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From: Richard D Riehle <laoXhai@ix.netcom.com>
Subject: Re: Ada and Java. different behaviour. casting long to int problem.
Date: 1999/06/16
Message-ID: <7k8mba$rf3@sjx-ixn9.ix.netcom.com>#1/1
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References: <7jt2c0$vrb@drn.newsguy.com> <f92d7yyweva.fsf@eng.sun.com>
 <7k57vb$1ipf@drn.newsguy.com> <7k5kef$1ghi@news1.newsguy.com>
 <FDDxsM.B9@stuyts.nl>
Organization: Netcom
X-NETCOM-Date: Wed Jun 16 10:19:38 AM PDT 1999
Newsgroups: comp.lang.ada
Date: 1999-06-16T10:19:38-07:00
List-Id: <comp.lang.ada>

In article <FDDxsM.B9@stuyts.nl>,
	jerry@jvdsys.stuyts.nl wrote:

>Of course, there was no overflow but an error. Banks use fixed point 
>arithmatic. It is actually a reason why PL/I is still in use, Cobol,
>like Ada, garantees 18 digits accuracy and that sometimes is not
>enough. IBM's PL/I compiler offers 22 digit accuracy for it's fixed point
>arithmatic.

Actually, U.S. banks do not use fixed point arithmetic.  They use
decimal arithmetic.  This is one reason COBOL is preferred over 
languages that do not have inherent support for decimal data types.
Ada has added decimal type capability with,
 
        type Yen is delta 0.01 digits 15;

There is no need for any kind of type casting.  

It should be of interest to note that Ada and COBOL are among the
few languages with direct support for decimal data types. In this
regard, Ada and COBOL are superior to C++, Eiffel, Java, Modula-3, 
etc, which  all require a decimal type class to make this work.
Unfortunately, this is one of those cases where defining a class is 
not as effective as intrinsic language support.  

Even better, with Ada we can easily express the proper relationships
and operations for accounting using the decimal fraction data type.

            package Money is
               type Dollars is delta 0.0001 digits 15;
               Money_Error : exception;
               ...
            end Money;

followed by an abstract type that can be used as the root for derivations
of asset, liability, equity, expense, and revenue account types.  For
example, a debit behaves differently for an asset than for a liability.

            package Money.Accounting is
               type Account_Type is abstract tagged private;
               procedure Debit
                            (Account : in out Account;
                             Amount  : in     Dollars) is abstract;
               procedure Credit 
                            (Account : in out Account;
                             Amount  : in     Dollars) is abstract;
            private
               type Account_Type is abstract tagged record
                  Amount : Dollars := 0.0;
                  ...
               end record;
            end Money.Accounting;
            
Decimal types is one of those cases where Ada has excellent potential 
for simple and direct solutions to a set of problems that is likely 
to be more complex in a language such as C++ or Java.  

Richard Riehle
richard@adaworks.com
http://www.adaworks.com