D语言关联数组的属性

import std.stdio;

void main () { 
   int[string] array1;

   array1[test] = 3; 
   array1[test2] = 20; 

   writeln(sizeof: ,array1.sizeof); 
   writeln(length: ,array1.length); 
   writeln(dup: ,array1.dup);  
   array1.rehash; 

   writeln(rehashed: ,array1);  
   writeln(keys: ,array1.keys); 
   writeln(values: ,array1.values);

   foreach (key; array1.byKey) { 
      writeln(by key: ,key); 
   }

   foreach (value; array1.byValue) { 
      writeln(by value ,value); 
   }

   writeln(get value for key test: ,array1.get(test,10)); 
   writeln(get value for key test3: ,array1.get(test3,10));  
   array1.remove(test); 
   writeln(array1); 
}