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7.4 Deferred Constants

(1)
Deferred constant declarations may be used to declare constants in the visible part of a package, but with the value of the constant given in the private part. They may also be used to declare constants imported from other languages (see Annex B).
Legality Rules
(2)
A deferred constant declaration is an object_declaration with the reserved word constant but no initialization expression. The constant declared by a deferred constant declaration is called a deferred constant. A deferred constant declaration requires a completion, which shall be a full constant declaration (called the full declaration of the deferred constant), or a pragma Import (see Annex B).
(3)
A deferred constant declaration that is completed by a full constant declaration shall occur immediately within the visible part of a package_specification. For this case, the following additional rules apply to the corresponding full declaration:
(4)
(5)
(6)
(7)
(8)
A deferred constant declaration that is completed by a pragma Import need not appear in the visible part of a package_specification, and has no full constant declaration.
(9)
The completion of a deferred constant declaration shall occur before the constant is frozen (see 7.4).
Dynamic Semantics
(10)
The elaboration of a deferred constant declaration elaborates the subtype_indication or (only allowed in the case of an imported constant) the array_type_definition.

(11)
Examples
(12)
Examples of deferred constant declarations:
(13)
       Null_Key : constant Key;      -- see 7.3.1
(14)
       CPU_Identifier : constant String(1..8);
       pragma Import(Assembler, CPU_Identifier, Link_Name => "CPU_ID");
                                     -- see B.1


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