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  • Why do I get "request for member in something not a struct or union" from this code?

    - by pyroxene
    I'm trying to teach myself C by coding up a linked list. I'm new to pointers and memory management and I'm getting a bit confused. I have this code: /* Remove a node from the list and rejiggle the pointers */ void rm_node(struct node **listP, int index) { struct node *prev; struct node *n = *listP; if (index == 0) { *listP = *listP->next; free(n); return; } for (index; index > 0; index--) { n = n->next; if (index == 2) { prev = n; } } prev->next = n->next; free(n); } to remove an element from the list. If I want to remove the first node, I still need some way of referring to the list, which is why the listP arg is a double pointer, so it can point to the first element of the list and allow me to free the node that used to be the head. However, when I try to dereference listP to access the pointer to the next node, the compiler tells me error: request for member ‘next’ in something not a structure or union . What am I doing wrong here? I think I might be hopelessly mixed up..?

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  • Unable to add multiple textviews into linearLayout within a loop

    - by Adam
    for(int i=0;i<object.size();i++){ FeaturedSingleEvent event = (FeaturedSingleEvent) object.get(i); images.add(event.getImage()); LinearLayout info = new LinearLayout(this); info.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT)); TextView title = new TextView(this); title.setText(event.getTitle()); title.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT)); info.addView(title); TextView by = new TextView(this); by.setText(event.getBy() + " " + event.getBy_name()); by.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT)); info.addView(by); TextView summary = new TextView(this); summary.setText(event.getSummary()); summary.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT)); info.addView(summary); layout.addView(info); if(i == 0){ info.setVisibility(View.VISIBLE); }else{ info.setVisibility(View.GONE); } } I'm attempting to have multiple LinearLayouts, only one being visible at a time, to create a slideshow. In a for loop, I create the layouts with their textViews, and set only the first one to be visible. The problem is that only one TextView seems to be displaying, ie. if everything but summary is deleted, then summary will display. As of right now, only title will display, because i'm assuming it's the first one. I'm most likely doing it wrong, so any help would be appreciated.

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  • SQL return ORDER BY result as an array

    - by EarthMind
    Is it possible to return groups as an associative array? I'd like to know if a pure SQL solution is possible. Note that I release that I could be making things more complex unnecessarily but this is mainly to give me an idea of the power of SQL. My problem: I have a list of words in the database that should be sorted alphabetically and grouped into separate groups according to the first letter of the word. For example: ape broom coconut banana apple should be returned as array( 'a' => 'ape', 'apple', 'b' => 'banana', 'broom', 'c' => 'coconut' ) so I can easily created sorted lists by first letter (i.e. clicking "A" only shows words starting with a, "B" with b, etc. This should make it easier for me to load everything in one query and make the sorted list JavaScript based, i.e. without having to reload the page (or use AJAX). Side notes: I'm using PostgreSQL but a solution for MySQL would be fine too so I can try to port it to PostgreSQL. Scripting language is PHP.

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  • Why does my binding break down on SilverLight ProgressBars?

    - by Bill Jeeves
    I asked a similar question about charts but I have given up on that and I am using progress bars instead. Essentially, I have ten progress bars in a Silverlight control. Each is showing a different value and updating every couple of seconds (it's a process monitor). Each progress bar has the same minimum value and maximum value so the bars can be compared. Trying to follow the M-V-VM model, I have bound the value of each bar to a property in my ViewModel. All of the maximum values for the bar are bound to a single property. When the model updates, the values and the maximum can all update. This allows the bars to re-scale as the sizes grow. I'm finding that the binding will stop working sometimes on one or more bars. I suspect it is because a bar's value becomes higher than the maximum occasionally. This is because if I update the maximums first and they are going down, the values will be to high. If I update the values first when the maximum needs increasing, the values are too high again. Is there a way to stop this behaviour? Some way, perhaps, to tell the progress bars that it's OK to temporarily go too high? Or some way to tell the bindings that they shouldn't be disabled when this happens? Or maybe I've got this completely wrong and there's some other issue with ProgressBar binding I don't know about?

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  • Pass object or id

    - by Charles
    This is just a question about best practices. Imagine you have a method that takes one parameter. This parameter is the id of an object. Ideally, I would like to be able to pass either the object's id directly, or just the object itself. What is the most elegant way to do this? I came up with the following: def method_name object object_id = object.to_param.to_i ### do whatever needs to be done with that object_id end So, if the parameter already is an id, it just pretty much stays the same; if it's an object, it gets its id. This works, but I feel like this could be better. Also, to_param returns a string, which could in some cases return a "real" string (i.e. "string" instead of "2"), hence returning 0 upon calling to_i on it. This could happen, for example, when using the friendly id gem for classes. Active record offers the same functionality. It doesn't matter if you say: Table.where(user_id: User.first.id) # pass in id or Table.where(user_id: User.first) # pass in object and infer id How do they do it? What is the best approach to achieve this effect?

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  • jQuery Fancy - popup window doesn't fully expand

    - by fmz
    I am using jQuery Fancybox to display a number of Flash videos on a site and I am having trouble with the window not opening fully on the first click in Firefox. It works fine in other browsers. Here is the jQuery: <script type="text/javascript"> $(document).ready(function() { $("a.videoLink").fancybox({ 'titleShow' : false, 'autoscale' : true, 'width' : '820', 'height' : '620', 'transitionIn' : 'elastic', 'transitionOut' : 'elastic' }); }); </script> Here is the html: <tr> <td class="title"><a class="videoLink" href="#video-content30">CPR Lesson 1 Movie</a></td> <td class="time">38:39</td> <td class="video" style="display:none"> <div id="video-content30"> <script type='text/javascript'> var flashvars = { file: 'http://www.stockmarketcpr.com/smsys/link/CPR-Lesson-1-Movie.flv', id: '30' }; var params = { wmode: 'opaque', bgcolor: '#CCCCCC', allowfullscreen: 'true', allowscriptaccess: 'always' }; swfobject.embedSWF('http://www.stockmarketcpr.com/_flash/player.swf', 'player30','800','600', '9.0.0','expressInstall.swf', flashvars, params); </script> <div id="player30"></div> </div> </td> </tr> I end up getting a quarter inch high, full-width window on the first click. The second click plays fine. I would appreciate any assistance. Thank you!

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  • For-Loop and LINQ's deferred execution don't play well together

    - by Tim Schmelter
    The title suggests that i've already an idea what's going on, but i cannot explain it. I've tried to order a List<string[]> dynamically by each "column", beginning with the first and ending with the minimum Length of all arrays. So in this sample it is 2, because the last string[] has only two elements: List<string[]> someValues = new List<string[]>(); someValues.Add(new[] { "c", "3", "b" }); someValues.Add(new[] { "a", "1", "d" }); someValues.Add(new[] { "d", "4", "a" }); someValues.Add(new[] { "b", "2" }); Now i've tried to order all by the first and second column. I could do it statically in this way: someValues = someValues .OrderBy(t => t[0]) .ThenBy(t => t[1]) .ToList(); But if i don't know the number of "columns" i could use this loop(that's what I thought): int minDim = someValues.Min(t => t.GetLength(0)); // 2 IOrderedEnumerable<string[]> orderedValues = someValues.OrderBy(t => t[0]); for (int i = 1; i < minDim; i++) { orderedValues = orderedValues.ThenBy(t => t[i]); } someValues = orderedValues.ToList(); // IndexOutOfRangeException But that doesn't work, it fails with an IndexOutOfRangeException at the last line. The debugger tells me that i is 2 at that time, so the for-loop condition seems to be ignored, i is already == minDim. Why is that so?

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  • Please suggest other ways of communicating between server & client.

    - by Geo
    I'm writing a TCP chat server ( programming language does not mather ). It's a school project for my nephew, so it won't be released, and all questions I'm asking are just for my knowledge :). . Some of the things it will support: chatting between users ( doh ), it will be multithreaded sending each other files I know I could easily get away with all the stuff above if I go with serialization, and just send objects from client to server and back. But, if I do that, it will be limited to a specific programming language ( meaning clients written in other programming languages may not be able to deserialize the objects ). What would be the way to go so that other clients written in other languages could be supported? One way to go, off the top of my head, would be to go in this direction: the server & the client communicate by sending messages & chunks ( in lieu of other names ). Here's what I mean by this: every time the client/server wants to send something ( text message or file ) it will first send a simple text message ( newline terminated ) with the number of the chunks it will send. Example: command 4,20,30,40,50 Where command would be something like instant-message or file,4 would be the number of chunks to be sent, 20 would be the size in bytes of the first chunk, 30 of the 2nd, and so forth. after the message was sent, the client/server will start sending chunks ( of sizes mentioned in the sent message ). What do you think about implementing the client/server communication this way? What better options are there?

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  • XCode Obj-C: Make new NSArray from one key each out of an Array of Dictionaries

    - by user323772
    This actually could be a multipart question. But here's the first part ... I have an array (actually in a plist) of dictionaries. Each dictionary has 3 keys in it: (title), (points), and (description). I am trying to make a NEW array with the values of the key "title" from each dictionary in that first array. Let me explain WHY I am doing this and maybe that will provide a better all around explanation. I am trying to let people pick from a pre-determined list. Heck, if this was a web page it would be very simple since all I really care about are the "points" and the "Title". On a web site I could simply do a drop down combo-box with the "points" being the value and the title being the text for each row. But this is not a web page. So what I am trying to do here is pop out a modal picker when they click the text field. The modal picker shows the alphabetical ordered "titles" from our new array. And whichever one they select, it closes the modal view and assigns that "title" text to the UITextField which cannot be edited by the user. I have some code to get my modal picker to pop out. But I need to feed it an array of just the "titles" of each dictionary in my real array. Thanks in advance (and yes I am a newbie)

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  • Jquery UI dialog does not disappear

    - by iamrohitbanga
    I am using jquery-ui tabs and dialog functionality. Each tab has a button on the page which opens a dialog. This works for one of the tabs. However if I go the second tab, the button does not work there. When I come back to the first tab, the dialog does show up but the problem is I notice as I make switches back and forth to the first tab, it keeps on inserting new div's while the old div's have display:none set on them. I am doing this using JSP. This is how the reusable jsp looks like: <script> $(function() { var formData = null; $.ajax({ url : "addFormGenerator.html", success : function(data) { formData = data; $("#addFormDialog").html(data); $("#addFormDialog").dialog({ autoOpen : false, height : 300, width : 350, modal : true, buttons : { "Add" : function() { $(this).dialog("close"); }, Cancel : function() { $(this).dialog("close"); } }, close : function() { } }); } }); $("#addButton").button().click(function() { $("#addFormDialog").html(formData); $("#addFormDialog").dialog("open"); }); }); </script> <button id="addButton">Click here to Add New</button> <div id="addFormDialog" title="Add New"></div> This jsp fragment is included in other jsp pages as well. I was assuming as I switch between tabs the old button will be garbage collected. Can you help me understand the problem and fix it?

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  • How to speed-up a simple method? (possibily without changing interfaces or data structures)

    - by baol
    Hello. I have some data structures: all_unordered_mordered_m is a big vector containing all the strings I need (all different) ordered_m is a small vector containing the indexes of a subset of the strings (all different) in the former vector position_m maps the indexes of objects from the first vector to their position in the second one. The string_after(index, reverse) method returns the string referenced by ordered_m after all_unordered_m[index]. ordered_m is considered circular, and is explored in natural or reverse order depending on the second parameter. The code is something like the following: struct ordered_subset { // [...] std::vector<std::string>& all_unordered_m; // size = n >> 1 std::vector<size_t> ordered_m; // size << n std::map<size_t, size_t> position_m; // positions of strings in ordered_m const std::string& string_after(size_t index, bool reverse) const { size_t pos = position_m.find(index)->second; if(reverse) pos = (pos == 0 ? orderd_m.size() - 1 : pos - 1); else pos = (pos == ordered.size() - 1 ? 0 : pos + 1); return all_unordered_m[ordered_m[pos]]; } }; Given that: I do need all of the data-structures for other purposes; I cannot change them because I need to access the strings: by their id in the all_unordered_m; by their index inside the various ordered_m; I need to know the position of a string (identified by it's position in the first vector) inside ordered_m vector; I cannot change the string_after interface without changing most of the program. How can I speed up the string_after method that is called billions of times and is eating up about 10% of the execution time?

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  • How can I compare the performance of log() and fp division in C++?

    - by Ventzi Zhechev
    Hi, I’m using a log-based class in C++ to store very small floating-point values (as the values otherwise go beyond the scope of double). As I’m performing a large number of multiplications, this has the added benefit of converting the multiplications to sums. However, at a certain point in my algorithm, I need to divide a standard double value by an integer value and than do a *= to a log-based value. I have overloaded the *= operator for my log-based class and the right-hand side value is first converted to a log-based value by running log() and than added to the left-hand side value. Thus the operations actually performed are floating-point division, log() and floating-point summation. My question whether it would be faster to first convert the denominator to a log-based value, which would replace the floating-point division with floating-point subtraction, yielding the following chain of operations: twice log(), floating-point subtraction, floating-point summation. In the end, this boils down to whether floating-point division is faster or slower than log(). I suspect that a common answer would be that this is compiler and architecture dependent, so I’ll say that I use gcc 4.2 from Apple on darwin 10.3.0. Still, I hope to get an answer with a general remark on the speed of these two operators and/or an idea on how to measure the difference myself, as there might be more going on here, e.g. executing the constructors that do the type conversion etc. Cheers!

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  • Visual C++ function suddenly 170 ms slower (4x longer)

    - by Mikael
    For the past few months I've been working on a Visual C++ project to take images from cameras and process them. Up until today this has taken about 65 ms to update the data but now it has suddenly increased significantly. What happens is: I launch my program and for the first 30 or so iterations it performs as expected, then suddenly the loop time increases from 65 ms to 250 ms. The odd thing is, after timing each function I found out that the part of the code which is causing the slowdown is fairly basic and has not been modified in over a month. The data which goes into it is unchanged and identical every iteration but the execution time which is initially less than 1 ms suddenly increases to 170 ms while the rest of the code is still performing as expected (time-wise). Basically, I am calling the same function over and over, for the first 30 calls it performs as it should, after that it slows down for no apparent reason. It might also be worth noting that it is a sudden change in execution time, not a gradual increase. What could be causing this? The code is leaking some memory (~50 kb/s) but not nearly enough to warrant a sudden 4x slowdown. If anyone has any ideas I'd love to hear them!

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  • Are there any shortcuts/easier(VB) style way for raising events in C#?

    - by Eric
    Example in VB I have a worker class Public Class worker Public Event EventNumber1(ByVal messages As Dictionary(Of Integer, String)) Public Event EventNumber2(ByVal message As String) Public Sub CallEventNumber1() Dim dict As New Dictionary(Of Integer, String) dict.Add(1, "EventNumber1 First message") dict.Add(2, "EventNumber1 Second message") RaiseEvent EventNumber1(dict) End Sub Public Sub CallEventNumber2() RaiseEvent EventNumber2("I am an EventNumber2 Message") End Sub End Class and wire them up in another class with AddHandler _worker.EventNumber1, AddressOf EventNumber1Handler AddHandler _worker.EventNumber2, AddressOf EventNumber2Handler and in C# the worker class class Worker { public delegate void EventNumber1Handler(Dictionary<int, string> messages); public delegate void EventNumber2Handler(string message); public event EventNumber1Handler EventNumber1; public event EventNumber2Handler EventNumber2; public void CallEventNumber1() { Dictionary<int, string> dict = new Dictionary<int, string>(); dict.Add(1, "EventNumber1 First message"); dict.Add(2, "EventNumber1 Second message"); if (EventNumber1 != null) EventNumber1(dict); } public void CallEventNumber2() { if (EventNumber2 != null) EventNumber2("I am an EventNumber2 Message"); } } and wire that up with worker.EventNumber1 += new Worker.EventNumber1Handler(worker_EventNumber1); worker.EventNumber2 += new Worker.EventNumber2Handler(worker_EventNumber2); So I guess my question is do I always need to add the delegate along with the event in c#? Is there any new syntax for c# 3.0/4.0? Regards _Eric

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  • Large Product catalog with statistics - alternatives to Sql Server?

    - by Eric P
    I am building UI for a large product catalog (millions of products). I am using Sql Server, FreeText search and ASP.NET MVC. Tables are normalized and indexed. Most queries take less then a second to return. The issue is this. Let's say user does the search by keyword. On search results page I need to display/query for: First 20 matching products (paged, sorted) Total count of matching products for paging List of stores only of matching products List of brands only of matching products List of colors only of matching products Each query takes about .5 to 1 seconds. Altogether it is like 5 seconds. I would like to get the whole page to load under 1 second. There are several approaches: Optimize queries even more. I already spent a lot of time on this one, so not sure it can be pushed further. Load products first, then load the rest of the information using AJAX. More like a workaround. Will need to revise UI. Re-organize data to be more Report friendly. Already aggregated a lot of fields. I checked out several similar sites. For ex. zappos.com. Not only they display the same information as I would like in under 1 second, but they also include statistics (number of results in each category). The following is the search for keyword "white" http://www.zappos.com/white How do sites like zappos, amazon make their results, filters and stats appear almost instantly?

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  • Taking wrong database configuration array

    - by user309076
    Hi, I have one application in which i have used 2 database connections. In my database config file i have given two arrays as below. $active_group = ‘default’; $active_record = TRUE; FIRST ARRAY $db[‘default’][‘hostname’] = ‘hostname’; .............. .......... SECOND ARRAY $db[‘another_db’][‘hostname’] = ‘hostname’; .............. .......... this is working fine. Now, I copied the entire CI folder to develop another application in which only one database connection needed. So, now, in the database config file, i deleted the second configuration array. But, the db class is taking first application’s second array i.e. “another_db” and it is giving the below error. “You have specified an invalid database connection group.” When i change the default (only one) array name to “another_db” in configuration file. It is working fine. Can’t understand from where it is taking the group name as “another_db”. My application autoloads database library. I have debugged the ci_auto_loader in Loader.php class where it calls $this-database() function with no parameters. But in function database($params, $, $) {}, if I echo $params it shows “another_db”.

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  • How do I vertcally align thumbnails of unknown height using jQuery?

    - by playahabana
    Ok, I am a complete beginner to this, in fact I am still building my first website. I am attempting to do this all by hand-coding without a CMS in order to try and learn as much possible as quickly as possible. If this post is in the wrong place I apologise, and a pointer to right place would be appreciated. Here goes, I am trying to peice together a bit of jQuery that will automatically vertically align my thumbnails in my image gallery (they are all different sizes). They are within fixed size div's and the function I am attempting looks something like this: <script type="text/javascript"> $('#ul.photo).bind(function() { var smartVert=$(this); var phty=ob.("ul.photo img").height(); //get height of photos var phtdif=Math.floor(208 - phty); //subtract height of photo from div height var phttop=Math.floor(phtdif / 2); //gets padding reqd. $ob.("ul.photo").css({'padding-top' : phttop}) //sets padding to center thumbnail }); smartVert(); unsurprisingly this doesn't work, if some kindly soul could take pity on a total noob, and point out where I am going wrong (probably in writing complete gibberish would be my first guess) it would be greatly appreciated- even if you could just point me in the direcion of a tutorial regarding these things, I have looked and found one reference that said such a function was easy to create, but it did not elaborate. thankyou in advance

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  • issue with keychain and updates from app store

    - by xonegirlz
    I am having a very frustrating error. I have tested for an app upgrade by first installing the previous version (1.0.1) and then running version (1.0.2). Everything worked fine. I submitted the app and then I am getting issues people are getting crashes when they upgrade. I tried doing the same thing, which is installing the 1.0.1 and then install the binary on the app store, then it crashed. I looked at the console and crash logs and I get this: Jul 7 08:07:45 unknown MyApp[1429] <Warning>: KeychainUtils keychainValueForKey: - Error finding keychain value for key. Status code = -25300 Jul 7 08:07:45 unknown MyApp[1429] <Warning>: AccountSession readUserDataFromDisk - Error finding keychain value for key /var/mobile/Applications/997B32E7-6FFC-4696-9CAA-129BADE2FE64/Documents/instagram_json Jul 7 08:07:45 unknown MyApp[1429] <Warning>: UISegmentedControlStyleBezeled is deprecated. Please use a different style. Jul 7 08:07:45 unknown MyApp[1429] <Error>: *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFDictionary setObject:forKey:]: attempt to insert nil value (key: username)' *** First throw call stack: (0x33ee688f 0x367e7259 0x33ee6789 0x33ee67ab 0x33e5368b 0x14fd99 0x152319 0x1530bb 0x170299 0x3270ec59 0x32711817 0x354e7dfb 0x354e7cd0) Jul 7 08:07:45 unknown UIKitApplication:com.firesnakelabs.pinstagram[0x14e4][1429] <Notice>: terminate called throwing an exception >

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  • In Firefox, how do I bring an existing popup window with multiple tabs to the front using javascript

    - by brahn
    I would like to have a button on a web page with the following behavior: On the first click, open a pop-up. On later clicks, if the pop-up is still open, just bring it to the front. If not, re-open. The below code generally works in Firefox, Safari, and IE8 (see here for Chrome woes). However, I have found a failure mode in Firefox that I don't know how to deal with: If for some reason the user has opened a second tab in the pop-up window and that second tab has focus within that window, the popupWindow.focus() command fails to have any effect. (If the first tab has focus within that window, everything works just great.) So, how can I focus the popup and the desired tab in Firefox? <head> <script type="text/javascript"> var popupWindow = null; var doPopup = function () { if (popupWindow && !popupWindow.closed) { popupWindow.focus(); } else { popupWindow = window.open("http://google.com", "_blank", "width=200,height=200"); } }; </script> </head> <body> <button onclick="doPopup(); return false"> create a pop-up </button> </body>

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  • Subitems are not all added to a list view in C# using XmlNodeList

    - by tim
    I'm working on extracting data from an RSS feed. In my listview (rowNews), I've got two columns: Title and URL. When the button is clicked, all of the titles of the articles are showing up in the title column, but only one URL is added to the URL column. I switched them around so that the URLs would be added to the first column and all of the correct URLs appeared... leading me to think this is a problem with my listview source (it's my first time working with subitems). Here's the original, before I started experimenting with the order: private void button1_Click(object sender, EventArgs e) { XmlTextReader rssReader = new XmlTextReader(txtUrl.Text); XmlDocument rssDoc = new XmlDocument(); rssDoc.Load(rssReader); XmlNodeList titleList = rssDoc.GetElementsByTagName("title"); XmlNodeList urlList = rssDoc.GetElementsByTagName("link"); ListViewItem lvi = new ListViewItem(); for (int i = 0; i < titleList.Count; i++) { rowNews.Items.Add(titleList[i].InnerXml); } for (int i = 0; i < urlList.Count; i++) { lvi.SubItems.Add(urlList[i].InnerXml); } rowNews.Items.Add(lvi); }

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  • issue with tab bar view displaying a compound view

    - by ambertch
    I created a tab bar application, and I make the first tab a table. So I create a tableView controller, and go about setting the class identity of the view controller for the first tab to my tableView controller. This works fine, and I see the contents of the table filling up the whole screen. However, this is not what I actually want in the end goal - I would like a compound window having multiple views: - the aforementioned table - a custom view with data in it So what I do is create a nib for this content (call it contentNib), change the tab's class from the tableView controller to a generic UIViewController, and set the nib of that tab to this new contentNib. In this new contentNib I drag on a tableView and set File's Owner to the TableViewController. I then link the dataSource and delegate to file's owner (which is TableViewController). Surprisingly this does not work and I receive the error: **Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[UIViewController tableView:numberOfRowsInSection:]: unrecognized selector sent to instance 0x3b0f910'** This is bewildering to me since the file's owner is the TableViewController, which has been assigned to be both the dataSource and delegate. Does someone have either insight into my confusions, or a link to an example of how to have a compound view include a tableView? *update* I see this in the Apple TableView programming guide: "Note: You should use a UIViewController subclass rather than a subclass of UITableViewController to manage a table view if the view to be managed is composed of multiple subviews, one of which is a table view. The default behavior of the UITableViewController class is to make the table view fill the screen between the navigation bar and the tab bar (if either are present)." <----- I don't really get what this is telling me to do though... if someone can explain or point me to an example I'd be much appreciated!

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  • Holding variables in memory, C++

    - by b-gen-jack-o-neill
    Today something strange came to my mind. When I want to hold some string in C (C++) the old way, without using string header, I just create array and store that string into it. But, I read that any variable definition in C in local scope of function ends up in pushing these values onto the stack. So, the string is actually 2* bigger than needed. Because first, the push instructions are located in memory, but then when they are executed (pushed onto the stack) another "copy" of the string is created. First the push instructions, than the stack space is used for one string. So, why is it this way? Why doesn't compiler just add the string (or other variables) to the program instead of creating them once again when executed? Yes, I know you cannot just have some data inside program block, but it could just be attached to the end of the program, with some jump instruction before. And than, we would just point to these data? Because they are stored in RAM when the program is executed. Thanks.

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  • Preview of code-only WPF controls in VS2010 - how?

    - by Christian
    Hi, I hope I am able to illustrate the problem using a lot of images. First of all, I was no real fan of XAML (Silverlight issues, crashes in Preview, and so on...) Now, with VS2010 the situation has become better. There are still a lot of things I like better in code, but I also want a preview in my VS. So, take a look at the following control: It is really simple, a todo details list. The first screenshot shows the code of the control, pretty straighforward: There is no XAML, so obviously no preview. Of course, I could encapsulate it in another control, like shown in the next screenshot: But, in that case I have an additional file I do not want or need. So I had the idea to move the init stuff inside the contructor of a XAML control. For simplicity, I used simple elements. But they do not show up in the preview... Finally, I know I could use the controls in other parts of my app when creating UIs. But I am using layout manager, PRISM and a lot of other stuff, so I just want an easy preview of some specific control I created (without having to have a XAML wrapper file for each control) Thanks for help, and sorry for the post structure, but I though with images it is better to understand... Chris

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  • Is there an efficient algorithm to distribute resources in a way that both avoids conflict and allows bias?

    - by Steve V.
    Background (Skip this if you only care about the algorithm) At the university where I work, one of the biggest hassles in our department is classroom scheduling. For illustration purposes and to lay out the scope of the problem, here's how we do scheduling now: Professors give us a list of the classes they're teaching with the time slots they'd prefer to teach, ranked in order of priority (most desired to least desired). Administration gives us a list of the rooms we may assign along with the times those rooms are available for our department's use. We start assigning professors to rooms trying (at first) to take into account the preferences of the various professors. Inevitably, conflicts arise, professors start asking for changes, and the plan falls to pieces somewhere around professor number 30, at which point we start assigning rooms basically wherever we can fit them in, crumpled pieces of paper are everywhere, and nobody's happy. (If you've ever wondered why your class was at 9.30 in the morning on Thursday but 4 pm every other day, now you know) I have been asked to quietly investigate whether software could do this more optimally. The Actual Question Is there an algorithm to efficiently schedule a set of resources such that the following criteria are met: The algorithm must never assign two professors to the same room at the same time. The task is not complete until every professor has been assigned a room / time. The algorithm need not worry about having too many professors for the amount of time slots available. (We're not that well funded.) As much as is possible the algorithm should respect the scheduling preferences of the individual professors. I feel like I can't be the first one to ask this. Is there a efficient algorithm for this, or is this the sort of problem that can only be brute-forced?

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  • C++ and its type system: How to deal with data with multiple types?

    - by sub
    "Introduction" I'm relatively new to C++. I went through all the basic stuff and managed to build 2-3 simple interpreters for my programming languages. The first thing that gave and still gives me a headache: Implementing the type system of my language in C++ Think of that: Ruby, Python, PHP and Co. have a lot of built-in types which obviously are implemented in C. So what I first tried was to make it possible to give a value in my language three possible types: Int, String and Nil. I came up with this: enum ValueType { Int, String, Nil }; class Value { public: ValueType type; int intVal; string stringVal; }; Yeah, wow, I know. It was extremely slow to pass this class around as the string allocator had to be called all the time. Next time I've tried something similar to this: enum ValueType { Int, String, Nil }; extern string stringTable[255]; class Value { public: ValueType type; int index; }; I would store all strings in stringTable and write their position to index. If the type of Value was Int, I just stored the integer in index, it wouldn't make sense at all using an int index to access another int, or? Anyways, the above gave me a headache too. After some time, accessing the string from the table here, referencing it there and copying it over there grew over my head - I lost control. I had to put the interpreter draft down. Now: Okay, so C and C++ are statically typed. How do the main implementations of the languages mentioned above handle the different types in their programs (fixnums, bignums, nums, strings, arrays, resources,...)? What should I do to get maximum speed with many different available types? How do the solutions compare to my simplified versions above?

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