+(If you need to print values of type T as well as pointers to T,
+the receiver for String must be of value type; this example used a pointer because
+that's more efficient and idiomatic for struct types.
+See the section below on pointers vs. value receivers for more information.)
+
Our String() method is able to call Sprintf because the
print routines are fully reentrant and can be used recursively.
We can even go one step further and pass a print routine's arguments directly to another such routine.