c++ - atof 函数在程序中不起作用

Question

在我的 C++ 程序中，我需要创建一个名为 ComplexNumber 的类来保存复数的信息。我已经在头文件中编写了所有函数，并将这些函数移到了 .cpp 文件中。

我当前程序的 atof 函数不起作用。它显示一条错误，指出 atof 不在 std 中。当我删除代码的 std::部分时，错误显示 atof 未在范围内声明。

以下是两个示例错误消息:

ComplexNumber.cpp:63:33: error: 'atof' was not declared in this scope o.realPart = atof(temp.c_str); ^ ComplexNumber.cpp:66:23: error: 'atof' is not a member of 'std' o.imaginaryPart = std::atof(temp.c_str);

错误来 self 的 ComplexNumber.cpp 文件，老实说，我对 C++ 的了解还不够，无法确定如何修复此类问题。任何帮助将不胜感激。

---

主要.cpp

/* 
 * File:   main.cpp
 * Author: Tyler Weaver
 *
 * Created on February 2, 2015, 4:08 PM
 */

#include <cstdlib>

using namespace std;

/*
 * 
 */
int main(int argc, char** argv) 
{

    return 0;
}

复数.h

/* 
 * File:   ComplexNumber.h
 * Author: Tyler Weaver
 *
 * Created on February 2, 2015, 4:10 PM
 */

#ifndef COMPLEXNUMBER_H
#define COMPLEXNUMBER_H

#include <cmath>
#include <ostream>
#include <istream>
#include <string>

class ComplexNumber {
public:
    ComplexNumber(float real = 0, float imaginary = 0);

    ComplexNumber operator+(ComplexNumber o);

    ComplexNumber operator-(ComplexNumber o);

    ComplexNumber operator*(ComplexNumber o);

    ComplexNumber operator/(ComplexNumber o);

    bool operator==(ComplexNumber o);

    friend std::ostream& operator<<(std::ostream& out, ComplexNumber o);

    friend std::istream& operator>>(std::istream& in, ComplexNumber o);

    double getMagnitude();

private:
    float realPart;
    float imaginaryPart;
};

#endif  /* COMPLEXNUMBER_H */

复杂数字.cpp

/* 
 * File:   ComplexNumber.cpp
 * Author: Tyler Weaver
 * 
 * Created on February 2, 2015, 4:10 PM
 */

#include "ComplexNumber.h"

ComplexNumber::ComplexNumber(float real, float imaginary) 
{
    realPart = real;
    imaginaryPart = imaginary;
}

ComplexNumber ComplexNumber::operator+(ComplexNumber o) 
{
    return ComplexNumber(realPart + o.realPart,
            imaginaryPart + o.imaginaryPart);
}

ComplexNumber ComplexNumber::operator-(ComplexNumber o) 
{
    return ComplexNumber(realPart - o.realPart,
            imaginaryPart - o.imaginaryPart);
}

ComplexNumber ComplexNumber::operator*(ComplexNumber o) 
{
    return ComplexNumber(realPart * o.realPart -
            imaginaryPart * o.imaginaryPart,
            realPart * o.imaginaryPart + imaginaryPart * o.realPart);
}

ComplexNumber ComplexNumber::operator/(ComplexNumber o) 
{
    double divisor = o.realPart * o.realPart +
            o.imaginaryPart * o.imaginaryPart;

    return ComplexNumber((realPart * o.realPart +
            imaginaryPart * o.imaginaryPart) / divisor,
            (imaginaryPart * o.realPart - realPart * o.imaginaryPart) /
            divisor);
}

bool ComplexNumber::operator==(ComplexNumber o) 
{
    return ((realPart == o.realPart) &&
            (imaginaryPart = o.imaginaryPart));
}

std::ostream& operator<<(std::ostream& out, ComplexNumber o) 
{
    out << o.realPart << " + " << o.imaginaryPart << "i\n";
    return out;
}

std::istream& operator>>(std::istream& in, ComplexNumber o) 
{
    std::string temp;

    getline(in, temp, '+');
    o.realPart = std::atof(temp.c_str);

    getline(in, temp, 'i');
    o.imaginaryPart = std::atof(temp.c_str);

    return in;
}

double ComplexNumber::getMagnitude() 
{
    return sqrt(realPart * realPart +
            imaginaryPart * imaginaryPart);
}

Answer 1

你忘了 #include <cstdlib>在 ComplexNumber.cpp 中，atof函数在该 header 中声明。

在 C++ 中，源文件是相互独立编译的，所有你想使用的函数都应该在某处声明。如果它们在单独的头文件中声明，则应在引用要调用的函数之前包含该文件。