State-Changed-From-To: open-analyzed
State-Changed-By: Manu
State-Changed-When: Wed Jan 31 14:06:53 PST 2001
State-Changed-Why:

Dear Grant,

Thanks for your message. I will try to answer all points in different
emails. For the moment, I would just like to discuss the issue between
and/and then and or/or else.

This is indeed the case that in ISE Eiffel and/and then and or/or else
do the exact same thing. The semantic as explained in ISE Eiffel is the
following. When you write:
- and then / or else: the compiler garantees that the second part of the
  boolean expression will be evaluated only if the first one is true in
  case of `and then', or if the first one is false in the case of
  `or else'.

- and / or have the following semantic: it is up to the compiler to
  decide in which order those expression will be evaluated at run-time.
  ETL does not specify that and/or should evaluate both left and right
  boolean expression. This is a compiler freedom for optimization.

Hope this is helpful,