数据结构1 C++类的编写的注意事项

int main(){
    Line line(10.0);
    cout<<" "<<line.getLength()<<endl;
    line.setLength(6.0);
    cout<<" "<<line.getLength()<<endl;
    return 0;
};
注意主函数中需先声明line，类型为Line
getLength setLength前一定要加line.!!! 

class Line
{
public:
  //成员函数的声明
  void  setLength(double len);
    double getLength(void);
//含参的构造函数的声明
    Line(double len);
private:
    double length;
};
定义类的最后分号不能忘

Line::Line(double len) {
    cout << "object is being created,length=" << len << endl;
    length = len;
}
void Line::setLength(double len){
    length=len;
}
double Line::getLength(void){
    return length;
} 

Line：：不能忘