Re: [Swarm-Support] Followup: found work-aroundfor missing~/swarmarchiver.scm too

[Marcus G. Daniels]

Bill Northcott wrote:
> As a result Objective-C programmers obsessively test for nil if there 
> is any possibility that an object may not be available.  That seems to 
> me a good habit that Swarm Objective-C programmers should also cultivate.
Not really sure what kind of object is?  Well, lucky you, you get to 
write a bunch of code to adapt to all possible cases including the one 
of no case at all and you get to conflate that signal inside of the one 
that carries the real one as well.   But wait, is it the error signal 
even a real one?  Why was there a nil object in the first place?    
Perhaps nil is supposed be a placeholder for some dead object in a fixed 
size thing?   Or maybe it is just a bug.   My experience is that 
modelers are thinking about other things and that it is usually a bug.   
Adding in a nil_method function or a conditional is far safer than 
having messages simply ignored silently. 

I understand that MacOS X runtime compatibility and/or similarity is a 
goal for you, but there are far bigger obstacles in your path than this 
little thing.  You've got to implement or ditch phases, for example.

> > Swarm also does Java, and so here the underlying Objective C code is 
> > just a means to an end.   Java users will expect null pointer 
> > exceptions.
>
> Is this not the whole point?  There exists a Java interface for people 
> who want/need the software to keep them on a tight leash and sweep up 
> behind.  The downside is reduced functionality.  That is a basic 
> trade-off in any computer language.
That's not the point.  The Java interface was and is for people that 
want to make Swarm simulations using that popular language using it's 
popular tools and libraries.    Having a Java virtual machine, and vast 
Java libraries, opens up many more possibilities than Objective C 
alone.   Sometimes low-level control and transparency are needed, and 
then C coding is more useful.   Depends on the problem.   With Swarm you 
can do them both at once, even.   The `right' behavior for exception 
handling depends on your perspective.  Ideally there would be tight 
integration with exception handling features in multiple languages, but 
that's a lot of work.