NetLogo 3.1 Available in Final Release

The NetLogo development team at the Center for Connected Learning and
Computer-Based Modeling at Northwestern University is pleased to
announce the release of NetLogo 3.1.  NetLogo 3.1 is available for
free download from our site at http://ccl.northwestern.edu/netlogo/ .

Please try it and out and send us bug reports at
bugs@ccl.northwestern.edu and other suggestions and comments at

Almost all models created in earlier versions of NetLogo will work
in NetLogo 3.1.  If you have any trouble running models from a previous release, please consult:

The following is a (partial) list of changes made and new features
added since NetLogo 3.0:

* system:
     + the 3D view now works on Intel-based Macs
     + for Windows users, our bundled Java version is now 1.5 (was
     + for Mac users, Java 1.5 is now used if it is available
* models:
     + new earth science model: Grand Canyon
     + new EvoLab evolution model: Sunflower Biomorphs
     + new social science model: Ethnocentrism
     + new mathematics model: Voronoi
     + new physics model: DLA Simple
     + new computer science models: Perceptron, Artificial Neural
     + new biology/system dynamics models: Tabonuco Yagrumo,
       Tabonuco Yagrumo Hybrid
     + new code examples: Moore & Von Neumann Example, Intersecting
       Lines Example, Diffuse Off Edges Example, Tie System Example
     + improved ProbLab model: Dice Stalagmite
     + improved social science models: Traffic Grid, Scatter
     + improved chemistry/physics model: GasLab Circular Particles
       (runs faster)
     + improved networks models (using experimental link
       primitives): Giant Component, Preferential Attachment, Small
* features:
     + randomized agent ordering: every agentset is now always in
       random order (a different random order each time you use it)
     + world topologies:
       - the world isn't always a torus anymore; by turning
      vertical and horizontal wrapping on or off, you can
    choose between a torus, a rectangle, or a vertical or
           horizontal cylinder
  - using primitives ending in -nowrap is no longer
         necessary; just turn off world wrapping instead
       - new can-move? reporter lets turtles sense the world
         - screen-edge-x and screen-edge-y have been renamed to
            max-pxcor and max-pycor (and new min-pxcor and min-pycor
        primitives have been added)
  - screen-size-x and screen-size-y have been renamed to
            world-width and world-height
          - see the Topology section of the Programming Guide for
           more information
     + new, experimental suite of link primitives, useful for
       network models and others; see Links sections of Programming
       Guide and Primitives Dictionary
     + model authors can now specify the singular form of a breed
  - the new syntax for declaring each breed is e.g. breed
           [wolves wolf]
         - you can ask for a breeded turtle by who number, e.g.
            wolf 0
        - in model output, breeded turtles also appear as e.g.
            wolf 0
        - added new reporter e.g. is-wolf?
      - this form also appears elsewhere in the user interface,
         e.g. when picking a turtle from the view, in turtle
    monitors, and so on
     + new command stamp-erase
     + new __tie and __untie primitives allow turtles to connect
       their movement to another turtle. See the Tie Section of the
       Programming Guide for details.
* other language changes:
     + the sort and sort-by primitives can now be used to convert an
       agentset to a sorted list of agents; if you use sort, turtles
       are sorted by who number, and patches are sorted
       left-to-right, top-to-bottom
     + new reporters random-xcor, random-ycor, random-pxcor, and
       random-pycor are handy for generating random coordinates
     + member? can now be used to check whether an agent is a member
       of an agentset (worked in 3.0, but was undocumented)
     + random-one-of and random-n-of have been renamed to just
       one-of and n-of
     + removed no-label from the language; use the empty string
     + renamed user-choice to user-one-of, user-choose-file to
       user-file, user-choose-new-file to user-new-file,
       user-choose-directory to user-directory
* interface changes:
     + minor improvements to look & feel, e.g. vertical buttons in
       toolbars instead of horizontal ones
     + the info tabs of saved applets are now more attractive, as in
       the application
     + user-one-of (formerly user-choice) now always shows the
       choices as a menu, never buttons
* engine fixes:
     + fixed 3.0-only bug where the repeat and let commands didn't
       always work correctly when used from the Command Center
     + in the System Dynamics Modeler, system-dynamics-t is now
       incremented at the end of each step, not the beginning
* interface fixes:
     + double clicking outside a bracket or parenthesis in the
       editor now selects all of the text between the matching
       brackets or parentheses
     + when shapes are off, shapes consisting of a single line now
       still draw as lines, not squares
     + fixed some incorrectly worded compiler error messages
       involving primitives that can take a variable number of
       inputs, such as list and sentence
     + fixed Windows-only bug where the Procedures menu had trouble
       showing very large number of procedure names
     + fixed Mac-only bug where pasting text from another
       application could cause a compiler error
* BehaviorSpace changes:
     + you can now use the stop command in an experiment's go
       commands, or in the procedure called by your experiment's go
       commands, to stop a model run, the same way it works to stop
       a forever button
     + you can now choose to save no results at all
     + the Abort button is now more often able to halt a stuck model
     + the Procedures tab is now always recompiled before an
       experiment begins
* HubNet changes:
     + new activities: Bug Hunters Camouflage, Walking, Disease
       Doctors, Function, Guppy Spots
     + improved activities: Predator Prey Game (formerly Herbivore
       Carnivore), Root Beer Game (formerly Beer Game)
* API changes:
     + documentation now recommends using the server VM for best

Reporting Bugs:

We would appreciate your comments and bug reports.  If you find a bug,
please send us a bug report (as detailed as you can -- including OS,
method of running NetLogo, commands used, attach your model if
possible, etc.) so that we can correct the bug as speedily as
possible. Please send bug reports to bugs@ccl.northwestern.edu.


To provide feedback to the NetLogo development team, please send email
to feedback@ccl.northwestern.edu or visit our contact page at
http://ccl.northwestern.edu/netlogo/contact.shtml .

Getting Started:

To get started using NetLogo, visit our web page:
http://ccl.northwestern.edu/netlogo/ .

Receiving Release Announcements:

To receive announcements of NetLogo releases and new features,
subscribe to the netlogo-announce mailing list. To subscribe to
netlogo-announce, send a message to:

The body of the message should say:
subscribe netlogo-announce your-first-name your-last-name

To be removed from the announcements list, send a message to:

The body of the message should say:
unsubscribe netlogo-announce

Joining the netlogo-users group:

We also have a Yahoo! group where users can discuss NetLogo
with each other and with the CCL team.  To join the group, or
just to browse the group's message archives, visit:


There is also a Yahoo! group specially designed for educators
using NetLogo. To join the group, or just to browse the group's
message archives, visit:


NetLogo 3.1 files

The release package for NetLogo 3.1 includes:

* "NetLogo" application
* "HubNet Client" application
* "NetLogo.jar", "NetLogoLite.jar", "lib" internal support
   files and folder
* "Docs" folder containing a "NetLogo User Manual" -- complete
   documentation in HTML and printable PDF formats
* "Models" folder with several hundred NetLogo models and HubNet
* "Extensions" folder containing support for music & sound
   and physical devices
* "readme.txt" file


NetLogo was designed and authored by Uri Wilensky, project leader and
director of the CCL.  The lead developer is Seth Tisue.  Many others
have greatly contributed.  HubNet was jointly designed by Uri Wilensky
and Walter Stroup.

The design of NetLogo was supported through funding from the National
Science Foundation (grants REC 9632612, REC 9814682, REC 0126227, CCR
0326542).  Additional support for the design of HubNet (calculator
version) was provided by Texas Instruments.


                Uri Wilensky
Associate Professor of Learning Sciences and Computer Science                               
Director, Center for Connected Learning and Computer Based Modeling
Executive Committee, Northwestern Institute on Complex  Systems
Northwestern University

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