Langton's Ant

Overview

• This repository implements a generalisation of Langton's Ant in C. Langton's ant is a 2 dimensional cellular automata that demonstrates emergent behaviour through a simple set of rules.
• I completed this project as part of my university's systems programming module, where it achieved a mark of 87/100.

Basic Rules

• Intially all cells are in state 1.
• When the ant is on a cell in state 1, it does the following:
  1. Turns left
  2. Changes the cell to state 2
  3. Moves forward 1 space
• Conversely, when the ant is on a cell in state 2, it does the following:
  1. Turns right
  2. Changes the cell to state 1
  3. Moves forward 1 space
• If the ant ever goes past the edge of grid, it wraps around to the other side

Advanced Rules

• A more general implementation exists for a n-state ant. The cells can be in states 1 through to n, with 'L' or 'R' indicating whether the ant should turn left or right, for a given state.
• For example, with the rule set LLRR, the ant would turn left in states 1 and 2, and right in states 3 and 4.
• After visting a cell in state i, the cell's state is incremented to i+1. For state n, it loops back around and to state 1.

Basic Rule Set (LR)

Advanced Rule Set (LLRR)

Set Up

Using GCC

• To compile the code, you will need gcc. If using windows, download WSL and install gcc using sudo apt install gcc. Alternatively, download mingw or any other support for the gcc compiler on windows.

• You will also need make to run the makefile. Install it with the linux command sudo apt install make.

Compilation

To compile the code please use the following commands in order:

1. make library
2. make

make library will compile the dynamically linked library into "libant.so"

make will compile main.c and libant.so into an executable, which will subsequently be run.

Running the Code

• To run the executable ./ant in a CLI, first run export LD_LIBRARY_PATH=$(pwd):$LD_LIBRARY_PATH. This will add the current directory to the path which the dynamic linker searches.
• The terminal will then display an empty grid with the ant in the middle. Press q to quit, and any other key to advance the ant.

Custom Rule Sets

Running ./ant, will use the default ruleset LR, where states 1 and 2 are represented by black and white tiles respectively.

To use a custom rule set, please add an argument of a strings of L's and R's i.e ./ant "LLRR".

Custom rule sets use characters to visualise different states:

• . is state 1
• 1-9 are states 2-10
• A-P are states 11-26

When there are more than 26 rules, characters are re-used in the visualisation, i.e state 27 is .