Ada Reference Manual (Ada 2022)
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
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;
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));
(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;
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)
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)
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.
