Re: [Swarm-Support] working with (indexed) lists: beginner's Q

[Paul Johnson]

If I understand, you want the bug to be able to review a list of options 
and find one? I do things like this all the time.

In the Bug, create an IVAR

in Bug.h:

id cargoList;

- (void)setCargoList: aList;

In Bug.m, at the top include the header file for the Cargo class


#import "Cargo.h"
//use a method to set that list:

- (void)setCargoList: aList
{
    cargoList = aList;
}

Now the bug can look at the cargoList to find what it wants.

It is recommended to traverse a collection like this:

cargoIndex = [cargoList begin: [self getZone]]; //note, in Model swarm,
                                           //use begin: self, in Bug,
                                        //use this
Cargo * anObject;  //specific declaration for clarity
for (anObject = [cargoIndex next]; [cargoIndex getLoc]==Member; 
anObject= [cargoIndex next])
{
   //do something to cargo objects

}
[cargoIndex drop];


All the other stuff about making the changes show on the grid is really 
a separate problem.

An exercise along these lines is from my modeling class: write a new 
class "Exterminator" and have it kill some bugs and make the thing show 
on the graphs.  One of the students even put little pictures of 
Exterminators.

http://lark.cc.ku.edu/~pauljohn/ps909/Agent-Based_Models/

The exterminator assignment is
Exercise9.1.txt

and I have some student results in a directory. I think there is also 
one in myExterminator.



Jurgen van der Pol wrote:
> Hi Swarmists,
>
> A beginners question on working with lists. The user/refbooks only get 
> me this far and I'm not quite succeeding so would appreciate some hints.
>
> Building on simpleobserverbug2 (BIG thanks, whomever...) , I have a 2d 
> world (GUI, display, EZGraph etc, all is working, I so proud!) in which 
> bugs represent trucks: if empty go to a depot, if at depot, pick up 
> cargo and deliver it. What I want the model to do is for a bug, when 
> arriving at the depot, look on a (for all bugs to 'see') list of cargo 
> and get one (later: bid on), based on a number of conditions. The bug 
> needs to 'look' at the cargo objects to get one that matches certain 
> creiteria (e.g. value, weigth etc) and, once chosen, get the cargo's 
> destination from the cargo object & get paid a value (also instilled in 
> the cargo object when delivering it. Hope intentions are somewhat clear.
>
> I have observerswarm.h/m, modelswarm.h/m, bug.h/m, cargo.h/m etc.
>
> My modelswarm.m - buildObjects builds me a number of cargo objects, and 
> the bug objects. Both are put on a list:
>
> //--8<-----
>     cargoList = [List create: self];
>     
>     for (y = 0; y < 1; y++)         // just one to begin with, this will 
> of course be different once it 'works'
>         {
>             aCargo = [Cargo createBegin: self];
>               [aCargo setWorld: world];
>             aCargo = [aCargo createEnd];
>               [aCargo setX: 20 Y: 20 V: 100]; // again for test purposes 
> hard data here, later different. V = value
>             cargoID = cargoID + 1;
>             [aCargo setID: cargoID];
>               [cargoList addLast: aCargo];    // the cargo list
>         }
> //--8<-----
>
> I also make an index of cargoList here:
>
> //--8<-----
>         cargoIndex = [cargoList begin: [self getZone]];
> //--8<-----
>
> This all seems to go OK.
>
> The bugs are also familiar:
>
> //--8<-----
>       bugList = [List create: self];
>
>     for (y = 0; y < numberOfTrucks; y++)
>         {
>             aBug = [Bug createBegin: self];
>              [aBug setWorld: world Food: food];
>                  aBug = [aBug createEnd];
>               [aBug setX: [uniformIntRand getIntegerWithMin: 0 withMax: 
> worldXSize]
>                                Y: [uniformIntRand getIntegerWithMin: 0 
> withMax: worldYSize]];
>             bugID = bugID + 1;
>             [aBug setID: bugID];
>             [aBug getMyCargoList: cargoIndex];        // *** here I 
> (think I)'m passing the cargoIndex to an (id) variable in the bug
>              [bugList addLast: aBug];
>         }
> //--8<-----
>
> Also seems to work. Stuff then goes on to display the bug on-screen, 
> etc. The cargo is not displayed in any way.
>
> Then - buildActions does (a.o)
>
> //--8<-----
>     modelActions = [ActionGroup create: self];
>     [modelActions createActionForEach: bugList    message: M(goAhead)];
> //--8<-----
>
> The goAhead method sits in bug.m and is basically an or/or:
>
> //--8<-----
> - goAhead
> {
>     if (haveEaten == 0)        // while not loaded - switch
>         [self getCargo];        // get to the depot
>     else
>         [self deliverCargo];    // deliver the cargo at the destination
>     return self;
> }
> //--8<-----
>
> - getCargo sets the destination to the coordinates of the depot and 
> makes it go there
> - deliverCargo is where the delivery action is.
>
> I'm not quite sure how to go on next. I thing I know how to pass either 
> the cargoList or the cargoIndex to the individual bugs.
>
> What I have trouble with is getting access to the cargo lists (and 
> particularly to and individual cargo object's variables) from within the 
> bug. In bug.m:
>
> //--8<-----
> - deliverCargo
> {
>     id temp;
>     temp = [myCargoList next];         //*** can this work? Is this 
> correct? What have I just done?
>     
>     if (deliveryPointSet == 0)
>         {
>             [self setDestinationX: [temp getXDest] Y: [temp getYDest]];  
> //*** ditto? is temp a cargo instance or not???            
> deliveryPointSet = 1;
>         }
> //--8<-----
>
> where - getXDest and - getYDest live in cargo.h/m and simply return the 
> X, Y values of the cargo instance:
>
> //--8<-----
> - getXDest
> {
>     return xPos;
> }
>
> - getYDest
> {
>     return yPos;
> }
> //--8<-----
>
>
> Now, can this work in any way? I know that the end result code will be 
> different, but I need to get the basics going first. Am I on the right 
> track? Should I pass the cargoList or the cargoIndex to the bug? In both 
> cases, how then to access the elements contained therein, and the 
> variables they hold? Apparently my ObjC/Swarm knowledge is still not 
> advanced enough to get this down quickly. I do know I'm close, though. 
> Any (off-list if this is too trivial) pointers are greatly appreciated!
>
> Cheers, TIA,
> Jurgen.
>
>
>
>
> _______________________________________________
> Support mailing list
> address@hidden
> http://www.swarm.org/mailman/listinfo/support


--
Paul E. Johnson                       email: address@hidden
Dept. of Political Science            http://lark.cc.ku.edu/~pauljohn
1541 Lilac Lane, Rm 504
University of Kansas                  Office: (785) 864-9086
Lawrence, Kansas 66044-3177           FAX: (785) 864-5700