Langton's Ant in Haskell

Langton's Ant implemented in the Haskell programming language.

I made this project to help me learn Haskell. It's the first real project I've done in the language, so it's probably not perfect, but it works well enough.

How to Use

With Stack you can just run stack run to run the program directly with arguments like so:

$ stack run -- -a "45,45,Up 55,55,Down 45,55,Left 55,45,Right" \
    -r "TurnLeft TurnRight" \
    -h 100 \
    -w 100 \
    -n 1000

Alternatively build it first with:

$ stack setup
$ stack build

You can also use stack install if you want to install the executable to your system.

Available Options

For a summary of available options, do langtons-ant --help

Usage: langtons-ant [OPTION]...
  -a ANTSTR   --ants=ANTSTR    ant string, like '20,20,Up, 15,10,Left'
  -r RULESTR  --rules=RULESTR  rule string, like 'TurnLeft, Continue, UTurn'
  -h N        --height=N       board height
  -w M        --width=M        board width
  -p          --wrap           ants wrap around board edges
  -n X        --number=X       number of iterations for non-graphical mode
  -g          --graphical      display steps in a graphical window
  -v          --version        output version information and exit
              --help           display this help and exit

Normally, the result of running the simulation for N steps will be printed to stdout. However, if the graphical mode flag (-g) is set, the simulation will be run graphically in a window until all ants fall off the board.

Default Options

If you omit any option its default will be substituted:

• -a (Ant string): "50,50,Up"
• -r (Rule string): "TurnLeft, TurnRight"
• -h (Height): 100
• -w (Width): 100
• -p (Wrap): no wrap
• -n (Iteration): 11000
• -g (Graphical): non-graphical

Invalid Options

If you pass the program impossible options, like a negative width, you'll get an informative error like Width too small. If you give the program legal but invalid options, like having no ants starting within the bounds of the board, you'll get no output. This is intentional.