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// An implementation of Conway's Game of Life.
package main
import (
"bytes"
"fmt"
"math/rand"
"time"
)
// Field represents a two-dimensional field of cells.
type Field struct {
s [][]bool
w, h int
}
// NewField returns an empty field of the specified width and height.
func NewField(w, h int) *Field {
s := make([][]bool, h)
for i := range s {
s[i] = make([]bool, w)
}
return &Field{s: s, w: w, h: h}
}
// Set sets the state of the specified cell to the given value.
func (f *Field) Set(x, y int, b bool) {
f.s[y][x] = b
}
// Alive reports whether the specified cell is alive.
// If the x or y coordinates are outside the field boundaries they are wrapped
// toroidally. For instance, an x value of -1 is treated as width-1.
func (f *Field) Alive(x, y int) bool {
x += f.w
x %= f.w
y += f.h
y %= f.h
return f.s[y][x]
}
// Next returns the state of the specified cell at the next time step.
func (f *Field) Next(x, y int) bool {
// Count the adjacent cells that are alive.
alive := 0
for i := -1; i <= 1; i++ {
for j := -1; j <= 1; j++ {
if (j != 0 || i != 0) && f.Alive(x+i, y+j) {
alive++
}
}
}
// Return next state according to the game rules:
// exactly 3 neighbors: on,
// exactly 2 neighbors: maintain current state,
// otherwise: off.
return alive == 3 || alive == 2 && f.Alive(x, y)
}
// Life stores the state of a round of Conway's Game of Life.
type Life struct {
a, b *Field
w, h int
}
// NewLife returns a new Life game state with a random initial state.
func NewLife(w, h int) *Life {
a := NewField(w, h)
for i := 0; i < (w * h / 4); i++ {
a.Set(rand.Intn(w), rand.Intn(h), true)
}
return &Life{
a: a, b: NewField(w, h),
w: w, h: h,
}
}
// Step advances the game by one instant, recomputing and updating all cells.
func (l *Life) Step() {
// Update the state of the next field (b) from the current field (a).
for y := 0; y < l.h; y++ {
for x := 0; x < l.w; x++ {
l.b.Set(x, y, l.a.Next(x, y))
}
}
// Swap fields a and b.
l.a, l.b = l.b, l.a
}
// String returns the game board as a string.
func (l *Life) String() string {
var buf bytes.Buffer
for y := 0; y < l.h; y++ {
for x := 0; x < l.w; x++ {
b := byte(' ')
if l.a.Alive(x, y) {
b = '*'
}
buf.WriteByte(b)
}
buf.WriteByte('\n')
}
return buf.String()
}
func main() {
l := NewLife(40, 15)
for i := 0; i < 300; i++ {
l.Step()
fmt.Print("\x0c", l) // Clear screen and print field.
time.Sleep(time.Second / 30)
}
}
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