Hamaze

A simple command line maze generator written in Haskell!

Motivation

This project implements a randomized depth first search algorithm to generate a maze; the algorithm itself is fairly simple, but is ususally described in a general manner and around iterative language concepts. In developing this project, I wanted to discover the differences between reading an algorithm described iteratively and then implementing it in a pure functional language.

Specific pain points I discovered was in translating sequences of steps into compositions of functions: particularly interesting was that functional languages seem to require a "reverse nesting" of logic: the steps that must take place first must be placed into functions that perform later steps: for example, the function which removes a wall between two cells must require the results of choosing an unvisited neighbour: syntactically, in Haskell, this often means that the logic choosing a cell comes after the logic for removing the wall.

Technically, this is obvious: the only way to use the result of a function in another function is to calculate it first. But, since most programmers are used to reading control flow from top-to-bottom and left-to-right, this kind of syntax can be a little difficult to reconcile.

Hamaze, the project

Building

This project uses cabal, and can be built with the command cabal build. It only has one dependency, random (which itself depends on the splitmix library), which it uses to generate random numbers (to facilitate maze randomness). Cabal will download and link this dependency automatically.

Exploring the code

Individual functions can be experimented with cabal's repl functions, but in order to access the full spectrum of functions, you'll want to target the exe: cabal repl exe:hamaze (other wise, the repl will only load the library, which only contains the non-user-interface logic).

Executable

The final executable will be called hamaze.exe (on Windows).

The command line interface includes input validation.

• Just the exe:

> hamaze
Usage: hamaze [OPTION...]
  -d Integer x Integer  --dimensions=Integer x Integer  The dimensions of the maze to generate, in nxn format.
  -s Single Integer     --seed=Single Integer           The seed to use to generate the maze

• Using all options:

> hamaze -d 5x5 -s 1234
#===#===#===#===#===#
|           |       |
#===#===#   #   #   #
|           |   |   |
#   #===#===#   #   #
|   |           |   |
#   #   #===#===#   #
|   |   |       |   |
#   #===#   #   #   #
|           |       |
#===#===#===#===#===#

• Invalid option syntax:

> hamaze -d 5xc -s 1234
The dimensions must be given in an nxn format (e.g. for a 5 by 3 maze, '-d 5x3')