remove vestigial prolog/ directory (#444)
This commit is contained in:
Mark Thom
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src/lib/tabling/double_linked_list.pl
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210
src/lib/tabling/double_linked_list.pl
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/* Part of SWI-Prolog
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Author: Benoit Desouter <Benoit.Desouter@UGent.be>
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Jan Wielemaker (SWI-Prolog port)
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Copyright (c) 2016, Benoit Desouter
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All rights reserved.
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Ported to Scryer Prolog by Mark Thom (2019/2020).
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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are met:
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1. Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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2. Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in
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the documentation and/or other materials provided with the
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distribution.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE.
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*/
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:- module(double_linked_list,
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[ dll_new_double_linked_list/1, % -List
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dll_append_right/2, % !List, +Element
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dll_append_left/2, % !List, +Element
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dll_append_right/3, % !List, +Element, -Pointer
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dll_append_left/3, % !List, +Element, -Pointer
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dll_get_data/2, % +List, -Head
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dll_get_pointer_to_next/2, % +List, -Pointer
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dll_get_pointer_to_previous/2, % +List, -Pointer
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dll_is_dummy_pointer/2, % +List, +Pointer
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dll_p_swap_adjacent_elements_/2, % +Pointer1, +Pointer2
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dll_get_contents/2,
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dll_get_reverse_contents/2
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]).
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:- use_module(library(atts)).
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:- attribute dll_element/1, dll_next/1, dll_prev/1.
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% A circular double linked list
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% =============================
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% Always have a unused-cell at the beginning.
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% I do not always inline unifications because the head is then more readable for users who don't need to know the details.
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% Due to lack of modules in hProlog, the following predicate names should not be used elsewhere:
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% - the heads of all following rules (starting with dll_, I reserve "the namespace"!)
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% dll_cell(Element,Next,Previous)
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% The following is perhaps odd:
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%
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% Next link = more to the front (the left)
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% Previous link = more to the back (the right)
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%
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% List structure
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% --------------
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% front-of-the-list | ... | back-of-the-list
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dll_new_double_linked_list(List) :-
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% Nonused cell dll_start at the beginning, points to itself (this is easy when adding elements).
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List = dll_cell(Start),
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put_atts(Start, [dll_next(List), dll_prev(List), dll_element(dll_start)]).
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dll_append_right(List, Element) :-
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dll_append_right(List, Element, _).
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dll_append_left(List, Element) :-
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dll_append_left(List, Element, _).
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% Append at the back of the list
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% Mode: + + -
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dll_append_right(List, Element, Pointer) :-
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% Get pointer to cell currently at the back. Done by taking the previous element from the unused element representing the list.
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dll_get_pointer_to_previous(List, OldBack),
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% Make the new cell point to OldBack as predecessor
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% Make the new cell point to the unused cell as successor.
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Pointer = dll_cell(NewCell),
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put_atts(NewCell, [dll_element(Element), dll_next(List), dll_prev(OldBack)]),
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% Make OldBack point to the new cell as successor
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dll_p_set_next_pointer(OldBack, Pointer),
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% Make the unused cell point to the new cell as predecessor
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dll_p_set_previous_pointer(List, Pointer).
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% Add to the front of the list
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% Mode: + + -
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dll_append_left(List, Element, Pointer) :-
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% Get pointer to cell currently at the front. Done by taking the next element from the unused element representing the list.
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dll_get_pointer_to_next(List, OldFront),
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% Make the new cell point to OldFront as successor
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% Make the new cell point to the unused cell as predecessor
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Pointer = dll_cell(NewCell),
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put_atts(NewCell, [dll_element(Element), dll_prev(List), dll_next(OldFront)]),
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% Make OldFront point to the new cell as predecessor
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dll_p_set_previous_pointer(OldFront, Pointer),
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% Make the unused cell point to the new cell as successor
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dll_p_set_next_pointer(List, Pointer).
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% get_next_cell?
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dll_get_pointer_to_next(dll_cell(Cell), PointerNext) :-
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get_atts(Cell, dll_next(PointerNext)).
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% get_previous_cell?
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dll_get_pointer_to_previous(dll_cell(Cell), PointerPrevious) :-
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get_atts(Cell, dll_prev(PointerPrevious)).
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% Will happily give you the "data" from the unused cell at the beginning. (We use this odd behaviour below, f.e. in dll_p_foreach_element_/2.)
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dll_get_data(dll_cell(Cell), Element) :-
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get_atts(Cell, dll_element(Element)).
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dll_is_dummy_pointer(List, Pointer) :-
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dll_get_contents(List, ListContents),
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dll_get_contents(Pointer, PointerContents),
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\+ PointerContents \= ListContents.
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% Special case of swapping - used in dll_swap/2.
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% This is also the case used for swapping a freshly created list with itself.
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%
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% Sketch: APrevious <-> PointerA <-> PointerB <-> BNext etc.
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dll_p_swap_adjacent_elements(PointerA, PointerB) :-
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% Order B A?
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( dll_get_pointer_to_next(PointerB, PointerA) ->
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dll_p_swap_adjacent_elements_(PointerB, PointerA)
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;
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% Order A B!
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dll_p_swap_adjacent_elements_(PointerA, PointerB)
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).
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% Assumes the order A B.
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dll_p_swap_adjacent_elements_(PointerA, PointerB) :-
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% Get A's previous and B's next
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dll_get_pointer_to_previous(PointerA, PointerAPrevious),
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dll_get_pointer_to_next(PointerB, PointerBNext),
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% Set A's previous to B
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dll_p_set_previous_pointer(PointerA, PointerB),
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% Set B's next to A
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dll_p_set_next_pointer(PointerB, PointerA),
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% Set A's next to BNext
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dll_p_set_next_pointer(PointerA, PointerBNext),
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% Set B's previous to APrevious
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dll_p_set_previous_pointer(PointerB, PointerAPrevious),
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% Set APrevious' next to B !!
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dll_p_set_next_pointer(PointerAPrevious, PointerB),
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% Set BNext's previous to A !!
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dll_p_set_previous_pointer(PointerBNext, PointerA).
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% Private
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% Careful: make sure this is called on the actual cell, and not some copy.
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% Mode: + +
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dll_p_set_previous_pointer(dll_cell(Cell), PointerToNewPrevious) :-
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put_atts(Cell, dll_prev(PointerToNewPrevious)).
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% Private
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% Careful: make sure this is called on the actual cell, and not some copy.
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% Mode: + +
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dll_p_set_next_pointer(dll_cell(Cell), PointerToNewNext) :-
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put_atts(Cell, dll_next(PointerToNewNext)).
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dll_extract_element(ElementFlag, Element) :-
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( ElementFlag = wkl_suspension_cluster(SuspensionClusterFlag) ->
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get_atts(SuspensionClusterFlag, batched_worklist, wkl_suspension_cluster(SuspensionCluster)),
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Element = wkl_suspension_cluster(SuspensionCluster)
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; ElementFlag = wkl_answer_cluster(AnswerClusterFlag) ->
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get_atts(AnswerClusterFlag, batched_worklist, wkl_answer_cluster(AnswerCluster)),
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Element = wkl_answer_cluster(AnswerCluster)
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).
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dll_get_contents(List, Contents) :-
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dll_get_pointer_to_next(List, Next),
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dll_get_contents_(Next, Contents).
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dll_get_contents_(List, Contents) :-
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dll_get_data(List, ElementFlag),
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( ElementFlag == dll_start ->
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Contents = []
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; dll_extract_element(ElementFlag, Element),
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Contents = [Element | Rest],
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dll_get_pointer_to_next(List, Next),
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dll_get_contents_(Next, Rest)
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).
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dll_get_reverse_contents(List, Contents) :-
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dll_get_pointer_to_previous(List, Prev),
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dll_get_reverse_contents_(Prev, Contents).
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dll_get_reverse_contents_(List, Contents) :-
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dll_get_data(List, ElementFlag),
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( ElementFlag == dll_start ->
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Contents = []
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; dll_extract_element(ElementFlag, Element),
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Contents = [Element | Rest],
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dll_get_pointer_to_previous(List, Prev),
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dll_get_reverse_contents_(Prev, Rest)
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).
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