一元多项式的实现

Term.h

#ifndef TERM_H
#define  TERM_H

#include  < iostream >
using   namespace  std;

class  Polynominal;
class  Term ... {
public:
    Term(int c,int e);
    Term(int c,int e,Term* nxt);
    Term* InsertAfter(int c,int e);
private:
    int coef;
    int exp;
    Term* link;
    friend ostream & operator<<(ostream &,const Term & );
    friend class Polynominal;
} ;

Term::Term( int  c, int  e):coef(c),exp(e) ... {
    link = NULL;
}

Term::Term( int  c, int  e,Term *  nxt):coef(c),exp(e) ... {
    link = nxt;
}

Term *  Term::InsertAfter( int  c, int  e) ... {
    link = new Term(c,e,link);
    return link;
}

ostream  &   operator << (ostream  &   out , const  Term &  val) ... {
    if(val.coef == 0) return out;
    out<<val.coef;
    switch(val.exp)...{
        case 0:break;
        case 1:out<<"X";break;
        default:out<<"X^"<<val.exp;break;
    }
    return out;
}
#endif   // TERM_H

Polynominal.h

#ifndef POLYNOMINAL_H
#define  POLYNOMINAL_H
#include  < iostream >

#include  " Term.h "
using   namespace  std;
class  Polynominal ... {
public:
    Polynominal();
    void AddTerms(istream& in);
    void AddLast(int c,int e);
    void Output(ostream& out) const;
    void PolyAdd(Polynominal& r);
    void MakeEmpty();
    void PolyMultiply(Polynominal& );
private:
    Term* theList;
    friend ostream & operator<<(ostream &, const Polynominal &);
    friend istream & operator>>(istream &, Polynominal &);
    friend Polynominal& operator+(Polynominal &, Polynominal &);
    friend Polynominal& operator*(Polynominal &, Polynominal &);
} ;

Polynominal::Polynominal() ... {
    theList = new Term(0,-1);
    theList->link = theList;
}

void  Polynominal::AddTerms(istream &   in ) ... {
    int c,e;
    Term *q = theList;
    while(true)...{
        cout<<"Input a term(coef,exp): "<<endl;
        in>>c>>e;
        if(e < 0) break;
        q = q->InsertAfter(c,e);
    }
}

void  Polynominal::MakeEmpty() ... {
     Term *p = theList->link;
     while(p->link != theList)...{
                   theList->link = p->link;
                   delete p;
                   p = theList->link;
     }
     theList->link = theList;
     delete p;
}

void  Polynominal::AddLast( int  c, int  e) ... {
     Term *p = theList;
     while(p->link != theList) p = p->link;
     Term *temp = new Term(c,e,theList);
     p->link = temp;
}
void  Polynominal::Output(ostream &   out )  const ... {
    int first = 1;
    Term *p = theList->link;
    while(p != theList)...{
        if(!first &&(p->coef > 0)) out<<"+";
        first = 0;
        out<<*p;
        p = p->link;
    }
}

void  Polynominal::PolyAdd(Polynominal &  r) ... {
    Term * p = r.theList->link;
    Term *q1 = theList;
    Term *q = theList->link;
    while(p != r.theList)...{
        while((q->exp > p->exp) && (q->link != theList))...{
            q = q->link;
            q1 = q1->link;
        }
        if(q->exp < p->exp) ...{
                  q1->InsertAfter(p->coef,p->exp);
                  q1 = q1->link;
        }
        else if(q->exp == p->exp)...{
            q->coef += p->coef;
        }
        else...{
             q->InsertAfter(p->coef,p->exp);
             q1 = q;
             q = q->link;
        }
        p = p->link;
    }
}

void  Polynominal::PolyMultiply(Polynominal &  b) ... {
     Term *p = theList->link;
     Term *q = b.theList->link;
     Polynominal result,temp; 
     if(p == theList || q == b.theList) return;
     while(p != theList)...{
             while( q != b.theList)...{
                    temp.AddLast(p->coef*q->coef,p->exp+q->exp);
                    q = q->link;
             }
            result.PolyAdd(temp);
            temp.MakeEmpty();
            p = p->link; 
            q = b.theList->link;
     }
     theList = result.theList;
}

ostream &   operator   << (ostream  & out , const  Polynominal  & x) ... {  
    x.Output(out);   
    return out;
}

istream &   operator   >> (istream &   in , Polynominal  & x) ... {  
    x.AddTerms(in);   
    return in;
}

Polynominal &   operator + (Polynominal  & a, Polynominal  & b)
... {  
    a.PolyAdd(b);
    return a;
}

Polynominal &   operator * (Polynominal  & a,Polynominal  & b) ... {
             a.PolyMultiply(b);
             return a;
}


#endif   // POLYNOMINAL_H

main.cpp

#include  < cstdlib >
#include  < iostream >
#include  " Polynominal.h "
using   namespace  std;

int  main( int  argc,  char   * argv[])
... {
    Polynominal x,y;
    cout<<"Input x :"<<endl;
    cin>>x;
    cout<<"x: "<<x<<endl;
    cout<<"Input y:"<<endl;
    cin>>y;    
    cout<<"y: "<<y<<endl;
    cout<<"x*y: "<<x*y<<endl;
    system("PAUSE");
    return EXIT_SUCCESS;
}

1.如果要把多项式a的值赋给多项式b:a.theList = b.theList,不能写成a.theList->link = b.theList->link
2.考虑如下两段代码段
Term *p = theList->link;
while( p != theList) {
    cout<<p->coef<<endl;
    p = p->link;
}
把theList之后的每项系数都打印出来，最后p指向theList
Term *p = theList->link;
while(p->link != theList){
    cout<<p->coef<<endl;
     p = p->link;
}
把theList之后的每项(除了最后一项)系数都打印出来，最后p指向最后一项
3.这些代码不能在vc 6.0上编译通过，提示友元类不能访问私有成员的错误，据说这是vc 6.0的bug,但在dev c++可以顺利编译通过.