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From: dewar@merv.cs.nyu.edu (Robert Dewar)
Subject: Re: Portability of Arithmetic (was: Java vs Ada 95)
Date: 1996/10/17
Message-ID: <dewar.845591699@merv>#1/1
X-Deja-AN: 190293896
references: <325D7F9B.2A8B@gte.net> <1996Oct15.174526.1@eisner>
 <DzDBw3.ILH@world.std.com> <dewar.845506499@merv> <DzFB5z.D6A@world.std.com>
organization: New York University
newsgroups: comp.lang.ada
Date: 1996-10-17T00:00:00+00:00
List-Id: <comp.lang.ada>


Bob Duff says

'True, but it's easy to do it wrong, and have it work just fine, and then
find that it doesn't work when you port the code.  Do all Ada
programmers understand that the above has to be written as you show
above?  I suspect not.  But I suspect all Java programmers understand
what the range of int is, and when arithmetic is supposed to work."


Harrumph! Arguing that Java programmers know Java and Ada programmers
do not know Ada seems to be getting rather thin don't you think?

One very important distinction is the following. In either language
you can write code where intermediate results are out of range of
the type.

In both languages, such code may or may not work.

In Java, if it does not work, the program execution is (in Ada-ese)
erroneous, and who knows what values you get.

In Ada, if it does not work, you will get a runtime exception.

Arguing that Java arithmetic is more portable seems completely
specious to me. The type:

   type int is range -2**31 .. +2**31-1;

is almost exactly equivalent to the Java type int. Why only "almost", well
to make it exatly equivalent, I have to do

   pragma Suppress (Overflow_Check, int);

Now it is true that Java guarantees the presence of 64-bit signed
binary arithmetic, and Ada does not. However, in my experience, by
far the most common need for such high precision arithmetic is
in connection with fiscal applications, and here Ada's Decimal
type is much more attractive than the use of manually scaled int
values.