Re: Implementation of "=" (Ada83)

[jsa@organon.com (Jon S Anthony)]

In article <mheaney-1307961304430001@news.ni.net> mheaney@ni.net (Matthew Heaney) writes:

> There's one other implementation technique I thought of, that I don't
> really like, but here it is:

> package T_Package is
> 
> ...
> 
> private
> 
>    type T_Representation is
>       record
>          A, B : Integer;
>       end record;
> 
>    type T is new T_Representation;
> 
> end;
> 
> package body T_Package is
> 
>    function "=" (L, R : T) return Boolean is
>    begin
>       return T_Representation (L) = T_Representation (R);
>    end;
> 
> end;

This should work in both Ada83 and Ada95.  Why don't you like it.  Well,
OK, maybe it isn't the most aesthetic thing, but this is kind of a "gotcha"
in the language and you probably can't expect anything really clean...

> Can anyone out there explain how they would implement the "=" for T?

Probably as above.  The trick is you have to separate the type definition
from the implementation.  Another hack would be:

private
     type T_Rep is ...

     type T is record
         The_Impl : T_Rep;
     end record;
...

    return L.The_Impl = R.The_Impl;


/Jon

-- 
Jon Anthony
Organon Motives, Inc.
1 Williston Road, Suite 4
Belmont, MA 02178

617.484.3383
jsa@organon.com