bugfix: used -1 with uint32 for x and y coordinates

On the edges the neighbor counter did not work correct.

Some testcases for the coordinate converter functions are needed
to proove this as fixed.

life.go

@@ -16,11 +16,11 @@ const MAXWORKERINDEX = 1
 
 type Field struct {
 	iteration             uint64
-	width, height         uint32
+	width, height         int32
 	currentArea, nextArea []byte
 }
 
-func NewField(width, height uint32) *Field {
+func NewField(width, height int32) *Field {
 	rand.Seed(time.Nanoseconds())
 
 	cells := width * height
@@ -49,25 +49,25 @@ func (f *Field) Clear() {
 	}
 }
 
-func (f *Field) Set(x, y uint32, value byte) {
+func (f *Field) Set(x, y int32, value byte) {
 	f.currentArea[f.toArea(x, y)] = value
 }
 
 func (f *Field) Step() {
 	f.iteration++
 
 	resChan := make(chan byte, MAXWORKERINDEX)
-	for workerIndex := uint32(1); workerIndex <= MAXWORKERINDEX; workerIndex++ {
+	for workerIndex := int32(1); workerIndex <= MAXWORKERINDEX; workerIndex++ {
 		go f.worker(workerIndex, resChan)
 	}
 
-	for workerIndex := uint32(1); workerIndex <= MAXWORKERINDEX; workerIndex++ {
+	for workerIndex := int32(1); workerIndex <= MAXWORKERINDEX; workerIndex++ {
 		<-resChan
 	}
 	f.swapFields()
 }
 
-func (f *Field) CellCount() uint32 {
+func (f *Field) CellCount() int32 {
 	return f.width * f.height
 }
 
@@ -77,8 +77,8 @@ func (f *Field) Iteration() uint64 {
 
 func (f *Field) String() string {
 	sbuffer := bytes.NewBufferString("")
-	for y := uint32(0); y < f.height; y++ {
-		for x := uint32(0); x < f.width; x++ {
+	for y := int32(0); y < f.height; y++ {
+		for x := int32(0); x < f.width; x++ {
 			index := f.toArea(x, y)
 			if f.currentArea[index] == 1 {
 				fmt.Fprint(sbuffer, "#")
@@ -93,18 +93,18 @@ func (f *Field) String() string {
 
 func (f *Field) StringNeighborMap() string {
 	sbuffer := bytes.NewBufferString("")
-	for y := uint32(0); y < f.height; y++ {
-		for x := uint32(0); x < f.width; x++ {
+	for y := int32(0); y < f.height; y++ {
+		for x := int32(0); x < f.width; x++ {
 			fmt.Fprint(sbuffer, f.countNeighbors(x, y))
 		}
 		fmt.Fprint(sbuffer, "\n")
 	}
 	return string(sbuffer.Bytes())
 }
 
-func (f *Field) worker(workerIndex uint32, resChan chan byte) {
+func (f *Field) worker(workerIndex int32, resChan chan byte) {
 	var neighbors byte
-	var x, y uint32
+	var x, y int32
 	for cellIndex := workerIndex - 1; cellIndex < f.CellCount(); cellIndex += workerIndex {
 		x, y = f.toReal(cellIndex)
 		neighbors = f.countNeighbors(x, y)
@@ -120,13 +120,13 @@ func (f *Field) worker(workerIndex uint32, resChan chan byte) {
 	resChan <- 0
 }
 
-func (f *Field) toReal(index uint32) (x, y uint32) {
+func (f *Field) toReal(index int32) (x, y int32) {
 	y = index / f.width
 	x = index - y*f.width
 	return
 }
 
-func (f *Field) toArea(x, y uint32) uint32 {
+func (f *Field) toArea(x, y int32) int32 {
 	if x < 0 {
 		x = f.width - 1
 	} else if x >= f.width {
@@ -141,7 +141,7 @@ func (f *Field) toArea(x, y uint32) uint32 {
 	return y*f.width + x
 }
 
-func (f *Field) countNeighbors(x, y uint32) (neighbors byte) {
+func (f *Field) countNeighbors(x, y int32) (neighbors byte) {
 	neighbors += f.currentArea[f.toArea(x-1, y-1)]
 	neighbors += f.currentArea[f.toArea(x, y-1)]
 	neighbors += f.currentArea[f.toArea(x+1, y-1)]

life_test.go

@@ -10,13 +10,13 @@ import (
 	"testing"
 )
 
-var testcases [][3]uint32
+var testcases [][3]int32
 
 func init() {
-	testcases = [][3]uint32{
-		[3]uint32{0, 0, 0},
-		[3]uint32{2, 1, 7},
-		[3]uint32{3, 2, 13},
+	testcases = [][3]int32{
+		[3]int32{0, 0, 0},
+		[3]int32{2, 1, 7},
+		[3]int32{3, 2, 13},
 	}
 }