From 3997769defff4ae3041827497d5a8ada4662de80 Mon Sep 17 00:00:00 2001
From: Doug Blank <doug.blank@gmail.com>
Date: Sat, 27 Sep 2014 15:57:01 -0400
Subject: [PATCH 1/2] Fixed off by one error in get_prev_cell

Not sure why this was a TODO. Maybe `find_cell_index()` returned zero at one time, but in the browsers I tested, it always returns null if not found.
---
 IPython/html/static/notebook/js/notebook.js | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/IPython/html/static/notebook/js/notebook.js b/IPython/html/static/notebook/js/notebook.js
index ac8b220a3..522216881 100644
--- a/IPython/html/static/notebook/js/notebook.js
+++ b/IPython/html/static/notebook/js/notebook.js
@@ -465,11 +465,9 @@ define([
      * @return {Cell} The previous cell
      */
     Notebook.prototype.get_prev_cell = function (cell) {
-        // TODO: off-by-one
-        // nb.get_prev_cell(nb.get_cell(1)) is null
         var result = null;
         var index = this.find_cell_index(cell);
-        if (index !== null && index > 1) {
+        if (index !== null && index > 0) {
             result = this.get_cell(index-1);
         }
         return result;

From 6c3d40bbcd438d974c8b4356f2453738de7abb9a Mon Sep 17 00:00:00 2001
From: Doug Blank <dblank@cs.brynmawr.edu>
Date: Sun, 28 Sep 2014 14:01:35 -0400
Subject: [PATCH 2/2] Update documentation for functions that can return null

---
 IPython/html/static/notebook/js/notebook.js | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/IPython/html/static/notebook/js/notebook.js b/IPython/html/static/notebook/js/notebook.js
index 522216881..7e17848da 100644
--- a/IPython/html/static/notebook/js/notebook.js
+++ b/IPython/html/static/notebook/js/notebook.js
@@ -430,7 +430,7 @@ define([
      * 
      * @method get_cell
      * @param {Number} index An index of a cell to retrieve
-     * @return {Cell} A particular cell
+     * @return {Cell} Cell or null if no cell was found.
      */
     Notebook.prototype.get_cell = function (index) {
         var result = null;
@@ -446,7 +446,7 @@ define([
      * 
      * @method get_next_cell
      * @param {Cell} cell The provided cell
-     * @return {Cell} The next cell
+     * @return {Cell} the next cell or null if no cell was found.
      */
     Notebook.prototype.get_next_cell = function (cell) {
         var result = null;
@@ -462,7 +462,7 @@ define([
      * 
      * @method get_prev_cell
      * @param {Cell} cell The provided cell
-     * @return {Cell} The previous cell
+     * @return {Cell} The previous cell or null if no cell was found.
      */
     Notebook.prototype.get_prev_cell = function (cell) {
         var result = null;
@@ -478,7 +478,7 @@ define([
      * 
      * @method find_cell_index
      * @param {Cell} cell The provided cell
-     * @return {Number} The cell's numeric index
+     * @return {Number} The cell's numeric index or null if no cell was found.
      */
     Notebook.prototype.find_cell_index = function (cell) {
         var result = null;