Re: Colormap, `createEnd' not implemented ... [Re: your mail]

[Alex Lancaster]

>>>>> "PT" == Pietro Terna <address@hidden> writes:

PT>     A delayed question:
KC> PS: Its my understanding that now the call to `getZone' may also
KC> be unnecessary since Swarms can now be used as Zones, is that
PT>                                  ^^^^^^^^^^^^^^^^^^^^^^^^
KC> true?
>>  Yep.

PT>     What does this mean? Have we to change from "...: [self
PT> getZone]]" to "...: self] all "create" lines; are there reasons to
PT> prefer one form or the other? I'm develpoing heavy apps and I
PT> would prefer to wirte a stanel code for the future.

The rule is simple:

1. You should use the "...: self]" form of creation *only* when the
object that you are creating these objects *within* is itself a Swarm
(or a subclass of a Swarm - in other words when creating objects
within a ModelSwarm or an ObserverSwarm).

2. At all other times you should still use the "...: [self getZone]"
form.  In other words, when creating objects within an ordinary
SwarmObject (not a Swarm!) you still need to get the Zone of that
object.

The reason for this, is that a Swarm is a special kind of object,
which is intended to form the basis of segregated storage allocation,
and in fact is also a "Zone".  An ordinary SwarmObject does not have
this property.  Since all SwarmObjects (or subclasses thereof) must
have been created at the top level in a Model or ObserverSwarm - then
the [self getZone] call returns the Zone (in other words - the Swarm)
in which that object was created.  In a future parallelised version of
Swarm - the notion of a Swarm as a storage Zone will come into its
own.

As an example, this means that you use the first kind of Zone
allocation, in the following way:

In the .h file, you might have:

@inteface ModelSwarm : Swarm {

  id agentList;
}

[....]

-buildObjects;

@end

In the .m file, you have:

@implementation ModelSwarm

[...]

- buildObjects
{
  [...]

  agentList = [List create: self];

  [...]
}
@end

*But*, if you are creating an object within an agent inside the
agentList created above, you would use the [self getZone] as an
argument to the create/createBegin function.

There are reasons to prefer the "... create: self]" version, one is
that it means that you never need to explictly create or refer to a
Zone (except at the very top level - i.e. in the main.m file).  So in
the heatbugs app file "HeatbugsObserverSwarm.m" you currently have:

-buildObjects
{

  modelZone = [Zone create: [self getZone]];
  modelSwarm = [ModelSwarm create: modelZone];

  [...]
}

You can now replace these two lines with one line:

  modelSwarm = [ModelSwarm create: self];

Remember that you are creating a "Swarm" within a "Swarm"!

I hope this makes it a little clearer.  The most recent distribution
of the tutorial application has been changed to following these
conventions, so have a look at any of those demo apps to clarify you
thinking on this coding issue.

Regards,

  --- Alex

-- 
  Alex Lancaster         |   e-mail: address@hidden
  Swarm Developer        |      web: http://www.santafe.edu/~alex
  Santa Fe Institute     |      tel: +1-(505) 984-8800
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