A.18.25 The Generic Package Containers.Bounded_Multiway_Trees
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The language-defined generic package Containers.Bounded_Multiway_Trees
provides a private type Tree and a set of operations. It provides the
same operations as the package Containers.Multiway_Trees (see A.18.10),
with the difference that the maximum storage is bounded.Static Semantics
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The declaration of the generic library package
Containers.Bounded_Multiway_Trees has the same contents and semantics
as Containers.Multiway_Trees except:3/3
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The
type Tree is declared with a discriminant that specifies the capacity
(maximum number of elements) as follows:
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type Tree (Capacity : Count_Type) is tagged private;
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The type Tree needs finalization
if and only if type Element_Type needs finalization.
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Implementation Note:
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The type Tree cannot depend on package Ada.Finalization
unless the element type depends on that package. The objects returned
from the Iterator and Reference functions probably do depend on package
Ada.Finalization. Restricted environments may need to avoid use of those
functions and their associated types.
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The allocation of internal
storage includes a check that the capacity is not exceeded, and Capacity_Error
is raised if this check fails.
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In procedure Assign, if Source
length is greater than Target capacity, then Capacity_Error is propagated.
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Function
Copy is declared as follows:
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function Copy (Source : Tree; Capacity : Count_Type := 0)
return List;
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If Capacity is 0,
then the tree capacity is the count of Source; if Capacity is equal to
or greater than Source.Count, the tree capacity equals the value of the
Capacity parameter; otherwise, the operation propagates Capacity_Error.
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In the five-parameter procedure Splice_Subtree,
if Source is not the same object as Target, and if the sum of Target.Count
and Subtree_Node_Count (Position) is greater than Target.Capacity, then
Splice_Subtree propagates Capacity_Error.13/3
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In the five-parameter procedure Splice_Children,
if Source is not the same object as Target, and if the sum of Target.Count
and Subtree_Node_Count (Source_Parent)-1 is greater than Target.Capacity,
then Splice_Children propagates Capacity_Error. Bounded (Run-Time) Errors
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It is a bounded error to use
a bounded tree if it was the target of an assignment_statement
whose source was in the middle of an operation that prohibits tampering
with elements [or cursors]. Either Program_Error is raised, or the operation
proceeds as defined. Implementation Requirements
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For each instance of Containers.Multiway_Trees
and each instance of Containers.Bounded_Multiway_Trees, if the two instances
meet the following conditions, then the output generated by the Tree'Output
or Tree'Write subprograms of either instance shall be readable by the
Tree'Input or Tree'Read of the other instance, respectively:16/3
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the Element_Type parameters of the two instances
are statically matching subtypes of the same type; and17/3
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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
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Bounded tree objects should be implemented without
implicit pointers or dynamic allocation. 18.a.1/3
Implementation Advice:
Bounded tree objects should be implemented
without implicit pointers or dynamic allocation.
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The implementation advice for procedure Move to
minimize copying does not apply. 19.a.1/3
Implementation Advice:
The implementation advice for procedure
Move to minimize copying does not apply to bounded trees.
Extensions to Ada 2005
19.a/3
Ada 2005 and 2012 Editions sponsored in part by Ada-Europe
