Code::Blocks环境下C++圆参数计算函数代码可编译但结果错误求助

现存错误点 #

• 输出环节未调用函数
  main函数中打印半径、周长、面积的代码，直接将函数名传入输出流，没有加括号传入参数执行调用逻辑，此时输出的是函数的内存地址，不是计算结果。对应问题代码：
  cout << "Circle's radius is: " << radius << endl;
cout << "Circle's circumference is: " << circumference << endl;
cout << "Circle's area is: " << area << endl;
• 圆面积公式书写错误
  面积函数内的计算逻辑为pow(PI*radius,2)，等价于(π×r)²，不符合圆面积πr²的数学定义，计算结果偏差较大。
• 函数参数设计冗余
  原radius函数定义要求传入5个参数，但函数内部完全没有使用前四个坐标参数，仅将传入的distance参数直接返回，属于无效的参数传递。
• 无用头文件引用
  代码中引入的<cctype>没有任何对应功能调用，可直接删除减少编译冗余。

修正后可正常运行的代码 #

#include <iostream>
#include <cmath>
#include <iomanip>

using namespace std;
const double PI = 3.1416;
double distance(double, double, double, double);
double radius(double);
double circumference(double);
double area(double);

int main()
{
    double x1, y1, x2, y2;
    cout << fixed << showpoint << setprecision(2);
    cout << "Enter the center X and Y coordinate of a circle (in that order with a space in between): ";
    cin >> x1 >> y1;
    cout << "Enter another X and Y coordinate in the same circle (in that order with a space in between): ";
    cin >> x2 >> y2;
    double line_dist = distance(x1, y1, x2, y2);
    double r = radius(line_dist);
    cout << "Circle's radius is: " << r << endl;
    cout << "Circle's circumference is: " << circumference(r) << endl;
    cout << "Circle's area is: " << area(r) << endl;
    double diameter = 2 * r;
    cout << "Circle's diameter is: " << diameter << endl;
    return 0;
}

double distance(double x1, double y1, double x2, double y2)
{
    return sqrt(pow(x2 - x1, 2) + pow(y2 - y1, 2));
}

double radius(double line_dist)
{
    return line_dist;
}

double circumference(double r)
{
    return 2 * PI * r;
}

double area(double r)
{
    return PI * pow(r, 2);
}

内容的提问来源于stack exchange，提问作者sticks_