⟩ How can f be used for both float and double arguments in printf? Are not they different types?
In the variable-length part of a variable-length argument list, the ``default argument promotions'' apply: types char and short int are promoted to int, and float is promoted to double. (These are the same promotions that apply to function calls without a prototype in scope, also known as ``old style'' function calls. Therefore, printf's %f format always sees a double. (Similarly, %c always sees an int, as does %hd.)
