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<H1><A NAME="SEC874" HREF="ciao_toc.html#TOC874">Double linked list</A></H1>
<P>
<A NAME="IDX9643"></A>
<P>
<STRONG>Author(s):</STRONG> David Trallero Mena.
<P>
<STRONG>Version:</STRONG> 1.10#7 (2006/4/26, 19:22:13 CEST)
<P>
<STRONG>Version of last change:</STRONG> 1.9#116 (2003/12/1, 22:4:57 CET)
<P>
This library allows the user to work with double linked lists. An index is used for referencing the current element in the list. Such index can be modified by <EM>next</EM> and <EM>prev</EM> predicated. The value of the current index can be obtained with <EM>top</EM> predicate
<UL>
<LI><A HREF="ciao_225.html#SEC875">Usage and interface (ddlist)</A>
<LI><A HREF="ciao_225.html#SEC876">Documentation on exports (ddlist)</A>
<LI><A HREF="ciao_225.html#SEC877">Other information (ddlist)</A>
</UL>
<H2><A NAME="SEC875" HREF="ciao_toc.html#TOC875">Usage and interface (<CODE>ddlist</CODE>)</A></H2>
<div class="cartouche">
<UL>
<LI><STRONG>Library usage:</STRONG>
<CODE>:- use_module(library(ddlist)).</CODE>
<LI><STRONG>Exports:</STRONG>
<UL>
<LI><EM>Predicates:</EM>
<A NAME="IDX9644"></A>
<CODE>null_list/1</CODE>,
<A NAME="IDX9645"></A>
<CODE>next/2</CODE>,
<A NAME="IDX9646"></A>
<CODE>prev/2</CODE>,
<A NAME="IDX9647"></A>
<CODE>insert/3</CODE>,
<A NAME="IDX9648"></A>
<CODE>insert_top/3</CODE>,
<A NAME="IDX9649"></A>
<CODE>insert_after/3</CODE>,
<A NAME="IDX9650"></A>
<CODE>delete/2</CODE>,
<A NAME="IDX9651"></A>
<CODE>delete_top/2</CODE>,
<A NAME="IDX9652"></A>
<CODE>delete_after/2</CODE>,
<A NAME="IDX9653"></A>
<CODE>top/2</CODE>,
<A NAME="IDX9654"></A>
<CODE>rewind/2</CODE>,
<A NAME="IDX9655"></A>
<CODE>forward/2</CODE>,
<A NAME="IDX9656"></A>
<CODE>length/2</CODE>,
<A NAME="IDX9657"></A>
<CODE>length_next/2</CODE>,
<A NAME="IDX9658"></A>
<CODE>length_prev/2</CODE>.
<LI><EM>Regular Types:</EM>
<A NAME="IDX9659"></A>
<CODE>ddlist/1</CODE>.
</UL>
<LI><STRONG>Other modules used:</STRONG>
<UL>
<LI><EM>System library modules:</EM>
<A NAME="IDX9660"></A>
<CODE>lists</CODE>.
</UL>
</UL>
</div class="cartouche">
<H2><A NAME="SEC876" HREF="ciao_toc.html#TOC876">Documentation on exports (<CODE>ddlist</CODE>)</A></H2>
<P>
<A NAME="IDX9661"></A>
<A NAME="IDX9662"></A>
<DL>
<DT><span class="define">PREDICATE:</span> <B>null_list/1:</B>
<DD><A NAME="IDX9663"></A>
<P>
<STRONG>Usage:</STRONG> <CODE>null_list(?NullList)</CODE>
<UL>
<LI><EM>Description:</EM> <CODE>NullList</CODE> is an empty list
<LI><EM>The following properties should hold at call time:</EM>
<CODE>A</CODE> is a free variable.
(<CODE>term_typing:var/1</CODE>)
<LI><EM>The following properties should hold upon exit:</EM>
<CODE>A</CODE> is double linked list
(<CODE>ddlist:ddlist/1</CODE>)
</UL>
</DL>
<P>
<A NAME="IDX9664"></A>
<A NAME="IDX9665"></A>
<DL>
<DT><span class="define">PREDICATE:</span> <B>next/2:</B>
<DD><A NAME="IDX9666"></A>
<P>
<STRONG>Usage:</STRONG> <CODE>next(OldList, NewList)</CODE>
<UL>
<LI><EM>Description:</EM> <CODE>NewList</CODE> is <CODE>OldList</CODE> but index is set to next element of current element of OldList. It satisfies next(A,B),prev(B,A)
<LI><EM>Call and exit should be <EM>compatible</EM> with:</EM>
<CODE>OldList</CODE> is double linked list
(<CODE>ddlist:ddlist/1</CODE>)
<CODE>NewList</CODE> is double linked list
(<CODE>ddlist:ddlist/1</CODE>)
</UL>
</DL>
<P>
<A NAME="IDX9667"></A>
<A NAME="IDX9668"></A>
<DL>
<DT><span class="define">PREDICATE:</span> <B>prev/2:</B>
<DD><A NAME="IDX9669"></A>
<P>
<STRONG>Usage:</STRONG> <CODE>prev(OldList, NewList)</CODE>
<UL>
<LI><EM>Description:</EM> <CODE>NewList</CODE> is <CODE>OldList</CODE> but index is set to previous element of current element of <CODE>OldList</CODE>op) of <CODE>OldList</CODE>
<LI><EM>Call and exit should be <EM>compatible</EM> with:</EM>
<CODE>OldList</CODE> is double linked list
(<CODE>ddlist:ddlist/1</CODE>)
<CODE>NewList</CODE> is double linked list
(<CODE>ddlist:ddlist/1</CODE>)
</UL>
</DL>
<P>
<A NAME="IDX9670"></A>
<A NAME="IDX9671"></A>
<DL>
<DT><span class="define">PREDICATE:</span> <B>insert/3:</B>
<DD><A NAME="IDX9672"></A>
<P>
<STRONG>Usage:</STRONG> <CODE>insert(List, Element, NewList)</CODE>
<UL>
<LI><EM>Description:</EM> <CODE>NewList</CODE> is like <CODE>List</CODE> but with <CODE>Element</CODE> inserted _BEFORE_ the current index It satisfies insert( X , A , Xp ) , delete( Xp , X ).
<LI><EM>Call and exit should be <EM>compatible</EM> with:</EM>
<CODE>List</CODE> is double linked list
(<CODE>ddlist:ddlist/1</CODE>)
<CODE>NewList</CODE> is double linked list
(<CODE>ddlist:ddlist/1</CODE>)
</UL>
</DL>
<P>
<A NAME="IDX9673"></A>
<A NAME="IDX9674"></A>
<DL>
<DT><span class="define">PREDICATE:</span> <B>insert_top/3:</B>
<DD><A NAME="IDX9675"></A>
<P>
<STRONG>Usage:</STRONG> <CODE>insert_top(List, Element, NewList)</CODE>
<UL>
<LI><EM>Description:</EM> Put <CODE>Element</CODE> as new top of <CODE>NewList</CODE> and push the rest of elements after it. It satisfies top( NewList , element )
<LI><EM>Call and exit should be <EM>compatible</EM> with:</EM>
<CODE>List</CODE> is double linked list
(<CODE>ddlist:ddlist/1</CODE>)
<CODE>NewList</CODE> is double linked list
(<CODE>ddlist:ddlist/1</CODE>)
</UL>
</DL>
<P>
<A NAME="IDX9676"></A>
<A NAME="IDX9677"></A>
<DL>
<DT><span class="define">PREDICATE:</span> <B>insert_after/3:</B>
<DD><A NAME="IDX9678"></A>
<P>
<STRONG>Usage:</STRONG> <CODE>insert_after(List, Element, NewList)</CODE>
<UL>
<LI><EM>Description:</EM> <CODE>NewList</CODE> is like <CODE>List</CODE> but with <CODE>Element</CODE> inserted _AFTER_ the current index It satisfies insert_after( X , A , Xp ) , delete_after( Xp , X ).
<LI><EM>Call and exit should be <EM>compatible</EM> with:</EM>
<CODE>List</CODE> is double linked list
(<CODE>ddlist:ddlist/1</CODE>)
<CODE>NewList</CODE> is double linked list
(<CODE>ddlist:ddlist/1</CODE>)
</UL>
</DL>
<P>
<A NAME="IDX9679"></A>
<A NAME="IDX9680"></A>
<DL>
<DT><span class="define">PREDICATE:</span> <B>delete/2:</B>
<DD><A NAME="IDX9681"></A>
<P>
<STRONG>Usage:</STRONG> <CODE>delete(OldList, NewList)</CODE>
<UL>
<LI><EM>Description:</EM> <CODE>NewList</CODE> does not have the previous element (top(prev)) of <CODE>OldList</CODE>
<LI><EM>Call and exit should be <EM>compatible</EM> with:</EM>
<CODE>OldList</CODE> is double linked list
(<CODE>ddlist:ddlist/1</CODE>)
<CODE>NewList</CODE> is double linked list
(<CODE>ddlist:ddlist/1</CODE>)
</UL>
</DL>
<P>
<A NAME="IDX9682"></A>
<A NAME="IDX9683"></A>
<DL>
<DT><span class="define">PREDICATE:</span> <B>delete_top/2:</B>
<DD><A NAME="IDX9684"></A>
<P>
<STRONG>Usage:</STRONG> <CODE>delete_top(OldList, NewList)</CODE>
<UL>
<LI><EM>Description:</EM> <CODE>NewList</CODE> does not have the current element (top) of <CODE>OldList</CODE>
<LI><EM>Call and exit should be <EM>compatible</EM> with:</EM>
<CODE>OldList</CODE> is double linked list
(<CODE>ddlist:ddlist/1</CODE>)
<CODE>NewList</CODE> is double linked list
(<CODE>ddlist:ddlist/1</CODE>)
</UL>
</DL>
<P>
<A NAME="IDX9685"></A>
<A NAME="IDX9686"></A>
<DL>
<DT><span class="define">PREDICATE:</span> <B>delete_after/2:</B>
<DD><A NAME="IDX9687"></A>
<P>
<STRONG>Usage:</STRONG> <CODE>delete_after(OldList, NewList)</CODE>
<UL>
<LI><EM>Description:</EM> <CODE>NewList</CODE> does not have next element to current element (top) of <CODE>OldList</CODE>
<LI><EM>Call and exit should be <EM>compatible</EM> with:</EM>
<CODE>OldList</CODE> is double linked list
(<CODE>ddlist:ddlist/1</CODE>)
<CODE>NewList</CODE> is double linked list
(<CODE>ddlist:ddlist/1</CODE>)
</UL>
</DL>
<P>
<A NAME="IDX9688"></A>
<A NAME="IDX9689"></A>
<DL>
<DT><span class="define">PREDICATE:</span> <B>top/2:</B>
<DD><A NAME="IDX9690"></A>
<P>
<STRONG>Usage:</STRONG> <CODE>top(List, Element)</CODE>
<UL>
<LI><EM>Description:</EM> <CODE>Element</CODE> is the element pointed by index
<LI><EM>Call and exit should be <EM>compatible</EM> with:</EM>
<CODE>List</CODE> is double linked list
(<CODE>ddlist:ddlist/1</CODE>)
</UL>
</DL>
<P>
<A NAME="IDX9691"></A>
<A NAME="IDX9692"></A>
<DL>
<DT><span class="define">PREDICATE:</span> <B>rewind/2:</B>
<DD><A NAME="IDX9693"></A>
<P>
<STRONG>Usage:</STRONG> <CODE>rewind(OldList, NewList)</CODE>
<UL>
<LI><EM>Description:</EM> <CODE>NewList</CODE> is the <CODE>OldList</CODE> but index is set to 0
<LI><EM>Call and exit should be <EM>compatible</EM> with:</EM>
<CODE>OldList</CODE> is double linked list
(<CODE>ddlist:ddlist/1</CODE>)
<CODE>NewList</CODE> is double linked list
(<CODE>ddlist:ddlist/1</CODE>)
</UL>
</DL>
<P>
<A NAME="IDX9694"></A>
<A NAME="IDX9695"></A>
<DL>
<DT><span class="define">PREDICATE:</span> <B>forward/2:</B>
<DD><A NAME="IDX9696"></A>
<P>
<STRONG>Usage:</STRONG> <CODE>forward(OldList, NewList)</CODE>
<UL>
<LI><EM>Description:</EM> <CODE>NewList</CODE> is the <CODE>OldList</CODE> but index is set to lentgh of <CODE>NewList</CODE>
<LI><EM>Call and exit should be <EM>compatible</EM> with:</EM>
<CODE>OldList</CODE> is double linked list
(<CODE>ddlist:ddlist/1</CODE>)
<CODE>NewList</CODE> is double linked list
(<CODE>ddlist:ddlist/1</CODE>)
</UL>
</DL>
<P>
<A NAME="IDX9697"></A>
<A NAME="IDX9698"></A>
<DL>
<DT><span class="define">PREDICATE:</span> <B>length/2:</B>
<DD><A NAME="IDX9699"></A>
<P>
<STRONG>Usage:</STRONG> <CODE>length(List, Len)</CODE>
<UL>
<LI><EM>Description:</EM> <CODE>Len</CODE> is the length of the <CODE>List</CODE>
<LI><EM>Call and exit should be <EM>compatible</EM> with:</EM>
<CODE>List</CODE> is double linked list
(<CODE>ddlist:ddlist/1</CODE>)
</UL>
</DL>
<P>
<A NAME="IDX9700"></A>
<A NAME="IDX9701"></A>
<DL>
<DT><span class="define">PREDICATE:</span> <B>length_next/2:</B>
<DD><A NAME="IDX9702"></A>
<P>
<STRONG>Usage:</STRONG> <CODE>length_next(List, Len)</CODE>
<UL>
<LI><EM>Description:</EM> <CODE>Len</CODE> is the length from the current index till the end
<LI><EM>Call and exit should be <EM>compatible</EM> with:</EM>
<CODE>List</CODE> is double linked list
(<CODE>ddlist:ddlist/1</CODE>)
</UL>
</DL>
<P>
<A NAME="IDX9703"></A>
<A NAME="IDX9704"></A>
<DL>
<DT><span class="define">PREDICATE:</span> <B>length_prev/2:</B>
<DD><A NAME="IDX9705"></A>
<P>
<STRONG>Usage:</STRONG> <CODE>length_prev(List, Len)</CODE>
<UL>
<LI><EM>Description:</EM> <CODE>Len</CODE> is the length from the beginning till the current index
<LI><EM>Call and exit should be <EM>compatible</EM> with:</EM>
<CODE>List</CODE> is double linked list
(<CODE>ddlist:ddlist/1</CODE>)
</UL>
</DL>
<P>
<A NAME="IDX9706"></A>
<A NAME="IDX9707"></A>
<DL>
<DT><span class="define">REGTYPE:</span> <B>ddlist/1:</B>
<DD><A NAME="IDX9708"></A>
<P>
<STRONG>Usage:</STRONG> <CODE>ddlist(X)</CODE>
<UL>
<LI><EM>Description:</EM> <CODE>X</CODE> is double linked list
</UL>
</DL>
<H2><A NAME="SEC877" HREF="ciao_toc.html#TOC877">Other information (<CODE>ddlist</CODE>)</A></H2>
<P>
<P>
Two simple examples of the use of the ddlist library package follow.
<UL>
<LI><A HREF="ciao_225.html#SEC878">Using insert_after</A>
<LI><A HREF="ciao_225.html#SEC879">More Complex example</A>
</UL>
<H3><A NAME="SEC878" HREF="ciao_toc.html#TOC878">Using insert_after</A></H3>
<P>
<PRE>
:- module( ddl1 , _ , [] ).
:- use_module( library(ddlist) ).
main(A,B):-
% L = []
null_list( L ),
% L = [1]
insert_after( L , 1 , L1 ),
% L = [1,2]
insert_after( L1 , 2 , L2 ),
% L = [1,3,2]
insert_after( L2 , 3 , L3 ),
% L = [1,3,2] => A = [1]
top( L3 , A ),
% L = [3,2]
next( L3 , PL3 ),
% L = [3,2] => A = [3]
top( PL3 , B ).
</PRE>
<P>
<H3><A NAME="SEC879" HREF="ciao_toc.html#TOC879">More Complex example</A></H3>
<P>
<PRE>
:- module( ddl2 , _ , [] ).
:- use_module( library(ddlist) ).
main(A,B):-
% L = []
null_list( L ),
% L = [1]
insert_after( L , 1 , L1 ),
% L = [1,2]
insert_after( L1 , 2 , L2 ),
% L = [1,2]
insert( L2 , 3 , L3 ),
% L = [3,1,2]
prev( L3 , PL3 ),
% L = [],
forward( PL3 , FOR ),
% L = [2]
prev( FOR , FOR1 ),
% L = [2] => A = 2
top( FOR1 , A ),
% L = [1,2]
prev( FOR1 , FOR2 ),
% L = [2]
delete_after( FOR2 , FOR3 ),
% L = [3,2]
prev( FOR3, FOR4 ),
% L = [3,2] => B = 3
top( FOR4 , B ).
</PRE>
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