#includeclass Fuel;class Engine{int a,b;public:Engine(int xa

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#include
class Fuel;
class Engine
{
int a,b;
public:
Engine(int xa=1,int xb=2){a=xa;b=xb;};
friend class Fuel;
int &geta(){return a;}
int &getb(){return b;}
};
class Fuel
{
Engine e;
public:
void show();
};
void Fuel::show()
{cout

楼主,把Fuel f(); 改为 Fuel f;就OK了
Fuel f; 调用无参构造函数,当无参构造函数没写时,系统自动默认.
// Fuel(){} //无参构造函数
// Fuel(Engine en){e=en;} //有参构造函数
当你写有参构造函数时,必要写无参构造函数,防止出错!
具体看看代码把：
#include
class Fuel;
class Engine
{
int a,b;
public:
Engine(int xa=1,int xb=2){a=xa;b=xb;};
friend class Fuel;
int &geta(){return a;}
int &getb(){return b;}
};
class Fuel
{
Engine e;
public:
// Fuel(){} //无参构造函数
// Fuel(Engine en){e=en;} //有参构造函数
void show();
};
void Fuel::show()
{cout

#includeclass Fuel;class Engine{int a,b;public:Engine(int xa #include class A { public: int n; }; class B:virtual public class A{int i,j;public:static int x;public:A(int a = 0,int b public class test(){ public Class a(int i) {} public static c++题天空#includeclass Point{public:void Init(int initX,int ini class A{ int a; public:A(const A& rhs){.} A b=(*this);////// ENGINE engine. #include class A { int a; public:A(int aa=0) { a=aa; } A(){c #include class A { public:A(int i,int j) { a1=i; a2=j; } vir #include using namespace std;class Box{public:Box(int a,int class Point{ protected int x,y; public Point(){} public Poin