C++函数的嵌套调用和递归调用学习教程

double root(double, double); //函数声明 int main( )

{ double x1,x2,f1,f2,x;

do {

cout<<"input x1,x2:"; cin>>x1>>x2;

f1=f(x1); f2=f(x2);

} while(f1*f2>=0); x=root(x1,x2);

cout<<setiosflags(ios::fixed)<<setprecision(7); //指定输出7位小数

cout<<"A root of equation is "<<x<<endl; return 0;

} double f(double x) //定义f函数,以实现f(x)

{ double y;

y=x*x*x-5*x*x+16*x-80; return y;

} double xpoint(double x1, double x2) //定义xpoint函数,求出弦与x轴交点

{ double y;

y=(x1*f(x2)-x2*f(x1))/(f(x2)-f(x1)); //在xpoint函数中调用f函数 return y;

} double root(double x1, double x2) //定义root函数,求近似根

{ double x,y,y1;

y1=f(x1); do

{ x=xpoint(x1,x2); //在root函数中调用xpoint函数

y=f(x); //在root函数中调用f函数 if (y*y1>0)

{ y1=y;

x1=x; }

else x2=x;

}while(fabs(y)>=0.00001); return x;

}

运行情况如下：

input x1, x2:2.5 6.7↙ A root of equation is 5.0000000
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