我正在尝试编写一组通用数学实用程序类(根查找器,集成器等),这些类在构造时接收指向基类的指针,该基类定义了我希望特定算法运行的函数。基类应该只定义可以由用户根据需要实现的公共虚拟接口(抽象或具有默认的简单功能)type operator()(type inputArg)
。这将允许用户仅实现所需的仿函数并执行所需的计算。我的母亲在下面:
第一个头定义了抽象接口类
// BaseFunctor.h
#ifndef _BASE_FUNCTOR_H_
#define _BASE_FUNCTOR_H_
class BaseFunctor
{
public:
virtual double operator() (double x) = 0;
};
#endif
这是其中一个解算器方法的类
// NewtonsMethod.h
#ifndef _NEWTONS_METHOD_H_
#define _NEWTONS_METHOD_H_
class BaseFunctor;
class NewtonsMethod
{
public:
NewtonsMethod(BaseFunctor *rhsIn,
BaseFunctor *rhsPrimeIn,
double x0In);
~NewtonsMethod();
bool DetermineRoot(double &root);
private:
double x0;
BaseFunctor *rhs;
BaseFunctor *rhsPrime;
static const double EPSILON;
static const unsigned int MAX_ITER;
};
#endif
这是解算器实现: // NewtonsMethod.cpp
#include "NewtonsMethod.h"
#include "BaseFunctor.h"
#include <cmath>
const double NewtonsMethod::EPSILON = 1e-9;
const unsigned int NewtonsMethod::MAX_ITER = 30;
NewtonsMethod::NewtonsMethod(BaseFunctor *rhsIn,
BaseFunctor *rhsPrimeIn,
double x0In) :
rhs (rhsIn),
rhsPrime(rhsPrimeIn),
x0 (x0In)
{ }
NewtonsMethod::~NewtonsMethod() { }
bool NewtonsMethod::DetermineRoot(double &root)
{
// This is obviously not implemented
root = rhs(1.0) / rhsPrime(2.0);
return false;
}
我做派生类实现的主要功能: // Main.cpp
#include "BaseFunctor.h"
#include "NewtonsMethod.h"
#include <iostream>
#include <iomanip>
class fOfX : public BaseFunctor
{
double operator() (double x)
{
return x * x - 2.0;
}
};
class fPrimeOfX : public BaseFunctor
{
double operator() (double x)
{
return 2.0 * x;
}
};
int main()
{
double x0 = 2.0;
BaseFunctor *f = new fOfX();
BaseFunctor *fPrime = new fPrimeOfX();
NewtonsMethod newton(f, fPrime, x0);
double root = 0.0;
bool converged = newton.DetermineRoot(root);
if (converged)
{
std::cout << "SUCCESS: root == " << std::setprecision(16) << root << std::endl;
}
else
{
std::cout << "FAILED: root == " << std::setprecision(16) << root << std::endl;
}
delete f;
delete fPrime;
}
我试着让它尽可能简短,如果太长,我很抱歉。基本上我得到错误:
g++ Main.cpp NewtonsMethod.cpp -o main
NewtonsMethod.cpp: In member function ‘bool NewtonsMethod::DetermineRoot(double&)’:
NewtonsMethod.cpp:29: error: ‘((NewtonsMethod*)this)->NewtonsMethod::rhs’ cannot be used as a function
NewtonsMethod.cpp:29: error: ‘((NewtonsMethod*)this)->NewtonsMethod::rhsPrime’ cannot be used as a function
如何解决此问题,保留所需功能或为各种所需功能派生类?
由于
答案 0 :(得分:1)
rhs
和rhsPrime
是指针。您需要引用它们才能调用函数调用操作符。
(*rhs)(1.0) / (*rhsPrime)(2.0)
如果需要rhs
和rhsPrime
(即不能为NULL)并且在NewtonsMethod
对象具有构造函数后无法更改,则应将它们声明为引用而不是指针。这也消除了取消引用它们来调用函数调用操作符的需要。
下面的示例显示了如何使用引用来引用仿函数。
class NewtonsMethod
{
public:
NewtonsMethod(BaseFunctor& rhsIn,
BaseFunctor& rhsPrimeIn,
double x0In);
~NewtonsMethod();
bool DetermineRoot(double &root);
private:
double x0;
BaseFunctor& rhs;
BaseFunctor& rhsPrime;
static const double EPSILON;
static const unsigned int MAX_ITER;
};
int main()
{
double x0 = 2.0;
fOfX f;
fPrimeOfX fPrime;
NewtonsMethod newton(f, fPrime, x0);
}
...或...
int main()
{
double x0 = 2.0;
BaseFunctor *f = new fOfX();
BaseFunctor *fPrime = new fPrimeOfX();
NewtonsMethod newton(*f, *fPrime, x0);
// ... other code including delete for the functors
}