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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 pragma Preelaborate is replaced with pragma Pure.
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. 

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