A.18.19 The Generic Package Containers.Bounded_Vectors
The language-defined generic package Containers.Bounded_Vectors
provides a private type Vector and a set of operations. It provides the
same operations as the package Containers.Vectors (see
A.18.2),
with the difference that the maximum storage is bounded.
Static Semantics
The declaration of
the generic library package Containers.Bounded_Vectors has the same contents
and semantics as Containers.Vectors except:
The aspect Preelaborate is replaced with aspect
Pure. Aspect Global is deleted.
The type Vector is
declared with a discriminant that specifies the capacity:
type Vector (Capacity : Count_Type) is tagged private...
The
aspect_definition
for Preelaborable_Initialization for type Vector is changed to:
Preelaborable_Initialization =>
Element_Type'Preelaborable_Initialization
The type Vector needs finalization if and only
if type Element_Type needs finalization.
Capacity is omitted from the Stable_Properties
of type Vector.
In function Empty,
the postcondition is altered to:
Post =>
Empty'Result.Capacity = Capacity and then
not Tampering_With_Elements_Prohibited (Empty'Result) and then
not Tampering_With_Cursors_Prohibited (Empty'Result) and then
Length (Empty'Result) = 0;
In function Copy, the postcondition is altered
to:
Post => Length (Copy'Result) = Length (Source) and then
(if Capacity > Length (Source) then
Copy'Result.Capacity = Capacity
else Copy'Result.Capacity >= Length (Source));
The description of
Reserve_Capacity is replaced with:
procedure Reserve_Capacity (Container : in out Vector;
Capacity : in Count_Type)
with Pre => Capacity <= Container.Capacity
or else raise Capacity_Error;
This operation has no effect, other than checking
the precondition.
The portion of the postcondition checking the capacity
is omitted from subprograms Set_Length, Assign, Insert, Insert_Space,
Prepend, Append, and Delete.
For procedures Insert,
Insert_Space, Prepend, and Append, the part of the precondition reading:
(<some length> <= Maximum_Length - <some other length>
or else raise Constraint_Error)
is replaced
by:
(<some length> <= Maximum_Length - <some other length>
or else raise Constraint_Error) and then
(<some length> <= Container.Capacity - <some other length>
or else raise Capacity_Error)
Bounded (Run-Time) Errors
It is a bounded error to assign
from a bounded vector object while tampering with elements or cursors
of that object is prohibited. Either Program_Error is raised by the assignment,
execution proceeds with the target object prohibiting tampering with
elements or cursors, or execution proceeds normally.
Erroneous Execution
When a bounded vector object
V is finalized,
if tampering with cursors is prohibited for
V other than due to
an assignment from another vector, then execution is erroneous.
Implementation Requirements
For each instance of
Containers.Vectors and each instance of Containers.Bounded_Vectors, if
the two instances meet the following conditions, then the output generated
by the Vector'Output or Vector'Write subprograms of either instance shall
be readable by the Vector'Input or Vector'Read of the other instance,
respectively:
the Element_Type parameters of the two instances
are statically matching subtypes of the same type; and
the output generated by Element_Type'Output or
Element_Type'Write is readable by Element_Type'Input or Element_Type'Read,
respectively (where Element_Type denotes the type of the two actual Element_Type
parameters); and
the preceding two conditions also hold for the
Index_Type parameters of the instances.
Implementation Advice
Bounded vector objects should be implemented without
implicit pointers or dynamic allocation.
The implementation advice for procedure Move to minimize
copying does not apply.
Ada 2005 and 2012 Editions sponsored in part by Ada-Europe
