- A type_declaration declares a type and its first subtype.
type_declaration ::= full_type_declaration
type defining_identifier [known_discriminant_part] is type_definition;
enumeration_type_definition | integer_type_definition
| real_type_definition | array_type_definition
| record_type_definition | access_type_definition
- A given type shall not have a subcomponent whose type is the given type
- The defining_identifier of a type_declaration denotes the first subtype
of the type. The known_discriminant_part, if any, defines the discriminants
of the type (see 3.7, ``Discriminants''). The remainder
of the type_declaration defines the remaining characteristics of (the view
of) the type.
- A type defined by a type_declaration is a named type; such a type has one
or more nameable subtypes. Certain other forms of declaration also include
type definitions as part of the declaration for an object (including a
parameter or a discriminant). The type defined by such a declaration is
anonymous -- it has no nameable subtypes. For explanatory purposes, this
International Standard sometimes refers to an anonymous type by a
pseudo-name, written in italics, and uses such pseudo-names at places where
the syntax normally requires an identifier. For a named type whose first
subtype is T, this International Standard sometimes refers to the type of T
as simply ``the type T.''
- A named type that is declared by a full_type_declaration, or an anonymous
type that is defined as part of declaring an object of the type, is called a
full type. The type_definition, task_definition, protected_definition, or
access_definition that defines a full type is called a full type definition.
Types declared by other forms of type_declaration are not separate types;
they are partial or incomplete views of some full type.
- The definition of a type implicitly declares certain predefined operators
that operate on the type, according to what classes the type belongs, as specified
in 4.5, ``Operators and Expression Evaluation''.
- The predefined types (for example the types Boolean, Wide_Character, Integer,
root_integer, and universal_integer) are the types that are defined in a predefined
library package called Standard; this package also includes the (implicit)
declarations of their predefined operators. The package Standard is described
- The elaboration of a full_type_declaration consists of the elaboration
of the full type definition. Each elaboration of a full type definition
creates a distinct type and its first subtype.
- Examples of type definitions:
(White, Red, Yellow, Green, Blue, Brown, Black)
range 1 .. 72
array(1 .. 10) of Integer
- Examples of type declarations:
type Color is (White, Red, Yellow, Green, Blue, Brown, Black);
type Column is range 1 .. 72;
type Table is array(1 .. 10) of Integer;
(3) Each of the above examples declares a named type. The identifier given
denotes the first subtype of the type. Other named subtypes of the type
can be declared with subtype_declarations (see 3.2.2).
Although names do not directly denote types, a phrase like ``the type Column''
is sometimes used in this International Standard to refer to the type of
Column, where Column denotes the first subtype of the type. For an example
of the definition of an anonymous type, see the declaration of the array
Color_Table in 3.3.1; its type is anonymous --
it has no nameable subtypes.
-- Email comments, additions, corrections, gripes, kudos, etc. to:
Magnus Kempe -- Magnus.Kempe@di.epfl.ch
Page last generated: 95-03-12