c – 对每个以逗号分隔的对象执行成员函数

#include "CImg.h"
using namespace cimg_library;

int main() {
  CImg<unsigned char> src("Tulips.jpg");
  int width = src.width();
  int height = src.height();
  int depth = src.depth();

  //New grayscale images.
  CImg<unsigned char> gray1(width,height,depth,1);
  CImg<unsigned char> gray2(width,1);

  // ... 

  (src,gray1,gray2).display("RGB to Grayscale");
}

线条如何(src,gray2).display(“RGB to Grayscale”);工作？如何将显示成员函数应用于逗号分隔列表中的每个对象？