[PPL-devel] generators

[P M Hill]

Hi,

I have two queries wrt the generators.

As I understand it (and as stated on page 14 of the user manual,
the linear expression used to define a vertex, ray or line should be
homogeneous.
After all, the constant part is irrelevant:
we say that the constant part is disregarded.
I think though that if it is really irrelevant and disregarded, we should
not allow it. Surely, if the user includes a constant term, the user must
have misunderstood the representation we are using.
It seems to me that it is better that the user gets an error message than
just ignore it.

The second query is similar. For a ray and line the expression begins with 
n ^ or n | where n is any number. I am not clear a) why we let the user
type anything here other than 1 (or even why the expression has to start
with a number at all, all we need is a means of indicating that the
following linear expression is to denote a line or a ray).
Also, can this number be 1.234 - ie a rational or must it be an integer.
Can it be 0?
So all these questions I have (and therefore, maybe other ignorant
users(!)), yet, if we just said it had to be 1 (and enforced that) then it
is much simpler.

ciao,
  Pat