Re: Predefined Language Attributes 'ADDRESS and 'ACCESS

["Jeffrey R. Carter" <spam.jrcarter.not@spam.not.acm.org>]

On 12/6/18 7:25 AM, ldries46 wrote:
> What is the principal difference between the Attributes 'ADDRESS and 'ACCESS? 
> When do you use them?

The principal difference is that 'Address returns a value of type System.Address 
and 'Access returns a value of an access type. They are not the same and there 
is not necessarily any relationship between them.

 From ARM K.2(2-7) Language-Defined Attributes:

2
P'Access
For a prefix P that denotes a subprogram:
3
P'Access yields an access value that designates the subprogram denoted by P. The 
type of P'Access is an access-to-subprogram type (S), as determined by the 
expected type. See 3.10.2.
4
X'Access
For a prefix X that denotes an aliased view of an object:
5
X'Access yields an access value that designates the object denoted by X. The 
type of X'Access is an access-to-object type, as determined by the expected 
type. The expected type shall be a general access type. See 3.10.2.
6/1
X'Address
For a prefix X that denotes an object, program unit, or label:
7
Denotes the address of the first of the storage elements allocated to X. For a 
program unit or label, this value refers to the machine code associated with the 
corresponding body or statement. The value of this attribute is of type 
System.Address. See 13.3.

http://www.ada-auth.org/standards/rm12_w_tc1/html/RM-K-2.html

-- 
Jeff Carter
"Why, the Mayflower was full of Fireflies, and a few
horseflies, too. The Fireflies were on the upper deck,
and the horseflies were on the Fireflies."
Duck Soup
95