library(list_collection)

Description

    A library for creation and management of list collections (LCOL).
    Internally the library uses either the a hashtable or arrays to store lists and their tails. 
    The advantage of a hash LCOL is that its size does not have to be known in advance and that 
    non number indexes can be used to address lists in the collection. The drawback of a hash LCOL 
    is that access to collection elements is slower than for array LCOL. Elements of array LCOL 
    can be addressed only by positive integers which internally are array indexes. See create/2 
    for more details.
    
    The motivation for creating this library was to be able to easily build input lists for global 
    constraints from collections of input structures (see example). For this purpose an array(3) LCOL 
    was usually sufficient, and only a limited set of predicates needed (create/2 , append_element/3, 
    terminate_all_lists/2, get_list/3).
    
    But the idea was extended, additional predicates were added for prefixing the lists, and 
    reinitialisation of lists. The support for hash LCOL has been added. Hash LCOL may be useful for 
    some filtering, grouping predicates in cases when the number of lists may vary or indexing by 
    atoms/ground terms is more readable/convenient.

    

Examples

llcol_example:-
    lib(ic),
    lib(ic_edge_finder),

    ActivityList=[
        act(4,7 ,2,machine_1),
        act(3,4 ,1,machine_2 ),
        act(2,4 ,2,removed),
        act(7,10,1,machine_1),
        act(6,15,3,machine_3)
        % ...
    ],
    
    %create a collection of activity lists for corresponding machines
    list_collection:create(hash,LCOL_Machines),
    
    %sort the activities for machines
    (foreach(Activity,ActivityList),
     param(LCOL_Machines) do 
        Activity=act(_Start,_End,_Resource,Machine),
        (Machine \= removed ->
            %add an activity to the list for the particular machine
            list_collection:append_element(LCOL_Machines,Machine,Activity)
        ;true)
    ),
    
    %close the lists get the machine names
    list_collection:terminate_all_lists(LCOL_Machines,Machines_Indexes),
    
    %for each machine
    (foreach(Machines_Index,Machines_Indexes),
     param(LCOL_Machines) do 
        %Note that get_list/3 can be used even if the lists are not terminated but in such a case the operation
        %is more time consuming, because all the list elements are copied to new closed list and then returned.
        %Instead of closing all the lists at once it is also possible to use terminate_and_get_list/3 to ensure 
        %that the list is closed.
        
        %get the activity list for the machine
        list_collection:get_list(LCOL_Machines,Machines_Index,MActivityList),
        
        %create a collection for start,duration and resource variable lists
        list_collection:create(array(3),LCOL_Start_Dur_Res),
        
        (foreach(MActivity,MActivityList),
         param(LCOL_Start_Dur_Res) do
         
            MActivity=act(Start,End,Resource,_Machine),
            ic:(Duration #= End - Start),
            list_collection:append_element(LCOL_Start_Dur_Res, 1, Start),
            list_collection:append_element(LCOL_Start_Dur_Res, 2, Duration),
            list_collection:append_element(LCOL_Start_Dur_Res, 3, Resource)
        ),
        
        %terminate the start,duration,resource lists
        list_collection:terminate_all_lists(LCOL_Start_Dur_Res,_Indexes),
        
        %get the lists for a cumulative constraint
        list_collection:get_list(LCOL_Start_Dur_Res, 1, StartList),
        list_collection:get_list(LCOL_Start_Dur_Res, 2, DurationList),
        list_collection:get_list(LCOL_Start_Dur_Res, 3, ResourceList),

        %post the constraint
        ic_edge_finder:cumulative(StartList, DurationList, ResourceList, 3)
    ).
    

About

• Author: Lukasz Domagala
• Copyright © Silesian University of Technology
• Date: $Date: 2009/07/16 09:11:23 $