Version 1.3 of ai12s/ai12-0443-1.txt
!standard 1.3(0) 22-06-01 AI12-0443-1/03
!standard N(0)
!class presentation 22-04-25
!status Amendment 1-2012 22-05-05
!status ARG Approved 14-0-0 22-05-05
!status work item 22-04-25
!status received 22-02-28
!priority Critical
!difficulty Medium
!qualifier Omission
!subject Convert the glossary into a separate Terms and Definitions clause
!summary
To conform to ISO formatting requirements, we move and restructure the
glossary to serve as the Terms and Definitions clause.
!question
ISO requires that important terms be gathered into a Terms and Definitions
clause (see comment #13 and #14). We define most terms in context within
the document, but we have created a relatively comprehensive glossary,
which could be the basis for such a chapter. Should we move the glossary
into the Terms and Definitions clause? (Yes.)
!recommendation
Turn the glossary into the Terms and Definitions clause.
!wording
[Editor's note: In this AI, we use Ada Reference Manual numbering
unless otherwise specified.]
Delete Annex N (the Glossary) in its entirity.
Augment subclause 1.3 (Clause 3 in the ISO standard), Terms and Definitions,
with the following definitions:
• Types, Objects, and their Properties [Group T]
* abstract type. a tagged type intended for use as an ancestor of
other types, but which is not allowed to have objects of its own
* access type. a type that has values that designate aliased objects
* Note 1 on entry: Access types correspond to “pointer types” or
“reference types” in some other languages.
* accessibility level. a 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. a view of an object that can be designated by an access
value
* Note 1 on entry: 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. the 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 1 on entry: Ancestor and descendant are inverse relationships.
* array type. a composite type whose components are all of the same type
* aspect. a specifiable property of an entity
* Note 1 on entry: An aspect can be specified by an
aspect_specification on the declaration of the entity. Some
aspects can be queried via attributes.
* attribute. a characteristic or property of an entity that can be
queried, and in some cases specified
* category of types. a set of types with one or more common properties,
such as primitive operations
* Note 1 on entry: A category of types that is closed under
derivation is also known as a class.
* character type. an enumeration type whose values include characters
* class of types. a 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 1 on entry: The set of types of a class share common
properties, such as their primitive operations.
* class-wide type. a type that represents all of the types derived,
directly or indirectly, from a given specific type
* Note 1 on entry: An object of a class-wide tagged type can be
used in a dispatching call; the tag of the object determines
which subprogram body to invoke.
* composite type. a type with components, such as an array or record
* container. a structured object that represents a collection of
elements all of the same (potentially class-wide) type, such as a
vector or a tree
* Note 1 on entry: Several predefined container types are
provided by the children of package Ada.Containers (see A.18.1).
* controlled type. a type that supports user-defined assignment and
finalization
* Note 1 on entry: Objects are always finalized before being
destroyed.
* default initial condition. a property
that holds for every default-initialized object of a given type
* derived type. a type defined in terms of a parent type and zero or
more progenitor types given in a derived type definition
* Note 1 on entry: A derived type inherits properties such as
components and primitive operations from its parent and
progenitors.
* Note 2 on entry: A type together with the types derived from
it (directly or indirectly) form a derivation class.
* descendant of a type. the type itself or a type derived (directly
or indirectly) from it
* Note 1 on entry: Descendant and ancestor are inverse
relationships.
* discrete type. a type that is either an integer type or an
enumeration type
* discriminant. a parameter for a composite type, which can control,
for example, the bounds of a component that is an array
* Note 1 on entry: A discriminant for a task type can be used to
pass data to a task of the type upon its creation.
* dispatching subprogram. a primitive operation of a tagged type
* Note 1 on entry: Dispatching subprograms provide run-time
polymorphism. A dispatching subprogram can be called with
statically tagged operands, in which case the subprogram body
invoked is determined at compile time. Alternatively, a
dispatching subprogram can be called using a dispatching call,
in which case the subprogram body invoked is determined at
run time.
* elementary type. a type that does not have components
* enumeration type. a type defined by an enumeration of its values,
which can be denoted by identifiers or character literals
* incomplete type. a view of a type that reveals only a few of its
properties
* Note 1 on entry: The remaining properties are provided by the
full view given elsewhere.
* Note 2 on entry: Incomplete types can be used for defining
recursive data structures.
* indexable container type. a type that has user-defined behavior for
indexing, via the Constant_Indexing or Variable_Indexing aspects
* integer type. a type that represents signed or modular integers
* Note 1 on entry: 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. an abstract tagged type that has no components or
concrete operations except possibly null procedures
* Note 1 on entry: 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. an 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. a type that has user-defined behavior for
iteration, via the Default_Iterator and Iterator_Element aspects
* limited type. a type for which copying (such as in an
assignment_statement) is not allowed
* Note 1 on entry: A nonlimited type is a type for which copying
is allowed.
* needed component. a component of a record type or record extension
that is required to have its value specified within a given aggregate
* needs finalization. a type whose objects require additional actions
performed at the point when they cease to exist
* Note 1 on entry: Any type with a part that is a task, a
protected object, or a controlled object needs finalization.
* nominal subtype of a view of an object. the subtype specified when
the view is defined
* object. an entity that contains a value, and is either a constant
or a variable
* Note 1 on entry: 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. an 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. the first ancestor type given in the
definition of the derived type
* Note 1 on entry: The parent can be almost any kind of type,
including an interface type.
* predicate. an assertion that is expected to be True for all objects
of a given subtype
* primitive operations of a type. the operations (such as subprograms)
declared together with the type declaration
* Note 1 on entry: Primitive operations are inherited by other types
in the same derivation class of types.
* private extension. a type that extends another type, with the
additional properties hidden from its clients
* private type. a view of a type that reveals only some of its properties
* Note 1 on entry: The remaining properties are provided by the
full view given elsewhere. Private types can be used for defining
abstractions that hide unnecessary details from their clients.
* progenitor of a derived type. one of the types given in the definition
of the derived type other than the first
* Note 1 on entry: A progenitor is always an interface type.
Interfaces, tasks, and protected types can also have progenitors.
* protected type. a composite type whose components are accessible
only through one of its protected operations, which synchronize
concurrent access by multiple tasks
* real type. a type that has values that are approximations of
the real numbers
* Note 1 on entry: Floating point and fixed point types are
real types.
* record extension. a type that extends another type optionally with
additional components
* record type. a composite type consisting of zero or more named
components, possibly of different types
* reference type. a type that has user-defined behavior for “.all”,
defined by the Implicit_Dereference aspect
* representation aspect. an 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
* specific type. an individual type within a class of types, as
distinguished from a class-wide type or a universal type
* stable property. a characteristic associated with objects of a given
type that is preserved by many of the primitive operations of the
type
* storage pool object. an 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 1 on entry: Some storage pools can be partitioned into
subpools in order to support finer-grained storage management.
* stream. a sequence of elements that can be used, along with the
stream-oriented attributes, to support marshalling and unmarshalling
of values of most types
* subtype. a 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 entity. an entity that can be safely operated on by
multiple tasks concurrently
* Note 1 on entry: A synchronized interface can be an ancestor
of a task or a protected type. Such a task or protected type is
called a synchronized tagged type.
* tagged type. a type whose objects each have a run-time type tag,
which indicates the specific type for which the object was
originally created
* Note 1 on entry: Tagged types can be extended with additional
components.
* task type. a composite type used to represent active entities which
execute concurrently and that can communicate via queued task entries
* Note 1 on entry: The top-level task of a partition is called the
environment task.
* type. a 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 1 on entry: Types are grouped into categories. Most
language-defined categories of types are also classes of types.
* type invariant. see Invariant
* universal type. a type that can be implicitly converted to or from
all the types within a given class of elementary types
* Note 1 on entry: There are four universal types – universal
integer, universal real, universal fixed, and universal access.
* view of an entity. a representation of an entity that reveals some
or all of the properties of the entity
* Note 1 on entry: A single entity can have multiple views.
• Subprograms and their Properties [Group S]
* function. a form of subprogram that returns a result and can be
called as part of an expression
* overriding operation. an operation that replaces an inherited
primitive operation
* Note 1 on entry: Operations can be marked explicitly as
overriding or not overriding.
* postcondition. an assertion that is expected to be True when a given
subprogram returns normally
* precondition. an assertion that is expected to be True when a given
subprogram is called
* procedure. a form of subprogram that does not return a result and
can only be invoked by a statement
* subprogram. a unit of a program that can be brought into execution
in various contexts, with the invocation being a subprogram call that
can parameterize the effect of the subprogram through the passing of
operands
* Note 1 on entry: There are two forms of subprograms: functions,
which return values, and procedures, which do not.
• Other Syntactic constructs [Group C]
* aggregate. a construct used to define a value of a composite type by
specifying the values of the components of the type
* compilation unit. a program unit that is separately compiled
* Note 1 on entry: A compilation_unit contains either
the declaration, the body, or a renaming of a program unit.
* construct. a piece of text (explicit or implicit) that is an instance
of a syntactic category defined under “Syntax”
* container aggregate. a construct used to define a value of a type that
represents a collection of elements, by explicitly specifying the
elements in the collection
* core language. a clause or annex in which are defined language constructs or
capabilities that are provided by all conforming implementations
* Note 1 on entry: A construct is said to be part of the core language
if it is defined in a core language clause or annex.
* declaration. a language construct that associates a name with (a
view of) an entity
* Note 1 on entry: A declaration can appear explicitly in the
program text (an explicit declaration), or can be supposed to
occur at a given place in the text as a consequence of the
semantics of another construct (an implicit declaration).
* generic unit. a template for a (nongeneric) program unit
* Note 1 on entry: The template can be parameterized by objects,
types, subprograms, and packages.
* Note 2 on entry: Generic units can be used to perform the role
that macros sometimes play in other languages.
* generic instance. a nongeneric unit created by the instantiation of
a generic unit
* iterator. a construct that is used to loop over the elements of an
array or container
* Note 1 on entry: Iterators can be user defined, and can perform
arbitrary computations to access elements from a container.
* iterator filter. a construct that is used to restrict the elements
produced by an iteration to those for which a boolean condition
evaluates to True
* library unit. a separately compiled program unit, which is a
package, a subprogram, or a generic unit
* Note 1 on entry: Library units can have other (logically nested)
library units as children, and can have other program units
physically nested within them. A root library unit, together
with its children and grandchildren and so on, form a subsystem.
* master construct. one of certain executable constructs for which
there can be objects or tasks whose lifetime ends when the construct
completes
* Note 1 on entry: Execution of a master construct is a master,
with which objects and tasks are associated for the purposes of
waiting and finalization.
* needed compilation unit. a compilation unit that is necessary to
produce an executable partition, because some entity declared or
defined within the unit is used elsewhere in the partition
* package. a program unit that defines the interface to a group of
logically related entities, along with their implementation
* Note 1 on entry: Typically, a package contains the declaration
of a type (often a private type or private extension) along with
the declarations of primitive subprograms of the type, which can
be called from outside the package, while their inner workings
remain hidden from outside users.
* parallel construct. an executable construct that defines multiple
activities of a single task that can proceed in parallel, via the
execution of multiple logical threads of control
* partition. a part of a program, which consists of a set of
interdependent library units
* Note 1 on entry: Each partition can run in a separate address
space, possibly on a separate computer. A program can contain
just one partition, or it can be distributed across multiple
partitions, which can execute concurrently.
* pragma. a compiler directive to provide control over and above that
provided by the other syntactic constructs of the language
* Note 1 on entry: There are language-defined pragmas that give
instructions for optimization, listing control, etc. An
implementation can support additional (implementation-defined)
pragmas.
* program. a set of partitions, each of which can execute in a
separate address space, possibly on a separate computer
* program unit. a language construct that is a package, a task unit, a
protected unit, a protected entry, a generic unit, or an explicitly
declared subprogram other than an enumeration literal
* Note 1 on entry: Certain kinds of program units can be
separately compiled. Alternatively, they can appear physically
nested within other program units.
* reduction expression. an expression that defines how to map or
transform a collection of values into a new set of values, and then
summarize the values by applying an operation to reduce the set to a
single value
* renaming. a declaration that does not define a new entity, but
instead defines a new view of an existing entity
* specialized needs annex. an annex in which are defined language
constructs or capabilities that are not necessarily provided by all
conforming implementations
* subunit. the body of a program unit that can be compiled
separately from its enclosing program unit
• Runtime Actions [Group R]
* assertion. a boolean expression that is expected to be True when
evaluated at certain specified places
* Note 1 on entry: Certain pragmas and aspects define various kinds
of assertions.
* elaboration. the process by which a declaration achieves its
run-time effect
* Note 1 on entry: Elaboration is one of the forms of execution.
* evaluation. the process by which an expression achieves its
run-time effect
* Note 1 on entry: Evaluation is one of the forms of execution.
* execution. the process by which a construct achieves its run-time effect
* Note 1 on entry: Execution of a declaration is also called
elaboration. Execution of an expression is also called evaluation.
* logical thread of control. an activity within the execution of a
program that can proceed in parallel with other activities of the
same task, or of separate tasks
* master. the execution of a master construct
* Note 1 on entry: Each object and task is associated with a
master. When a master is left, associated tasks are awaited
and associated objects are finalized.
• Exceptional Situations [Group E]
* check. a test made during execution to determine whether a language
rule has been violated
* exception. a kind of exceptional situation
* exception occurrence. a run-time occurrence of an exceptional situation
* handle an exception. performing some actions in response to the
arising of an exception
* raise an exception. to abandon normal program execution so as to
draw attention to the fact that the corresponding situation has
arisen
* suppress a check. to assert that the check cannot fail, and to
request that the compiler optimize by disabling the check
* Note 1 on entry: The compiler is not required to honor this
request. Suppressing checks that can fail can cause a program to
behave in arbitrary ways.
!discussion
The glossary is adequate to form the basis for the required Terms and
Definitions clause. In the Ada Reference Manual, it will be added to
section 1.3 Terms and Definitions. In the ISO standard it will be its
own clause. For the ISO version, we will use the boilerplate required
by ISO instead of the current text in 1.3.
An alternative that would still be responsive to the ISO comment would be
to put the above into the ISO FDIS but do nothing to the Ada Reference
Manual, including leaving the Glossary as it is. That would complicate
future maintenance somewhat (since the Glossary and the T&D would both need
to be updated when either is, and the wording is somewhat different between
them). As such, we suggest the simpler long-term solution.
[Editor's note: The Webster's dictionary reference isn't the one allowed
anymore. It's "Webster’s New World College Dictionary" in the latest
Directives; we ought to consider changing the reference to that. OTOH,
since the dictionary won't appear in the ISO version, doing nothing is
acceptable.]
!example
None needed.
!ACATS test
No tests required.
!appendix
****************************************************************
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