再给函数指针变量赋值是，只需给变量名无需给参数（来至二级c的模拟题）

#include
double f1(double x)
{ return xx; }
double f2(double x, double y)
{ return xy; }
double fun(double a, double b)
{
/**found**/
double (*f)();
double r1, r2;//再给函数指针变量赋值是，只需给变量名无需给参数
/**found**/
f = f1 ;
r1 = f(a);
/**found**/
f = f2 ;
r2 = (f)(a, b);
return r1 + r2;
}
void main()
{ double x1=5, x2=3, r;
r = fun(x1, x2);
printf("\nx1=%f, x2=%f, x1x1+x1*x2=%f\n",x1, x2, r);
}