Add B3/S23 rules

These are the B3/S23 rules as displayed on wikipedia, except for the
edge squares due to array indexing.

diff --git a/source/main.lua b/source/main.lua
index cc8aee4..0b94cc8 100644 (file)
--- a/source/main.lua
+++ b/source/main.lua
@@ -4,29 +4,63 @@ local gfx <const> = playdate.graphics
 local WIDTH <const> = 12
 local HEIGHT <const> = 7
 
-local cells = {}
-for i=1, WIDTH do
-    cells[i] = {}
-      for j=1, HEIGHT do
-          r = pd.geometry.rect.new(32 * (i-1), 32 * (j-1), 32, 32)
-          cells[i][j] = { cell = r, live = false }
-      end
+-- Convenience function for iterating over 8 neighbors
+function neighbors(g1, x, y)
+    if (x - 1) > 0 and x < WIDTH and (y - 1) > 0 and y < HEIGHT then
+        return ipairs({
+            g1[x-1][y-1],
+            g1[x-1][y],
+            g1[x-1][y+1],
+            g1[x][y-1],
+            g1[x][y+1],
+            g1[x+1][y-1],
+            g1[x+1][y],
+            g1[x+1][y+1]})
+    else
+        -- TODO corners
+        return ipairs({
+            { live = false },
+            { live = false },
+            { live = false },
+            { live = false },
+            { live = false },
+            { live = false },
+            { live = false },
+            { live = false },
+            { live = false },
+        })
+    end
 end
 
-local x = 1
-local y = 1
-
-local running = false
-
-function generation(cells)
-    local tab = {}
-    for i,row in ipairs(cells) do
-        tab[i] = {}
+function generation(g1)
+    local g2 = {}
+    for i,row in ipairs(g1) do
+        g2[i] = {}
         for j,cell in ipairs(row) do
-            tab[i][j] = { cell = cell.cell, live = not cell.live }
+            liveNeighbors = 0
+            for r,neighbor in neighbors(g1, i, j) do
+                if neighbor.live then
+                    liveNeighbors = liveNeighbors + 1
+                end
+            end
+
+            -- All other live cells die in the next generation. Similarly, all other dead cells stay dead.
+            live = false
+            if cell.live then
+                -- Any live cell with two or three live neighbours survives.
+                if liveNeighbors == 2 or liveNeighbors == 3 then
+                    live = true
+                end
+            elseif not cell.live then
+                -- Any dead cell with three live neighbours becomes a live cell.
+                if liveNeighbors == 3 then
+                    live = true
+                end
+            end
+            g2[i][j] = { cell = cell.cell, live = live }
         end
     end
-    return tab
+    return g2
 end
 
 function draw(cells)
@@ -46,6 +80,19 @@ function draw(cells)
     end
 end
 
+local cells = {}
+for i=1, WIDTH do
+    cells[i] = {}
+      for j=1, HEIGHT do
+          r = pd.geometry.rect.new(32 * (i-1), 32 * (j-1), 32, 32)
+          cells[i][j] = { cell = r, live = false }
+      end
+end
+
+local x = 1
+local y = 1
+
+local running = false
 function playdate.update()
     if playdate.buttonJustPressed("b") then
         running = not running