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• Broken corba object references

  - by cube

  I'm working on a homework and got stuck. The task is to serve objects using a default servant. But when I try to use the reference, weird things happen. Some part of corba prints a stack trace, but no exception is thrown. The problem happens when the server receives the reference and should call some method on it. The reference is then shortened and doesn't contain the object ID (which means that my servant implementation can't do anything reasonable). This is the implementation of the servant, where the problem appears: public class ModelFileImpl extends ModelFilePOA{ @Override public String getName() { try { return new String(_poa().reference_to_id(_this_object())); } catch (Throwable e) {} assert false; return null; } } If I take _this_object().toString() inside the try block and put it into dior -i i get this: ------IOR components----- TypeId : IDL:termproject/idl/ModelFile:1.0 TAG_INTERNET_IOP Profiles: Profile Id: 0 IIOP Version: 1.2 Host: 127.0.0.1 Port: 45954 Object key (URL): %AF%AB%CB%00%00%00%00%20Q%BA%F4%FF%00%00%00%01%00%00%00%00%00%00%00%01%0000%00%08RootPOA%00%00%00%00%08%00%00%00%02%00%00%00%00%14 Object key (hex): 0xAF AB CB 00 00 00 00 20 51 BA F4 FF 00 00 00 01 00 00 00 00 00 00 00 01 00 00 00 08 52 6F 6F 74 50 4F 41 00 00 00 00 08 00 00 00 02 00 00 00 00 14 -- Found 2 Tagged Components-- #0: TAG_CODE_SETS ForChar native code set Id: ISO8859_1 Char Conversion Code Sets: UTF8 , Unknown TCS: 10020 ForWChar native code set Id: UTF16 WChar Conversion Code Sets: Unknown TCS: 10100 Unknown tag : 38 however the part of server that makes the reference and the client see the reference as ------IOR components----- TypeId : IDL:termproject/idl/ModelFile:1.0 TAG_INTERNET_IOP Profiles: Profile Id: 0 IIOP Version: 1.2 Host: 127.0.0.1 Port: 45954 Object key (URL): %AF%AB%CB%00%00%00%00%20Q%BA%F4%FF%00%00%00%01%00%00%00%00%00%00%00%02%00%00%00%08RootPOA%00%00%00%00%09modelPoa%00%00%00%00%00%00%00%10testModel1.MyIDL%14 Object key (hex): 0xAF AB CB 00 00 00 00 20 51 BA F4 FF 00 00 00 01 00 00 00 00 00 00 00 02 00 00 00 08 52 6F 6F 74 50 4F 41 00 00 00 00 09 6D 6F 64 65 6C 50 6F 61 00 00 00 00 00 00 00 10 74 65 73 74 4D 6F 64 65 6C 31 2E 4D 79 49 44 4C 14 -- Found 2 Tagged Components-- #0: TAG_CODE_SETS ForChar native code set Id: ISO8859_1 Char Conversion Code Sets: UTF8 , Unknown TCS: 10020 ForWChar native code set Id: UTF16 WChar Conversion Code Sets: Unknown TCS: 10100 Unknown tag : 38 ("modelPoa" (the name of the poa working with default clients) and "testModel1.MyIDL" (the identifier of the object) in the object key are missing in the first one) I've tried sniffing the traffic and found out that the client still sends the correct reference. This is how i create the references: ret[i] = ModelFileHelper.narrow(modelFilePoa.create_reference_with_id(files[i].getBytes(), ModelFileHelper.id())); And this is how i set up the server: // init ORB ORB orb = ORB.init(args, null); // init POA POA poa = POAHelper.narrow(orb.resolve_initial_references("RootPOA")); // create the POA for the models. Policy[] policies = { poa.create_request_processing_policy(RequestProcessingPolicyValue.USE_DEFAULT_SERVANT), poa.create_servant_retention_policy(ServantRetentionPolicyValue.NON_RETAIN), poa.create_id_assignment_policy(IdAssignmentPolicyValue.USER_ID) }; POA modelPoa = poa.create_POA("modelPoa", poa.the_POAManager(), policies); modelPoa.the_POAManager().activate(); modelPoa.set_servant(new ModelFileImpl()); modelPoa.the_POAManager().activate(); ModelStoreImpl impl = new ModelStoreImpl(modelPoa); // create the object reference org.omg.CORBA.Object obj = poa.servant_to_reference(impl); // ... store the IOR file ... orb.run(); I'd be really grateful for any pointers (or references :-) )

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• Why might a System.String object not cache its hash code?

  - by Dan Tao

  A glance at the source code for string.GetHashCode using Reflector reveals the following (for mscorlib.dll version 4.0): public override unsafe int GetHashCode() { fixed (char* str = ((char*) this)) { char* chPtr = str; int num = 0x15051505; int num2 = num; int* numPtr = (int*) chPtr; for (int i = this.Length; i > 0; i -= 4) { num = (((num << 5) + num) + (num >> 0x1b)) ^ numPtr[0]; if (i <= 2) { break; } num2 = (((num2 << 5) + num2) + (num2 >> 0x1b)) ^ numPtr[1]; numPtr += 2; } return (num + (num2 * 0x5d588b65)); } } Now, I realize that the implementation of GetHashCode is not specified and is implementation-dependent, so the question "is GetHashCode implemented in the form of X or Y?" is not really answerable. I'm just curious about a few things: If Reflector has disassembled the DLL correctly and this is the implementation of GetHashCode (in my environment), am I correct in interpreting this code to indicate that a string object, based on this particular implementation, would not cache its hash code? Assuming the answer is yes, why would this be? It seems to me that the memory cost would be minimal (one more 32-bit integer, a drop in the pond compared to the size of the string itself) whereas the savings would be significant, especially in cases where, e.g., strings are used as keys in a hashtable-based collection like a Dictionary<string, [...]>. And since the string class is immutable, it isn't like the value returned by GetHashCode will ever even change. What could I be missing? UPDATE: In response to Andras Zoltan's closing remark: There's also the point made in Tim's answer(+1 there). If he's right, and I think he is, then there's no guarantee that a string is actually immutable after construction, therefore to cache the result would be wrong. Whoa, whoa there! This is an interesting point to make (and yes it's very true), but I really doubt that this was taken into consideration in the implementation of GetHashCode. The statement "therefore to cache the result would be wrong" implies to me that the framework's attitude regarding strings is "Well, they're supposed to be immutable, but really if developers want to get sneaky they're mutable so we'll treat them as such." This is definitely not how the framework views strings. It fully relies on their immutability in so many ways (interning of string literals, assignment of all zero-length strings to string.Empty, etc.) that, basically, if you mutate a string, you're writing code whose behavior is entirely undefined and unpredictable. I guess my point is that for the author(s) of this implementation to worry, "What if this string instance is modified between calls, even though the class as it is publicly exposed is immutable?" would be like for someone planning a casual outdoor BBQ to think to him-/herself, "What if someone brings an atomic bomb to the party?" Look, if someone brings an atom bomb, party's over.

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• HttpClient multithread performance

  - by pepper

  I have an application which downloads more than 4500 html pages from 62 target hosts using HttpClient (4.1.3 or 4.2-beta). It runs on Windows 7 64-bit. Processor - Core i7 2600K. Network bandwidth - 54 Mb/s. At this moment it uses such parameters: DefaultHttpClient and PoolingClientConnectionManager; Also it hasIdleConnectionMonitorThread from http://hc.apache.org/httpcomponents-client-ga/tutorial/html/connmgmt.html; Maximum total connections = 80; Default maximum connections per route = 5; For thread management it uses ForkJoinPool with the parallelism level = 5 (Do I understand correctly that it is a number of working threads?) In this case my network usage (in Windows task manager) does not rise above 2.5%. To download 4500 pages it takes 70 minutes. And in HttpClient logs I have such things: DEBUG ForkJoinPool-2-worker-1 [org.apache.http.impl.conn.PoolingClientConnectionManager]: Connection released: [id: 209][route: {}-http://stackoverflow.com][total kept alive: 6; route allocated: 1 of 5; total allocated: 10 of 80] Total allocated connections do not raise above 10-12, in spite of that I've set it up to 80 connections. If I'll try to rise parallelism level to 20 or 80, network usage remains the same but a lot connection time-outs will be generated. I've read tutorials on hc.apache.org (HttpClient Performance Optimization Guide and HttpClient Threading Guide) but they does not help. Task's code looks like this: public class ContentDownloader extends RecursiveAction { private final HttpClient httpClient; private final HttpContext context; private List<Entry> entries; public ContentDownloader(HttpClient httpClient, List<Entry> entries){ this.httpClient = httpClient; context = new BasicHttpContext(); this.entries = entries; } private void computeDirectly(Entry entry){ final HttpGet get = new HttpGet(entry.getLink()); try { HttpResponse response = httpClient.execute(get, context); int statusCode = response.getStatusLine().getStatusCode(); if ( (statusCode >= 400) && (statusCode <= 600) ) { logger.error("Couldn't get content from " + get.getURI().toString() + "\n" + response.toString()); } else { HttpEntity entity = response.getEntity(); if (entity != null) { String htmlContent = EntityUtils.toString(entity).trim(); entry.setHtml(htmlContent); EntityUtils.consumeQuietly(entity); } } } catch (Exception e) { } finally { get.releaseConnection(); } } @Override protected void compute() { if (entries.size() <= 1){ computeDirectly(entries.get(0)); return; } int split = entries.size() / 2; invokeAll(new ContentDownloader(httpClient, entries.subList(0, split)), new ContentDownloader(httpClient, entries.subList(split, entries.size()))); } } And the question is - what is the best practice to use multi threaded HttpClient, may be there is a some rules for setting up ConnectionManager and HttpClient? How can I use all of 80 connections and raise network usage? If necessary, I will provide more code.

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• Editing a Gridview row with drop-down lists gets too wide - how can I use popup panels instead?

  - by David

  I have a series of GridViews in a Tab Panel - databound to a generic List of Business Objects. The columns in the Gridview are all similar to the following: <asp:TemplateField HeaderText="Company" SortExpression="Company.ShortName"> <ItemTemplate> <asp:Label ID="lblCompany" runat="server" Text='<%# Bind("Company.ShortName") %>'></asp:Label> </ItemTemplate> <EditItemTemplate> <asp:DropDownList ID="ddlCompany" runat="server"></asp:DropDownList> </EditItemTemplate> </asp:TemplateField> The GridView generates the "Edit" link at the beginning of the row, all the events fire ok. The problem is that the data is getting long. When in 'display mode', it's fine because the GridView control is smart enough to break some text into multiple lines (in particular Project, Title and Worker names can get pretty long). The problem come in editing mode. Drop-down lists DON'T break entries into multiple lines (for obvious reasons). Going into Edit ode on a row in the Gridview can make the Griview expand horizontally to twice the screen size (blowing through the width limits in the Master page and CSS but that's only a related problem). What I need is something like the ModalPopup - but trying to tie it to an ID in an EditItemTemplate gives me errors when the page renders (because the 'ddlXXXX' doesn't exist at the time). In addition I don't know how to dynamically populate the panel so that I can get a response from it (like the ID of the Company they selected). I'm also trying to avoid javascript and would like this to be a 'pure' aspx/code-behind solution (for simplicity's sake among others). All the examples I find are of Modal Popups with the panels pre-defined. Even if it (the popup panel) were something like a list of checkboxes, it could be databound to the SortedList I have ready to go and an OK/Cancel button combination to accept or ignore things. I'm just not sure of what goes where. I'm open to suggestions. Thanks in advance. EDIT: Final solution looks as follows: <asp:TemplateField HeaderText="Company" SortExpression="Company.ShortName"> <ItemTemplate> <asp:Label ID="lblCompany" runat="server" Text='<%# Bind("Company.ShortName") %>'></asp:Label> </ItemTemplate> <EditItemTemplate> <asp:LinkButton ID="lnkCompany" runat="server" Text='<%# Bind("Company.ShortName") %>'></asp:LinkButton> <asp:Panel ID="pnlCompany" runat="server" style="display:none"> <div> <asp:DropDownList ID="ddlCompany" runat="server" ></asp:DropDownList> <br/> <asp:ImageButton ID="btnOKCo" runat="server" ImageUrl="~/Images/greencheck.gif" OnCommand="PopupButton_Command" CommandName="SelectCO" /> <asp:ImageButton ID="btnCxlCo" runat="server" ImageUrl="~/Images/RedX.gif" /> </div> </asp:Panel> <cc1:ModalPopupExtender ID="mpeCompany" runat="server" TargetControlID="lnkCompany" PopupControlID="pnlCompany" BackgroundCssClass="modalBackground" CancelControlID="btnCxlCo" DropShadow="true" PopupDragHandleControlID="pnlCompany" /> </EditItemTemplate> </asp:TemplateField> And in the code-behind, lstIDLabor is the generic List of data lines (of which Company is one of the properties that is also a business object) that is bound to the GridView: Sub PopupButton_Command(ByVal sender As Object, ByVal e As CommandEventArgs) Dim intRow As Integer Dim intVal As Integer RestoreFromSessionVariables() Select Case e.CommandName Case "SelectCO" intRow = grdIDCostLabor.EditIndex Dim ddlCo As DropDownList = CType(grdIDCost.Rows(intRow).FindControl("ddlCompany"), DropDownList) intVal = ddlCo.SelectedValue lstIDLabor(intRow).CompanyID = intVal lstIDLabor(intRow).Company = Company.Read(intVal) Case Else ' End Select MakeSessionVariables() BindGrids() End Sub

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• What does the `forall` keyword in Haskell/GHC do?

  - by JUST MY correct OPINION

  I've been banging my head on this one for (quite literally) years now. I'm beginning to kinda/sorta understand how the foreach keyword is used in so-called "existential types" like this: data ShowBox = forall s. Show s => SB s (This despite the confusingly-worded explanations of it in the fragments found all around the web.) This is only a subset, however, of how foreach is used and I simply cannot wrap my mind around its use in things like this: runST :: forall a. (forall s. ST s a) -> a Or explaining why these are different: foo :: (forall a. a -> a) -> (Char,Bool) bar :: forall a. ((a -> a) -> (Char, Bool)) Or the whole RankNTypes stuff that breaks my brain when "explained" in a way that makes me want to do that Samuel L. Jackson thing from Pulp Fiction. (Don't follow that link if you're easily offended by strong language.) The problem, really, is that I'm a dullard. I can't fathom the chicken scratchings (some call them "formulae") of the elite mathematicians that created this language seeing as my university years are over two decades behind me and I never actually had to put what I learnt into use in practice. I also tend to prefer clear, jargon-free English rather than the kinds of language which are normal in academic environments. Most of the explanations I attempt to read on this (the ones I can find through search engines) have these problems: They're incomplete. They explain one part of the use of this keyword (like "existential types") which makes me feel happy until I read code that uses it in a completely different way (like runST, foo and bar above). They're densely packed with assumptions that I've read the latest in whatever branch of discrete math, category theory or abstract algebra is popular this week. (If I never read the words "consult the paper whatever for details of implementation" again, it will be too soon.) They're written in ways that frequently turn even simple concepts into tortuously twisted and fractured grammar and semantics. (I suspect that the last two items are the biggest problem. I wouldn't know, though, since I'm too much a dullard to comprehend them.) It's been asked why Haskell never really caught on in industry. I suspect, in my own humble, unintelligent way, that my experience in figuring out one stupid little keyword -- a keyword that is increasingly ubiquitous in the libraries being written these days -- are also part of the answer to that question. It's hard for a language to catch on when even its individual keywords cause years-long quests to comprehend. Years-long quests which end in failure. So... On to the actual question. Can anybody completely explain the foreach keyword in clear, plain English (or, if it exists somewhere, point to such a clear explanation which I've missed) that doesn't assume I'm a mathematician steeped in the jargon?

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• Opinions on Dual-Salt authentication for low sensitivity user accounts?

  - by Heleon

  EDIT - Might be useful for someone in the future... Looking around the bcrypt class in php a little more, I think I understand what's going on, and why bcrypt is secure. In essence, I create a random blowfish salt, which contains the number of crypt rounds to perform during the encryption step, which is then hashed using the crypt() function in php. There is no need for me to store the salt I used in the database, because it's not directly needed to decrypt, and the only way to gain a password match to an email address (without knowing the salt values or number of rounds) would be to brute force plain text passwords against the hash stored in the database using the crypt() function to verify, which, if you've got a strong password, would just be more effort than it's worth for the user information i'm storing... I am currently working on a web project requiring user accounts. The application is CodeIgniter on the server side, so I am using Ion Auth as the authentication library. I have written an authentication system before, where I used 2 salts to secure the passwords. One was a server-wide salt which sat as an environment variable in the .htaccess file, and the other was a randomly generated salt which was created at user signup. This was the method I used in that authentication system for hashing the password: $chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"; //create a random string to be used as the random salt for the password hash $size = strlen($chars); for($i = 0; $i < 22; $i++) { $str .= $chars[rand(0, $size - 1)]; } //create the random salt to be used for the crypt $r_blowfish_salt = "$2a$12$" . $str . "$"; //grab the website salt $salt = getenv('WEBSITE_SALT'); //combine the website salt, and the password $password_to_hash = $pwd . $salt; //crypt the password string using blowfish $password = crypt($password_to_hash, $r_blowfish_salt); I have no idea whether this has holes in it or not, but regardless, I moved over to Ion Auth for a more complete set of functions to use with CI. I noticed that Ion only uses a single salt as part of its hashing mechanism (although does recommend that encryption_key is set in order to secure the database session.) The information that will be stored in my database is things like name, email address, location by country, some notes (which will be recommended that they do not contain sensitive information), and a link to a Facebook, Twitter or Flickr account. Based on this, i'm not convinced it's necessary for me to have an SSL connection on the secure pages of my site. My question is, is there a particular reason why only 1 salt is being used as part as the Ion Auth library? Is it implied that I write my own additional salting in front of the functionality it provides, or am I missing something? Furthermore, is it even worth using 2 salts, or once an attacker has the random salt and the hashed password, are all bets off anyway? (I assume not, but worth checking if i'm worrying about nothing...)

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• PHP returning part of the code document

  - by The.Anti.9

  I have a PHP page that does a couple of different things depending on what action is set to in the GET data. Depending, it is supposed to return some JSON, but instead of doing anything it is supposed to it returns the bottom half of the code document itself, starting in the middle of the line. Heres the snippit from where it starts: ... } elseif ($_GET['action'] == 'addtop') { if (!isset($_GET['pname']) || !isset($_GET['url']) || !isset($_GET['artist']) || !isset($_GET['album']) || !isset($_GET['file'])) { die('Error: Incomplete data!'); } if (!file_exists($_GET['pname'].".txt")) { die('Error: No such playlist!'); } $plist = json_decode(file_get_contents($_GET['pname'].".txt"), true); $fh = fopen($_GET['pname'].".txt", 'w') or die('Could not open playlist!'); array_push($plist, array("artist" => $_GET['artist'], "album" => $_GET['album'], "file" => $_GET['file'], "url" => $_GET['url'])); fwrite($fh,json_encode($plist)); } elseif ($_GET['action'] == 'delfromp') { ... And here is what I get when I go to the page: $_GET['artist'], "album" = $_GET['album'], "file" = $_GET['file'], "url" = $_GET['url'])); fwrite($fh,json_encode($plist)); } elseif ($_GET['action'] == 'delfromp') { if (!isset($_GET['pname']) || !isset($_GET['id'])) { die('Error: Incomplete data!'); } if (!file_exists($_GET['pname'].".txt")) { die('Error: No such playlist!'); } $plist = json_decode(file_get_contents($_GET['pname'].".txt"), true); $fh = fopen($_GET['pname'].".txt", 'w') or die('Could not open playlist!'); unset($plist[$_GET['id']]); $plist = array_values($plist); fwrite($fh,json_encode($plist)); } elseif ($_GET['action'] == 'readp') { if (!file_exists($_GET['pname'].".txt")) { die('Error: No such playlist!'); } $plist = json_decode(file_get_contents($_GET['pname'].".txt"), true); $arr = array("entries" = $plist); $json = json_encode($arr); echo $json; } elseif ($_GET['action'] == 'getps') { $plists = array(); if ($handle = opendir('Playlists')) { while (false !== ($playlist = readdir($handle))) { if ($playlist != "." && $playlist != "..") { array_push($plists, substr($playlist, 0, strripos($playlist, '.')-1)); } } } else { die('Error: Can\'T open playlists!'); } $arr = array("entries"=$plists); $json = json_encode($arr); echo $json; } else { die('Error: No such action!'); } ? It starts in the middle of the array_push(... line. I really can't think of what it is doing. Theres no echos anywhere around it. Any ideas?

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• evaluating cost/benefits of using extension methods in C# => 3.0

  - by BillW

  Hi, In what circumstances (usage scenarios) would you choose to write an extension rather than sub-classing an object ? < full disclosure : I am not an MS employee; I do not know Mitsu Furota personally; I do know the author of the open-source Componax library mentioned here, but I have no business dealings with him whatsoever; I am not creating, or planning to create any commercial product using extensions : in sum : this post is from pure intellectal curiousity related to my trying to (continually) become aware of "best practices" I find the idea of extension methods "cool," and obviously you can do "far-out" things with them as in the many examples you can in Mitsu Furota's (MS) blog postslink text. A personal friend wrote the open-source Componax librarylink text, and there's some remarkable facilities in there; but he is in complete command of his small company with total control over code guidelines, and every line of code "passes through his hands." While this is speculation on my part : I think/guess other issues might come into play in a medium-to-large software team situation re use of Extensions. Looking at MS's guidelines at link text, you find : In general, you will probably be calling extension methods far more often than implementing your own. ... In general, we recommend that you implement extension methods sparingly and only when you have to. Whenever possible, client code that must extend an existing type should do so by creating a new type derived from the existing type. For more information, see Inheritance (C# Programming Guide). ... When the compiler encounters a method invocation, it first looks for a match in the type's instance methods. If no match is found, it will search for any extension methods that are defined for the type, and bind to the first extension method that it finds. And at Ms's link text : Extension methods present no specific security vulnerabilities. They can never be used to impersonate existing methods on a type, because all name collisions are resolved in favor of the instance or static method defined by the type itself. Extension methods cannot access any private data in the extended class. Factors that seem obvious to me would include : I assume you would not write an extension unless you expected it be used very generally and very frequently. On the other hand : couldn't you say the same thing about sub-classing ? Knowing we can compile them into a seperate dll, and add the compiled dll, and reference it, and then use the extensions : is "cool," but does that "balance out" the cost inherent in the compiler first having to check to see if instance methods are defined as described above. Or the cost, in case of a "name clash," of using the Static invocation methods to make sure your extension is invoked rather than the instance definition ? How frequent use of Extensions would affect run-time performance or memory use : I have no idea. So, I'd appreciate your thoughts, or knowing about how/when you do, or don't do, use Extensions, compared to sub-classing. thanks, Bill

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• Why doesn't my QsciLexerCustom subclass work in PyQt4 using QsciScintilla?

  - by Jon Watte

  My end goal is to get Erlang syntax highlighting in QsciScintilla using PyQt4 and Python 2.6. I'm running on Windows 7, but will also need Ubuntu support. PyQt4 is missing the necessary wrapper code for the Erlang lexer/highlighter that "base" scintilla has, so I figured I'd write a lightweight one on top of QsciLexerCustom. It's a little bit problematic, because the Qsci wrapper seems to really want to talk about line+index rather than offset-from-start when getting/setting subranges of text. Meanwhile, the lexer gets arguments as offset-from-start. For now, I get a copy of the entire text, and split that up as appropriate. I have the following lexer, and I apply it with setLexer(). It gets all the appropriate calls when I open a new file and sets this as the lexer, and prints a bunch of appropriate lines based on what it's doing... but there is no styling in the document. I tried making all the defined styles red, and the document is still stubbornly black-on-white, so apparently the styles don't really "take effect" What am I doing wrong? If nobody here knows, what's the appropriate discussion forum where people might actually know these things? (It's an interesting intersection between Python, Qt and Scintilla, so I imagine the set of people who would know is small) Let's assume prefs.declare() just sets up a dict that returns the value for the given key (I've verified this -- it's not the problem). Let's assume scintilla is reasonably properly constructed into its host window QWidget. Specifically, if I apply a bundled lexer (such as QsciLexerPython), it takes effect and does show styled text. prefs.declare('font.name.margin', "MS Dlg") prefs.declare('font.size.margin', 8) prefs.declare('font.name.code', "Courier New") prefs.declare('font.size.code', 10) prefs.declare('color.editline', "#d0e0ff") class LexerErlang(Qsci.QsciLexerCustom): def __init__(self, obj = None): Qsci.QsciLexerCustom.__init__(self, obj) self.sci = None self.plainFont = QtGui.QFont() self.plainFont.setPointSize(int(prefs.get('font.size.code'))) self.plainFont.setFamily(prefs.get('font.name.code')) self.marginFont = QtGui.QFont() self.marginFont.setPointSize(int(prefs.get('font.size.code'))) self.marginFont.setFamily(prefs.get('font.name.margin')) self.boldFont = QtGui.QFont() self.boldFont.setPointSize(int(prefs.get('font.size.code'))) self.boldFont.setFamily(prefs.get('font.name.code')) self.boldFont.setBold(True) self.styles = [ Qsci.QsciStyle(0, QtCore.QString("base"), QtGui.QColor("#000000"), QtGui.QColor("#ffffff"), self.plainFont, True), Qsci.QsciStyle(1, QtCore.QString("comment"), QtGui.QColor("#008000"), QtGui.QColor("#eeffee"), self.marginFont, True), Qsci.QsciStyle(2, QtCore.QString("keyword"), QtGui.QColor("#000080"), QtGui.QColor("#ffffff"), self.boldFont, True), Qsci.QsciStyle(3, QtCore.QString("string"), QtGui.QColor("#800000"), QtGui.QColor("#ffffff"), self.marginFont, True), Qsci.QsciStyle(4, QtCore.QString("atom"), QtGui.QColor("#008080"), QtGui.QColor("#ffffff"), self.plainFont, True), Qsci.QsciStyle(5, QtCore.QString("macro"), QtGui.QColor("#808000"), QtGui.QColor("#ffffff"), self.boldFont, True), Qsci.QsciStyle(6, QtCore.QString("error"), QtGui.QColor("#000000"), QtGui.QColor("#ffd0d0"), self.plainFont, True), ] print("LexerErlang created") def description(self, ix): for i in self.styles: if i.style() == ix: return QtCore.QString(i.description()) return QtCore.QString("") def setEditor(self, sci): self.sci = sci Qsci.QsciLexerCustom.setEditor(self, sci) print("LexerErlang.setEditor()") def styleText(self, start, end): print("LexerErlang.styleText(%d,%d)" % (start, end)) lines = self.getText(start, end) offset = start self.startStyling(offset, 0) print("startStyling()") for i in lines: if i == "": self.setStyling(1, self.styles[0]) print("setStyling(1)") offset += 1 continue if i[0] == '%': self.setStyling(len(i)+1, self.styles[1]) print("setStyling(%)") offset += len(i)+1 continue self.setStyling(len(i)+1, self.styles[0]) print("setStyling(n)") offset += len(i)+1 def getText(self, start, end): data = self.sci.text() print("LexerErlang.getText(): " + str(len(data)) + " chars") return data[start:end].split('\n') Applied to the QsciScintilla widget as follows: _lexers = { 'erl': (Q.SCLEX_ERLANG, LexerErlang), 'hrl': (Q.SCLEX_ERLANG, LexerErlang), 'html': (Q.SCLEX_HTML, Qsci.QsciLexerHTML), 'css': (Q.SCLEX_CSS, Qsci.QsciLexerCSS), 'py': (Q.SCLEX_PYTHON, Qsci.QsciLexerPython), 'php': (Q.SCLEX_PHP, Qsci.QsciLexerHTML), 'inc': (Q.SCLEX_PHP, Qsci.QsciLexerHTML), 'js': (Q.SCLEX_CPP, Qsci.QsciLexerJavaScript), 'cpp': (Q.SCLEX_CPP, Qsci.QsciLexerCPP), 'h': (Q.SCLEX_CPP, Qsci.QsciLexerCPP), 'cxx': (Q.SCLEX_CPP, Qsci.QsciLexerCPP), 'hpp': (Q.SCLEX_CPP, Qsci.QsciLexerCPP), 'c': (Q.SCLEX_CPP, Qsci.QsciLexerCPP), 'hxx': (Q.SCLEX_CPP, Qsci.QsciLexerCPP), 'tpl': (Q.SCLEX_CPP, Qsci.QsciLexerCPP), 'xml': (Q.SCLEX_XML, Qsci.QsciLexerXML), } ... inside my document window class ... def addContentsDocument(self, contents, title): handler = self.makeScintilla() handler.title = title sci = handler.sci sci.append(contents) self.tabWidget.addTab(sci, title) self.tabWidget.setCurrentWidget(sci) self.applyLexer(sci, title) EventBus.bus.broadcast('command.done', {'text': 'Opened ' + title}) return handler def applyLexer(self, sci, title): (language, lexer) = language_and_lexer_from_title(title) if lexer: l = lexer() print("making lexer: " + str(l)) sci.setLexer(l) else: print("setting lexer by id: " + str(language)) sci.SendScintilla(Qsci.QsciScintillaBase.SCI_SETLEXER, language) linst = sci.lexer() print("lexer: " + str(linst)) def makeScintilla(self): sci = Qsci.QsciScintilla() sci.setUtf8(True) sci.setTabIndents(True) sci.setIndentationsUseTabs(False) sci.setIndentationWidth(4) sci.setMarginsFont(self.smallFont) sci.setMarginWidth(0, self.smallFontMetrics.width('00000')) sci.setFont(self.monoFont) sci.setAutoIndent(True) sci.setBraceMatching(Qsci.QsciScintilla.StrictBraceMatch) handler = SciHandler(sci) self.handlers[sci] = handler sci.setMarginLineNumbers(0, True) sci.setCaretLineVisible(True) sci.setCaretLineBackgroundColor(QtGui.QColor(prefs.get('color.editline'))) return handler Let's assume the rest of the application works, too (because it does :-)

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• Isn't it better to use a single try catch instead of tons of TryParsing and other error handling sometimes?

  - by Ryan Peschel

  I know people say it's bad to use exceptions for flow control and to only use exceptions for exceptional situations, but sometimes isn't it just cleaner and more elegant to wrap the entire block in a try-catch? For example, let's say I have a dialog window with a TextBox where the user can type input in to be parsed in a key-value sort of manner. This situation is not as contrived as you might think because I've inherited code that has to handle this exact situation (albeit not with farm animals). Consider this wall of code: class Animals { public int catA, catB; public float dogA, dogB; public int mouseA, mouseB, mouseC; public double cow; } class Program { static void Main(string[] args) { string input = "Sets all the farm animals CAT 3 5 DOG 21.3 5.23 MOUSE 1 0 1 COW 12.25"; string[] splitInput = input.Split(' '); string[] animals = { "CAT", "DOG", "MOUSE", "COW", "CHICKEN", "GOOSE", "HEN", "BUNNY" }; Animals animal = new Animals(); for (int i = 0; i < splitInput.Length; i++) { string token = splitInput[i]; if (animals.Contains(token)) { switch (token) { case "CAT": animal.catA = int.Parse(splitInput[i + 1]); animal.catB = int.Parse(splitInput[i + 2]); break; case "DOG": animal.dogA = float.Parse(splitInput[i + 1]); animal.dogB = float.Parse(splitInput[i + 2]); break; case "MOUSE": animal.mouseA = int.Parse(splitInput[i + 1]); animal.mouseB = int.Parse(splitInput[i + 2]); animal.mouseC = int.Parse(splitInput[i + 3]); break; case "COW": animal.cow = double.Parse(splitInput[i + 1]); break; } } } } } In actuality there are a lot more farm animals and more handling than that. A lot of things can go wrong though. The user could enter in the wrong number of parameters. The user can enter the input in an incorrect format. The user could specify numbers too large or too small for the data type to handle. All these different errors could be handled without exceptions through the use of TryParse, checking how many parameters the user tried to use for a specific animal, checking if the parameter is too large or too small for the data type (because TryParse just returns 0), but every one should result in the same thing: A MessageBox appearing telling the user that the inputted data is invalid and to fix it. My boss doesn't want different message boxes for different errors. So instead of doing all that, why not just wrap the block in a try-catch and in the catch statement just display that error message box and let the user try again? Maybe this isn't the best example but think of any other scenario where there would otherwise be tons of error handling that could be substituted for a single try-catch. Is that not the better solution?

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• Need to hide displayed div when I show others

  - by adrian collins

  I am stuck. I have a page with 3 buttons, the 3 buttons do a couple things - they change the style of a div, and they also show/hide a content div. The changing of the div style works fine, but I am having issues with the content div. If you land on the page and click the "Our Brands" tab, then click the other 2 tabs, it works fine. If you land on the page, and click "What's New" or "About Us" first, then the show/hide does not work correctly - it does not until you actually click on "Our Brands." http://www.adriancollins.net/clients/kennys/ Any help would be appreciated, I am a designer first, a developer about 9000th. Show/Hide Code <script type="text/javascript"> var _hidediv = null; function showdiv(id) { if(_hidediv) _hidediv(); var div = document.getElementById(id); div.style.display = 'block'; _hidediv = function () { div.style.display = 'none'; }; } </script> Tab Divs <div id="brand_button"><a href="#" onClick="showdiv('brands_content'); lower.className='blue';angle.className='blue_angle';return false"><img src="wp-content/uploads/2012/10/brands_button.png"></a></div> <div id="whatsnew_button"><a href="#" onClick="showdiv('new_content');lower.className='black';angle.className='black_angle';return false"><img src="wp-content/uploads/2012/10/whatsnew_button.png"></a></div> <div id="about_button"><a href="#" onClick="showdiv('about_content');lower.className='green';angle.className='green_angle';return false"><img src="wp-content/uploads/2012/10/about_button.png"></a></div> Content Divs <div id="brands_content">Content...</div> <div id="whats_content">Content...</div> <div id="about_content">Content...</div> CSS #brands_content { position: relative; display: block; width: 990px; top: 10px; height: auto; min-height: 800px; margin-left: auto; margin-top: 0px; margin-right: auto; border: 0px; padding: 0px 0px 0px 0px; z-index: 12; } #new_content { position: relative; display: none; width: 990px; top: 10px; height: auto; min-height: 800px; margin-left: auto; margin-top: 0px; margin-right: auto; border: 0px; padding: 0px 0px 0px 0px; z-index: 999; color: #fff; } #about_content { position: relative; display: none; width: 990px; top: 10px; height: auto; min-height: 800px; margin-left: auto; margin-top: 0px; margin-right: auto; border: 0px; padding: 0px 0px 0px 0px; z-index: 999; } Thanks

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• Languages and VMs: Features that are hard to optimize and why

  - by mrjoltcola

  I'm doing a survey of features in preparation for a research project. Name a mainstream language or language feature that is hard to optimize, and why the feature is or isn't worth the price paid, or instead, just debunk my theories below with anecdotal evidence. Before anyone flags this as subjective, I am asking for specific examples of languages or features, and ideas for optimization of these features, or important features that I haven't considered. Also, any references to implementations that prove my theories right or wrong. Top on my list of hard to optimize features and my theories (some of my theories are untested and are based on thought experiments): 1) Runtime method overloading (aka multi-method dispatch or signature based dispatch). Is it hard to optimize when combined with features that allow runtime recompilation or method addition. Or is it just hard, anyway? Call site caching is a common optimization for many runtime systems, but multi-methods add additional complexity as well as making it less practical to inline methods. 2) Type morphing / variants (aka value based typing as opposed to variable based) Traditional optimizations simply cannot be applied when you don't know if the type of someting can change in a basic block. Combined with multi-methods, inlining must be done carefully if at all, and probably only for a given threshold of size of the callee. ie. it is easy to consider inlining simple property fetches (getters / setters) but inlining complex methods may result in code bloat. The other issue is I cannot just assign a variant to a register and JIT it to the native instructions because I have to carry around the type info, or every variable needs 2 registers instead of 1. On IA-32 this is inconvenient, even if improved with x64's extra registers. This is probably my favorite feature of dynamic languages, as it simplifies so many things from the programmer's perspective. 3) First class continuations - There are multiple ways to implement them, and I have done so in both of the most common approaches, one being stack copying and the other as implementing the runtime to use continuation passing style, cactus stacks, copy-on-write stack frames, and garbage collection. First class continuations have resource management issues, ie. we must save everything, in case the continuation is resumed, and I'm not aware if any languages support leaving a continuation with "intent" (ie. "I am not coming back here, so you may discard this copy of the world"). Having programmed in the threading model and the contination model, I know both can accomplish the same thing, but continuations' elegance imposes considerable complexity on the runtime and also may affect cache efficienty (locality of stack changes more with use of continuations and co-routines). The other issue is they just don't map to hardware. Optimizing continuations is optimizing for the less-common case, and as we know, the common case should be fast, and the less-common cases should be correct. 4) Pointer arithmetic and ability to mask pointers (storing in integers, etc.) Had to throw this in, but I could actually live without this quite easily. My feelings are that many of the high-level features, particularly in dynamic languages just don't map to hardware. Microprocessor implementations have billions of dollars of research behind the optimizations on the chip, yet the choice of language feature(s) may marginalize many of these features (features like caching, aliasing top of stack to register, instruction parallelism, return address buffers, loop buffers and branch prediction). Macro-applications of micro-features don't necessarily pan out like some developers like to think, and implementing many languages in a VM ends up mapping native ops into function calls (ie. the more dynamic a language is the more we must lookup/cache at runtime, nothing can be assumed, so our instruction mix is made up of a higher percentage of non-local branching than traditional, statically compiled code) and the only thing we can really JIT well is expression evaluation of non-dynamic types and operations on constant or immediate types. It is my gut feeling that bytecode virtual machines and JIT cores are perhaps not always justified for certain languages because of this. I welcome your answers.

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• How to notify client about updated UpdatePanel content on server side

  - by csh1981

  I have a problem with UpdatePanel.Update() which works initially but then stops. I have tumbled with this problem for some time and some background is needed so please read ahead. I have an ASP.net application in which I have a subpage that display computed information in graphs. Each graph is embedded in an UpdatePanel. The graph is a user control that uses the standard asp:Chart for display. My task is to enable this page with AJAX capabilities so the page is responsive during postbacks. When I access this page from another page, during the initial page rendering, I use a wait dialog for each graph and a pageload event on the client side. In the client event, a hidden button is clicked which a server event handles (the hidden button is inside an UpdatePanel so the postback is asynchronous). Each graph is computed and the UpdatePanels are in turn updated with the Chart content. This is done using UpdatePanel.Update. And it is successful. However, I also have some RadioButtons on the page. These are dynamically created. The purpose of them is to switch graph type --- to show the same data in a different way. Same type of time consuming computation is needed in order to do so. I subscribe on each RadioButton's OnCheckedChanged event and the postback is asynchronous since the radiobuttons are inside an UpdatePanel. In the server event handler I determine the type of graph and use this as an input to the Chart control. I then remove the old Chart control from my Panel and adds new Chart and then I call UpdatePanel.Update(). But with no success. Nothing happens, no errors, nothing. Why is this?? I think this is strange because if I compute every Chart data in the initial rendering instead of using the "Wait dialog"-solution described earlier then I can select graph types successfully and all subsequent AJAX requests work as intended. Also, the same code (computing the chart, removal, and adding the Chart control to Panel and UpdatePanel.Update()) is hit during the initial rendering of the page, and it works only the first time. Here is the method that computes the graph and adds it to the panel and update the UpdatePanel: public void UpdateGraph(GraphType type, GraphMapper mapper) { //Panel is the content of UpdatePanelGraph's Panel.Controls.Clear(); chart = new Chart(type, mapper); //Computation happens inside here panel.Controls.Add(chart); //UpdatePanelGraph is in UpdateMode Conditional and has //ChildrenAsTriggers set to false UpdatePanelGraph.Update(); } I really need a way for these radiobuttons to work, possible using some clientside JavaScript or another way of handling things on the server side. I have thought about using a JavaScript postback call on the UpdatePanel instead of the UpdatePanel.Update(). However, the issue I have here is how to notify the client side when the server side is finished with computing the graph? An plausible explanation of the strange behavior is also much appreciated. Any help appreciated, thanks

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• Entity Framework RC1 DbContext query issue

  - by Steve

  I'm trying to implement the repository pattern using entity framework code first rc 1. The problem I am running into is with creating the DbContext. I have an ioc container resolving the IRepository and it has a contextprovider which just news up a new DbContext with a connection string in a windsor.config file. With linq2sql this part was no problem but EF seems to be choking. I'll describe the problem below with an example. I've pulled out the code to simplify things a bit so that is why you don't see any repository pattern stuff here. just sorta what is happening without all the extra code and classes. using (var context = new PlssContext()) { var x = context.Set<User>(); var y = x.Where(u => u.UserName == LogOnModel.UserName).FirstOrDefault(); } using (var context2 = new DbContext(@"Data Source=.\SQLEXPRESS;Initial Catalog=PLSS.Models.PlssContext;Integrated Security=True;MultipleActiveResultSets=True")) { var x = context2.Set<User>(); var y = x.Where(u => u.UserName == LogOnModel.UserName).FirstOrDefault(); } PlssContext is where I am creating my DbContext class. The repository pattern doesn't know anything about PlssContext. The best I thought I could do was create a DbContext with the connection string to the sqlexpress database and query the data that way. The connection string in the var context2 was grabbed from the context after newing up the PlssContext object. So they are pointing at the same sqlexpress database. The first query works. The second query fails miserably with this error: The model backing the 'DbContext' context has changed since the database was created. Either manually delete/update the database, or call Database.SetInitializer with an IDatabaseInitializer instance. For example, the DropCreateDatabaseIfModelChanges strategy will automatically delete and recreate the database, and optionally seed it with new data. on this line var y = x.Where(u => u.UserName == LogOnModel.UserName).FirstOrDefault(); Here is my DbContext namespace PLSS.Models { public class PlssContext : DbContext { public DbSet<User> Users { get; set; } public DbSet<Corner> Corners { get; set; } public DbSet<Lookup_County> Lookup_County { get; set; } public DbSet<Lookup_Accuracy> Lookup_Accuracy { get; set; } public DbSet<Lookup_MonumentStatus> Lookup_MonumentStatus { get; set; } public DbSet<Lookup_CoordinateSystem> Lookup_CoordinateSystem { get; set; } public class Initializer : DropCreateDatabaseAlways<PlssContext> { protected override void Seed(PlssContext context) { I've tried all of the Initializer strategies with the same errors. I don't think the database is changing. If I remove the modelBuilder.Conventions.Remove<IncludeMetadataConvention>(); Then the error returns is The entity type User is not part of the model for the current context. Which sort of makes sense. But how do you bring this all together?

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• tkinter frame does not show on startup

  - by Jzz

  this is my first question on SO, so correct me please if I make a fool of myself. I have this fairly complicated python / Tkinter application (python 2.7). On startup, the __init__ loads several frames, and loads a database. When that is finished, I want to set the application to a default state (there are 2 program states, 'calculate' and 'config'). Setting the state of the application means that the appropriate frame is displayed (using grid). When the program is running, the user can select a program state in the menu. Problem is, the frame is not displayed on startup. I get an empty application (menu bar and status bar are displayed). When I select a program state in the menu, the frame displays as it should. Question: What am I doing wrong? Should I update idletasks? I tried, but no result. Anything else? Background: I use the following to switch program states: def set_program_state(self, state): '''sets the program state''' #try cleaning all the frames: try: self.config_frame.grid_forget() except: pass try: self.tidal_calculations_frame.grid_forget() except: pass try: self.tidal_grapth_frame.grid_forget() except: pass if state == "calculate": print "Switching to calculation mode" self.tidal_calculations_frame.grid() #frame is preloaded self.tidal_calculations_frame.fill_data(routes=self.routing_data.routes, deviations=self.misc_data.deviations, ship_types=self.misc_data.ship_types) self.tidal_grapth_frame.grid() self.program_state = "calculate" elif state == "config": print "Switching to config mode" self.config_frame = GUI_helper.config_screen_frame(self, self.user) #load frame first (contents depend on type of user) self.config_frame.grid() self.program_state = "config" I understand that this is kind of messy to read, so I simplified things for testing, using this: def set_program_state(self, state): '''sets the program state''' #try cleaning all the frames: try: self.testlabel_1.grid_forget() except: pass try: self.testlabel_2.grid_forget() except: pass if state == "calculate": print "switching to test1" self.testlabel_1 = tk.Label(self, text="calculate", borderwidth=1, relief=tk.RAISED) self.testlabel_1.grid(row=0, sticky=tk.W+tk.E) elif state == "config": print "switching to test1" self.testlabel_2 = tk.Label(self, text="config", borderwidth=1, relief=tk.RAISED) self.testlabel_2.grid(row=0, sticky=tk.W+tk.E) But the result is the same. The frame (or label in this test) is not displayed at startup, but when the user selects the state (calling the same function) the frame is displayed. UPDATE the sample code in the comments (thanks for that!) pointed me in another direction. Further testing revealed (what I think) the cause of the problem. Disabling the display of the status bar made the program work as expected. Turns out, I used pack to display the statusbar and grid to display the frames. And they are in the same container, so problems arise. I fixed that by using only pack inside the main container. But the same problem is still there. This is what I use for the statusbar: self.status = GUI_helper.StatusBar(self.parent) self.status.pack(side=tk.BOTTOM, fill=tk.X) And if I comment out the last line (pack), the config frame loads on startup, as per this line: self.set_program_state("config") But if I let the status bar pack inside the main window, the config frame does not show. Where it does show when the user asks for it (with the same command as above).

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• IE7 is making my life miserable! Getting gaps between html table columns (w/ colspan) with css togg

  - by Art Peterson

  Copy/paste this html code snippet and try it out in IE7. When you toggle the hidden columns it leaves a gap between the columns. In Firefox it works fine, the columns touch when minimized. Haven't tried IE8 yet, would be curious to hear how it works there. Any ideas? I've tried a bunch of things in the CSS like table-layout:fixed but no luck. Note: Not looking for a different toggling method because the table I'm really dealing with is 50+ columns wide and 4000+ rows so looping/jquery techniques are too slow. Here's the code - if someone can re-post a working version of it I'll instantly give them the check and be forever in your debt! <DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <script> function toggle() { var tableobj = document.getElementById("mytable"); if (tableobj.className == "") { tableobj.className = "hide1 hide2"; } else { tableobj.className = ""; } } </script> <style> table { border-collapse: collapse; } td, th { border: 1px solid silver; } .hide1 .col1 { display: none; } .hide2 .col2 { display: none; } </style> </head> <body> <input type="button" value="toggle" onclick="toggle();" /> <table id="mytable"> <tr> <th>A</th> <th colspan="2">B</th> <th colspan="2" class="col1">B1</th> <th colspan="2">C</th> <th colspan="2" class="col2">C1</th> </tr> <tr> <td>123</td> <td>456</td> <td>789</td> <td class="col1">123</td> <td class="col1">456</td> <td>789</td> <td>123</td> <td class="col2">456</td> <td class="col2">789</td> </tr> </table> </body> </html>

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• Php template caching design

  - by Thomas

  Hello to all, I want to include caching in my app design. Caching templates for starters. The design I have used so far is very modular. I have created an ORM implementation for all my tables and each table is represented by the corresponding class. All the requests are handled by one controller which routes them to the appropriate webmethod functions. I am using a template class for handling UI parts. What I have in mind for caching includes the implementation of a separate Cache class for handling caching with the flexibility to either store in files, apc or memcache. Right now I am testing with file caching. Some thoughts Should I include the logic of checking for cached versions in the Template class or in the webmethods which handle the incoming requests and which eventually call the Template class. In the first case, things are pretty simple as I will not have to change anything more than pass the template class an extra argument (whether to load from cache or not). In the second case however, I am thinking of checking for a cached version immediately in the webmethod and if found return it. This will save all the processing done until the logic reaches the template (first case senario). Both senarios however, rely on an accurate mechanism of invalidating caches, which brings as to Invalidating caches As I see it (and you can add your input freely) a template cached file, becomes invalidate if: a. the expiration set, is reached. b. the template file itself is updated (ie by the developer when adding a new line) c. the webmethod that handles the request changes (ie the developer adds/deletes something in the code) d. content coming from the db and ending in the template file is modified I am thinking of storing a json encoded array inside the cached file. The first value will be the expiration timestamp of the cache. The second value will be the modification time of the php file with the code handling the request (to cope with option c above) The third will be the content itself The validation process I am considering, according to the above senarios, is: a. If the expiration of the cached file (stored in the array) is reached, delete the cache file b. if the cached file's mod time is smaller than the template's skeleton file mod time, delete the cached file c. if the mod time of the php file is greated than the one stored in the cache, delete the cached file. d. This is tricky. In the ORM implementation I ahve added event handlers (which fire when adding, updating, deleting objects). I could delete the cache file every time an object thatprovides content to the template, is modified. The problem is how to keep track which cached files correpond to each schema object. Take this example, a user has his shortprofile page and a full profile page (2 templates) These templates can be cached. Now, every time the user modifies his profile, the event handler would need to know which templates or cached files correspond to the User, so that these files can be deleted. I could store them in the db but I am looking for a beter approach

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• Parsing google feed with linq to xml

  - by the_V

  Hi I'm trying to parse XML feed that I get via Google Contacts API with LINQ 2 XML. That's what feed looks like: <feed xmlns="http://www.w3.org/2005/Atom" xmlns:openSearch="http://a9.com/-/spec/opensearchrss/1.0/" xmlns:gContact="http://schemas.google.com/contact/2008" xmlns:batch="http://schemas.google.com/gdata/batch" xmlns:gd="http://schemas.google.com/g/2005"> <id>[email protected]</id> <updated>2010-06-11T17:37:06.561Z</updated> <category scheme="http://schemas.google.com/g/2005#kind" term="http://schemas.google.com/contact/2008#contact" /> <title type="text">My Contacts</title> <link rel="alternate" type="text/html" href="http://www.google.com/" /> <link rel="http://schemas.google.com/g/2005#feed" type="application/atom+xml" href="http://www.google.com/m8/feeds/contacts/myemailaddress%40gmail.com/full" /> <link rel="http://schemas.google.com/g/2005#post" type="application/atom+xml" href="http://www.google.com/m8/feeds/contacts/myemailaddress%40gmail.com/full" /> <link rel="http://schemas.google.com/g/2005#batch" type="application/atom+xml" href="http://www.google.com/m8/feeds/contacts/myemailaddress%40gmail.com/full/batch" /> <link rel="self" type="application/atom+xml" href="http://www.google.com/m8/feeds/contacts/myemailaddress%40gmail.com/full?max-results=25" /> <author> <name>My NAme</name> <email>[email protected]</email> </author> <generator version="1.0" uri="http://www.google.com/m8/feeds">Contacts</generator> <openSearch:totalResults>19</openSearch:totalResults> <openSearch:startIndex>1</openSearch:startIndex> <openSearch:itemsPerPage>25</openSearch:itemsPerPage> <entry> <id>http://www.google.com/m8/feeds/contacts/myemailaddress%40gmail.com/base/0</id> <updated>2010-01-26T20:34:03.802Z</updated> <category scheme="http://schemas.google.com/g/2005#kind" term="http://schemas.google.com/contact/2008#contact" /> <title type="text">Contact name</title> <link rel="http://schemas.google.com/contacts/2008/rel#edit-photo" type="image/*" href="http://www.google.com/m8/feeds/photos/media/myemailaddress%40gmail.com/0/O-ydnzWMJcfZWqT-6gGetw" /> <link rel="http://schemas.google.com/contacts/2008/rel#photo" type="image/*" href="http://www.google.com/m8/feeds/photos/media/myemailaddress%40gmail.com/0" /> <link rel="self" type="application/atom+xml" href="http://www.google.com/m8/feeds/contacts/myemailaddress%40gmail.com/full/0" /> <link rel="edit" type="application/atom+xml" href="http://www.google.com/m8/feeds/contacts/myemailaddress%40gmail.com/full/0/1264538043802000" /> <gd:email rel="http://schemas.google.com/g/2005#other" address="[email protected]" primary="true" /> </entry> </feed> I've tried a number of things with linq 2 sql, but they didn't work. Even this simple code snipped doesn't work: using (FileStream stream = File.OpenRead("response.xml")) { XmlReader reader = XmlReader.Create(stream); XDocument doc = XDocument.Load(reader); XElement feed = doc.Element("feed"); if (feed == null) { Console.WriteLine("feed not found"); } XElement id = doc.Element("id"); if (id == null) { Console.WriteLine("id is null"); } } Problem is that both id and feed are null here. What wrong am I doing?

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• Apache/PHP serving file multiple times

  - by easement

  I have a system with a download.php page. The page takes and id and loads a file based on from the DB Record and then serves it up. I've noticed a couple instances where files are requested multiple times in short time spans (20ms). Times that are too quick for human input. There are plenty of instances where the downloader functions fine. However, in taking a closer look at the downloader’s usage, I did see some interesting behavior. For instance, the IP address xxx.xxx.xxx.xxx (which is one in a range owned by xxxxxx.de in Germany) came to the site through Google. They browsed around and then came to the page http://site.com/xxxx/press+125.php There they issued a request for /download.php?id=/ZZ/n+aH55Y= (a PDF) at 9:04:23AM. That alone is not a big deal. However, what is interesting is that the server seems to have been quite preoccupied with serving that request. In the logs the request first completes between 9:09:48 and 9:10:00. It looks like the user must have gotten tired of waiting during that time and requested the document two more times. Between 09:14:47 and 09:15:00 the same request appears again, except it is from 9:04:43AM, 20ms later than the first request. Then it pops up a third time, with a request that started at 09:05:06 completing between 09:19:55 and 09:19:58! I’m suspicious of that document. In looking through the logs I see other instances where it takes the server a little while to handle that specific file. Check out this list of requests from zzz.zzz.zzz.zzz[different than above] for the file /download.php?id=/ZZ/n+aH55Y= (the same docuemnt as before): Request time Complete Time 04:32:43 04:33:36 04:32:50 04:33:36 04:32:51 04:33:38 04:33:05 04:33:38 04:33:34 04:33:42 04:33:05 04:33:42 So something is definitely going on. Whether it has to do with this specific document tripping up the server, the download.php page’s code, or if we’re just seeing the evidence of some server level overload as it plays out in real time I’m not yet sure. In fairness, there are other instances of people downloading /download.php?id=/ZZ/n+aH55Y= (the same PDF) without error. However, it is interesting that the multiple processes only seem to happen with this one file, and then only when it is accessed through the page http://site.com/press+125.php . It bears further investigation if there’s something amiss inside the code that causes the system to fire off multiple download requests that occupy the server. I don't know if this press+125.php is a rabbit hole, but there is weird consicence. Any ideas? I'm totally out of ideas. Apache maxed out? Things like that. ///DOWNLOAD.php $file = new files(); $file->comparison_filter("id", "=", $id); //sql to load if ($file->load()) { $file->serve(); } //FILES function serve() { if ($this->is_loaded) { if (file_exists($this->get_value("filename"))) { if ($this->get_value("content_type") != "") { header("Content-Type: " . $this->get_value("content_type")); } header("Content-Length: " . filesize($this->get_value("filename"))); if ($this->get_value("flag_image") == 0 || $this->get_value("flag_image") == false) { header("Cache-Control: private"); header("Content-Disposition: attachment; filename=" . urlencode($this->get_value("original_filename"))); } set_time_limit(0); @readfile($this->get_value("filename")); exit; } } }

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• QGraphicsView and custom Cursors

  - by Etienne de Martel

  I am trying to make use of a mix of custom cursors and preset cursors for my QGraphicsView. In my implementation we have created a notion of "modes" for the view. Meaning that depending on what "mode" the user is in, different things will happen on the left-click, or left-click drag. Anyway, none of that is the problem, just the context. The problem arises when I try to change the cursor for each mode. For instance, for mode 1 we want to show the regular Arrow cursor, but for mode 2, we want to use a custom pixmap. Seemingly simple we call graphicsview->viewport()->setCursor(Qt::QArrowCursor)  when we are switching to mode 1, and graphicsview->viewport()->setCursor(our custom cursor) for mode 2. Except it doesn't work at all. Firstly, the cursor does not change to the custom cursor. That is the first problem. However, if through another operation the drag mode of the graphics view gets set to ScrollHandDrag, the cursor will switch to the custom cursor once the drag operation is complete. Weird. But the plot thickens... Once we switch to the custom cursor, it can never be changed back to the ArrorCursor no matter how many times we call setCursor(Qt::QArrowCursor). it also doesn't seem to matter whether I call setCursor on the viewport or the graphics view itself. So, just for fun, I added a call to graphicsview->unsetCursor() just before we want to change the cursor, and that at least rectifies the second problem. The cursor changes just fine so long as we do a little HandDragging in between. Better, but certainly not optimal. However it should be noted, that doing the unsetCursor on the viewport doesn't work. it must absolutely be done on the graphicsview - regardless of the fact that we are setting the cursor on the viewport. To completely patch over the problem I have added these two lines after I set the cursor: graphicsview->setDragMode(QGraphicsView::ScrollHandDrag); graphicsview->setDragMode(QGraphicsView::NoDrag); Which works, but ye gads!! So something magical is happening inside these two methods that fixes the problem, but glancing at the code I don't see what. Something to do with the fact that the drag mode is changing the cursor I imagine. Just for completeness, I should also mention that the thing that triggers the mode change, is a QPushButton that has been added to the scene using QGraphicsScene->addWidget(). I don't know if that has anything to do with it, but you never know. I am hoping that either someone could clarify why I need to make these seemingly random calls. I don't think I am doing anything wrong anywhere. Thanks in advance for any help. EDIT: Here is an actual code example with the cursor patches as described above. You can look at and/or download them from the link below. It was a little long to paste here. I included the framework around which the cursors are changed, because I have a funny feeling that that is important somehow. https://gist.github.com/712654 The code where the problem lies is in MyGraphicsView.cpp starting at line 104. This is where the cursor is set in the graphics view. It is exactly as described above. Keep in mind, with the very ugly patches in place the cursors do work - more or less. Without those lines you will see very clearly the problems listed in the post above. Also included in the link, is all the code for a mainWindow that uses the view, etc... the only thing missing are the images I am using. But the images themselves don't matter, any 16x16 pngs will do.

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• Using inheritance and polymorphism to solve a common game problem

  - by Barry Brown

  I have two classes; let's call them Ogre and Wizard. (All fields are public to make the example easier to type in.) public class Ogre { int weight; int height; int axeLength; } public class Wizard { int age; int IQ; int height; } In each class I can create a method called, say, battle() that will determine who will win if an Ogre meets and Ogre or a Wizard meets a Wizard. Here's an example. If an Ogre meets an Ogre, the heavier one wins. But if the weight is the same, the one with the longer axe wins. public Ogre battle(Ogre o) { if (this.height > o.height) return this; else if (this.height < o.height) return o; else if (this.axeLength > o.axeLength) return this; else if (this.axeLength < o.axeLength) return o; else return this; // default case } We can make a similar method for Wizards. But what if a Wizard meets an Ogre? We could of course make a method for that, comparing, say, just the heights. public Wizard battle(Ogre o) { if (this.height > o.height) return this; else if (this.height < o.height) return o; else return this; } And we'd make a similar one for Ogres that meet Wizard. But things get out of hand if we have to add more character types to the program. This is where I get stuck. One obvious solution is to create a Character class with the common traits. Ogre and Wizard inherit from the Character and extend it to include the other traits that define each one. public class Character { int height; public Character battle(Character c) { if (this.height > c.height) return this; else if (this.height < c.height) return c; else return this; } } Is there a better way to organize the classes? I've looked at the strategy pattern and the mediator pattern, but I'm not sure how either of them (if any) could help here. My goal is to reach some kind of common battle method, so that if an Ogre meets an Ogre it uses the Ogre-vs-Ogre battle, but if an Ogre meets a Wizard, it uses a more generic one. Further, what if the characters that meet share no common traits? How can we decide who wins a battle?

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• Devise / Rails 4 Windows mobile authentication failure

  - by Nic Willemse

  Im using devise with a rails 4 application. Authentication works fine on most devices, including some old feature phones. I am however running into problems with the Nokia Lumia. Please see log snippet below. By the looks of things this appears to be a rails issue rather than a devise problem. Please Help! 014-05-30T09:47:38.668478+00:00 app[web.1]: Started POST "/users/sign_in" for 197.111.223.249 at 2014-05-30 09:47:38 +0000 2014-05-30T09:47:38.668505+00:00 app[web.1]: Started POST "/users/sign_in" for 197.111.223.249 at 2014-05-30 09:47:38 +0000 2014-05-30T09:47:38.672961+00:00 app[web.1]: Processing by Devise::SessionsController#create as HTML 2014-05-30T09:47:38.672968+00:00 app[web.1]: Processing by Devise::SessionsController#create as HTML 2014-05-30T09:47:38.674163+00:00 app[web.1]: Can't verify CSRF token authenticity 2014-05-30T09:47:38.673021+00:00 app[web.1]: Parameters: {"utf8"="?", "authenticity_token"="Ckyw9vAfxbgksugLMainfWoG2jRdq7GB5xBBGxqYhCs=", "user"={"email"="", "password"="[FILTERED]", "remember_me"="0"}, "commit"="Sign in"} 2014-05-30T09:47:38.673027+00:00 app[web.1]: Parameters: {"utf8"="?", "authenticity_token"="Ckyw9vAfxbgksugLMainfWoG2jRdq7GB5xBBGxqYhCs=", "user"={"email"="", "password"="[FILTERED]", "remember_me"="0"}, "commit"="Sign in"} 2014-05-30T09:47:38.674170+00:00 app[web.1]: Can't verify CSRF token authenticity 2014-05-30T09:47:38.677792+00:00 app[web.1]: Completed 422 Unprocessable Entity in 5ms 2014-05-30T09:47:38.677799+00:00 app[web.1]: Completed 422 Unprocessable Entity in 5ms 2014-05-30T09:47:38.683294+00:00 app[web.1]: ActionController::InvalidAuthenticityToken (ActionController::InvalidAuthenticityToken): 2014-05-30T09:47:38.683299+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/actionpack-4.0.1/lib/action_controller/metal/request_forgery_protection.rb:170:in handle_unverified_request' 2014-05-30T09:47:38.683289+00:00 app[web.1]: 2014-05-30T09:47:38.683298+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/actionpack-4.0.1/lib/action_controller/metal/request_forgery_protection.rb:163:inhandle_unverified_request' 2014-05-30T09:47:38.683303+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/actionpack-4.0.1/lib/action_controller/metal/request_forgery_protection.rb:177:in verify_authenticity_token' 2014-05-30T09:47:38.683305+00:00 app[web.1]: vendor/bundle/ruby/2.0.0/gems/activesupport-4.0.1/lib/active_support/callbacks.rb:417:in_run__3672081613755604432__process_action__callbacks' Form : <%= form_for(resource, :as => resource_name, :url => session_path(resource_name), :html => {:class => "form-signin"}) do |f| %> <h2 class="form-signin-heading">Sign in</h2> <%= devise_error_messages! %> <div><%= f.label :email %><br /> <%= f.email_field :email, :autofocus => true, :class=> "form-control" %></div> <div><%= f.label :password %><br /> <%= f.password_field :password , :class=> "form-control"%></div> <% if devise_mapping.rememberable? -%> <div><%= f.check_box :remember_me, :class=> "form-control"%> <%= f.label :remember_me %></div> <% end -%> <div><%= f.submit "Sign in" ,:class => "btn btn-lg btn-primary btn-block"%></div> <input name="authenticity_token" type="hidden" value="<%= form_authenticity_token %>"/> <%= render "devise/shared/links" %> <% end %>

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• Limiting TCP sends with a "to-be-sent" queue and other design issues.

  - by Poni

  Hello all! This question is the result of two other questions I've asked in the last few days. I'm creating a new question because I think it's related to the "next step" in my understanding of how to control the flow of my send/receive, something I didn't get a full answer to yet. The other related questions are: http://stackoverflow.com/questions/3028376/an-iocp-documentation-interpretation-question-buffer-ownership-ambiguity http://stackoverflow.com/questions/3028998/non-blocking-tcp-buffer-issues In summary, I'm using Windows I/O Completion Ports. I have several threads that process notifications from the completion port. I believe the question is platform-independent and would have the same answer as if to do the same thing on a *nix, *BSD, Solaris system. So, I need to have my own flow control system. Fine. So I send send and send, a lot. How do I know when to start queueing the sends, as the receiver side is limited to X amount? Let's take an example (closest thing to my question): FTP protocol. I have two servers; One is on a 100Mb link and the other is on a 10Mb link. I order the 100Mb one to send to the other one (the 10Mb linked one) a 1GB file. It finishes with an average transfer rate of 1.25MB/s. How did the sender (the 100Mb linked one) knew when to hold the sending, so the slower one wouldn't be flooded? Another way to ask this: Can I get a "hold-your-sendings" notification from the remote side? Is it built-in in TCP or the so called "reliable network protocol" needs me to do so? Again, I have a loop with many sends to a remote server, and at some point, within that loop I'll have to determine if I should queue that send or I can pass it on to the transport layer (TCP). How do I do that? What would you do? Of course that when I get a completion notification from IOCP that the send was done I'll issue other pending sends, that's clear. Another design question related to this: Since I am to use a custom buffers with a send queue, and these buffers are being freed to be reused (thus not using the "delete" keyword) when a "send-done" notification has been arrived, I'll have to use a mutual exlusion on that buffer pool. Using a mutex slows things down, so I've been thinking; Why not have each thread have its own buffers pool, thus accessing it , at least when getting the required buffers for a send operation, will require no mutex, because it belongs to that thread only. The buffers pool is located at the thread local storage (TLS) level. No mutual pool implies no lock needed, implies faster operations BUT also implies more memory used by the app, because even if one thread already allocated 1000 buffers, the other one that is sending right now and need 1000 buffers to send something will need to allocated these to its own. This is a long question and I hope none got hurt (: Thank you all!

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• Advanced Regex: Smart auto detect and replace URLs with anchor tags

  - by Robert Koritnik

  I've written a regular expression that automatically detects URLs in free text that users enter. This is not such a simple task as it may seem at first. Jeff Atwood writes about it in his post. His regular expression works, but needs extra code after detection is done. I've managed to write a regular expression that does everything in a single go. This is how it looks like (I've broken it down into separate lines to make it more understandable what it does): 1 (?<outer>\()? 2 (?<scheme>http(?<secure>s)?://)? 3 (?<url> 4 (?(scheme) 5 (?:www\.)? 6 | 7 www\. 8 ) 9 [a-z0-9] 10 (?(outer) 11 [-a-z0-9/+&@#/%?=~_()|!:,.;cšžcd]+(?=\)) 12 | 13 [-a-z0-9/+&@#/%?=~_()|!:,.;cšžcd]+ 14 ) 15 ) 16 (?<ending>(?(outer)\))) As you may see, I'm using named capture groups (used later in Regex.Replace()) and I've also included some local characters (cšžcd), that allow our localised URLs to be parsed as well. You can easily omit them if you'd like. Anyway. Here's what it does (referring to line numbers): 1 - detects if URL starts with open braces (is contained inside braces) and stores it in "outer" named capture group 2 - checks if it starts with URL scheme also detecting whether scheme is SSL or not 3 - start parsing URL itself (will store it in "url" named capture group) 4-8 - if statement that says: if "sheme" was present then www. part is optional, otherwise mandatory for a string to be a link (so this regular expression detects all strings that start with either http or www) 9 - first character after http:// or www. should be either a letter or a number (this can be extended if you'd like to cover even more links, but I've decided not to because I can't think of a link that would start with some obscure character) 10-14 - if statement that says: if "outer" (braces) was present capture everything up to the last closing braces otherwise capture all 15 - closes the named capture group for URL 16 - if open braces were present, capture closing braces as well and store it in "ending" named capture group First and last line used to have \s* in them as well, so user could also write open braces and put a space inside before pasting link. Anyway. My code that does link replacement with actual anchor HTML elements looks exactly like this: value = Regex.Replace( value, @"(?<outer>\()?(?<scheme>http(?<secure>s)?://)?(?<url>(?(scheme)(?:www\.)?|www\.)[a-z0-9](?(outer)[-a-z0-9/+&@#/%?=~_()|!:,.;cšžcd]+(?=\))|[-a-z0-9/+&@#/%?=~_()|!:,.;cšžcd]+))(?<ending>(?(outer)\)))", "${outer}<a href=\"http${secure}://${url}\">http${secure}://${url}</a>${ending}", RegexOptions.Compiled | RegexOptions.CultureInvariant | RegexOptions.IgnoreCase); As you can see I'm using named capture groups to replace link with an Anchor tag: "${outer}<a href=\"http${secure}://${url}\">http${secure}://${url}</a>${ending}" I could as well omit the http(s) part in anchor display to make links look friendlier, but for now I decided not to. Question I would like my links to be replaced with shortenings as well. So when user copies a very long link (for instance if they would copy a link from google maps that usually generates long links) I would like to shorten the visible part of the anchor tag. Link would work, but visible part of an anchor tag would be shortened to some number of characters. I could as well append ellipsis at the end of at all possible (and make things even more perfect). Does Regex.Replace() method support replacement notations so that I can still use a single call? Something similar as string.Format() method does when you'd like to format values in string format (decimals, dates etc...).

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• Problems manipulating strings through a stdcall to a dll

  - by ibiza

  I need to create a C++ dll that will be called from another program through stdcall. What is needed : the caller program will pass an array of string to the dll and the dll should change the string values in the array. The caller program will then continue to work with these string values that came from the dll. I made a simple test project and I am obviously missing something... Here is my test C++ dll : #ifndef _DLL_H_ #define _DLL_H_ #include <string> #include <iostream> struct strStruct { int len; char* string; }; __declspec (dllexport) int __stdcall TestFunction(strStruct* s) { std::cout << "Just got in dll" << std::endl; std::cout << s[0].string << std::endl; //////std::cout << s[1].string << std::endl; /* char str1[] = "foo"; strcpy(s[0].string, str1); s[0].len = 3; char str2[] = "foobar"; strcpy(s[1].string, str2); s[1].len = 6; */ //std::cout << s[0].string << std::endl; //std::cout << s[1].string << std::endl; std::cout << "Getting out of dll" << std::endl; return 1; } #endif and here is a simple C# program that I am using to test my test dll : using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Runtime.InteropServices; namespace TestStr { class Program { [DllImport("TestStrLib.dll", CharSet = CharSet.Ansi, CallingConvention = CallingConvention.StdCall)] public static extern int TestFunction(string[] s); static void Main(string[] args) { string[] test = new string[2] { "a1a1a1a1a1", "b2b2b2b2b2" }; Console.WriteLine(test[0]); Console.WriteLine(test[1]); TestFunction(test); Console.WriteLine(test[0]); Console.WriteLine(test[1]); Console.ReadLine(); } } } And here is the output produced : a1a1a1a1a1 b2b2b2b2b2 Just got in dll b2b2b2b2b2 Getting out of dll a1a1a1a1a1 b2b2b2b2b2 I have some questions : 1) Why is it outputting the element in the second position of the array rather than in the first position?? 2) If I uncomment the line commented with ////// in the dll file, the program crashes. Why? 3) Obviously I wanted to do more things in the dll (the parts in /* */) than what it does right now, but I am blocked by the first 2 questions... Thanks for all your help

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