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From: Mats_Ohlin_FOA2@QZCOM.MAILNET.UUCP
Newsgroups: comp.lang.ada
Subject: Re: Tasks and Simulation
Message-ID: <231892@QZCOM>
Date: Tue, 3-Mar-87 21:19:51 EST
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Posted: Tue Mar  3 21:19:51 1987
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My impression (shared with many other people having knowledge
of both SIMULA and Ada) is that Ada will NOT be a good simulation
language in its current form. It will gives simulation capabilities
similar to those that may be built in say Pascal.

The two main things Ada lacks for general purpose simulation
are:

1. Lack of a simple and fast co-routine mechanism.

2. Lack of a general task type (which is needed for efficient
   and general handling of event lists /built, of course, as
   priority trees/).

A subclass mechanism (what Intel calls "extended objects") would
facilitate the transgression from SIMULA experience and modelling
techniques, but goes contrary to the path Ada has selected for
this problem, i.e. generics. According to an object-oriented
approach to modelling, I cannot help thinking that the subclass
concept in many cases is superior. Experience from the use of
SIMULA clearly indicates that qualification checks in many cases
can be done during compilation time, those few that are checked
during execution gives a very small overhead (contrary to the
belief of many otherwise well-informed specialists, especially
in the US I have to say).

-- Mats Ohlin, Swedish National Defense Research Institute

   Mats_Ohlin_FOA2%QZCOM@MULTICS.MIT.EDU