12.5.4 Formal Access Types

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The class determined for a formal access type is the class of all access types.


formal_access_type_definition ::= access_type_definition

Legality Rules

For a formal access-to-object type, the designated subtypes of the formal and actual types shall statically match.

If and only if the general_access_modifier constant applies to the formal, the actual shall be an access-to-constant type. If the general_access_modifier all applies to the formal, then the actual shall be a general access-to-variable type (see 3.10).

For a formal access-to-subprogram subtype, the designated profiles of the formal and the actual shall be mode-conformant, and the calling convention of the actual shall be protected if and only if that of the formal is protected.


Example of formal access types:

--  the formal types of the generic package 

    type Node is private;
    type Link is access Node;
package P is 
end P;

--  can be matched by the actual types 

type Car;
type Car_Name is access Car;

type Car is 
        Pred, Succ : Car_Name;
        Number     : License_Number;
        Owner      : Person; 
    end record;

--  in the following generic instantiation 

package R is new P(Node => Car, Link => Car_Name);

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Copyright © 2000 The MITRE Corporation, Inc. Ada Reference Manual