don't return a bool from IndexInParent

ki.go

@@ -104,10 +104,10 @@ type Ki interface {
 	// one-parent, no-cycles structure -- see SetParent.
 	Parent() Ki
 
-	// IndexInParent returns our index within our parent object -- caches the
+	// IndexInParent returns our index within our parent object. It caches the
 	// last value and uses that for an optimized search so subsequent calls
-	// are typically quite fast.  Returns false if we don't have a parent.
-	IndexInParent() (int, bool)
+	// are typically quite fast. Returns -1 if we don't have a parent.
+	IndexInParent() int
 
 	// ParentLevel finds a given potential parent node recursively up the
 	// hierarchy, returning level above current node that the parent was

node.go

@@ -171,18 +171,19 @@ func (n *Node) Parent() Ki {
 	return n.Par
 }
 
-// IndexInParent returns our index within our parent object -- caches the
+// IndexInParent returns our index within our parent object. It caches the
 // last value and uses that for an optimized search so subsequent calls
-// are typically quite fast.  Returns false if we don't have a parent.
-func (n *Node) IndexInParent() (int, bool) {
+// are typically quite fast. Returns -1 if we don't have a parent.
+func (n *Node) IndexInParent() int {
 	if n.Par == nil {
-		return -1, false
+		return -1
 	}
 	idx, ok := n.Par.Children().IndexOf(n.This(), n.index) // very fast if index is close..
-	if ok {
-		n.index = idx
+	if !ok {
+		return -1
 	}
-	return idx, ok
+	n.index = idx
+	return idx
 }
 
 // ParentLevel finds a given potential parent node recursively up the

walki.go

@@ -37,8 +37,8 @@ func Prev(nd Ki) Ki {
 	if nd.Parent() == nil {
 		return nil
 	}
-	myidx, ok := nd.IndexInParent()
-	if ok && myidx > 0 {
+	myidx := nd.IndexInParent()
+	if myidx > 0 {
 		nn := nd.Parent().Child(myidx - 1)
 		return LastChild(nn)
 	}
@@ -61,11 +61,9 @@ func NextSibling(nd Ki) Ki {
 	if nd.Parent() == nil {
 		return nil
 	}
-	myidx, ok := nd.IndexInParent()
-	if ok {
-		if myidx < nd.Parent().NumChildren()-1 {
-			return nd.Parent().Child(myidx + 1)
-		}
+	myidx := nd.IndexInParent()
+	if myidx >= 0 && myidx < nd.Parent().NumChildren()-1 {
+		return nd.Parent().Child(myidx + 1)
 	}
 	return NextSibling(nd.Parent())
 }