自定义C++一元多项式类

 自己定义了一个一元多项式的简单类，主要是用来实现一个简单的框架，另外就是验证编译器默认情况下会为我们的类添加那些构造函数。

 

/*
* polynomial.h
* 该类定义一元多项式
* MAXDEGREE ：定义该类最大可表示的次数
* MINCOEFF：定义绝对值最小的系数
* coefficient[  ] :存放一元多项式的系数
* currentDegree：存放当前对象的最高次数
* 构造函数：默认构造函数设置coefficient[]和currentDegree全为0
*                可以使用一个float数组和数组长度来构造一个一元多项式
* display( ) :用于显示对象的信息
* value(  ):计算给定x时的一元多项式的值
* operator +/-():计算多项式之间的加减
* power(  ) ：用于计算给定x值的x的degree次幂的值
*/
class polynomial
{
public:
    polynomial(  );
    polynomial( float coeff [ ],int size );
    ~polynomial(  ){}

    void  display(  );
    double value(float xx);

    friend polynomial operator +( const polynomial& one,const polynomial& two );
    friend polynomial operator -( const polynomial& one,const polynomial& two );

private:
    double power( float xx,int degree );


private:
    static const int MAXDEGREE=20;
    static const float MINCOEFF=0.000001;
    float coefficient[ MAXDEGREE+1 ];
    int currentDegree;

};

 

/*
 *polynomial.cpp
 */
#include "polynomial.h"
#include <iostream>
#include <cstdlib>

polynomial::polynomial(  )
{
    for( int i=0;i<MAXDEGREE+1;i++ )
        coefficient[ i ]=0.0;
    currentDegree=0;

}

polynomial::polynomial( float coeff [  ],int size )
{
   if( size>MAXDEGREE )
       {
           std::cout<<"the degree is bigger than the MAXDEGREE\n";
           exit( -1 );

       }
   if( coeff==NULL )
       {
           std::cout<<"you have input nothing\n";
           exit( -1 );

       }

   for( int i=0;i<size;i++ )
       coefficient[ i ]=coeff[ i ];

   currentDegree=size-1;

}

void polynomial::display(  )
    {
        std::cout<<"The MAXDEGREE = "<<MAXDEGREE<<"\n";

        std::cout<<coefficient[ 0 ];
        for( int i=1;i<currentDegree+1;++i )
            {
                if( (coefficient[ i ] > (0.0-MINCOEFF)) && (coefficient[ i ] <MINCOEFF )) ;
                else
                {
                    if( coefficient[ i ]>0.0 )
                        std::cout<<"+"<<coefficient[ i ]<<"x^"<<i;
                    else
                        std::cout<<coefficient[ i ]<<"x^"<<i;
                }
            }
        std::cout<<std::endl;
    }

double polynomial::power( float xx,int degree )
    {
        double temp=1.0;
        while( degree-- )
            temp*=xx;
        return temp;

    }

double polynomial::value( float xx )
    {
        double sum=0.0;
        for( int i=0;i<currentDegree+1;++i )
            {
                sum = sum+coefficient[ i ]*power( xx,i );

            }
        return sum;

    }

polynomial operator +( const polynomial& one,const polynomial& two )
    {
        polynomial temp;

        int biggerDegree=( one.currentDegree > two.currentDegree ?one.currentDegree:two.currentDegree );
        for( int i=0;i<biggerDegree+1;++i )
            {
                temp.coefficient[ i ] = one.coefficient[ i ]+two.coefficient[ i ];

            }
        temp.currentDegree=biggerDegree;

        return temp;

    }

polynomial operator -( const polynomial& one,const polynomial& two )
    {
        polynomial temp;

        int biggerDegree=( one.currentDegree > two.currentDegree ?one.currentDegree:two.currentDegree );
        for( int i=0;i<biggerDegree+1;++i )
            {
                temp.coefficient[ i ] = one.coefficient[ i ]-two.coefficient[ i ];

            }
        temp.currentDegree=biggerDegree;

        return temp;

    }

 

/*
* test.cpp
*/
#include <iostream>
#include "polynomial.h"

int main(  )
    {
        float one[  ]={1,2,3,4,5};
        polynomial poly_one( one,5 );
        poly_one.display(  );
        std::cout<< poly_one.value( 1.0 )<<"\n";

        float two[  ]={1.2,2.5,-3.5,4.5,-5.5};
        polynomial poly_two( two,5 );
        poly_two.display(  );
        std::cout<< poly_two.value( 1.0 )<<"\n";

        polynomial poly_three;
        poly_three=poly_two;
        poly_three.display(  );

        polynomial poly_four(poly_two);
        poly_four.display(  );


        return 0;

    }
/*
* test.cpp
*/
#include <iostream>
#include "polynomial.h"

int main(  )
    {
        float one[  ]={1,2,3,4,5};
        polynomial poly_one( one,5 );
        poly_one.display(  );
        std::cout<< poly_one.value( 1.0 )<<"\n";

        float two[  ]={1.2,2.5,-3.5,4.5,-5.5};
        polynomial poly_two( two,5 );
        poly_two.display(  );
        std::cout<< poly_two.value( 1.0 )<<"\n";

        polynomial poly_three;
        poly_three=poly_two;
        poly_three.display(  );

        polynomial poly_four(poly_two);
        poly_four.display(  );


        return 0;

    }

从main中，poly_three和poly_four可知，如果我们没有声明复制构造函数和赋值构造函数的化，编译器会为我们自动添加。

另外，如果我们没有定义类的默认构造函数的话，编译器会为我们添加一个函数体为空的默认构造函数。

还有就是operator =()函数也会被自动添加，但是只满足同类对象之间相互赋值。