Ada Reference Manual (Ada 2022)
1.3.1 Types, Objects, and their Properties
abstract type
tagged type intended for use as an ancestor of other types, but which is not allowed to have objects of its own
access type
type that has values that designate aliased objects
Note: Access types correspond to “pointer types” or “reference types” in some other languages.
accessibility level
representation of the lifetime of an entity in terms of the level of dynamic nesting within which the entity is known to exist
aliased view
view of an object that can be designated by an access value
Note: Objects allocated by allocators are aliased. Objects can also be explicitly declared as aliased with the reserved word aliased. The Access attribute can be used to create an access value designating an aliased object.
ancestor of a type
type itself or, in the case of a type derived from other types, its parent type or one of its progenitor types or one of their ancestors
Note: Ancestor and descendant are inverse relationships.
array type
composite type whose components are all of the same type
aspect
specifiable property of an entity
Note: An aspect can be specified by an aspect_specification on the declaration of the entity. Some aspects can be queried via attributes.
attribute
characteristic or property of an entity that can be queried, and in some cases specified
category of types
set of types with one or more common properties, such as primitive operations
Note: A category of types that is closed under derivation is also known as a class.
character type
enumeration type whose values include characters
class of types
set of types that is closed under derivation, which means that if a given type is in the class, then all types derived from that type are also in the class
Note: The set of types of a class share common properties, such as their primitive operations.
composite type
type with components, such as an array or record
controlled type
type that supports user-defined assignment and finalization
Note: Objects are always finalized before being destroyed.
default initial condition
property that holds for every default-initialized object of a given type
derived type
type defined in terms of a parent type and zero or more progenitor types given in a derived type definition
Note 1: A derived type inherits properties such as components and primitive operations from its parent and progenitors.
Note 2: A type together with the types derived from it (directly or indirectly) form a derivation class.
descendant of a type
type itself or a type derived (directly or indirectly) from it
Note: Descendant and ancestor are inverse relationships.
discrete type
type that is either an integer type or an enumeration type
discriminant
parameter for a composite type, which can control, for example, the bounds of a component that is an array
Note: A discriminant for a task type can be used to pass data to a task of the type upon its creation.
elementary type
type that does not have components
enumeration type
type defined by an enumeration of its values, which can be denoted by identifiers or character literals
full type
type that defines a full view
full view
view of a type that reveals all of its properties
Note: There can be other views of the type that reveal fewer properties.
incomplete type
type that defines an incomplete view
Note: Incomplete types can be used for defining recursive data structures.
incomplete view
view of a type that reveals minimal properties
Note: The remaining properties are defined by the full view given elsewhere.
indexable container type
type that has user-defined behavior for indexing, via the Constant_Indexing or Variable_Indexing aspects
integer type
type that represents signed or modular integers
Note: A signed integer type has a base range that includes both positive and negative numbers, and has operations that can raise an exception when the result is outside the base range. A modular type has a base range whose lower bound is zero, and has operations with “wraparound” semantics. Modular types subsume what are called “unsigned types” in some other languages.
interface type
abstract tagged type that has no components or concrete operations except possibly null procedures
Note: Interface types are used for composing other interfaces and tagged types and thereby provide multiple inheritance. Only an interface type can be used as a progenitor of another type.
invariant
assertion that is expected to be True for all objects of a given private type when viewed from outside the defining package
iterable container type
type that has user-defined behavior for iteration, via the Default_Iterator and Iterator_Element aspects
limited type
type for which copying (such as in an assignment_statement) is not allowed
Note: All types are either limited types or nonlimited types.
needed component
component of a record type or record extension that is required to have its value specified within a given aggregate
nominal subtype
subtype specified when a view of an object is defined
nonlimited type
type for which copying is allowed
object
entity that contains a value, and is either a constant or a variable
Note: An object is created by an object_declaration or by an allocator. A formal parameter is (a view of) an object. A subcomponent of an object is an object.
operational aspect
aspect that indicates a logical property of an entity, such as the precondition of a subprogram, or the procedure used to write a given type of object to a stream
parent of a derived type
first ancestor type given in the definition of the derived type
Note: The parent can be almost any kind of type, including an interface type.
partial view
view of a type that reveals only some of its properties
Note: The remaining properties are defined by the full view given elsewhere.
primitive operations of a type
operations (such as subprograms) declared together with the type declarations
Note: Primitive operations are inherited by other types in the same derivation class of types.
private extension
type that extends another type, with the additional properties hidden from its clients
private type
type that defines a partial view
Note: Private types can be used for defining abstractions that hide unnecessary details from their clients.
progenitor
type given in the interface list, if any, of an interface, task, protected, or derived type definition
Note: A progenitor is always an interface type.
protected type
composite type whose components are accessible only through one of its protected operations, which synchronize concurrent access by multiple tasks
real type
type that has values that are approximations of the real numbers
Note: Floating point and fixed point types are real types.
record extension
type that extends another type optionally with additional components
record type
composite type consisting of zero or more named components, possibly of different types
reference type
type that has user-defined behavior for “.all”, defined by the Implicit_Dereference aspect
representation aspect
aspect that indicates how an entity is mapped onto the underlying hardware, for example the size or alignment of an object
scalar type
either a discrete type or a real type
stable property
characteristic associated with objects of a given type that is preserved by many of the primitive operations of the type
storage pool object
object associated with one or more access types from which the storage for objects created by allocators of the access type(s) is obtained
Note: Some storage pools can be partitioned into subpools in order to support finer-grained storage management.
stream
sequence of elements that can be used, along with the stream-oriented attributes, to support marshalling and unmarshalling of values of most types
subtype
type together with optional constraints, null exclusions, and predicates, which constrain the values of the type to the subset that satisfies the implied conditions
synchronized
can be safely operated on by multiple tasks concurrently
Note: Synchronized is used to qualify entities, as in a synchronized interface.
tagged type
type whose objects each have a run-time type tag, which indicates the specific type for which the object was originally created
Note: Tagged types can be extended with additional components.
task type
composite type used to represent active entities which execute concurrently and that can communicate via queued task entries
Note: The top-level task of a partition is called the environment task.
type
defining characteristic of each object and expression of the language, with an associated set of values, and a set of primitive operations that implement the fundamental aspects of its semantics
Note: Types are grouped into categories. Most language-defined categories of types are also classes of types.
view of an entity
representation of an entity that reveals some or all of the properties of the entity
Note: A single entity can have multiple views.
