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conway.go
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conway.go
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package main
import (
"bufio"
"fmt"
"os"
"strconv"
"strings"
)
type Coord struct {
x, y int
}
type Matrix struct {
xSize, ySize int
data [][]bool
}
// Converts the number in string s to int
// Trimming it in case there are whitespaces
// In case of error exits with rc 1
func readNumber(s string) int {
trimmed := strings.Trim(s, " ")
num, err := strconv.ParseInt(trimmed, 10, 0)
if err != nil {
fmt.Fprint(os.Stderr, "Expected numbers, got: \"", trimmed, "\"\n")
fmt.Fprint(os.Stderr, err, "\n")
os.Exit(1)
}
if num < 0 {
fmt.Fprint(os.Stderr, "Expected positive integers!\n")
os.Exit(1)
}
return int(num)
}
// Reads coordinates in the format "%d, %d\n" from file on filename
// Returns slice of read coordinates
// In case of error exits with rc 1
func readCoords(filename string) []Coord {
// Read the starting positions
var ret []Coord
file, err := os.Open(filename)
if err != nil {
fmt.Fprint(os.Stderr, err, "\n")
os.Exit(1)
}
defer file.Close()
scanner := bufio.NewScanner(file)
for scanner.Scan() {
sep := strings.Split(scanner.Text(), ",")
if len(sep) != 2 {
fmt.Fprint(os.Stderr, "Invalid input format\n")
os.Exit(1)
}
x := readNumber(sep[0])
y := readNumber(sep[1])
ret = append(ret, Coord{x, y})
}
return ret
}
func newMatrix(xSize, ySize int) Matrix {
data := make([][]bool, xSize)
for x := 0; x < xSize; x++ {
data[x] = make([]bool, ySize)
}
return Matrix{xSize, ySize, data}
}
func (m Matrix) String() string {
ret := ""
for y := 0; y < m.ySize; y++ {
for x := 0; x < m.xSize; x++ {
if m.data[x][y] {
ret += "X"
} else {
ret += "_"
}
}
ret += "\n"
}
return ret
}
func (m Matrix) isAlive(x, y int) bool {
xn := x % m.xSize
if xn < 0 {
xn += m.xSize
}
yn := y % m.ySize
if yn < 0 {
yn += m.ySize
}
return m.data[xn][yn]
}
// Will return number of alive neighbours for cell at coordinates x and y
func (m Matrix) aliveNeighbours(x, y int) int {
ret := 0
if m.isAlive(x-1, y-1) {
ret++
}
if m.isAlive(x, y-1) {
ret++
}
if m.isAlive(x+1, y-1) {
ret++
}
if m.isAlive(x-1, y) {
ret++
}
if m.isAlive(x+1, y) {
ret++
}
if m.isAlive(x-1, y+1) {
ret++
}
if m.isAlive(x, y+1) {
ret++
}
if m.isAlive(x+1, y+1) {
ret++
}
return ret
}
func (m Matrix) NextTurn() Matrix {
ret := newMatrix(m.xSize, m.ySize)
for y := 0; y < m.ySize; y++ {
for x := 0; x < m.xSize; x++ {
// 1. Any live cell with two or three live neighbours survives.
if m.isAlive(x, y) {
neighbours := m.aliveNeighbours(x, y)
if neighbours == 2 || neighbours == 3 {
ret.data[x][y] = true
}
}
// 2. Any dead cell with three live neighbours becomes a live cell.
if !m.isAlive(x, y) {
if m.aliveNeighbours(x, y) == 3 {
ret.data[x][y] = true
}
}
// 3. All other live cells die in the next generation. Similarly, all other dead cells stay dead.
// No need to do anything as by default all booleans are false in go
}
}
return ret
}
func main() {
if len(os.Args) != 4 {
fmt.Fprint(os.Stderr, "usage: ./conway width height file\n")
os.Exit(1)
}
width, err := strconv.ParseInt(os.Args[1], 10, 0)
if err != nil {
fmt.Fprint(os.Stderr, err, "\n")
os.Exit(1)
}
if width <= 0 {
fmt.Fprint(os.Stderr, "Expected integers larger than 0\n")
os.Exit(1)
}
height, err := strconv.ParseInt(os.Args[2], 10, 0)
if err != nil {
fmt.Fprint(os.Stderr, err, "\n")
os.Exit(1)
}
if height <= 0 {
fmt.Fprint(os.Stderr, "Expected integers larger than 0\n")
os.Exit(1)
}
m := newMatrix(int(width), int(height))
seed := readCoords(os.Args[3])
for _, c := range seed {
if c.x >= m.xSize || c.y >= m.ySize {
fmt.Fprint(os.Stderr, "Invalid starting seed, larger than size of field!\n")
}
m.data[c.x][c.y] = true
}
gen := 0
for {
fmt.Println("Generation ", gen, ":")
gen++
fmt.Println(m)
fmt.Println("Pres return for next generation, Ctrl-c to stop.")
bufio.NewReader(os.Stdin).ReadBytes('\n')
m = m.NextTurn()
}
}