D语言输出范围

import std.algorithm; 
import std.stdio; 

struct MultiFile { 
   string delimiter;
   File[] files;

   this(string delimiter, string[] fileNames ...) { 
      this.delimiter = delimiter; 

      /* stdout is always included */ 
      this.files ~= stdout; 

      /* A File object for each file name */ 
      foreach (fileName; fileNames) { 
         this.files ~= File(fileName, w); 
      } 
   }
   void put(T)(T element) { 
      foreach (file; files) { 
         file.write(element, delimiter); 
      } 
   }
}
void main() { 
   auto output = MultiFile(\n, output_0, output_1); 
   copy([ 1, 2, 3], output);  
   copy([ red, blue, green ], output); 
}