> > > What Random stream should we be using (if any) to determine if a
> > > Customer is an Express/Normal.  In particular I'm looking at
> > > implementing the Items Bought algorithm.
> >
> > You would probably have to add another random stream to the
> > SupermarketSim class and use it for making the decision.
> 
>    Can we just use one of the streams already in place?  We would have
> to seed this new stream somehow which would mean adding a new
> command line parameter unless we seed it with time() which would
> make the output different every time.  Are you expecting that all of
> our outputs will be identical for given seeds and parameters?

It is desirable that your output be predictable and consistent when
using the same random seeds.  It is also desirable that the various
random streams be seeded independantly (see section 2.7.2 of the notes
for an explanation).  It also makes for an ugly design to have 2
random streams controlling 3 sets of random numbers.  We should either
have 1 or 3 random streams.

I propose that we have 3 random streams.  It's an easier change to add
a random stream, rather than subtract one.

On the other hand, I feel it's too late to require that the input
format be changed, from inputting 2 seeds to 3 seeds.

So, in summary, you should add a 3rd random stream to the code, but
use the second seed (the one for the items stream) to seed this new
random stream.

> Also it's getting really annoying and time consuming having to
> rewrite sections of code every time these questions come up ... On
> the other hand, with this assignment it seems really difficult to
> know what exactly is expected.

Unfortunately, it is difficult to write an assignment which addresses
all possible issues before the assignment is handed out.  In order to
try and handle issues which come up after the assignment is started,
we have setup a Q&A page, into which all new issues are addressed.  We
try our best to minimise the changes required (see above for an
example), but these changes should not be that painful if you keep
yourself up to date with the Q&A page, say once per day.

I really don't think the changes are that significant, especially
compared to the many last minute "design change requirements" you will
encounter when developing for a project as a software developer.

Carl.