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From: "Manuel Wenger" <manuel@thunder.ch*>
Subject: Equality operator overloading in ADA 83
Date: 1997/04/21
Message-ID: <01bc4e9b$ac0e7fa0$72041dc2@lightning>#1/1
X-Deja-AN: 236496922
Organization: Unisource Business Networks
Newsgroups: comp.lang.ada
Date: 1997-04-21T00:00:00+00:00
List-Id: <comp.lang.ada>


Hi,
I've started doing some DecADA 83 programming at a technical engineering
school ... and I've run into a problem that I was unable to solve (and my
teacher didn't know any better either :-))

I've tried to overload the "=" operator for fractions in a package. It
obviously doesn't work if the type isn't defined as "limited private", and
I don't want that. As an alternative, I found out that I might as well do a
renaming declaration, just by defining the type as "private" - so I've
tried doing that as well, and then using the following to rename the equal
sign:

function equal (n,m:fraction) return boolean;
function "=" (n,n:fraction) return boolean renames equal;

And what do I get? (I love VMS :-))
%ADAC-E-NOTEQOP, (1) Equal is not an equality operator [LRM 6.7(5)]

Now - we've tried to look at manuals and everything, but we don't seem able
to figure how to define an operator to be an "equality operator". We've
just found some weird definitions like "A renaming declaration whose
designator is the equality operator is only allowed to rename another
equality operator. (For example, such a renaming declaration can be used
when equality is visible by selection but not directly visible.)" (DEC
Bookreader, ADA reference). 

In other words, how do I tell my "equal" function to be an equality
operator, authorized to be renamed into "="? HELP! :)

Please reply via e-mail

Thanks in advance

-Manuel (to reply, please remove the asterisk at the end of my address)