help with first Swarm app

[James Marshall]

Hello all,
  I'm new to Swarm and am trying to write/compile my first app, 
following Chris Langton's SimpleBug tutorial. I'm trying to create a 
class which inherits from Discrete2d, as done in SimpleBug. Here's 
the code I've written

//EPDWorld.h EPD

#import <space.h>
#import <collections.h>
#import <random.h>

@interface EPDWorld : Discrete2d
{
  int maxAgents, startAgents, population, strategyLength;
  float deathProbability, mutationRate;
}

-setup: (int) x ySize: (int) y maxAgents: (int) maxPop startAgents:
(int) startPop strategyLength: (int) stratLen deathProbability:
(float) deathProb mutationRate: (float) mu;

-createEnd;

-(int)getMaxAgents;
-(int)getPopulation;
-(int)getStrategyLength;
-(float)getDeathProbability;
-(float)getMutationRate;

@end

-------------------------------------

//EPDWorld.m EPD

#import "EPDWorld.h"
#import "EPDAgent.h"

@implementation EPDWorld

-setup: (int) x ySize: (int) y maxAgents: (int) maxPop startAgents:
(int) startPop strategyLength: (int) stratLen deathProbability:
(float) deathProb mutationRate: (float) mu {
  int l1;
//  [super init];
  [super setSizeX: x Y: y];
  maxAgents=maxPop;
  startAgents=startPop;
  population=startAgents;
  strategyLength=stratLen;
  deathProbability=deathProb;
  mutationRate=mu;
  for (x=0; x<xsize; x++)
  {
    for (y=0; y<ysize; y++)
    {
      [self putObject:[List alloc] atX: x Y: y];
      [[self getObjectAtX: x Y: y] init];
    }
  }
  for (l1=0; l1<startAgents; l1++)
  {
    x=[uniformIntRand getIntegerWithMin: 0 withMax: xsize-1];
    y=[uniformIntRand getIntegerWithMin: 0 withMax: ysize-1];
    [[self getObjectAtX: x Y: y] addFirst: [EPDAgent alloc]];
    [[[self getObjectAtX: x Y: y] getFirst] init];
  }

  return self;
}

-(int)getMaxAgents
{
  return maxAgents;
}

-(int)getPopulation
{
  return population;
}

-(int)getStrategyLength
{
  return strategyLength;
}

-(float)getDeathProbability
{
  return deathProbability;
}

-(float)getMutationRate
{
  return mutationRate;
}

@end

And here's what the compiler tells me:

gcc -g -Lc:/swarm/swarm-1.1/lib -L/Swarm/packages/libffi/lib
-L/Swarm/packages/b lt8.0-unoff/lib -L/Swarm/packages/tclobjc/lib  -o
EPD main.o EPDSwarm.o EPDWorld .o EPDAgent.o  -lanalysis -lsimtools
-lsimtoolsgui -ltkobjc -lactivity -lrandom -lobjectbase -lcollections
-ldefobj -lmisc -ltclobjc -lBLT80 -ltk80 -ltcl80  -lf fi -lobjc  -lm 
-luser32 -lgdi32 EPDWorld.o:/Swarm/swarmapps-1.1/EPD/EPDWorld.m:36:
undefined reference to `__obj c_class_name_Discrete2d' make: *** [EPD]
Error 1

Can anyone help? Additionally/alternatively can anyone recommend a 
good book on Objective C, which really does start with the basics? I 
have experience of coding in C++, but less in C. Thanks!
        James
--
James Marshall - Postgraduate Research Student (MPhil/PhD)
Artificial Intelligence Group - Department of Computer and Information Sciences
De Montfort University - Milton Keynes Campus
Web:- http://www.mk.dmu.ac.uk/~jmarshall/

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