, char *); *sval; sval++)
					putchar(*sval);
				break;
			default:
				putchar(*p);
				break;
		}
	}
	va_end(ap);	/* clean up when done, it is necessary, must be called before the function returns. */
}