1As with functions, macros can also contain declarations, but you don’t need to worry about those for now.

3Another function, **MACROEXPAND**, keeps expanding the result as long as the first element of the resulting expansion is the name of the macro. However, this will often show you a much lower-level view of what the code is doing than you want, since basic control constructs such as are also implemented as macros. In other words, while it can be educational to see what your macro ultimately expands into, it isn’t a very useful view into what your own macros are doing.

5This is from Joel on Software by Joel Spolsky, also available at . Spolsky’s point in the essay is that all abstractions leak to some extent; that is, there are no perfect abstractions. But that doesn’t mean you should tolerate leaks you can easily plug.

7It may not be obvious that this loop is necessarily infinite given the nonuniform occurrences of prime numbers. The starting point for a proof that it is in fact infinite is Bertrand’s postulate, which says for any n > 1, there exists a prime p, n < p < 2n. From there you can prove that for any prime number, P less than the sum of the preceding prime numbers, the next prime, P’, is also smaller than the original sum plus P.