What is the role of the "generating server" and/or "Reporting-MTA" in an Exchange NDR?

Question

Here is a macro which I wrote to test a number for primality:

(defmacro primep (num)
  `(not (or ,@(loop for p in *primes* collecting `(= (mod ,num ,p) 0)))))

*primes* is a dynamic variable which contains a list of the primes generated so far (the context is a 'next prime generator' function). Here are the results of a few eval-ed statements:

(let ((*primes* (list 2 3)))
  (primep 6))
-> T

(let ((*primes* (list 2 3)))
  (macroexpand-1 '(primep 6))
-> (NOT (OR (= (MOD 6 2) 0) (= (MOD 6 3) 0)))
-> T

(NOT (OR (= (MOD 6 2) 0) (= (MOD 6 3) 0)))
-> NIL

What is going on?

Solution

The generating server is the server that gave back the 5.1.1

5.1.1 > Is in the bad-address failure category, meaning the server received the message, did an internal lookup and couldnt find a mailbox to deliver to and generated an NDR.

A detailed explanation is given here: http://technet.microsoft.com/en-us/library/bb232118.aspx

Comments

[jkiiski]

You should use a function for this. Macros are for generating code. The problem here is that the LET binding for *PRIMES* happens at run-time, not during macroexpansion.

[shardulc]

@jkiiski How can I generate all those (= (mod ... statements using a function? I thought that was what macros are for (I've just started learning Common Lisp).

[jkiiski]

You don't need to generate them. Use a loop just like in any other language.

[shardulc]

@jkiiski OK, thanks. I will try that. Can you add that (and maybe an example) as an answer so I can accept it?

[shardulc]

Is there any advantage to using loop with thereis over dolist?

[jkiiski]

No real advantage, but a LOOP is simpler to use. With DOLIST you have to write the exit from the loop yourself.