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1 281 jeremybenn
------------------------------------------------------------------------------
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--                                                                          --
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--                         GNAT COMPILER COMPONENTS                         --
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--                                                                          --
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--                   G N A T . D Y N A M I C _ T A B L E S                  --
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--                                                                          --
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--                                 S p e c                                  --
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--                                                                          --
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--                     Copyright (C) 2000-2009, AdaCore                     --
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--                                                                          --
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-- GNAT is free software;  you can  redistribute it  and/or modify it under --
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-- terms of the  GNU General Public License as published  by the Free Soft- --
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-- ware  Foundation;  either version 2,  or (at your option) any later ver- --
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-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
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-- for  more details.  You should have  received  a copy of the GNU General --
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-- Public License  distributed with GNAT;  see file COPYING.  If not, write --
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-- to  the  Free Software Foundation,  51  Franklin  Street,  Fifth  Floor, --
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-- Boston, MA 02110-1301, USA.                                              --
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--                                                                          --
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-- As a special exception,  if other files  instantiate  generics from this --
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-- unit, or you link  this unit with other files  to produce an executable, --
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-- this  unit  does not  by itself cause  the resulting  executable  to  be --
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-- covered  by the  GNU  General  Public  License.  This exception does not --
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-- however invalidate  any other reasons why  the executable file  might be --
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-- covered by the  GNU Public License.                                      --
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--                                                                          --
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-- GNAT was originally developed  by the GNAT team at  New York University. --
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-- Extensive contributions were provided by Ada Core Technologies Inc.      --
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--                                                                          --
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------------------------------------------------------------------------------
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--  Resizable one dimensional array support
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--  This package provides an implementation of dynamically resizable one
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--  dimensional arrays. The idea is to mimic the normal Ada semantics for
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--  arrays as closely as possible with the one additional capability of
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--  dynamically modifying the value of the Last attribute.
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--  This package provides a facility similar to that of GNAT.Table, except
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--  that this package declares a type that can be used to define dynamic
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--  instances of the table, while an instantiation of GNAT.Table creates a
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--  single instance of the table type.
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--  Note that this interface should remain synchronized with those in
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--  GNAT.Table and the GNAT compiler source unit Table to keep as much
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--  coherency as possible between these three related units.
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pragma Compiler_Unit;
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generic
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   type Table_Component_Type is private;
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   type Table_Index_Type     is range <>;
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   Table_Low_Bound : Table_Index_Type;
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   Table_Initial   : Positive;
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   Table_Increment : Natural;
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package GNAT.Dynamic_Tables is
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   --  Table_Component_Type and Table_Index_Type specify the type of the
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   --  array, Table_Low_Bound is the lower bound. Index_type must be an
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   --  integer type. The effect is roughly to declare:
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   --    Table : array (Table_Low_Bound .. <>) of Table_Component_Type;
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   --    Note: since the upper bound can be one less than the lower
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   --    bound for an empty array, the table index type must be able
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   --    to cover this range, e.g. if the lower bound is 1, then the
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   --    Table_Index_Type should be Natural rather than Positive.
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   --  Table_Component_Type may be any Ada type, except that controlled
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   --  types are not supported. Note however that default initialization
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   --  will NOT occur for array components.
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   --  The Table_Initial values controls the allocation of the table when
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   --  it is first allocated, either by default, or by an explicit Init
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   --  call.
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   --  The Table_Increment value controls the amount of increase, if the
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   --  table has to be increased in size. The value given is a percentage
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   --  value (e.g. 100 = increase table size by 100%, i.e. double it).
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   --  The Last and Set_Last subprograms provide control over the current
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   --  logical allocation. They are quite efficient, so they can be used
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   --  freely (expensive reallocation occurs only at major granularity
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   --  chunks controlled by the allocation parameters).
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   --  Note: we do not make the table components aliased, since this would
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   --  restrict the use of table for discriminated types. If it is necessary
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   --  to take the access of a table element, use Unrestricted_Access.
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   type Table_Type is
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     array (Table_Index_Type range <>) of Table_Component_Type;
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   subtype Big_Table_Type is
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     Table_Type (Table_Low_Bound .. Table_Index_Type'Last);
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   --  We work with pointers to a bogus array type that is constrained with
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   --  the maximum possible range bound. This means that the pointer is a thin
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   --  pointer, which is more efficient. Since subscript checks in any case
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   --  must be on the logical, rather than physical bounds, safety is not
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   --  compromised by this approach. These types should not be used by the
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   --  client.
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   type Table_Ptr is access all Big_Table_Type;
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   for Table_Ptr'Storage_Size use 0;
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   --  The table is actually represented as a pointer to allow reallocation.
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   --  This type should not be used by the client.
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   type Table_Private is private;
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   --  Table private data that is not exported in Instance
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   type Instance is record
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      Table : aliased Table_Ptr := null;
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   --  The table itself. The lower bound is the value of Low_Bound.
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   --  Logically the upper bound is the current value of Last (although
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   --  the actual size of the allocated table may be larger than this).
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   --  The program may only access and modify Table entries in the
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   --  range First .. Last.
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      P : Table_Private;
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   end record;
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   procedure Init (T : in out Instance);
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   --  This procedure allocates a new table of size Initial (freeing any
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   --  previously allocated larger table). Init must be called before using
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   --  the table. Init is convenient in reestablishing a table for new use.
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   function Last (T : Instance) return Table_Index_Type;
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   pragma Inline (Last);
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   --  Returns the current value of the last used entry in the table,
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   --  which can then be used as a subscript for Table. Note that the
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   --  only way to modify Last is to call the Set_Last procedure. Last
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   --  must always be used to determine the logically last entry.
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   procedure Release (T : in out Instance);
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   --  Storage is allocated in chunks according to the values given in the
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   --  Initial and Increment parameters. A call to Release releases all
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   --  storage that is allocated, but is not logically part of the current
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   --  array value. Current array values are not affected by this call.
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   procedure Free (T : in out Instance);
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   --  Free all allocated memory for the table. A call to init is required
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   --  before any use of this table after calling Free.
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   First : constant Table_Index_Type := Table_Low_Bound;
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   --  Export First as synonym for Low_Bound (parallel with use of Last)
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   procedure Set_Last (T : in out Instance; New_Val : Table_Index_Type);
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   pragma Inline (Set_Last);
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   --  This procedure sets Last to the indicated value. If necessary the
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   --  table is reallocated to accommodate the new value (i.e. on return
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   --  the allocated table has an upper bound of at least Last). If
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   --  Set_Last reduces the size of the table, then logically entries are
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   --  removed from the table. If Set_Last increases the size of the
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   --  table, then new entries are logically added to the table.
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   procedure Increment_Last (T : in out Instance);
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   pragma Inline (Increment_Last);
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   --  Adds 1 to Last (same as Set_Last (Last + 1)
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   procedure Decrement_Last (T : in out Instance);
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   pragma Inline (Decrement_Last);
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   --  Subtracts 1 from Last (same as Set_Last (Last - 1)
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   procedure Append (T : in out Instance; New_Val : Table_Component_Type);
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   pragma Inline (Append);
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   --  Equivalent to:
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   --    Increment_Last (T);
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   --    T.Table (T.Last) := New_Val;
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   --  i.e. the table size is increased by one, and the given new item
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   --  stored in the newly created table element.
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   procedure Append_All (T : in out Instance; New_Vals : Table_Type);
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   --  Appends all components of New_Vals
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   procedure Set_Item
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     (T     : in out Instance;
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      Index : Table_Index_Type;
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      Item  : Table_Component_Type);
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   pragma Inline (Set_Item);
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   --  Put Item in the table at position Index. The table is expanded if
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   --  current table length is less than Index and in that case Last is set to
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   --  Index. Item will replace any value already present in the table at this
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   --  position.
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   procedure Allocate (T : in out Instance; Num : Integer := 1);
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   pragma Inline (Allocate);
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   --  Adds Num to Last
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   generic
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     with procedure Action
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       (Index : Table_Index_Type;
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        Item  : Table_Component_Type;
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        Quit  : in out Boolean) is <>;
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   procedure For_Each (Table : Instance);
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   --  Calls procedure Action for each component of the table Table, or until
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   --  one of these calls set Quit to True.
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   generic
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     with function Lt (Comp1, Comp2 : Table_Component_Type) return Boolean;
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   procedure Sort_Table (Table : in out Instance);
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   --  This procedure sorts the components of table Table into ascending
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   --  order making calls to Lt to do required comparisons, and using
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   --  assignments to move components around. The Lt function returns True
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   --  if Comp1 is less than Comp2 (in the sense of the desired sort), and
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   --  False if Comp1 is greater than Comp2. For equal objects it does not
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   --  matter if True or False is returned (it is slightly more efficient
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   --  to return False). The sort is not stable (the order of equal items
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   --  in the table is not preserved).
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private
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   type Table_Private is record
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      Max : Integer;
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      --  Subscript of the maximum entry in the currently allocated table
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      Length : Integer := 0;
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      --  Number of entries in currently allocated table. The value of zero
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      --  ensures that we initially allocate the table.
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      Last_Val : Integer;
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      --  Current value of Last
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   end record;
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end GNAT.Dynamic_Tables;

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