47.c

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#include <stdarg.h>
#include <stdio.h>

double average ( char *format, ... )
{
	double arg, total = 0.0, result = 0.0;	/* 定义临时浮点变量 */
	int num = 0;				/* num记录参数表中正数个数 */
	va_list ap;				/* */
	va_start ( ap, format );
	while ( num*2 < strlen ( format ))
	{
		if ( format[num*2 + 1] == 'd' )
		{
			arg = va_arg ( ap, int );
		}
		else if ( format[num*2 + 1] == 'f' )
		{
			arg = va_arg ( ap, double );
		}
		else
		{
			printf ( "参数格式错误!" );
			num = 0;
			break;
		}
		total +=arg;
		num ++;
	}
	va_end ( ap );
	if ( num > 0 )
	{
		result = total/num;
	}
	return result;
}

void main()
{
	int a, b, c, d, e;
	double u, v, x, y, z;
	double result;
	a = 1;	b = 2;	c = 3;	d = 4; 	e = 5;
	u = 6.0; v = 7.0; x = 8.0; y = 9.0; z = 10.0;
	result = 0.0;
	result = average ( "%d%d%d%f%f%f", a, b, c, x, y, z);
	printf ( "a, b, c, x, y, z 的平均值是:%f\n", result );
	result = average ( "%d%d%f%f", d, e, u, v );
	printf ( "d, e, u, v 的平均值是::%f\n", result );
	result = average ( "%d%d%f%", d, e, u, v );	//注意此处调用错误的参数时的结果
	printf ( "d, e, u, v的平均值是:%f\n", result );
}