🚀 go-pugleaf

Harini Swaminathan writes:
>
> Hi everyone.
>
> I'm doing a comparison between Simula and MODSIM, and I would be grateful for
> your comments, or references to papers on this.

 I suggest you contact John Salt who has used both systems. The last
 e-mail address I have for him is: jds@unik.no .

 Below is part of a communication I had with him last year when I asked
 him the major pros and cons of MODSIM against SIMULA.

 Cheers....Ron

 P.S. In addition to John's points, I imagine that price is also a
 factor!

------------------------------------------------------------------------
  Ron Kerr, Computing Service, Newcastle University, NE1 7RU, England.
 Tel. +44 191 222 8187       Fax. +44 191 222 8765  (NOTE new area code)
------------------------------------------------------------------------


 John Salt's comments:
 --------------------

 I'd say the main advantages of MODSIM II over Simula are:

     More modern-looking syntax (like Modula-2)
     Slightly tighter encapsulation
     Easier to modularize (explicit IMPORT statements)
     Built-in portable graphics for animation & presentation
     Multiple rather than simple inheritance
     An object can participate in multiple concurrent activities
     An object can belong to multiple queue objects
     Defined syntax for ON INTERRUPT clause
     No need to explicitly define classes as VIRTUAL

....but, on the other hand, its disadvantages are:


     No nesting of methods/procedures
     No formal language specification
     No automatic garbage collection
     No references kept from LINK to HEAD objects (or equivalent)
     Inadequate documentation
     Less competent (IMHO) implementation
     Baffling run-time error messages

The thing that swung the Eurotunnel decision was the question of
graphics.  The management *insisted* that they have pretty pictures
to watch.  I have to admit, it's great fun having a language that
lets you make animated simulations interactive just by overriding
the "BeSelected" method of a graphical object.

MODSIM II also includes a concept called PROTO classes, which are
the same idea as Meyer's parameterized classes in Eiffel.  It's
not an indispensable feature, but it's nice to have.  MODSIM II
also follows the Ada convention of separating definition and
implementation modules, which I find rather annoying.  I gave
a talk at Software Development '92 in Wembley about the differences
between Simula and MODSIM II ("The Silver Anniversary of the
Silver Bullet" -- catchy, huh?), and came to the conclusion that,
while I *just* preferred MODSIM II on balance, we really didn't
have a hell of a lot of progress to show for the last quarter of
a century.

If I had my druthers, my perfect language would be quite like
MODSIM II, but with the pre-condition/post-condition idea stolen
from Eiffel, and, of course, garbage collection.

CACI has also constructed an environment on top of MODSIM II
to add higher-level features for discrete-event simulation and
user interface construction.  None of the people in La Jolla
would know what I was talking about if I mentioned DEMOS, but
the idea sounds familiar, no?