Re: Help request from a SWARM newbie

[Marshall James]

Hi,
is myList a List or a ListIndex? If it's a ListIndex then the line
[myList remove: enemyBug];
would cause a status access violation... instead you'd need to have the line
[[myList getCollection] remove: enemyBug];
James

A 15:52 27/01/99 +0100, vous avez écrit : 
>>>>
> I'd like to modify simpleSwarmBug2 in this way: 
>
> Each Bug has a certain amount of strenght (a float value initially set to 0) that increases of ,let's say, 0.1 every time it eats. 
> Then, when a Bug  wants to move to anather location (-step) that is already occupied by another Bug, it checks if its own strenght is higher than that of its "enemy" :if it's so, 
> it destroys it (in my mind,that would mean to make the bugList remove the defeated Bug), otherwise goes on. 
> Here are the parts of source I've modified: 
> In "Bug.h": 
>
> added inst.variables id bugEnemy and float strenght; 
> added inst.var id myList; (the List whose the bug is part) 
> added method -getStrenght (returns Bug's strenght) 
> added method -setList:(id) aList (sent by bugList as a message to set itself 
> as the bug list) 
>
> In "Bug.m",I added the following lines to the -step method: 
> ..... 
> //Check that no other bug is at the new site 
>
> if ((enemy=[world getObjectAtX: newX Y: newY])==nil) 
> { 
>
> [world putObject:nil atX:xPos Y:yPos]; 
> [world putObject:self atX:newX Y: newY]; 
> xPos=newX; 
> yPos=newY; 
>
> } 
> else if (strenght >= [enemyBug getStrenght]) //space is not free and   
>
> //you're stronger 
> { 
>  [myList remove:enemyBug]; 
> } 
>
>
> if ([foodSpace getValueAtX: xPos Y: yPos]==1) 
> { 
> [foodSpace putValue:0 AtX: xPos Y: yPos]; 
> strenght+=0.1; 
> } ......... 
>
> In "ModelSwarm.m" I added the following bold line: 
> ..... 
> aBug = [Bug createBegin: self]; 
> [aBug setWorld: world Food: food]; 
> [aBug setList:bugList]; 
> aBug = [aBug createEnd]; 
> ....... 
>
> The rest of code is left unchanged. 
> Because it's only three days since I begun to study SWARM,I couldn't pretend my varation would have worked,infact the runtime system complains:Exception:STATUS_ACCES_VIOLATION 
> What was my error? 
> Finally a question on leaving unspecified the return value of a method (making it to return the default type id) even when it hasn't to return any value:it's a matter of  style or is there something behind that? 
>
> Thank you in advance for your advice. 
> _______________________________________________________________ 
> Fabio Mascelloni. 
> Dept. of Computer Science - University of Pisa,Italy 
> e-mail: address@hidden 
<<<<



--

James Marshall - Research Assistant - COTCOS Project
Institut de Recherche en Informatique de Toulouse
WWW: http://www.mk.dmu.ac.uk/~jmarshall
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