Action interaction - specifically discard+keep and discard+reject

Hi folks.  I see Janurary has passed without the annual Action interaction 
debate :o).  I'm not suggesting we restart it, but after spending 3 hours 
reading the old postings I'm getting very confused and was wondering if someone 
could clear this lot up for me...


--------------------------------------------------------------------------------

Suppose this is my script:
  if A { keep; }
  if B { discard; }
It is obvious what I've to do if either A or B is true, and if neither A nor B 
is true, but what do I do when A AND B are true?

I think that I am meant to interpret it this way:  When I start processing the 
script, the action on my list is "Implicit Keep".  When I am told to "keep" 
then I cancel the "Implicit Keep", and replace it with an explicit "keep".  
When I am told to "discard" the message, I would normally cancel the "Implicit 
Keep" but as I have already canceled the "Implicit Keep", the "discard" has no 
effect here.

Were the script to be the other way round, ie:
  discard;
  keep;
Then when I read the "discard" I cancel the "Implicit Keep", leaving me with no 
actions on my list, and when I read the "keep", I place an explicit "keep" on 
the list.

Or am I meant to be producing a compile time/run time error?

So in terms of what we can conveniently tell the user in a rule based GUI a 
discard says "Discard the message unless explicitly told to keep it by another 
rule" and if they don't want other rules to mess them about then they have to 
follow it with a "stop", and ensure that no previous rule explicitly asked to 
keep this message.  But the discard action isn't really a hard and fast "chuck 
away this message" unless followed by a stop, and not preceeded by any keep 
commands?


--------------------------------------------------------------------------------

Sticking to this precise definition of a "discard" to be cancelling the 
implicit keep, am I right in saying that:

discard+reject = reject;
reject+(keep or redirect or fileinto or reject) = error;

as reject presumably cancels the implicit keep too so the addition of discard 
and reject isn't really an error as it just ends up with a reject.


--------------------------------------------------------------------------------

2.10.2
   An implicit keep is performed if a message is not written to a
   mailbox, redirected to a new address, or explicitly thrown out.  That
   is, if a fileinto, a keep, a redirect, or a discard is performed, an
   implicit keep is not.

Presumably this list should include reject, or are we happy enough that it is 
implied in the "Implementations SHOULD prohibit reject when used with other 
actions" statement of section 2.10.4

--------------------------------------------------------------------------------


Cheers for reading,

Nigel