Conway's Game of Life in Go.

conwayGoL.go

package main

import (
	"fmt"
	"math/rand"
	"time"

	"github.com/nsf/termbox-go"
)

// RULES
// < 2 neighors = DIE
// >=2 <=3 = LIVE
// >3 neighors = DIE
// if DEAD and 3 neighbors = LIVE (reproduction!)

const gridsize = 40
const evolutions = 50
const animationSpeed = 150 * time.Millisecond

func main() {

	var beings [gridsize][gridsize]bool
	seedSimulation(&beings)

	// setup GUI
	err := termbox.Init()
	if err != nil {
		panic(err)
	}
	defer termbox.Close()

	for i := 0; i < evolutions; i++ {
		updateGridState(&beings)
		renderScreen(&beings)
		time.Sleep(animationSpeed)
	}

}

func seedSimulation(beings *[gridsize][gridsize]bool) {

	for i := 0; i < gridsize; i++ {
		for j := 0; j < gridsize; j++ {
			// Set this being to "ALIVE" (true) based on random value.
			if rand.Intn(100) > 85 {
				beings[i][j] = true
			}
		}
	}

}

// iterate over the entire grid, changing states on each "being" based on the rules of the game.
func updateGridState(beings *[gridsize][gridsize]bool) {

	for i := 0; i < gridsize; i++ {
		for j := 0; j < gridsize; j++ {

			var liveNeighborCount = determineLiveNeighbors(i, j, beings)

			if beings[i][j] == true { // if alive, determine if the being should live or die
				if liveNeighborCount < 2 {
					beings[i][j] = false // die..."under population"
				} else if (liveNeighborCount >= 2) && (liveNeighborCount <= 3) {
					beings[i][j] = true
				} else if liveNeighborCount > 3 {
					beings[i][j] = false // die..."over crowding"
				}
			} else { // if currently dead, determine if the being should come back to life.
				if liveNeighborCount == 3 {
					beings[i][j] = true // "reproduction"
				}
			}

		}
	}

}

func determineLiveNeighbors(x int, y int, beings *[gridsize][gridsize]bool) int {

	var neighborNorthPosition, neighborSouthPosition,
		neighborEastPosition, neighborWestPosition int

	var aliveNeighbors int

	// determine "west" neighbor location
	if (x - 1) >= 0 {
		neighborWestPosition = x - 1
	} else {
		neighborWestPosition = gridsize - 1
	}

	// determine "east" neighbor location
	if (x + 1) < gridsize {
		neighborEastPosition = x + 1
	} else {
		neighborEastPosition = 0
	}

	// determine "north" neighbor location
	if (y + 1) < gridsize {
		neighborNorthPosition = y + 1
	} else {
		neighborNorthPosition = 0
	}

	// determine "south" neighbor location
	if (y - 1) >= 0 {
		neighborSouthPosition = y - 1
	} else {
		neighborSouthPosition = gridsize - 1
	}

	// Now determine which neighbors are alive
	if beings[neighborWestPosition][y] == true {
		aliveNeighbors++ // neighbor directly west
	}
	if beings[neighborWestPosition][neighborNorthPosition] == true {
		aliveNeighbors++ // neighbor to NW
	}
	if beings[x][neighborNorthPosition] == true {
		aliveNeighbors++ // neighbor directly north
	}
	if beings[neighborEastPosition][neighborNorthPosition] == true {
		aliveNeighbors++ // neighbor to NE
	}
	if beings[neighborEastPosition][y] == true {
		aliveNeighbors++ // neighbor directly east
	}
	if beings[neighborEastPosition][neighborSouthPosition] == true {
		aliveNeighbors++ // neighbor to SE
	}
	if beings[x][neighborSouthPosition] == true {
		aliveNeighbors++ // neighbor directly south
	}
	if beings[neighborWestPosition][neighborSouthPosition] == true {
		aliveNeighbors++ // neighbor to SW
	}

	return aliveNeighbors
}

// print the state of the grid to STDOUT
func printGrid(beings *[gridsize][gridsize]bool) {

	fmt.Println("~~~~~~~~~~~~~~~~")

	for i := 0; i < gridsize; i++ {
		for j := 0; j < gridsize; j++ {
			if beings[i][j] == true {
				fmt.Printf("X")
			} else {
				fmt.Printf("_")
			}
		}
		fmt.Printf("\n")
	}

	fmt.Println("~~~~~~~~~~~~~~~~")
}

// leverage the termbox library to render to the terminal
func renderScreen(beings *[gridsize][gridsize]bool) {

	termbox.Clear(termbox.ColorBlack, termbox.ColorBlack)

	for i := 0; i < gridsize; i++ {
		for j := 0; j < gridsize; j++ {
			if beings[i][j] == true {
				termbox.SetCell(i, j, ' ', termbox.ColorGreen, termbox.ColorGreen) // paint "alive" being
			} else {
				termbox.SetCell(i, j, ' ', termbox.ColorBlack, termbox.ColorBlack) // paint "dead" being
			}
		}
	}

	termbox.Flush()
}