Conway's Game of Life

The Game of Life, also known simply as Life, is a cellular automaton devised by the British mathematician John Horton Conway in 1970.

The "game" is a zero-player game, meaning that its evolution is determined by its initial state, requiring no further input. One interacts with the Game of Life by creating an initial configuration and observing how it evolves.

Rules

The universe of the Game of Life is an infinite two-dimensional orthogonal grid of square cells, each of which is in one of two possible states, alive or dead. Every cell interacts with its eight neighbours, which are the cells that are horizontally, vertically, or diagonally adjacent. At each step in time, the following transitions occur:

• Any live cell with fewer than two live neighbours dies, as if caused by under-population.

• Any live cell with two or three live neighbours lives on to the next generation.

• Any live cell with more than three live neighbours dies, as if by overcrowding.

• Any dead cell with exactly three live neighbours becomes a live cell, as if by reproduction.

The initial pattern constitutes the seed of the system. The first generation is created by applying the above rules simultaneously to every cell in the seed—births and deaths occur simultaneously, and the discrete moment at which this happens is sometimes called a tick (in other words, each generation is a pure function of the preceding one). The rules continue to be applied repeatedly to create further generations.

The code

This is a Crystal implementation of Conway's Game of Life.

The idea was to use this challenge to learn Crystal.

Every commit will add more complexity to the implementation and I've noted everything I've learned in the commit messages, so anyone can see how it has evolved.

Dependencies

In order to run the project you must install Crystal: https://crystal-lang.org/docs/installation/.

Specs

This code has been fully tested TDD. To run specs execute on terminal:

crystal spec

Running

I provide a basic terminal client interface to the game. It generates a 10 x 10 population with random alive cells and prints the next generation when you press ENTER.

crystal run src/main.cr