A.18.22 The Generic Package Containers.Bounded_Ordered_Maps
The language-defined generic package Containers.Bounded_Ordered_Maps
provides a private type Map and a set of operations. It provides the
same operations as the package Containers.Ordered_Maps (see
A.18.6),
with the difference that the maximum storage is bounded.
Static Semantics
The declaration of
the generic library package Containers.Bounded_Ordered_Maps has the same
contents and semantics as Containers.Ordered_Maps except:
The type Map is declared
with a discriminant that specifies the capacity (maximum number of elements)
as follows:
type Map (Capacity : Count_Type) is tagged private;
The type Map needs finalization if and only if
type Key_Type or type Element_Type needs finalization.
The allocation of a new node includes a check that
the capacity is not exceeded, and Capacity_Error is raised if this check
fails.
In procedure Assign, if Source length is greater
than Target capacity, then Capacity_Error is propagated.
The function Copy
is replaced with:
function Copy (Source : Map;
Capacity : Count_Type := 0)
return Map;
Returns a map with key/element pairs initialized
from the values in Source. If Capacity is 0, then the map capacity is
the length of Source; if Capacity is equal to or greater than the length
of Source, the map capacity is the specified value; otherwise, the operation
propagates Capacity_Error.
Bounded (Run-Time) Errors
It is a bounded error to assign
from a bounded map 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 map object
M is finalized,
if tampering with cursors is prohibited for
M other than due to
an assignment from another map, then execution is erroneous.
Implementation Requirements
For each instance
of Containers.Ordered_Maps and each instance of Containers.Bounded_Ordered_Maps,
if the two instances meet the following conditions, then the output generated
by the Map'Output or Map'Write subprograms of either instance shall be
readable by the Map'Input or Map'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
Key_Type parameters of the instances.
Implementation Advice
Bounded ordered map 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
