C ++，在for（）函数内将复数与普通双精度组合时出错

Question

如果这个问题很明显，我很抱歉，但我无法弄清楚我的代码有什么问题。下面的解释，这里是代码：

#include <iostream>
#include <cmath>
#include <complex>

using namespace std;

int main(){

  //Variables:
  complex<double> c;  //Coordinate
  complex<double> zn;
  complex<double> znp1;


  double iteration;  //Iteration counter
  double limit = 1.0e3;  //zn must exceed limit


  double resolution = 50.0;     //Points/pixels per axis

  double realrangeplus =5.0;    //Coordinate system
  double realrangeminus = -5.0;
  double realsubdiv = (realrangeplus - realrangeminus)/resolution;

  double imagrangeplus = 5.0;
  double imagrangeminus = -5.0;
  double imagsubdiv = (imagrangeplus - imagrangeminus)/resolution;



  //cycle through real axis with c
  for(real(c) = realrangeminus; real(c) <= realrangeplus; real(c) = real(c) + realsubdiv){

    //cycle through imaginary axis with c
    for(imag(c) = imagrangeminus; imag(c) <= imagrangeplus; imag(c) = imag(c) + imagsubdiv){
      //==========================================

      iteration = 0.0;  //reset
      zn = (0.0, 0.0);
      znp1 = (0.0, 0.0);

      //Start iterating:
      do{
        iteration = iteration + 1.0; //count iterations

        zn = znp1;
        znp1 = zn*zn + c;

      }while(abs(zn)<=limit);



      cout << real(c) << " " << imag(c) << "      " << real(zn) << " " << imag(zn) << "    " << iteration << endl;

      //==========================================
    }

  }

  return 0;
}

这是在 Ubuntu 终端或 eclipse 中使用 g++ mandelbrot_skript.cpp 编译它时的错误：

mandelbrot_skript.cpp: In function ‘int main()’:
mandelbrot_skript.cpp:32:17: error: lvalue required as left operand of assignment
   for(real(c) = realrangeminus; real(c) <= realrangeplus; real(c) = real(c) + realsubdiv){
                 ^~~~~~~~~~~~~~
mandelbrot_skript.cpp:32:79: error: lvalue required as left operand of assignment
   for(real(c) = realrangeminus; real(c) <= realrangeplus; real(c) = real(c) + realsubdiv){
                                                                               ^~~~~~~~~~
mandelbrot_skript.cpp:35:19: error: lvalue required as left operand of assignment
     for(imag(c) = imagrangeminus; imag(c) <= imagrangeplus; imag(c) = imag(c) + imagsubdiv){
                   ^~~~~~~~~~~~~~
mandelbrot_skript.cpp:35:81: error: lvalue required as left operand of assignment
     for(imag(c) = imagrangeminus; imag(c) <= imagrangeplus; imag(c) = imag(c) + imagsubdiv){

                                                                             ^~~~~~~~~~

我正在尝试创建 mandelbrot 集的图像，代码可能完全错误，但这不是重点。

我不明白为什么会出现错误信息。据我所知，没有拼写错误，所有变量都具有正确的数据类型（我认为）并且我已经成功地尝试将实部和虚部与普通双精度变量相加和相乘。只有当我在 for() 函数中执行此操作时才会出现此错误。奇怪的是，完全相同的代码在名为 "CPP N-IDE".

的 android 应用程序中执行时没有问题

基本上，我做错了什么？

Answer 1

real(c) 是一个 reader 函数。 c.real(value) 是写函数。 source

因此：

for (c.real(realrangeminus); real(c) <= realrangeplus; c.real(real(c) + realsubdiv)) {

等等

Answer 2

cpp reference

For any pointer to an element of an array of complex named p and any valid array index i, reinterpret_cast(p)[2*i] is the real part of the complex number p[i], and reinterpret_cast(p)[2*i + 1] is the imaginary part of the complex number p[i]

因此，如前所述，real(c) 和 imag(c) 将是 reader 读取变量的方法，而不是设置变量的方法。

可以找到有关复数使用的更多信息on Whosebug here

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