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The following document is a draft of the corresponding chapter of the
version of the Ada Reference Manual produced in response to the Ansi
Canvass. It is given a limited circulation to Ada implementers and to
other groups contributing comments (according to the conventions defined in
RRM.comments). This draft should not be referred to in any publication.
ANSI-RM-D-v23 - Draft Chapter
D Glossary
version 23
83-03-11
This revision has considered all comments up to #5795
> D. Glossary
This appendix is informative and is not part of the standard definition of
the Ada programming language. Italicized terms in the abbreviated
descriptions below either have glossary entries themselves or are described
in entries for related terms.
Accept statement. See entry.
Access type. A value of an access type (an access value) is either a null
value, or a value that designates an object created by an allocator. The
designated object can be read and updated via the access value. The
definition of an access type specifies the type of the objects designated
by values of the access type. See also collection.
Actual parameter. See parameter.
Aggregate. The evaluation of an aggregate yields a value of a composite
type. The value is specified by giving the value of each of the
components. Either positional association or named association may be used
to indicate which value is associated with which component.
Allocator. The evaluation of an allocator creates an object and returns a
new access value which designates the object.
Array type. A value of an array type consists of components which are all
of the same subtype (and hence, of the same type). Each component is
uniquely distinguished by an index (for a one-dimensional array) or by a
sequence of indices (for a multidimensional array). Each index must be a
value of a discrete type and must lie in the correct index range.
Assignment. Assignment is the operation that replaces the current value of
a variable by a new value. An assignment statement specifies a variable on
the left, and on the right, an expression whose value is to be the new
value of the variable.
Attribute. The evaluation of an attribute yields a predefined
characteristic of a named entity; some attributes are functions.
Block statement. A block statement is a single statement that may contain
a sequence of statements. It may also include a declarative part, and
exception handlers; their effects are local to the block statement.
Body. A body defines the execution of a subprogram, package, or task. A
body stub is a form of body that indicates that this execution is defined
in a separately compiled subunit.
Collection. A collection is the entire set of objects created by
evaluation of allocators for an access type.
Compilation unit. A compilation unit is the declaration or the body of a
program unit, presented for compilation as an independent text. It is
optionally preceded by a context clause, naming other compilation units
upon which it depends by means of one more with clauses.
Component. A component is a value that is a part of a larger value, or an
object that is part of a larger object.
Composite type. A composite type is one whose values have components.
There are two kinds of composite type: array types and record types.
Constant. See object.
Constraint. A constraint determines a subset of the values of a type. A
value in that subset satisfies the constraint.
Context clause. See compilation unit.
Declaration. A declaration associates an identifier (or some other
notation) with an entity. This association is in effect within a region of
text called the scope of the declaration. Within the scope of a
declaration, there are places where it is possible to use the identifier to
refer to the associated declared entity. At such places the identifier is
said to be a simple name of the entity; the name is said to denote the
associated entity.
Declarative Part. A declarative part is a sequence of declarations. It
may also contain related information such as subprogram bodies and
representation clauses.
Denote. See declaration.
Derived Type. A derived type is a type whose operations and values are
replicas of those of an existing type. The existing type is called the
parent type of the derived type.
Designate. See access type, task.
Direct visibility. See visibility.
Discrete Type. A discrete type is a type which has an ordered set of
distinct values. The discrete types are the enumeration and integer types.
Discrete types are used for indexing and iteration, and for choices in case
statements and record variants.
Discriminant. A discriminant is a distinguished component of an object or
value of a record type. The subtypes of other components, or even their
presence or absence, may depend on the value of the discriminant.
Discriminant constraint. A discriminant constraint on a record type or
private type specifies a value for each discriminant of the type.
Elaboration. The elaboration of a declaration is the process by which the
declaration achieves its effect (such as creating an object); this process
occurs during program execution.
Entry. An entry is used for communication between tasks. Externally, an
entry is called just as a subprogram is called; its internal behavior is
specified by one or more accept statements specifying the actions to be
performed when the entry is called.
Enumeration type. An enumeration type is a discrete type whose values are
represented by enumeration literals which are given explicitly in the type
declaration. These enumeration literals are either identifiers or
character literals.
Evaluation. The evaluation of an expression is the process by which the
value of the expression is computed. This process occurs during program
execution.
Exception. An exception is an error situation which may arise during
program execution. To raise an exception is to abandon normal program
execution so as to signal that the error has taken place. An exception
handler is a portion of program text specifying a response to the
exception. Execution of such a program text is called handling the
exception.
Expanded name. An expanded name denotes an entity which is declared
immediately within some construct. An expanded name has the form of a
selected component: the prefix denotes the construct (a program unit; or
a block, loop, or accept statement); the selector is the simple name of
the entity.
Expression. An expression defines the computation of a value.
Fixed point type. See real type.
Floating point type. See real type.
Formal parameter. See parameter.
Function. See subprogram.
Generic unit. A generic unit is a template either for a set of subprograms
or for a set of packages. A subprogram or package created using the
template is called an instance of the generic unit. A generic
instantiation is the kind of declaration that creates an instance. A
generic unit is written as a subprogram or package but with the
specification prefixed by a generic formal part which may declare generic
formal parameters. A generic formal parameter is either a type, a
subprogram, or an ob