Re: Overloading attributes

[anon@att.net]

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From time to time this forum has discussed the concept of the 
"attribute definition clause" (Representation Attributes). Some have 
even say it would cause an increase of 4_000 lines of code to be 
written to include this feature in a compiler.


From Ada 95 RM

13.3 Representation Attributes

2   attribute_definition_clause ::=
          for local_name'attribute_designator use expression;
        | for local_name'attribute_designator use name;


                               Legality Rules

5     (95)
5/1 (2005)

An attribute_designator is allowed in an attribute_definition_clause only
if this International Standard explicitly allows it, or for an
implementation-defined attribute if the implementation allows it.  Each
specifiable attribute constitutes an aspect of representation.

This clause does not forbid the creation of new attribute it only states 
that it is up to the implementation to allow it if the Standard does not 
explicitly allows it.

For instant, the implementation could say that the programmer can create 
new attributes for types created by the programmer only. Aka like the 
attribute "Image" (which is define for scalar objects), for a programmer 
defined record. Or the implementation could predefine a set of "attribute 
designators" that could be used by a programmer.


And for Ada 83, the complete syntax and implementation of must be 
documented in Appendix F for the allowed representation clauses.

So, Ada 83 allows the creation with just documentation. As for Standards 
Ada 95, Ada 2005 and Ada 2012 they started to limit the usage, but still 
allow with the implementation permission.

Which means that Ada can allow a programmer to create "Representation 
Attributes" aka "Attributes" with some limitations if the Standard
or the Implementation allows it.


In <jasnea$ac1$1@dont-email.me>, "J-P. Rosen" <rosen@adalog.fr> writes:
>Le 27/11/2011 04:36, anon@att.net a �crit :
>> In Ada, Overloading is allow for all attributes include programmers 
>> created attributes. 
>please point me at the RM paragraphe that allows programmers created
>attributes, I must have missed something!
>
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