C ++错误：'没有从[类名称]到“int”的适当转换'' [英] C++ error: 'No suitable conversion from [class name] to "int" '

问题描述

我正在处理一个类，用于多项式的加，减和乘法。

我遇到以下错误：

'没有合适的转换函数从[class name] int'

在语句中：

  （加法函数）
 
 return deriv; 
  

任何人都可以提供有关如何纠正这些问题的指导？

非常感谢提前，
Ryan

这是我的代码：

  #includestdafx.h
 #include< iostream> 
 
 using namespace std; 
 
 class Poly 
 {
 private：
 
 // int ord; //多项式的阶数
 // int coeff [100]; 
 
 public：
 
 int ord; //多项式的阶数
 int coeff [100]; 
 
 
 int a，b，c; 
 Poly（）; // constructor 
 int addition（int）; //添加2个多项式
 int subtraction（int）; // subtracts 2 polynomials 
 int multiplication（int）; //将2个多项式相乘
 void evaluate（int）; //使用Horner的方法来计算并返回在x 
处求值的多项式int differentiate（int）; // 
 void set（int，int）; // mutator function 
 int order（）; 
 void print（）; //打印结果
}; 
 
 Poly :: Poly（）//默认构造函数
 {
 for（int i = 0; i <100; i ++）
 {
 coeff [i] = 0; 
} 
} 
 
 void Poly :: set（int a，int b）// mutator function 
 {
 // coeff = new Poly [ b + 1]。 
 coeff [b] = a; 
 ord = order（）; 
} 
 
 int Poly :: order（）
 {
 int d = 0; 
 for（int i = 0; i <100; i ++）
 if（coeff [i]！= 0）d = 
 return d; 
} 
 
 void print（）
 {
 int coeff [] = {0}; 
 
 for（int i = 99; i> = 0; i--）
 {
 if（coeff [i]！= 0）
 {
 cout<< coeff [i]< x ^<< i<< ; 
} 
} 
} 
 
 int evaluate（int x）
 {
 int p = 0; 
 for（int i = ord; i> = 0; i--）
 p = coeff [i] +（x * p） 
 return p; 
} 
 
 int Poly :: differentiate（int）
 {
 if（ord == 0）
 {
 Poly t; 
 t.set（0，0）; 
 return t; 
} 
 
聚衍生; 
 deriv.ord = ord  -  1; 
 
 for（int i = 0; i  deriv.coeff [i] =（i + 1）* coeff [i + 1] 
 return deriv; 
} 
 
 int Poly :: addition（Poly b）
 {
 Poly a = * this; 
 Poly c; 
 
 for（int i = 0; i <= a.ord; i ++）
 c.coeff [i] + = a.coeff [i] 
 for（int i = 0; i <= b.ord; i ++）
 c.coeff [i] + = b.coeff [i] 
 
 c.ord = c.order（）; 
 
 return c; 
} 
 
多边形减法（Poly b）
 {
 Poly a = * this; 
 Poly c; 
 
 for（int i = 0; i <= a.ord; i ++）
 c.coeff [i] + = a.coeff [i] 
 for（int i = 0; i <= b.ord; i ++）
 c.coeff [i]  -  = b.coeff [i] 
 
 c.ord = c.order（）; 
 
 return c; 
} 
 
 int Poly ::乘法（Poly b）
 {
 Poly a = * this; 
 Poly c; 
 
 for（int i = 0; i <= a.ord; i ++）
 for（int j = 0; j <= b.ord; j ++）
 c.coeff [i + j] + =（a.coeff [i] * b.coeff [j]）; 
 c.order = c.order（）; 
} 
 
 int main（）
 {
 Poly a，b，c，d; 
 a.set（7，4）; // 7x ^ 4 
 a.set（1，2）; // x ^ 2 
 
 b.set（6，3）; // 6x ^ 3 
 b.set（-3，2）; // -3x ^ 2 
 
 c = a.subtraction（b）; //（7x ^ 4 + x ^ 2） - （6x ^ 3  -  3x ^ 2）
 
 c.print（）; 
 
 cout<< \\\
; 
 
 d = c.differentiate（）。differentiate（）; 
 
 d.print（）; 
 
 cout<< \\\
; 
 
 cout<< （2）; // replace 2 with 2 
 cin.get（）; 
 
 return 0; 
} 
  

解决方案

在此函数中：

  int Poly :: addition（Poly b）
 {
 Poly a =这个; 
 Poly c; 
 
 for（int i = 0; i <= a.ord; i ++）
 c.coeff [i] + = a.coeff [i] 
 for（int i = 0; i <= b.ord; i ++）
 c.coeff [i] + = b.coeff [i] 
 
 c.ord = c.order（）; 
 
 return c; 
} 
  

你说你会返回一个int：

  int Poly :: addition（Poly b）
 // ^ ------承诺返回int 
  

但您返回 c 其中 c 是 Poly 。更改返回类型：

 聚Poly :: addition（Poly b）
  

int Poly :: differentiate（int）有同样的问题。
将其更改为

  Poly Poly :: differentiate（int）
  
 
 
 
 BTW  - 为什么会忽略它 int ？
 
 
 
此外， int Poly :: multiplication（Poly b）不返回任何东西。
 
 
 
您还有其他问题。例如，print和evaluate函数应该是成员函数，使用std :: vector存储系数可能更有意义。
 
 
 
编译器可能告诉你如果你仔细看看错误的行号。
 
I'm working on a class for the addition, subtraction and multiplication of polynomials.  

I'm getting the following errors:

'No suitable conversion function from [class name] to "int" '

in statements:
return c;    (addition function)

return deriv;
Can anyone offer any guidance on how to correct these?

Thanks very much in advance,
Ryan

Here is my code:
#include "stdafx.h"
#include <iostream>

using namespace std;

class Poly
{
private:

//  int ord;                            // the order of the polynomial
//  int coeff[100];

public:

    int ord;                            // the order of the polynomial
    int coeff[100];


    int a, b, c;
    Poly();                             // constructor
    int addition(int);                  // adds 2 polynomials
    int subtraction(int);               // subtracts 2 polynomials
    int multiplication(int);            // multiplies 2 polynomials
    void evaluate(int);                 // uses Horner's method to compute and return the polynomial evaluated at x
    int differentiate(int);         // 
    void set(int, int);                 // mutator function
    int order();
    void print();                       // prints the results
};

Poly::Poly()            // the default constructor
{
    for (int i = 0; i < 100; i++)
    {
        coeff[i] = 0;
    }
}

void Poly::set(int a, int b)    // mutator function
{
    // coeff = new Poly[b + 1];
    coeff[b] = a;
    ord = order();
}

int Poly::order()
{
    int d = 0;
    for (int i = 0; i < 100; i++)
        if (coeff[i] != 0) d = i;
        return d;
}

void print()
{
    int coeff[] = { 0 };

    for (int i = 99; i >= 0; i--)
    {
        if (coeff[i] != 0)
        {
            cout << coeff[i] << "x^" << i << " ";
        }
    }
}

int evaluate(int x)
{
    int p = 0;
    for (int i = ord; i >= 0; i--)
        p = coeff[i] + (x * p);
    return p;
}

int Poly::differentiate(int)
{
    if (ord == 0)
    {
        Poly t;
        t.set(0, 0);
        return t;
    }

    Poly deriv;
    deriv.ord = ord - 1;

    for (int i = 0; i < ord; i++)
        deriv.coeff[i] = (i + 1) * coeff[i + 1];
    return deriv;
}

int Poly::addition(Poly b)
{
    Poly a = *this;
    Poly c;

    for (int i = 0; i <= a.ord; i++)
        c.coeff[i] += a.coeff[i];
    for (int i = 0; i <= b.ord; i++)
        c.coeff[i] += b.coeff[i];

    c.ord = c.order();

    return c;
}

Poly subtraction(Poly b)
{
    Poly a = *this;
    Poly c;

    for (int i = 0; i <= a.ord; i++)
        c.coeff[i] += a.coeff[i];
    for (int i = 0; i <= b.ord; i++)
        c.coeff[i] -= b.coeff[i];

    c.ord = c.order();

    return c;
}

int Poly::multiplication(Poly b)
{
    Poly a = *this;
    Poly c;

    for (int i = 0; i <= a.ord; i++)
    for (int j = 0; j <= b.ord; j++)
        c.coeff[i + j] += (a.coeff[i] * b.coeff[j]);
    c.order = c.order();
}

int main()
{
    Poly a, b, c, d;
    a.set(7, 4);                //  7x^4
    a.set(1, 2);                //   x^2

    b.set(6, 3);                //   6x^3
    b.set(-3, 2);               //  -3x^2

    c = a.subtraction(b);       // (7x^4 + x^2) - (6x^3 - 3x^2)

    c.print();

    cout << "\n";

    d = c.differentiate().differentiate();

    d.print();

    cout << "\n";

    cout << c.evaluate(2);  // substitute x with 2
    cin.get();

    return 0;
}

解决方案
Your (first) problem is in this function:
int Poly::addition(Poly b)
{
    Poly a = *this;
    Poly c;

    for (int i = 0; i <= a.ord; i++)
        c.coeff[i] += a.coeff[i];
    for (int i = 0; i <= b.ord; i++)
        c.coeff[i] += b.coeff[i];

    c.ord = c.order();

    return c;
}
You say you will return an int:
int Poly::addition(Poly b)
//^------ promise to return int
but you return c where c is a Poly. change the return type:
Poly Poly::addition(Poly b)
int Poly::differentiate(int) has the same problem.
Change it to
Poly Poly::differentiate(int)
BTW - Why does this take a int which it ignores?

Furthermore, int Poly::multiplication(Poly b) doesn't return anything as it stands.

You have further problems. For example the print and evaluate functions should be member functions and it may make more sense to use a std::vector to store the coefficients.

The compiler probably told you the line number of the error if you look closely.

                        
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