在构造函数中使用参数初始化对数据初始化

#include <iostream>
#include <cmath>
using namespace std;

class Triangle
{
public:
void showMessage();
Triangle (double x=1,double y=1,double z=1):a(x),b(y),c(z){}     //重点  a(x),b(y),c(z){}    实参（形参）
double  perimeter(void );
double area(void);

private:
double  a,b,c;

};

double Triangle::perimeter(void)
{
double l;
l=a+b+c;
return l;
}
double Triangle:: area(void)
{
double  p,s;
p=(a+b+c)/2;
s=sqrt(p*(p-a)*(p-b)*(p-c));
return s;
void Triangle::showMessage()
{
cout<<"该三角形的三条边为:"<<'\t'<<a<<'\t'<<b<<'\t'<<c<<endl;
cout<<"                                                "<<endl;
cout<<"该三角形的周长为:"<<perimeter()<<endl;
cout<<"                                                "<<endl;
cout<<"该三角形的面积为:"<<area();

}
int main()
{
Triangle  t1;
t1.showMessage ();
cout<<"                           " <<endl;
Triangle t2(3,4,5);
t2.showMessage ();
return 0;
}