第十二章 异常处理2021-10-04

//带析构语义的类c++异常处理 12-2
#include <iostream>
#include <string>
using namespace std;
class MyException{
public:
    MyException(const string &message):message(message){}
    ~MyException(){}
    const string &getMessage() const{return message;}
private:
    string message;
};

class Demo{
public:
    Demo(){cout << "Constructor of Demo" << endl;}
    ~Demo(){cout << "Destructor of Demo" << endl;}
};

void func() throw(MyException){
    Demo d;
    cout << "Throw MyException in func()" << endl;
    throw MyException("exception thrown by func()");
}

int main(){
    cout << "In main function" << endl;
    try{
        func();
    }catch (MyException& e){
        cout << "Caught an exception: " << e.getMessage() << endl;
    }
    return 0;
}

#include <iostream>
#include <cmath>
using namespace std;
//给出三角形三边长，计算三角形面积
double area(double a,double b,double c) throw (invalid_argument)
{
    //判断三角形边长是否为正
    if(a <= 0 || b <= 0 || c <= 0)
        throw invalid_argument("the side length should be positive");
    //判断三边长是否满足三角不等式
    if(a+b <= c || b+c <= a || c+a <= b)
        throw invalid_argument("the side length should fit the triangle inequation ");
    //由Heron公式计算三角形面积
    double s = (a+b+c) / 2;
    return sqrt(s * (s - a) * (s - b) * (s - c));
}

int main(){
    double a,b,c;       //三角形三边长
    cout << "Please input the side lengths of a triangle:";
    cin >> a >> b >> c;
    try{
        double s = area(a,b,c);     //尝试计算三角形面积
        cout << "Area: " << s << endl;
    }catch(exception &e){
        cout << "Error: " << e.what() << endl;
    }
    return 0;

}