Variables

The last complication in getting to grips with NetLogo is the way variables work.

You can define a global variable that is available to every function using

globals [myVariable]


and you can then use myVariable to store a value using set. For example:

set myVariable=10


You can also create a local variable within a function using the let keyword:

let myLocalVariable=20


Local variables only exist after the let statement and if the let is within square brackets it only exists within those brackets.

Of course agents have variables and we have already been using many built in variables. You can also add your own variables to agents so that you can create custom states. Each type of agent has its own set of variables. You can add to the set of variables using something like:

turtles-own [myTurtleVariable]


This adds the new variable myTurtleVariable to every turtle. Each turtle gets its own separate new variable and can hold a value that is potentially different for all turtles. You can do the same for patches and links.

Notice that turtles and patched have a special relationship in that a turtle can access the variables of the patch it is "standing" on. For this reason turtles and patches cannot have a variable with the same name.

Where Next?

There is so much that we haven't covered. You need to learn about links, the third type of agent. You also need to find out more about general Logo - if, repeat, functions with parameters, and so on. NetLogo also has good facilities for building user interfaces and for presenting the results of simulations.

However, you have now been introduced to the main elements of the NetLogo language and what makes it special - and hence what makes it difficult to get started with.

 

• Mike James is the author of Programmers Guide To Kotlin written for Java programmers, Android developers and programmers wanting to discover why Kotlin is a better Java and Programmer's Python: Everything is an Object  for those who want to understand the deeper logic in the approach that Python 3 takes to classes and objects. His other titles include Android Programming in Kotlin: Starting With An App and Android Programming In Java: Starting With An App, 3nd Ed.

 

More Information

NetLogo Website

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Small Basic - The Programmer's Guide

Getting Started With TypeScript

Getting Started With Google App Script

Getting Started with Python

 

A Programmers Guide To Languages

Contents

1. Octave
2. Scratch 3 *revised
3. Node.js *revised
4. App Inventor 2 *revised
5. Getting Started With .NET IL
6. NetLogo *revised
7. Small Basic  *revised
8. TypeScript *revised
9. Google Apps Script
10. Guide to F#
11. Python
12. Google's Go
    
    1. A Programmer's Guide To Go With Visual Studio Code *revised
    2. A Programmer's Guide To Go Part 2 - Objects And Interfaces *revised
    3. A Programmer's Guide To Go Part 3 - Goroutines And Concurrency *revised
13. Guide to F#
14. The Prolog Way ***NEW!
15. Ruby
    1. Object-Oriented Approach
    2.    A Functional Language

 

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