D语言ref函数

import std.stdio;

ref int greater(ref int first, ref int second) { 
   return (first > second) ? first : second; 
} 

void main() {
   int a = 1; 
   int b = 2;  

   greater(a, b) += 10;   
   writefln("a: %s, b: %s", a, b);   
}