Ada Programming/Keywords/use

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Use clause

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

At library level

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
begin
   Put_Line("Hello, world!");
   New_Line;
   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 level

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

For types

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 clauses

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.

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`	`parallel` (Ada 2022)	`terminate`
`body`		`pragma`	`then`
	`if`	`private`	`type`
`case`	`in`	`procedure`
`constant`	`interface` (Ada 2005)	`protected` (Ada 95)	`until` (Ada 95)
	`is`		`use`
`declare`		`raise`
`delay`	`limited`	`range`	`when`
`delta`	`loop`	`record`	`while`
`digits`		`rem`	`with`
`do`	`mod`	`renames`
		`requeue` (Ada 95)	`xor`

Ada Programming/Keywords/use

Contents

Use clause

At library level

At declaration level

For types

Representation clauses

See also

Wikibook

Ada Reference Manual

Ada Quality and Style Guide