D语言访问已修改的联合体成员

import std.stdio;

union Data { 
   int i; 
   float f; 
   char str[13]; 
};  
void main( ) { 
   Data data; 
   writeln( "size of : ", data.sizeof);  

   data.i = 10; 
   writeln( "data.i : ", data.i); 

   data.f = 220.5; 
   writeln( "data.f : ", data.f);  

   data.str = "D Programming".dup; 
   writeln( "data.str : ", data.str); 
}