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); 
}