And it doesn't really matter -- I don't want you understand why it doesn't have the if statement, but I want you to understand that sometimes you can see a problem in a different way and rewrite it so that a special case goes away and becomes the normal case.
E, realmente, non importa. Eu non quero que entendas por que non ten a condición if, quero que entendas que, ás veces, podes ver  un problema doutra forma e reescribilo para que  desapareza un caso especial e se converta nun caso normal.