store nonexistent prompt number as null

IPython/frontend/html/notebook/static/js/codecell.js

@@ -1,843 +1,843
 //----------------------------------------------------------------------------
 //  Copyright (C) 2008-2011  The IPython Development Team
 //
 //  Distributed under the terms of the BSD License.  The full license is in
 //  the file COPYING, distributed as part of this software.
 //----------------------------------------------------------------------------
 
 //============================================================================
 // CodeCell
 //============================================================================
 
 var IPython = (function (IPython) {
 
     var utils = IPython.utils;
 
     var CodeCell = function (notebook) {
         this.code_mirror = null;
-        this.input_prompt_number = ' ';
+        this.input_prompt_number = null;
         this.is_completing = false;
         this.completion_cursor = null;
         this.outputs = [];
         this.collapsed = false;
         this.tooltip_timeout = null;
         IPython.Cell.apply(this, arguments);
     };
 
 
     CodeCell.prototype = new IPython.Cell();
 
 
     CodeCell.prototype.create_element = function () {
         var cell =  $('<div></div>').addClass('cell border-box-sizing code_cell vbox');
         cell.attr('tabindex','2');
         var input = $('<div></div>').addClass('input hbox');
         input.append($('<div/>').addClass('prompt input_prompt'));
         var input_area = $('<div/>').addClass('input_area box-flex1');
         this.code_mirror = CodeMirror(input_area.get(0), {
             indentUnit : 4,
             mode: 'python',
             theme: 'ipython',
             readOnly: this.read_only,
             onKeyEvent: $.proxy(this.handle_codemirror_keyevent,this)
         });
         input.append(input_area);
         var output = $('<div></div>').addClass('output vbox');
         cell.append(input).append(output);
         this.element = cell;
         this.collapse();
     };
 
     //TODO, try to diminish the number of parameters.
     CodeCell.prototype.request_tooltip_after_time = function (pre_cursor,time){
         var that = this;
         if (pre_cursor === "" || pre_cursor === "(" ) {
             // don't do anything if line beggin with '(' or is empty
         } else {
             // Will set a timer to request tooltip in `time`
             that.tooltip_timeout = setTimeout(function(){
                     IPython.notebook.request_tool_tip(that, pre_cursor)
                 },time);
         }
     };
 
     CodeCell.prototype.handle_codemirror_keyevent = function (editor, event) {
         // This method gets called in CodeMirror's onKeyDown/onKeyPress
         // handlers and is used to provide custom key handling. Its return
         // value is used to determine if CodeMirror should ignore the event:
         // true = ignore, false = don't ignore.
         
         if (this.read_only){
             return false;
         }
 
         // note that we are comparing and setting the time to wait at each key press.
         // a better wqy might be to generate a new function on each time change and
         // assign it to CodeCell.prototype.request_tooltip_after_time
         tooltip_wait_time = this.notebook.time_before_tooltip;
         tooltip_on_tab    = this.notebook.tooltip_on_tab;
         var that = this;
         // whatever key is pressed, first, cancel the tooltip request before
         // they are sent, and remove tooltip if any
         if(event.type === 'keydown' ){
             that.remove_and_cancel_tooltip();
         }
 
         if (event.keyCode === 13 && (event.shiftKey || event.ctrlKey)) {
             // Always ignore shift-enter in CodeMirror as we handle it.
             return true;
         }else if (event.which === 40 && event.type === 'keypress' && tooltip_wait_time >= 0) {
             // triger aon keypress (!) otherwise inconsistent event.which depending on plateform
             // browser and keyboard layout !
             // Pressing '(' , request tooltip, don't forget to reappend it
             var cursor = editor.getCursor();
             var pre_cursor = editor.getRange({line:cursor.line,ch:0},cursor).trim()+'(';
             that.request_tooltip_after_time(pre_cursor,tooltip_wait_time);
         } else if (event.keyCode === 9 && event.type == 'keydown') {
             // Tab completion.
             var cur = editor.getCursor();
             //Do not trim here because of tooltip
             var pre_cursor = editor.getRange({line:cur.line,ch:0},cur);
             if (pre_cursor.trim() === "") {
                 // Don't autocomplete if the part of the line before the cursor
                 // is empty.  In this case, let CodeMirror handle indentation.
                 return false;
             } else if ((pre_cursor.substr(-1) === "("|| pre_cursor.substr(-1) === " ") && tooltip_on_tab ) {
                 that.request_tooltip_after_time(pre_cursor,0);
             } else {
                 pre_cursor.trim();
                 // Autocomplete the current line.
                 event.stop();
                 var line = editor.getLine(cur.line);
                 this.is_completing = true;
                 this.completion_cursor = cur;
                 IPython.notebook.complete_cell(this, line, cur.ch);
                 return true;
             }
         } else if (event.keyCode === 8 && event.type == 'keydown') {
             // If backspace and the line ends with 4 spaces, remove them.
             var cur = editor.getCursor();
             var line = editor.getLine(cur.line);
             var ending = line.slice(-4);
             if (ending === '    ') {
                 editor.replaceRange('',
                     {line: cur.line, ch: cur.ch-4},
                     {line: cur.line, ch: cur.ch}
                 );
                 event.stop();
                 return true;
             } else {
                 return false;
             }
         } else if (event.keyCode === 76 && event.ctrlKey && event.shiftKey
                    && event.type == 'keydown') {
             // toggle line numbers with Ctrl-Shift-L
             this.toggle_line_numbers();
         }
         else {
             // keypress/keyup also trigger on TAB press, and we don't want to
             // use those to disable tab completion.
             if (this.is_completing && event.keyCode !== 9) {
                 var ed_cur = editor.getCursor();
                 var cc_cur = this.completion_cursor;
                 if (ed_cur.line !== cc_cur.line || ed_cur.ch !== cc_cur.ch) {
                     this.is_completing = false;
                     this.completion_cursor = null;
                 }
             }
             return false;
         };
         return false;
     };
 
     CodeCell.prototype.remove_and_cancel_tooltip = function() {
         // note that we don't handle closing directly inside the calltip
         // as in the completer, because it is not focusable, so won't
         // get the event.
         if (this.tooltip_timeout != null){
             clearTimeout(this.tooltip_timeout);
             $('#tooltip').remove();
             this.tooltip_timeout = null;
         }
     }
 
     CodeCell.prototype.finish_tooltip = function (reply) {
         // Extract call tip data; the priority is call, init, main.
         defstring = reply.call_def;
         if (defstring == null) { defstring = reply.init_definition; }
         if (defstring == null) { defstring = reply.definition; }
 
         docstring = reply.call_docstring;
         if (docstring == null) { docstring = reply.init_docstring; }
         if (docstring == null) { docstring = reply.docstring; }
         if (docstring == null) { docstring = "<empty docstring>"; }
 
         name=reply.name;
 
         var that = this;
         var tooltip = $('<div/>').attr('id', 'tooltip').addClass('tooltip');
         // remove to have the tooltip not Limited in X and Y
         tooltip.addClass('smalltooltip');
         var pre=$('<pre/>').html(utils.fixConsole(docstring));
         var expandlink=$('<a/>').attr('href',"#");
             expandlink.addClass("ui-corner-all"); //rounded corner
             expandlink.attr('role',"button");
             //expandlink.addClass('ui-button');
             //expandlink.addClass('ui-state-default');
         var expandspan=$('<span/>').text('Expand');
             expandspan.addClass('ui-icon');
             expandspan.addClass('ui-icon-plus');
         expandlink.append(expandspan);
         expandlink.attr('id','expanbutton');
         expandlink.click(function(){
             tooltip.removeClass('smalltooltip');
             tooltip.addClass('bigtooltip');
             $('#expanbutton').remove();
             setTimeout(function(){that.code_mirror.focus();}, 50);
         });
         var morelink=$('<a/>').attr('href',"#");
             morelink.attr('role',"button");
             morelink.addClass('ui-button');
             //morelink.addClass("ui-corner-all"); //rounded corner
             //morelink.addClass('ui-state-default');
         var morespan=$('<span/>').text('Open in Pager');
             morespan.addClass('ui-icon');
             morespan.addClass('ui-icon-arrowstop-l-n');
         morelink.append(morespan);
         morelink.click(function(){
             var msg_id = IPython.notebook.kernel.execute(name+"?");
             IPython.notebook.msg_cell_map[msg_id] = IPython.notebook.selected_cell().cell_id;
             that.remove_and_cancel_tooltip();
             setTimeout(function(){that.code_mirror.focus();}, 50);
         });
 
         var closelink=$('<a/>').attr('href',"#");
             closelink.attr('role',"button");
             closelink.addClass('ui-button');
             //closelink.addClass("ui-corner-all"); //rounded corner
             //closelink.adClass('ui-state-default'); // grey background and blue cross
         var closespan=$('<span/>').text('Close');
             closespan.addClass('ui-icon');
             closespan.addClass('ui-icon-close');
         closelink.append(closespan);
         closelink.click(function(){
             that.remove_and_cancel_tooltip();
             setTimeout(function(){that.code_mirror.focus();}, 50);
             });
         //construct the tooltip
         tooltip.append(closelink);
         tooltip.append(expandlink);
         tooltip.append(morelink);
         if(defstring){
             defstring_html = $('<pre/>').html(utils.fixConsole(defstring));
             tooltip.append(defstring_html);
         }
         tooltip.append(pre);
         var pos = this.code_mirror.cursorCoords();
         tooltip.css('left',pos.x+'px');
         tooltip.css('top',pos.yBot+'px');
         $('body').append(tooltip);
 
         // issues with cross-closing if multiple tooltip in less than 5sec
         // keep it comented for now
         // setTimeout(that.remove_and_cancel_tooltip, 5000);
     };
 
     // As you type completer
     CodeCell.prototype.finish_completing = function (matched_text, matches) {
         //return if not completing or nothing to complete
         if (!this.is_completing || matches.length === 0) {return;}
 
         // for later readability
         var key = { tab:9,
                     esc:27,
                     backspace:8,
                     space:32,
                     shift:16,
                     enter:13,
                     // _ is 95
                     isCompSymbol : function (code)
                         {
                         return (code > 64 && code <= 90)
                             || (code >= 97 && code <= 122)
                             || (code == 95)
                         },
                     dismissAndAppend : function (code)
                         {
                         chararr = '()[]+-/\\. ,=*'.split("");
                         codearr = chararr.map(function(x){return x.charCodeAt(0)});
                         return jQuery.inArray(code, codearr) != -1;
                         }
 
                     }
 
         // smart completion, sort kwarg ending with '='
         var newm = new Array();
         if(this.notebook.smart_completer)
         {
             kwargs = new Array();
             other = new Array();
             for(var i = 0 ; i<matches.length ; ++i){
                 if(matches[i].substr(-1) === '='){
                     kwargs.push(matches[i]);
                 }else{other.push(matches[i]);}
             }
             newm = kwargs.concat(other);
             matches = newm;
         }
         // end sort kwargs
 
         // give common prefix of a array of string
         function sharedStart(A){
             if(A.length == 1){return A[0]}
             if(A.length > 1 ){
                 var tem1, tem2, s, A = A.slice(0).sort();
                 tem1 = A[0];
                 s = tem1.length;
                 tem2 = A.pop();
                 while(s && tem2.indexOf(tem1) == -1){
                     tem1 = tem1.substring(0, --s);
                 }
                 return tem1;
             }
             return "";
         }
 
 
         //try to check if the user is typing tab at least twice after a word
         // and completion is "done"
         fallback_on_tooltip_after = 2
         if(matches.length == 1 && matched_text === matches[0])
         {
             if(this.npressed >fallback_on_tooltip_after  && this.prevmatch==matched_text)
             {
                 console.log('Ok, you really want to complete after pressing tab '+this.npressed+' times !');
                 console.log('You should understand that there is no (more) completion for that !');
                 console.log("I'll show you the tooltip, will you stop bothering me ?");
                 this.request_tooltip_after_time(matched_text+'(',0);
                 return;
             }
             this.prevmatch = matched_text
             this.npressed = this.npressed+1;
         }
         else
         {
             this.prevmatch = "";
             this.npressed = 0;
         }
         // end fallback on tooltip
         //==================================
         // Real completion logic start here
         var that = this;
         var cur = this.completion_cursor;
         var done = false;
 
         // call to dismmiss the completer
         var close = function () {
             if (done) return;
             done = true;
             if (complete != undefined)
             {complete.remove();}
             that.is_completing = false;
             that.completion_cursor = null;
         };
 
         // update codemirror with the typed text
         prev = matched_text
         var update = function (inserted_text, event) {
             that.code_mirror.replaceRange(
                 inserted_text,
                 {line: cur.line, ch: (cur.ch-matched_text.length)},
                 {line: cur.line, ch: (cur.ch+prev.length-matched_text.length)}
             );
             prev = inserted_text
             if(event != null){
                 event.stopPropagation();
                 event.preventDefault();
             }
         };
         // insert the given text and exit the completer
         var insert = function (selected_text, event) {
             update(selected_text)
             close();
             setTimeout(function(){that.code_mirror.focus();}, 50);
         };
 
         // insert the curent highlited selection and exit
         var pick = function () {
             insert(select.val()[0],null);
         };
 
 
         // Define function to clear the completer, refill it with the new
         // matches, update the pseuso typing field. autopick insert match if
         // only one left, in no matches (anymore) dismiss itself by pasting
         // what the user have typed until then
         var complete_with = function(matches,typed_text,autopick,event)
         {
             // If autopick an only one match, past.
             // Used to 'pick' when pressing tab
             if (matches.length < 1) {
                 insert(typed_text,event);
                 if(event != null){
                 event.stopPropagation();
                 event.preventDefault();
                 }
             } else if (autopick && matches.length == 1) {
                 insert(matches[0],event);
                 if(event != null){
                 event.stopPropagation();
                 event.preventDefault();
                 }
             }
             //clear the previous completion if any
             update(typed_text,event);
             complete.children().children().remove();
             $('#asyoutype').html("<b>"+matched_text+"</b>"+typed_text.substr(matched_text.length));
             select = $('#asyoutypeselect');
             for (var i = 0; i<matches.length; ++i) {
                     select.append($('<option/>').html(matches[i]));
             }
             select.children().first().attr('selected','true');
         }
 
         // create html for completer
         var complete = $('<div/>').addClass('completions');
             complete.attr('id','complete');
         complete.append($('<p/>').attr('id', 'asyoutype').html('<b>fixed part</b>user part'));//pseudo input field
 
         var select = $('<select/>').attr('multiple','true');
             select.attr('id', 'asyoutypeselect')
             select.attr('size',Math.min(10,matches.length));
         var pos = this.code_mirror.cursorCoords();
 
         // TODO: I propose to remove enough horizontal pixel
         // to align the text later
         complete.css('left',pos.x+'px');
         complete.css('top',pos.yBot+'px');
         complete.append(select);
 
         $('body').append(complete);
 
         // So a first actual completion.  see if all the completion start wit
         // the same letter and complete if necessary
         fastForward = sharedStart(matches)
         typed_characters = fastForward.substr(matched_text.length);
         complete_with(matches,matched_text+typed_characters,true,null);
         filterd = matches;
         // Give focus to select, and make it filter the match as the user type
         // by filtering the previous matches. Called by .keypress and .keydown
         var downandpress = function (event,press_or_down) {
             var code = event.which;
             var autopick = false; // auto 'pick' if only one match
             if (press_or_down === 0){
                 press = true; down = false; //Are we called from keypress or keydown
             } else if (press_or_down == 1){
                 press = false; down = true;
             }
             if (code === key.shift) {
                 // nothing on Shift
                 return;
             }
             if (key.dismissAndAppend(code) && press) {
                 var newchar = String.fromCharCode(code);
                 typed_characters = typed_characters+newchar;
                 insert(matched_text+typed_characters,event);
                 return
             }
             if (code === key.enter) {
                 // Pressing ENTER will cause a pick
                 event.stopPropagation();
                 event.preventDefault();
                 pick();
             } else if (code === 38 || code === 40) {
                 // We don't want the document keydown handler to handle UP/DOWN,
                 // but we want the default action.
                 event.stopPropagation();
             } else if ( (code == key.backspace)||(code == key.tab && down) || press  || key.isCompSymbol(code)){
                 if( key.isCompSymbol(code) && press)
                 {
                     var newchar = String.fromCharCode(code);
                     typed_characters = typed_characters+newchar;
                 } else if (code == key.tab) {
                     fastForward = sharedStart(filterd)
                     ffsub = fastForward.substr(matched_text.length+typed_characters.length);
                     typed_characters = typed_characters+ffsub;
                     autopick = true;
                 } else if (code == key.backspace && down) {
                     // cancel if user have erase everything, otherwise decrease
                     // what we filter with
                     event.preventDefault();
                     if (typed_characters.length <= 0)
                     {
                         insert(matched_text,event)
                         return
                     }
                     typed_characters = typed_characters.substr(0,typed_characters.length-1);
                 } else if (press && code != key.backspace && code != key.tab && code != 0){
                     insert(matched_text+typed_characters,event);
                     return
                 } else {
                     return
                 }
                 re = new RegExp("^"+"\%?"+matched_text+typed_characters,"");
                 filterd = matches.filter(function(x){return re.test(x)});
                 complete_with(filterd,matched_text+typed_characters,autopick,event);
             } else if( code == key.esc) {
                 // dismiss the completer and go back to before invoking it
                 insert(matched_text,event);
             } else if( press ){ // abort only on .keypress or esc
                 // abort with what the user have pressed until now
                 console.log('aborting with keycode : '+code+' is down :'+down);
             }
         }
         select.keydown(function (event) {
             downandpress(event,1)
         });
         select.keypress(function (event) {
             downandpress(event,0)
         });
         // Double click also causes a pick.
         // and bind the last actions.
         select.dblclick(pick);
         select.blur(close);
         select.focus();
     };
 
     CodeCell.prototype.toggle_line_numbers = function () {
         if (this.code_mirror.getOption('lineNumbers') == false) {
             this.code_mirror.setOption('lineNumbers', true);
         } else {
             this.code_mirror.setOption('lineNumbers', false);
         }
         this.code_mirror.refresh();
     };
 
     CodeCell.prototype.select = function () {
         IPython.Cell.prototype.select.apply(this);
         // Todo: this dance is needed because as of CodeMirror 2.12, focus is
         // not causing the cursor to blink if the editor is empty initially.
         // While this seems to fix the issue, this should be fixed
         // in CodeMirror proper.
         var s = this.code_mirror.getValue();
         this.code_mirror.focus();
         if (s === '') this.code_mirror.setValue('');
     };
 
 
     CodeCell.prototype.select_all = function () {
         var start = {line: 0, ch: 0};
         var nlines = this.code_mirror.lineCount();
         var last_line = this.code_mirror.getLine(nlines-1);
         var end = {line: nlines-1, ch: last_line.length};
         this.code_mirror.setSelection(start, end);
     };
 
 
     CodeCell.prototype.append_output = function (json) {
         this.expand();
         if (json.output_type === 'pyout') {
             this.append_pyout(json);
         } else if (json.output_type === 'pyerr') {
             this.append_pyerr(json);
         } else if (json.output_type === 'display_data') {
             this.append_display_data(json);
         } else if (json.output_type === 'stream') {
             this.append_stream(json);
         };
         this.outputs.push(json);
     };
 
 
     CodeCell.prototype.create_output_area = function () {
         var oa = $("<div/>").addClass("hbox output_area");
         oa.append($('<div/>').addClass('prompt'));
         return oa;
     };
 
 
     CodeCell.prototype.append_pyout = function (json) {
         n = json.prompt_number || ' ';
         var toinsert = this.create_output_area();
         toinsert.find('div.prompt').addClass('output_prompt').html('Out[' + n + ']:');
         this.append_mime_type(json, toinsert);
         this.element.find('div.output').append(toinsert);
         // If we just output latex, typeset it.
         if ((json.latex !== undefined) || (json.html !== undefined)) {
             this.typeset();
         };
     };
 
 
     CodeCell.prototype.append_pyerr = function (json) {
         var tb = json.traceback;
         if (tb !== undefined && tb.length > 0) {
             var s = '';
             var len = tb.length;
             for (var i=0; i<len; i++) {
                 s = s + tb[i] + '\n';
             }
             s = s + '\n';
             var toinsert = this.create_output_area();
             this.append_text(s, toinsert);
             this.element.find('div.output').append(toinsert);
         };
     };
 
 
     CodeCell.prototype.append_stream = function (json) {
         // temporary fix: if stream undefined (json file written prior to this patch),
         // default to most likely stdout:
         if (json.stream == undefined){
             json.stream = 'stdout';
         }
         var subclass = "output_"+json.stream;
         if (this.outputs.length > 0){
             // have at least one output to consider
             var last = this.outputs[this.outputs.length-1];
             if (last.output_type == 'stream' && json.stream == last.stream){
                 // latest output was in the same stream,
                 // so append directly into its pre tag
                 // escape ANSI & HTML specials:
                 var text = utils.fixConsole(json.text);
                 this.element.find('div.'+subclass).last().find('pre').append(text);
                 return;
             }
         }
         
         // If we got here, attach a new div
         var toinsert = this.create_output_area();
         this.append_text(json.text, toinsert, "output_stream "+subclass);
         this.element.find('div.output').append(toinsert);
     };
 
 
     CodeCell.prototype.append_display_data = function (json) {
         var toinsert = this.create_output_area();
         this.append_mime_type(json, toinsert);
         this.element.find('div.output').append(toinsert);
         // If we just output latex, typeset it.
         if ( (json.latex !== undefined) || (json.html !== undefined) ) {
             this.typeset();
         };
     };
 
 
     CodeCell.prototype.append_mime_type = function (json, element) {
         if (json.html !== undefined) {
             this.append_html(json.html, element);
         } else if (json.latex !== undefined) {
             this.append_latex(json.latex, element);
         } else if (json.svg !== undefined) {
             this.append_svg(json.svg, element);
         } else if (json.png !== undefined) {
             this.append_png(json.png, element);
         } else if (json.jpeg !== undefined) {
             this.append_jpeg(json.jpeg, element);
         } else if (json.text !== undefined) {
             this.append_text(json.text, element);
         };
     };
 
 
     CodeCell.prototype.append_html = function (html, element) {
         var toinsert = $("<div/>").addClass("box_flex1 output_subarea output_html rendered_html");
         toinsert.append(html);
         element.append(toinsert);
     };
 
 
     CodeCell.prototype.append_text = function (data, element, extra_class) {
         var toinsert = $("<div/>").addClass("box_flex1 output_subarea output_text");
         // escape ANSI & HTML specials in plaintext:
         data = utils.fixConsole(data);
         if (extra_class){
             toinsert.addClass(extra_class);
         }
         toinsert.append($("<pre/>").html(data));
         element.append(toinsert);
     };
 
 
     CodeCell.prototype.append_svg = function (svg, element) {
         var toinsert = $("<div/>").addClass("box_flex1 output_subarea output_svg");
         toinsert.append(svg);
         element.append(toinsert);
     };
 
 
     CodeCell.prototype.append_png = function (png, element) {
         var toinsert = $("<div/>").addClass("box_flex1 output_subarea output_png");
         toinsert.append($("<img/>").attr('src','data:image/png;base64,'+png));
         element.append(toinsert);
     };
 
 
     CodeCell.prototype.append_jpeg = function (jpeg, element) {
         var toinsert = $("<div/>").addClass("box_flex1 output_subarea output_jpeg");
         toinsert.append($("<img/>").attr('src','data:image/jpeg;base64,'+jpeg));
         element.append(toinsert);
     };
 
 
     CodeCell.prototype.append_latex = function (latex, element) {
         // This method cannot do the typesetting because the latex first has to
         // be on the page.
         var toinsert = $("<div/>").addClass("box_flex1 output_subarea output_latex");
         toinsert.append(latex);
         element.append(toinsert);
     };
 
 
     CodeCell.prototype.clear_output = function (stdout, stderr, other) {
         var output_div = this.element.find("div.output");
         if (stdout && stderr && other){
             // clear all, no need for logic
             output_div.html("");
             this.outputs = [];
             return;
         }
         // remove html output
         // each output_subarea that has an identifying class is in an output_area
         // which is the element to be removed.
         if (stdout){
             output_div.find("div.output_stdout").parent().remove();
         }
         if (stderr){
             output_div.find("div.output_stderr").parent().remove();
         }
         if (other){
             output_div.find("div.output_subarea").not("div.output_stderr").not("div.output_stdout").parent().remove();
         }
         
         // remove cleared outputs from JSON list:
         for (var i = this.outputs.length - 1; i >= 0; i--){
             var out = this.outputs[i];
             var output_type = out.output_type;
             if (output_type == "display_data" && other){
                 this.outputs.splice(i,1);
             }else if (output_type == "stream"){
                 if (stdout && out.stream == "stdout"){
                     this.outputs.splice(i,1);
                 }else if (stderr && out.stream == "stderr"){
                     this.outputs.splice(i,1);
                 }
             }
         }
     };
 
 
     CodeCell.prototype.clear_input = function () {
         this.code_mirror.setValue('');
     };
 
 
     CodeCell.prototype.collapse = function () {
         if (!this.collapsed) {
             this.element.find('div.output').hide();
             this.collapsed = true;
         };
     };
 
 
     CodeCell.prototype.expand = function () {
         if (this.collapsed) {
             this.element.find('div.output').show();
             this.collapsed = false;
         };
     };
 
 
     CodeCell.prototype.toggle_output = function () {
         if (this.collapsed) {
             this.expand();
         } else {
             this.collapse();
         };
     };
 
     CodeCell.prototype.set_input_prompt = function (number) {
-        var n = number || '&nbsp;';
-        this.input_prompt_number = n;
-        this.element.find('div.input_prompt').html('In&nbsp;[' + n + ']:');
+        this.input_prompt_number = number;
+        var ns = number || "&nbsp;";
+        this.element.find('div.input_prompt').html('In&nbsp;[' + ns + ']:');
     };
 
 
     CodeCell.prototype.get_code = function () {
         return this.code_mirror.getValue();
     };
 
 
     CodeCell.prototype.set_code = function (code) {
         return this.code_mirror.setValue(code);
     };
 
 
     CodeCell.prototype.at_top = function () {
         var cursor = this.code_mirror.getCursor();
         if (cursor.line === 0) {
             return true;
         } else {
             return false;
         }
     };
 
 
     CodeCell.prototype.at_bottom = function () {
         var cursor = this.code_mirror.getCursor();
         if (cursor.line === (this.code_mirror.lineCount()-1)) {
             return true;
         } else {
             return false;
         }
     };
 
 
     CodeCell.prototype.fromJSON = function (data) {
         console.log('Import from JSON:', data);
         if (data.cell_type === 'code') {
             if (data.input !== undefined) {
                 this.set_code(data.input);
             }
             if (data.prompt_number !== undefined) {
                 this.set_input_prompt(data.prompt_number);
             } else {
                 this.set_input_prompt();
             };
             var len = data.outputs.length;
             for (var i=0; i<len; i++) {
                 this.append_output(data.outputs[i]);
             };
             if (data.collapsed !== undefined) {
                 if (data.collapsed) {
                     this.collapse();
                 };
             };
         };
     };
 
 
     CodeCell.prototype.toJSON = function () {
         var data = {};
         data.input = this.get_code();
         data.cell_type = 'code';
-        if (this.input_prompt_number !== ' ') {
+        if (this.input_prompt_number) {
             data.prompt_number = this.input_prompt_number;
         };
         var outputs = [];
         var len = this.outputs.length;
         for (var i=0; i<len; i++) {
             outputs[i] = this.outputs[i];
         };
         data.outputs = outputs;
         data.language = 'python';
         data.collapsed = this.collapsed;
         // console.log('Export to JSON:',data);
         return data;
     };
 
 
     IPython.CodeCell = CodeCell;
 
     return IPython;
 }(IPython));