fix typo

char.go

@@ -16,7 +16,7 @@ const (
 	CharPrev      = 16
 	CharBckSearch = 18
 	CharFwdSearch = 19
-	CharTransform = 20
+	CharTranspose = 20
 	CharCtrlW     = 23
 	CharEsc       = 27
 	CharEscapeEx  = 91
@@ -28,5 +28,5 @@ const (
 	MetaNext
 	MetaDelete
 	MetaBackspace
-	MetaTransform
+	MetaTranspose
 )

operation.go

@@ -60,8 +60,8 @@ func (l *Operation) ioloop() {
 			l.buf.Kill()
 		case MetaNext:
 			l.buf.MoveToNextWord()
-		case CharTransform:
-			l.buf.Transform()
+		case CharTranspose:
+			l.buf.Transpose()
 		case MetaPrev:
 			l.buf.MoveToPrevWord()
 		case MetaDelete:

runebuf.go

@@ -123,7 +123,7 @@ func (r *RuneBuffer) Kill() {
 	r.Refresh()
 }
 
-func (r *RuneBuffer) Transform() {
+func (r *RuneBuffer) Transpose() {
 	if len(r.buf) < 2 {
 		if len(r.buf) == 1 {
 			r.idx++
@@ -133,6 +133,8 @@ func (r *RuneBuffer) Transform() {
 	}
 	if r.idx == 0 {
 		r.idx = 1
+	} else if r.idx >= len(r.buf) {
+		r.idx = len(r.buf) - 1
 	}
 	r.buf[r.idx], r.buf[r.idx-1] = r.buf[r.idx-1], r.buf[r.idx]
 	r.idx++

utils.go

@@ -52,8 +52,8 @@ func escapeKey(r rune) rune {
 		r = MetaNext
 	case 'd':
 		r = MetaDelete
-	case CharTransform:
-		r = MetaTransform
+	case CharTranspose:
+		r = MetaTranspose
 	case CharBackspace:
 		r = MetaBackspace
 	case CharEsc: