Re: success/feedback

[Paul Johnson]

Ralf Stephan wrote:
> 
> Here is one datapoint for you.  The time needed for building a first
> model was about 20 hours.  No prior working experience with Swarm or
> ObjC, but years of C and gdb, as well as OOP.  No outside help apart
> from documentation, code, and an ObjC online book.
> 
> http://www.in-berlin.de/User/rws/swarm.html
> 
> This is a very crude, of course, and debatable model (see README).
> Most of the time was spent hunting a few idiotic bugs, and I had to
> use gdb plus common sense extensively.  No major problems with Swarm
> was found but I have a few picks/ideas:
> 
> - when messages are going into nirvana, there should be a fast way,
>   esp. for beginners, to see if it's the object or the selector.
> - of course, it's a big no-no to change members of an ActionForEach
>   while executing it, so I immediately stepped into that.  Finding
>   the bug was horrible (at the end I commented out whole chunks of
>   code), and it reminded me vividly of my first stack overflow.
> - uninitialized pointers don't always seem to contain 0x0, so one can't
>   be sure if it's memory corruption.  So there is no way out of
>   defensive programming.

Thanks for the feedback. My estimate agrees with yours. FOr experienced
programmers, Swarm and Obj-C do not present massive hurdles.  For the
people enticed into programming by Swarm, the hurdles are sharper. 

WHen I run your program, I get a lot of these:

*** event raised for warning: WarningMessage
Grid2d: you're overwriting object 8175de8 at (27,22) with object
8174268.
Grid2d does not support two objects in one place.
*** execution continuing...
*** event raised for warning: WarningMessage
Grid2d: you're overwriting object 8174318 at (64,92) with object
8174d10.
Grid2d does not support two objects in one place.
*** execution continuing...

THis creates a memory leak and makes the simulation difficult to
interpret.

Sven T wrote a class that he put in a package called "svenSpaces" as I
recall, and it had a Grid2d in which multiple occupancy was permitted. 
I did some revamping to allow the elements in the Grid to serve more
general purposes, that's in 

http://lark.cc.ukans.edu/~pauljohn/Swarm/MySwarmCode/WrappedListGrid2d-990817.tar.gz

-- 
Paul E. Johnson                       email: address@hidden
Dept. of Political Science            http://lark.cc.ukans.edu/~pauljohn
University of Kansas                  Office: (785) 864-9086
Lawrence, Kansas 66045                FAX: (785) 864-5700

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