- A package is generally provided in two parts: a package_specification and
a package_body. Every package has a package_specification, but not all
packages have a package_body.
package_declaration ::= package_specification;
package defining_program_unit_name is
- If an identifier or parent_unit_name.identifier appears at the end of
a package_specification, then this sequence of lexical elements shall
repeat the defining_program_unit_name.
- A package_declaration or generic_package_declaration requires a
completion (a body) if it contains any declarative_item that requires a
completion, but whose completion is not in its package_specification.
- The first list of declarative_items of a package_specification of a
package other than a generic formal package is called the visible part of the
package. The optional list of declarative_items after the reserved word
private (of any package_specification) is called the private part of the
package. If the reserved word private does not appear, the package has an
implicit empty private part.
- An entity declared in the private part of a package is visible only within
the declarative region of the package itself (including any child units --
see 10.1.1). In contrast, expanded names denoting
entities declared in the visible part can be used even outside the package;
furthermore, direct visibility of such entities can be achieved by means of
use_clauses (see 4.1.3 and 8.4).
- The elaboration of a package_declaration consists of the elaboration of
its basic_declarative_items in the given order.
(1) The visible part of a package contains all the information that
another program unit is able to know about the package.
(2) If a declaration occurs immediately within the specification of a
package, and the declaration has a corresponding completion that is a
body, then that body has to occur immediately within the body of the
- Example of a package declaration:
package Rational_Numbers is
type Rational is
Numerator : Integer;
Denominator : Positive;
function "="(X,Y : Rational) return Boolean;
function "/" (X,Y : Integer) return Rational; -- to construct a rational number
function "+" (X,Y : Rational) return Rational;
function "-" (X,Y : Rational) return Rational;
function "*" (X,Y : Rational) return Rational;
function "/" (X,Y : Rational) return Rational;
- There are also many examples of package declarations in the predefined language
environment (see Annex A).
-- Email comments, additions, corrections, gripes, kudos, etc. to:
Magnus Kempe -- Magnus.Kempe@di.epfl.ch
Page last generated: 95-03-12