class hean
{
    int shangren;
    int puren;
public:
    friend boats::Load(int s,int p,hean &lingshi);
    friend boats::Unload(hean &lingshi);
    hean(int s,int p):shangren(s),puren(p){}
    bool Inspect(){ return shangren>=puren?true:false;}
};
class boats
{
    int shangren;
    int puren;
public:
    boats():shangren(0),puren(0){}
    void Load(int s,int p,hean &lingshi);
    void Unload(hean &lingshi);
};
void boats::Load(int s,int p,hean &lingshi)
{
    shangren+=s;
    puren+=p;
    lingshi.shangren-=s;
    lingshi.puren-=p;
}
void boats::Unload(hean &lingshi)
{
    lingshi.shangren+=shangren;
    lingshi.puren+=puren;
}

如上,我发现如果先定义娄hean,在编译"friend boats::Load(int s,int p,hean &lingshi);"这句时,提示boats不是一个娄名或名字空间.
换先定义娄boats时,在编译" void Load(int s,int p,hean &lingshi);"这句时,提示使用了未定义的标示符 hean

对这个问题求助....