个人技术分享

cerr的使用

代码：

#include <iostream>
#include <math.h>

using namespace std;

class Triangle 
{
private:
    float a_len;
    float b_len;
    float c_len;
public:
    //Triangle();
    //Triangle(float a, float b, float c): a_len(a), b_len(b), c_len(c){};
    void printArea() const;
    void set(float a, float b, float c);
    //~Triangle();
};

void Triangle::set(float a, float b, float c) {
    if(a + b <= c || a + c <= b || b + c <= a) {
        cerr << "input error!" << endl;
    } else {
        a_len = a;
        b_len = b;
        c_len = c;
    }
}
void Triangle::printArea() const {
    float p = (a_len + b_len + c_len)/2;
    cout << "Triangle Area = " << sqrt(p*(p-a_len)*(p-b_len)*(p-c_len)) <<endl;
}
int main() {
    float