Ada Reference Manual (Ada 2022)
A.18.24 The Generic Package Containers.Bounded_Ordered_Sets
The language-defined generic package Containers.Bounded_Ordered_Sets provides a private type Set and a set of operations. It provides the same operations as the package Containers.Ordered_Sets (see A.18.9), with the difference that the maximum storage is bounded.
Static Semantics
The declaration of the generic library package Containers.Bounded_Ordered_Sets has the same contents and semantics as Containers.Ordered_Sets except:
- The aspect Preelaborate is replaced with aspect Pure. Aspect Global is deleted.
- The type Set is declared with a discriminant that specifies the capacity (maximum number of elements) as follows:
type Set (Capacity : Count_Type) is tagged private...
- The aspect_definition for Preelaborable_Initialization for type Set is changed to:
Preelaborable_Initialization =>
Element_Type'Preelaborable_Initialization
Element_Type'Preelaborable_Initialization
- The type Set needs finalization if and only if type Element_Type needs finalization.
- The function Empty is replaced by:
function Empty (Capacity : Count_Type := implementation-defined)
return Set
with Post =>
Empty'Result.Capacity = Capacity and then
not Tampering_With_Cursors_Prohibited (Empty'Result) and then
Length (Empty'Result) = 0;
return Set
with Post =>
Empty'Result.Capacity = Capacity and then
not Tampering_With_Cursors_Prohibited (Empty'Result) and then
Length (Empty'Result) = 0;
- For procedures Insert and Include, the part of the precondition reading:
(<some length> <= Count_Type'Last - <some other length>
or else raise Constraint_Error)
or else raise Constraint_Error)
is replaced by:
(<some length> <= Count_Type'Last - <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)
- In procedure Assign, the precondition is altered to:
Pre => (not Tampering_With_Cursors_Prohibited (Target)
or else raise Program_Error) and then
(Length (Source) <= Target.Capacity
or else raise Capacity_Error),
or else raise Program_Error) and then
(Length (Source) <= Target.Capacity
or else raise Capacity_Error),
- The function Copy is replaced with:
function Copy (Source : Set;
Capacity : Count_Type := 0) return Map
with Pre => Capacity = 0 or else Capacity >= Length (Source)
or else raise Capacity_Error,
Post =>
Length (Copy'Result) = Length (Source) and then
not Tampering_With_Cursors_Prohibited (Copy'Result) and then
Copy'Result.Capacity = (if Capacity = 0 then
Length (Source) else Capacity);
Capacity : Count_Type := 0) return Map
with Pre => Capacity = 0 or else Capacity >= Length (Source)
or else raise Capacity_Error,
Post =>
Length (Copy'Result) = Length (Source) and then
not Tampering_With_Cursors_Prohibited (Copy'Result) and then
Copy'Result.Capacity = (if Capacity = 0 then
Length (Source) else Capacity);
Returns a set with key/element pairs initialized from the values in Source.
Bounded (Run-Time) Errors
It is a bounded error to assign from a bounded set 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 set object S is finalized, if tampering with cursors is prohibited for S other than due to an assignment from another set, then execution is erroneous.
Implementation Requirements
For each instance of Containers.Ordered_Sets and each instance of Containers.Bounded_Ordered_Sets, if the two instances meet the following conditions, then the output generated by the Set'Output or Set'Write subprograms of either instance shall be readable by the Set'Input or Set'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).
Implementation Advice
Bounded ordered set objects should be implemented without implicit pointers or dynamic allocation.
The implementation advice for procedure Move to minimize copying does not apply.
