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From: Robert Dewar <robert_dewar@my-dejanews.com>
Subject: Re: Does this model work ?
Date: 1999/05/16
Message-ID: <7hmda1$khp$1@nnrp1.deja.com>#1/1
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Date: 1999-05-16T00:00:00+00:00
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In article <7hhj6q$cjn$1@nnrp1.deja.com>,
  dennison@telepath.com wrote:
> I don't think this feat would be possible in any other
> language.

Such claims alway make me uneasy.

It is perfectly possible to write code that is in practice
close to perfectly portable in COBOL, Fortran, C, or several
other standardized languages.

As in Ada, the main barrier to portability is deliberate or
accidental use of implementation dependent features.

Yes, it is fair to say that Ada makes achieving this portability
easier. I think there are four reasons for that.

1. Portability requires discipline, and the Ada programming
   culture tends to be more disciplined.

2. Ada discourages extensions, which are a frequent cause of
   non-portability.

3. Ada programmers tend to be more familiar with the standard
   for the language

4. Ada is designed to promote portability (e.g. portable
   integer types).

However, Ada is no panacea. Over and over again, we run into
cases where incompetence or deliberate (in-retrospect-poort)
decisions have lead to highly non-portable code, and this can
often be eacerbated by management or incompetent Ada vendor
sales people who have sold the idea that Ada guarantees
100% portability. That's wrong, it does not.

However, the above four factors are quite powerful, and in
practice have lead to many success stories like the one quoted
here!

For an example of a highly portable C program, consider the
gcc compiler itself. This is one of the portable benchmarks
in the Spec suite, and runs unchanged on all targets with C
compilers that run Spec (which is essentially 100% of all
C compatible targets).



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