Signed integer representation

draw.go

@@ -147,6 +147,8 @@ func drawHexadecimal (xOffset, yOffset int, number uint64) {
 	application.SetColor(xOffset, yOffset, stone.ColorBlue)
 	application.SetColor(xOffset + 1, yOffset, stone.ColorBlue)
 
+	number = drawSign(xOffset, yOffset, number)
+	
 	for x := 0; x < 16; x ++ {
 		bitOffset -= 4
 		
@@ -181,6 +183,8 @@ func drawDecimal (xOffset, yOffset int, number uint64) {
 	application.SetColor(xOffset, yOffset, stone.ColorBlue)
 	application.SetColor(xOffset + 1, yOffset, stone.ColorBlue)
 
+	number = drawSign(xOffset, yOffset, number)
+
 	for x := 0; x < 20; x ++ {
 		trueX := x + xOffset + 5
 		character := rune((number / divisor) % 10) + '0'
@@ -230,3 +234,22 @@ func drawOctal (xOffset, yOffset int, number uint64) {
 		}
 	}
 }
+
+func drawSign (xOffset, yOffset int, number uint64) (alteredNumber uint64) {
+	alteredNumber = number
+	
+	if showSigned {
+		if int64(alteredNumber) >= 0 {
+			application.SetRune(xOffset + 3, yOffset, '+')
+			application.SetColor (
+				xOffset + 3, yOffset, stone.ColorGreen)
+		} else {
+			application.SetRune(xOffset + 3, yOffset, '-')
+			application.SetColor (
+				xOffset + 3, yOffset, stone.ColorRed)
+			alteredNumber = uint64(int64(number) * -1)
+		}
+	}
+
+	return
+}

main.go

@@ -15,7 +15,8 @@ var application = &stone.Application { }
 var expressionRoot Expression
 var inputBuffer stone.DamageBuffer
 var showLeftColumn bool
-var showEndResult  bool
+var showEndResult  bool = true
+var showSigned     bool = true
 
 func main () {
 	application.SetTitle("MathPan")
@@ -81,11 +82,6 @@ func onPress (button stone.Button, modifiers stone.Modifiers) {
 		redraw()
 		application.Draw()
 
-	case stone.KeyTab:
-		showEndResult = !showEndResult
-		redraw()
-		application.Draw()
-
 	case stone.KeyDelete:
 		if selectedExpression == nil { break }
 		parent := selectedExpression.Parent()
@@ -211,6 +207,16 @@ func onPress (button stone.Button, modifiers stone.Modifiers) {
 		
 		redraw()
 		application.Draw()
+
+	case 's':
+		showSigned = !showSigned
+		redraw()
+		application.Draw()
+
+	case stone.KeyTab:
+		showEndResult = !showEndResult
+		redraw()
+		application.Draw()
 	}
 }