Next: , Previous: 8.3.1, Up: 8


8.4 Use Clauses

1
A use_package_clause achieves direct visibility of declarations that appear in the visible part of a package; a use_type_clause achieves direct visibility of the primitive operators of a type.

Syntax

2

use_clause::= use_package_clause use_type_clause

3

use_package_clause::= use package_name {, package_name};

4

use_type_clause::= use type subtype_mark {, subtype_mark};
Legality Rules

5/2
A package_name of a use_package_clause shall denote a nonlimited view of a package.

Static Semantics

6
For each use_clause, there is a certain region of text called the scope of the use_clause. For a use_clause within a context_clause of a library_unit_declaration or library_unit_renaming_declaration, the scope is the entire declarative region of the declaration. For a use_clause within a context_clause of a body, the scope is the entire body and any subunits (including multiply nested subunits). The scope does not include context_clauses themselves.

7
For a use_clause immediately within a declarative region, the scope is the portion of the declarative region starting just after the use_clause and extending to the end of the declarative region. However, the scope of a use_clause in the private part of a library unit does not include the visible part of any public descendant of that library unit.

7.1/2
A package is named in a use_package_clause if it is denoted by a package_name of that clause. A type is named in a use_type_clause if it is determined by a subtype_mark of that clause.8/2
For each package named in a use_package_clause whose scope encloses a place, each declaration that occurs immediately within the declarative region of the package is potentially use−visible at this place if the declaration is visible at this place. For each type T or T'Class named in a use_type_clause whose scope encloses a place, the declaration of each primitive operator of type T is potentially use−visible at this place if its declaration is visible at this place.

9
A declaration is use−visible if it is potentially use−visible, except in these naming−conflict cases:

10

11

Dynamic Semantics

12
The elaboration of a use_clause has no effect.

Examples

13
Example of a use clause in a context clause:

14

     with Ada.Calendar; use Ada;

15
Example of a use type clause:

16

     use type Rational_Numbers.Rational; −− see 7.1
     Two_Thirds: Rational_Numbers.Rational := 2/3;