在 C++ 中计算圆的尺寸

calculate dimensions of a circle in c++

本文关键字：计算 C++      更新时间：2023-10-16
#ifndef CIRCLE_H
#define CIRCLE_H
#include <QString>
#include <string>
using namespace std;

class Circle {
public:
  //constructors
  Circle();
  Circle(double r);
  //setter
  void setRadius(double r);
  //getter
  double getRadius();
  //calculate the diameter of a circle
  double computeDiameter()const;
  //calculate the area of a circle
  double computeArea()const;
  //calculate the Circumference of a circle
  double computeCircumference()const;
  //checks if radius of circle is bigger
  **bool isBigger(const Circle& other) const;**
private:
  //private data members
  double m_Radius;
};
#endif // CIRCLE_H

#include "circle.h"
#include "math.h"
#include <iostream>
#include <QString>
#include <sstream>
using namespace std;
Circle::Circle()
{
  m_Radius =  0;
}
Circle::Circle(double r)
{
  m_Radius = r;
}
void Circle::setRadius(double r){
    m_Radius = r ;
}
double Circle::getRadius(){
    return m_Radius;
}
double Circle::computeDiameter()const{
    return 2* m_Radius;
}
double Circle::computeArea()const {
    return ( m_Radius* m_Radius*M_PI);
}
double Circle::computeCircumference()const {
    return (2* m_Radius*M_PI);
}

#include <iostream>
#include <QTextStream>
#include "circle.h"
using namespace std;
int main(){
    QTextStream cout(stdout);
    Circle c1,c2;     // input
    c1.setRadius(3);
    c2.setRadius(7);
    cout << "Circle with radius " << c1.getRadius() << " has: " << endl;
    cout<< "Diameter " << c1.computeDiameter() << " cm " <<endl;
    cout<< "Area " << c1.computeArea() << " cm" <<endl;
    cout<< "Circumference " << c1.computeCircumference()<< " cm " <<endl<<endl;
    cout << "Circle with radius " << c2.getRadius() << " has: " << endl;
    cout<< "Diameter " << c2.computeDiameter() << " cm " <<endl;
    cout<< "Area " << c2.computeArea() << " cm" <<endl;
    cout<< "Circumference " << c2.computeCircumference()<< " cm " <<endl<<endl;
return 0;
}
如果调用函数的 Circle 实例的半径大于(或小于(传递给

函数的 Circle 实例的半径，则函数 isBigger(( 返回 true(或false(：我不知道如何实现这个函数。有人可以用简单的英语解释一下吗？

实现将如下所示：

bool Circle::isBiggerThan(const Circle& other) const
{
    return m_Radius > other.m_Radius;
}

但是，使用运算符更习惯

： 
class Circle
{
    // ...
    friend bool operator >(Circle const &, Circle const &) const;
};
bool operator >(Circle const& lhs, Circle const& rhs) const
{
    return lhs.m_Radius > rhs.m_Radius;
}

如果你知道自己的半径(m_Radius或getRadius()(和另一个圆的半径(other.getRadius()(，那么你可以简单地比较它们，看看哪个半径更大，就像这样：

bool Circle::isBigger(const Circle &other) const
{
    return m_Radius > other.getRadius();
}

举个例子，如果你有：

Circle c1;
Circle c2;

那么当且仅当c1的半径大于c2时，c1.isBigger(c2)应该为真。

(我可能会isBiggerThan调用该函数，以便更容易大声说出来。

你的意思是：

bool Circle::isBigger(const Circle& other) const
{
    return m_Radius > other.getRadius();
}

这将简单地检查当前圆的半径(m_Radius(与给定圆的半径。

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