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From: Matt Borchers <mattborchers@gmail.com>
Newsgroups: comp.lang.ada
Subject: Overloading attributes
Date: Sat, 26 Nov 2011 15:13:17 -0800 (PST)
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Date: 2011-11-26T15:13:17-08:00
List-Id: <comp.lang.ada>

Why is it that one cannot overload the 'Image and 'Value attribute
similar to how we can overload 'Input, 'Output, 'Read, and 'Write?  I
think it would be nice to be able to do the following:

type FOO is ...;

function Image( f : FOO ) return String;
for FOO'Image use Image;

function To_Foo( s : String ) return FOO;
for FOO'Value use To_Foo;

Is there a reason that this is not allowed?  Why limit 'Image and
'Value to only scalar types.
Why expose a routine to "stringify" an object through the package
specification when a language construct already exists that could do
this?

I can also imagine how overloading 'Pred and 'Succ would be kinda nice
for link list traversals (and possibly other linked structures):

type A_FOO is access FOO;  --FOO has a field that points to next
record via pointer

function Succ( f : A_FOO ) return A_FOO;
for A_FOO'Succ use Succ;
--similar for 'Pred if it is a doubly linked list

x : A_FOO;
x := x'Succ;

Why expose a Next routine through the package specification when a
language construct already exists that can do this?

How about other Attributes like 'Pos, 'Val, 'First, 'Last, etc?  Could
they be overloaded on user-defined types?