Firstly, I think you're taking this waaaayyyy more seriously than it was intended. Secondly

  double foo = 1.2;
  printf(foo);
  puts(foo);

won't compile, while

  double foo = 1.2;
  display(foo);

works fine.

Incidentally I actually think display is the only thing on this list that is probably worth using, you could also probably extend it to accept multiple arguments relatively simply as well.