Ada Programming/Keywords/use

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Use clauseEdit

There are two versions of use clauses, a use_package_clause and a use_type_clause.

At library levelEdit

This use_package_clause makes the content of a package directly visible. If applied on the library level, its scope is the complete library unit.

A use clause never hides anything that is already directly visible without it. All use clauses in effect in a certain scope act on the same level: Two homographs in different packages must still be named as selected components.

with Ada.Text_IO;   use Ada.Text_IO;

procedure Hello is
   Put_Line("Hello, world!");
   Put_Line("I am an Ada program with package use.");
end Hello;

If readability is your main concern then you should avoid this kind of use clause. Either make it more local or use a use_type_clause.

At declaration levelEdit

The effect is the same as above, but the scope is the directly enclosing declaration region.

File: hello_world_3.adb (view, plain text, download page, browse all)
with Ada.Text_IO;

procedure Hello is
   use Ada.Text_IO;
   Put_Line("Hello, world!");
   Put_Line("I am an Ada program with package use.");
end Hello;

For typesEdit

Use type clauses come in two versions.

use type Type_Name;

makes the operators of the type directly visible.

use all type Type_Name;

makes the primitive operations of the type directly visible.

Representation clausesEdit

The keywords for, use and at are used for representation clauses.

A record representation clause specifies the Layout aspect of a record.

An enumeration representation clause specifies the Coding aspect of an enumeration type.

See Ada Programming/Representation_clauses.

See alsoEdit


Ada Reference ManualEdit

Ada Quality and Style GuideEdit

Ada Keywords
abort else new return
abs elsif not reverse
abstract (Ada 95) end null
accept entry select
access exception of separate
aliased (Ada 95) exit or some (Ada 2012)
all others subtype
and for out synchronized (Ada 2005)
array function overriding (Ada 2005)
at tagged (Ada 95)
generic package task
begin goto pragma terminate
body private then
if procedure type
case in protected (Ada 95)
constant interface (Ada 2005) until (Ada 95)
is raise use
declare range
delay limited record when
delta loop rem while
digits renames with
do mod requeue (Ada 95) xor