D语言if…else语句

import std.stdio;

int main () { 
   /* local variable definition */ 
   int a = 100; 

   /* check the boolean condition */ 
   if( a < 20 ) { 
      /* if condition is true then print the following */ 
      writefln("a is less than 20" ); 
   } else { 
      /* if condition is false then print the following */
      writefln("a is not less than 20" ); 
   } 
   writefln("value of a is : %d", a); 

   return 0; 
}