| ------------------------------------------------------------------------------ |
| -- -- |
| -- GNAT RUN-TIME COMPONENTS -- |
| -- -- |
| -- G N A T . L I S T S -- |
| -- -- |
| -- S p e c -- |
| -- -- |
| -- Copyright (C) 2018-2021, Free Software Foundation, Inc. -- |
| -- -- |
| -- GNAT is free software; you can redistribute it and/or modify it under -- |
| -- terms of the GNU General Public License as published by the Free Soft- -- |
| -- ware Foundation; either version 3, or (at your option) any later ver- -- |
| -- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- |
| -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- |
| -- or FITNESS FOR A PARTICULAR PURPOSE. -- |
| -- -- |
| -- As a special exception under Section 7 of GPL version 3, you are granted -- |
| -- additional permissions described in the GCC Runtime Library Exception, -- |
| -- version 3.1, as published by the Free Software Foundation. -- |
| -- -- |
| -- You should have received a copy of the GNU General Public License and -- |
| -- a copy of the GCC Runtime Library Exception along with this program; -- |
| -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- |
| -- <http://www.gnu.org/licenses/>. -- |
| -- -- |
| -- GNAT was originally developed by the GNAT team at New York University. -- |
| -- Extensive contributions were provided by Ada Core Technologies Inc. -- |
| -- -- |
| ------------------------------------------------------------------------------ |
| |
| pragma Compiler_Unit_Warning; |
| |
| package GNAT.Lists is |
| |
| ------------------------ |
| -- Doubly_Linked_List -- |
| ------------------------ |
| |
| -- The following package offers a doubly linked list abstraction with the |
| -- following characteristics: |
| -- |
| -- * Creation of multiple instances, of different sizes |
| -- * Iterable elements |
| -- |
| -- The following use pattern must be employed with this list: |
| -- |
| -- List : Doubly_Linked_List := Create; |
| -- |
| -- <various operations> |
| -- |
| -- Destroy (List); |
| -- |
| -- The destruction of the list reclaims all storage occupied by it. |
| |
| generic |
| type Element_Type is private; |
| |
| with function "=" |
| (Left : Element_Type; |
| Right : Element_Type) return Boolean; |
| |
| with procedure Destroy_Element (Elem : in out Element_Type); |
| -- Element destructor |
| |
| package Doubly_Linked_Lists is |
| |
| --------------------- |
| -- List operations -- |
| --------------------- |
| |
| type Doubly_Linked_List is private; |
| Nil : constant Doubly_Linked_List; |
| |
| -- The following exception is raised when the list is empty, and an |
| -- attempt is made to delete an element from it. |
| |
| List_Empty : exception; |
| |
| procedure Append |
| (L : Doubly_Linked_List; |
| Elem : Element_Type); |
| -- Insert element Elem at the end of list L. This action will raise |
| -- Iterated if the list has outstanding iterators. |
| |
| function Contains |
| (L : Doubly_Linked_List; |
| Elem : Element_Type) return Boolean; |
| -- Determine whether list L contains element Elem |
| |
| function Create return Doubly_Linked_List; |
| -- Create a new list |
| |
| procedure Delete |
| (L : Doubly_Linked_List; |
| Elem : Element_Type); |
| -- Delete element Elem from list L. The routine has no effect if Elem is |
| -- not present. This action will raise |
| -- |
| -- * List_Empty if the list is empty. |
| -- * Iterated if the list has outstanding iterators. |
| |
| procedure Delete_First (L : Doubly_Linked_List); |
| -- Delete an element from the start of list L. This action will raise |
| -- |
| -- * List_Empty if the list is empty. |
| -- * Iterated if the list has outstanding iterators. |
| |
| procedure Delete_Last (L : Doubly_Linked_List); |
| -- Delete an element from the end of list L. This action will raise |
| -- |
| -- * List_Empty if the list is empty. |
| -- * Iterated if the list has outstanding iterators. |
| |
| procedure Destroy (L : in out Doubly_Linked_List); |
| -- Destroy the contents of list L. This routine must be called at the |
| -- end of a list's lifetime. This action will raise Iterated if the |
| -- list has outstanding iterators. |
| |
| function Equal |
| (Left : Doubly_Linked_List; |
| Right : Doubly_Linked_List) return Boolean; |
| -- Determine whether lists Left and Right have the same characteristics |
| -- and contain the same elements. |
| |
| function First (L : Doubly_Linked_List) return Element_Type; |
| -- Obtain an element from the start of list L. This action will raise |
| -- List_Empty if the list is empty. |
| |
| procedure Insert_After |
| (L : Doubly_Linked_List; |
| After : Element_Type; |
| Elem : Element_Type); |
| -- Insert new element Elem after element After in list L. The routine |
| -- has no effect if After is not present. This action will raise |
| -- Iterated if the list has outstanding iterators. |
| |
| procedure Insert_Before |
| (L : Doubly_Linked_List; |
| Before : Element_Type; |
| Elem : Element_Type); |
| -- Insert new element Elem before element Before in list L. The routine |
| -- has no effect if After is not present. This action will raise |
| -- Iterated if the list has outstanding iterators. |
| |
| function Is_Empty (L : Doubly_Linked_List) return Boolean; |
| -- Determine whether list L is empty |
| |
| function Last (L : Doubly_Linked_List) return Element_Type; |
| -- Obtain an element from the end of list L. This action will raise |
| -- List_Empty if the list is empty. |
| |
| procedure Prepend |
| (L : Doubly_Linked_List; |
| Elem : Element_Type); |
| -- Insert element Elem at the start of list L. This action will raise |
| -- Iterated if the list has outstanding iterators. |
| |
| function Present (L : Doubly_Linked_List) return Boolean; |
| -- Determine whether list L exists |
| |
| procedure Replace |
| (L : Doubly_Linked_List; |
| Old_Elem : Element_Type; |
| New_Elem : Element_Type); |
| -- Replace old element Old_Elem with new element New_Elem in list L. The |
| -- routine has no effect if Old_Elem is not present. This action will |
| -- raise Iterated if the list has outstanding iterators. |
| |
| function Size (L : Doubly_Linked_List) return Natural; |
| -- Obtain the number of elements in list L |
| |
| ------------------------- |
| -- Iterator operations -- |
| ------------------------- |
| |
| -- The following type represents an element iterator. An iterator locks |
| -- all mutation operations, and ulocks them once it is exhausted. The |
| -- iterator must be used with the following pattern: |
| -- |
| -- Iter := Iterate (My_List); |
| -- while Has_Next (Iter) loop |
| -- Next (Iter, Element); |
| -- end loop; |
| -- |
| -- It is possible to advance the iterator by using Next only, however |
| -- this risks raising Iterator_Exhausted. |
| |
| type Iterator is private; |
| |
| function Has_Next (Iter : Iterator) return Boolean; |
| -- Determine whether iterator Iter has more elements to examine. If the |
| -- iterator has been exhausted, restore all mutation functionality of |
| -- the associated list. |
| |
| function Iterate (L : Doubly_Linked_List) return Iterator; |
| -- Obtain an iterator over the elements of list L. This action locks all |
| -- mutation functionality of the associated list. |
| |
| procedure Next |
| (Iter : in out Iterator; |
| Elem : out Element_Type); |
| -- Return the current element referenced by iterator Iter and advance |
| -- to the next available element. If the iterator has been exhausted |
| -- and further attempts are made to advance it, this routine restores |
| -- mutation functionality of the associated list, and then raises |
| -- Iterator_Exhausted. |
| |
| private |
| -- The following type represents a list node |
| |
| type Node; |
| type Node_Ptr is access all Node; |
| type Node is record |
| Elem : Element_Type; |
| |
| Next : Node_Ptr := null; |
| Prev : Node_Ptr := null; |
| end record; |
| |
| -- The following type represents a list |
| |
| type Doubly_Linked_List_Attributes is record |
| Elements : Natural := 0; |
| -- The number of elements in the list |
| |
| Iterators : Natural := 0; |
| -- Number of outstanding iterators |
| |
| Nodes : aliased Node; |
| -- The dummy head of the list |
| end record; |
| |
| type Doubly_Linked_List is access all Doubly_Linked_List_Attributes; |
| Nil : constant Doubly_Linked_List := null; |
| |
| -- The following type represents an element iterator |
| |
| type Iterator is record |
| Curr_Nod : Node_Ptr := null; |
| -- Reference to the current node being examined. The invariant of the |
| -- iterator requires that this field always points to a valid node. A |
| -- value of null indicates that the iterator is exhausted. |
| |
| List : Doubly_Linked_List := null; |
| -- Reference to the associated list |
| end record; |
| end Doubly_Linked_Lists; |
| |
| end GNAT.Lists; |
