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A generic_declaration declares a generic unit, which is either a generic subprogram or a generic package. A generic_declaration includes a generic_formal_part declaring any generic formal parameters. A generic formal parameter can be an object; alternatively (unlike a parameter of a subprogram), it can be a type, a subprogram, or a package.
Syntax
generic_declaration ::= generic_subprogram_declaration | generic_package_declaration generic_subprogram_declaration ::= generic_formal_part subprogram_specification; generic_package_declaration ::= generic_formal_part package_specification; generic_formal_part ::= generic {generic_formal_parameter_declaration | use_clause} generic_formal_parameter_declaration ::= formal_object_declaration | formal_type_declaration | formal_subprogram_declaration | formal_package_declaration
Static Semantics
A generic_declaration declares a generic unit -- a generic package, generic procedure or generic function, as appropriate.
An entity is a generic formal entity if it is declared by a generic_formal_parameter_declaration. ``Generic formal,'' or simply ``formal,'' is used as a prefix in referring to objects, subtypes (and types), functions, procedures and packages, that are generic formal entities, as well as to their respective declarations. Examples: ``generic formal procedure'' or a ``formal integer type declaration.''
Dynamic Semantics
The elaboration of a generic_declaration has no effect.
Examples
Examples of generic formal parts:
generic -- parameterless generic Size : Natural; -- formal object generic Length : Integer := 200; -- formal object with a default expression Area : Integer := Length*Length; -- formal object with a default expression generic type Item is private; -- formal type type Index is (<>); -- formal type type Row is array(Index range <>) of Item; -- formal type with function "<"(X, Y : Item) return Boolean; -- formal subprogram
Examples of generic declarations declaring generic subprograms Exchange and Squaring:
generic type Elem is private; procedure Exchange(U, V : in out Elem); generic type Item is private; with function "*"(U, V : Item) return Item is <>; function Squaring(X : Item) return Item;
Example of a generic declaration declaring a generic package:
generic type Item is private; type Vector is array (Positive range <>) of Item; with function Sum(X, Y : Item) return Item; package On_Vectors is function Sum (A, B : Vector) return Vector; function Sigma(A : Vector) return Item; Length_Error : exception; end On_Vectors;
About DocAda Light:
Preface / Preliminary
/ Help
/ TOC
/ Copyright
DocAda Online at the Ada Home:
Complete RM95
/ Updates
/ News
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