250 lines
11 KiB
Ada
250 lines
11 KiB
Ada
------------------------------------------------------------------------------
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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) 2000-2016, 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 3, 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. --
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-- --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception, --
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-- version 3.1, as published by the Free Software Foundation. --
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-- --
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-- You should have received a copy of the GNU General Public License and --
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-- a copy of the GCC Runtime Library Exception along with this program; --
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-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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-- <http://www.gnu.org/licenses/>. --
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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 these three interfaces should remain synchronized to keep as much
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-- coherency as possible among these three related units:
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--
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-- GNAT.Dynamic_Tables
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-- GNAT.Table
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-- Table (the compiler unit)
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pragma Compiler_Unit_Warning;
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with Ada.Unchecked_Conversion;
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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 := 8;
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Table_Increment : Natural := 100;
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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 array,
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-- Table_Low_Bound is the lower bound. The effect is roughly to declare:
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-- Table : array (Table_Low_Bound .. <>) of Table_Component_Type;
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-- The lower bound of Table_Index_Type is ignored.
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pragma Assert (Table_Low_Bound /= Table_Index_Type'Base'First);
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function First return Table_Index_Type;
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pragma Inline (First);
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-- Export First as synonym for Table_Low_Bound (parallel with use of Last)
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subtype Valid_Table_Index_Type is Table_Index_Type'Base
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range Table_Low_Bound .. Table_Index_Type'Base'Last;
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subtype Table_Count_Type is Table_Index_Type'Base
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range Table_Low_Bound - 1 .. Table_Index_Type'Base'Last;
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-- Table_Component_Type must not be a type with controlled parts.
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-- The Table_Initial value controls the allocation of the table when
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-- it is first allocated.
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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 (Valid_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 .. Valid_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.
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-- To get subscript checking, rename a slice of the Table, like this:
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-- Table : Table_Type renames T.Table (First .. Last (T));
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-- and the refer to components of Table.
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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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type Table_Private is private;
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-- Table private data that is not exported in Instance
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-- Private use only:
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subtype Empty_Table_Array_Type is
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Table_Type (Table_Low_Bound .. Table_Low_Bound - 1);
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type Empty_Table_Array_Ptr is access all Empty_Table_Array_Type;
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Empty_Table_Array : aliased Empty_Table_Array_Type;
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function Empty_Table_Array_Ptr_To_Table_Ptr is
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new Ada.Unchecked_Conversion (Empty_Table_Array_Ptr, Table_Ptr);
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-- End private use only. The above are used to initialize Table to point to
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-- an empty array.
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type Instance is record
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Table : aliased Table_Ptr :=
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Empty_Table_Array_Ptr_To_Table_Ptr (Empty_Table_Array'Access);
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-- The table itself. The lower bound is the value of First. Logically
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-- the upper bound is the current value of Last (although the actual
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-- size of the allocated table may be larger than this). The program may
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-- only access and modify Table entries in the range First .. Last.
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--
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-- It's a good idea to access this via a renaming of a slice, in order
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-- to ensure bounds checking, as in:
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--
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-- Tab : Table_Type renames X.Table (First .. X.Last);
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Locked : Boolean := False;
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-- Table expansion is permitted only if this switch is set to False. A
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-- client may set Locked to True, in which case any attempt to expand
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-- the table will cause an assertion failure. Note that while a table
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-- is locked, its address in memory remains fixed and unchanging.
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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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-- Reinitializes the table to empty. There is no need to call this before
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-- using a table; tables default to empty.
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function Last (T : Instance) return Table_Count_Type;
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pragma Inline (Last);
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-- Returns the current value of the last used entry in the table, which can
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-- then be used as a subscript for Table.
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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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-- Table_Initial and Table_Increment parameters. A call to Release releases
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-- all 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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-- Same as Init
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procedure Set_Last (T : in out Instance; New_Val : Table_Count_Type);
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pragma Inline (Set_Last);
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-- This procedure sets Last to the indicated value. If necessary the table
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-- is reallocated to accommodate the new value (i.e. on return the
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-- allocated table has an upper bound of at least Last). If Set_Last
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-- reduces the size of the table, then logically entries are removed from
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-- the table. If Set_Last increases the size of the table, then new entries
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-- 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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-- Appends New_Val onto the end of the table
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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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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 : Valid_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. If Index points to an existing
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-- item (i.e. it is in the range First .. Last (T)), the item is replaced.
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-- Otherwise (i.e. Index > Last (T), the table is expanded, and Last is set
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-- to Index.
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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 : Valid_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, or until one of
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-- 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 the 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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Last_Allocated : Table_Count_Type := Table_Low_Bound - 1;
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-- Subscript of the maximum entry in the currently allocated table.
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-- Initial value ensures that we initially allocate the table.
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Last : Table_Count_Type := Table_Low_Bound - 1;
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-- Current value of Last function
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-- Invariant: Last <= Last_Allocated
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end record;
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end GNAT.Dynamic_Tables;
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