From 817c7e645395c99f50eae724650913d4b046a890 Mon Sep 17 00:00:00 2001
From: "Brian C. Lane" <bcl@brianlane.com>
Date: Mon, 8 Apr 2019 19:06:08 -0700
Subject: [PATCH] Fix life algorithm

You have to update the whole field atomically, you cannot change them as
you scan the cells. So move the alive update into the draw function.

Fixes #1
---
 cell.go | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/cell.go b/cell.go
index e778241..699f26c 100644
--- a/cell.go
+++ b/cell.go
@@ -35,9 +35,6 @@ type cell struct {
 
 // checkState determines the state of the cell for the next tick of the game.
 func (c *cell) checkState(cells [][]*cell) {
-	c.alive = c.nextState
-	c.nextState = c.alive
-
 	liveCount := c.liveNeighbors(cells)
 	if c.alive {
 		// 1. Any live cell with fewer than two live neighbours dies, as if caused by underpopulation.
@@ -97,6 +94,7 @@ func (c *cell) liveNeighbors(cells [][]*cell) int {
 
 // draw draws the cell if it is alive.
 func (c *cell) draw() {
+	c.alive = c.nextState
 	if !c.alive {
 		return
 	}