Brainteaser

 def twice[A](func: A=>A)= (a:A) => func(func(a));
 def chain[A](f1: A=>A, f2: A=>A)= (a:A) => f1(f2(a));

 val appendMark = (a:String) => a + "!";
 val prependMark = (a:String) => "!" + a;
 
 println( twice(chain(appendMark,prependMark))("Hello"));