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• C++ Exception Handling

  - by user1413793

  So I was writing some code and I noticed that apart from syntactical, type, and other compile-time errors, C++ does not throw any other exceptions. So I decided to test this out with a very trivial program: #include<iostream> int main() { std::count<<5/0<<std::endl; return 1 } When I compiled it using g++, g++ gave me a warning saying I was dividing by 0. But it still compiled the code. Then when I ran it, it printed some really large arbitrary number. When I want to know is, how does C++ deal with exceptions? Integer division by 0 should be a very trivial example of when an exception should be thrown and the program should terminate. Do I have to essentially enclose my entire program in a huge try block and then catch certain exceptions? I know in Python when an exception is thrown, the program will immediately terminate and print out the error. What does C++ do? Are there even runtime exceptions which stop execution and kill the program?

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• How can I pass a const array or a variable array to a function in C?

  - by CSharperWithJava

  I have a simple function Bar that uses a set of values from a data set that is passed in in the form of an Array of data structures. The data can come from two sources: a constant initialized array of default values, or a dynamically updated cache. The calling function determines which data is used and should be passed to Bar. Bar doesn't need to edit any of the data and in fact should never do so. How should I declare Bar's data parameter so that I can provide data from either set? union Foo { long _long; int _int; } static const Foo DEFAULTS[8] = {1,10,100,1000,10000,100000,1000000,10000000}; static Foo Cache[8] = {0}; void Bar(Foo* dataSet, int len);//example function prototype Note, this is C, NOT C++ if that makes a difference; Edit Oh, one more thing. When I use the example prototype I get a type qualifier mismatch warning, (because I'm passing a mutable reference to a const array?). What do I have to change for that?

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• HOWTO: implement a jQuery version of ASP.Net MVC "Strongly Typed Partial Views"

  - by Sam Carleton

  I am working on a multi-page assessment form where the questions/responses are database driven. Currently I the basic system working with Html.BeginForm via standard ASP.Net MVC. At this point in time, the key to the whole system is the 'Strongly Typed Partial Views'. When the question/response is read from the database, the response type determines which derived model is created and added to the collection. The main view it iterates through the collection and uses the 'Strongly Typed Partial Views' system of ASP.Net MVC to determine which view to render the correct type of response (radio button, drop down, or text box). I would like to change this process from a Html.BeginForm to Ajax.BeginForm. The problem is I don't have a clue as to how to implement the dynamic creation of the question/response in the JavaScript/jQuery world. Any thoughts and/or suggestions? Here is the current code to generate the dynamic form: @using (Html.BeginForm(new { mdsId = @Model.MdsId, sectionId = @Model.SectionId })) { <div class="SectionTitle"> <span>Section @Model.SectionName - @Model.SectionDescription</span> <span style="float: right">@Html.CheckBoxFor(x => x.ShowUnansweredQuestions) Show only unaswered questions</span> </div> @Html.HiddenFor(x => x.PrevSectionId) @Html.HiddenFor(x => x.NextSectionId) for (var i = 0; i < Model.answers.Count(); i++) { @Html.EditorFor(m => m.answers[i]); } }

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• json parsing problems

  - by C.

  Hi I have the following Json : "{\"doc\":{\"info\":{\"allowDistribution\":\"true\",\"allowSearch\":\"true\",\"calaisRequestID\":\"67a02f61-7e45-cfc4-1276-e123c5f7422f\",\"externalID\":\"\",\"id\":\"http://id.opencalais.com/dBo1YRiQeqS-kfO-m9UeWA\",\"docId\":\"http://d.opencalais.com/dochash-1/8edabb36-eece-3f67-b187-ab64cd885ecb\",\"document\":\"What type of music do you listen to? How much would you pay for a cd? Do you still buy cds? Do you like Shakira? What genre of music do you listen to?\",\"docTitle\":\"\",\"docDate\":\"2010-03-17 17:40:41.323\",\"externalMetadata\":\"\",\"submitter\":\"\"},\"meta\":{\"contentType\":\"text/raw\",\"emVer\":\"7.1.1103.5\",\"langIdVer\":\"DefaultLangId\",\"processingVer\":\"CalaisJob01\",\"submitionDate\":\"2010-03-17 17:40:41.183\",\"submitterCode\":\"b54c734e-b865-185b-c83a-66e1c66272de\",\"signature\":\"digestalg-1|FXnvwLovOsqVoSPX0JfGvj3tp7s=|cyV2tZWY9OXG1RBO0SuND4kd3Pkvqv0cS2YpsEBQhXDfSV4KoE61sQ==\",\"language\":\"English\",\"messages\":[]}},\"http://d.opencalais.com/dochash-1/8edabb36-eece-3f67-b187-ab64cd885ecb/cat/1\":{\"_typeGroup\":\"topics\",\"category\":\"http://d.opencalais.com/cat/Calais/EntertainmentCulture\",\"classifierName\":\"Calais\",\"categoryName\":\"Entertainment_Culture\",\"score\":1},\"http://d.opencalais.com/dochash-1/8edabb36-eece-3f67-b187-ab64cd885ecb/cat/2\":{\"_typeGroup\":\"topics\",\"category\":\"http://d.opencalais.com/cat/Calais/HumanInterest\",\"classifierName\":\"Calais\",\"categoryName\":\"Human Interest\",\"score\":1},\"http://d.opencalais.com/dochash-1/8edabb36-eece-3f67-b187-ab64cd885ecb/cat/3\":{\"_typeGroup\":\"topics\",\"category\":\"http://d.opencalais.com/cat/Calais/TechnologyInternet\",\"classifierName\":\"Calais\",\"categoryName\":\"Technology_Internet\",\"score\":0.932}}" Can you please tell me why it won't parse this? This is my code: JObject o = JObject.Parse(json); String category = (string)o["doc"]["_typeGroup"]["categoryName"]; It tells me: Object reference not set to an instance of an object. Thanks :)

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• Wireshark Dissector: How to Identify Missing UDP Frames?

  - by John Dibling

  How do you identify missing UDP frames in a custom Wireshark dissector? I have written a custom dissector for the CQS feed (reference page). One of our servers gaps when receiving this feed. According to Wireshark, some UDP frames are never received. I know that the frames were sent because all of our other servers are gap-free. A CQS frame consists of multiple messages, each having its own sequence number. My custom dissector provides the following data to Wireshark: cqs.frame_gaps - the number of gaps within a UDP frame (always zero) cqs.frame_first_seq - the first sequence number in a UDP frame cqs.frame_expected_seq - the first sequence number expected in the next UDP frame cqs.frame_msg_count - the number of messages in this UDP frame And I am displaying each of these values in custom columns, as shown in this screenshot: I tried adding code to my dissector that simply saves the last-processed sequence number (as a local static), and flags gaps when the dissector processes a frame where current_sequence != (previous_sequence + 1). This did not work because the dissector can be called in random-access order, depending on where you click in the GUI. So you could process frame 10, then frame 15, then frame 11, etc. Is there any way for my dissector to know if the frame that came before it (or the frame that follows) is missing? The dissector is written in C. (See also a companion post on serverfault.com)

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• how often should the entire suite of a system's unit tests be run?

  - by gerryLowry

  Generally, I'm still very much a unit testing neophyte. BTW, you may also see this question on other forums like xUnit.net, et cetera, because it's an important question to me. I apoligize in advance for my cross posting; your opinions are very important to me and not everyone in this forum belongs to the other forums too. I was looking at a large decade old legacy system which has had over 700 unit tests written recently (700 is just a small beginning). The tests happen to be written in MSTest but this question applies to all testing frameworks AFAIK. When I ran, via vs2008 "ALL TESTS", the final count was only seven tests. That's about 1% of the total tests that have been written to date. MORE INFORMATION: The ASP.NET MVC 2 RTM source code, including its unit tests, is available on CodePlex; those unit tests are also written in MSTest even though (an irrelevant fact) Brad Wilson later joined the ASP.NET MVC team as its Senior Programmer. All 2000 plus tests get run, not just a few. QUESTION: given that AFAIK the purpose of unit tests is to identify breakages in the SUT, am I correct in thinking that the "best practice" is to always, or at least very frequently, run all of the tests? Thank you. Regards, Gerry (Lowry)

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• Search function on listview

  - by Luke

  Is it possible to search a listview and restrict the items in the listview by the search criteria? private void displayDeliveries() { lstDeliveryDetails.Items.Clear(); foreach (Delivery d in mainForm.myDeliveries) { ListViewItem item = lstDeliveryDetails.Items.Add(d.DeliveryName); item.SubItems.Add(d.DeliveryAddress); item.SubItems.Add(d.DeliveryDay); item.SubItems.Add(d.DeliveryTime); item.SubItems.Add(d.DeliveryMeal); item.SubItems.Add(d.DeliveryInstructions); item.SubItems.Add(d.DeliveryStatus); } } At the moment that code populates the listview. private void btnSearch_Click(object sender, EventArgs e) { //reset the selection and get the searched text iDeliverySelected = -1; string searchValue = txtSearchBox.Text; //loop through to find the search for (int i = 0; i < myDeliveries.Count; i++) { Delivery d = (Delivery)mainForm.myDeliveries[i]; if (d.DeliveryName == searchValue) MessageBox.Show("name matched"); } } So far this is what I have for search, I'm struggling to take it to the next level! Could anyone offer an ideas? Thanks

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• Convert SQL with Inner AND Outer Join to L2S

  - by Refracted Paladin

  I need to convert the below Sproc to a Linq query. At the very bottom is what I have so far. For reference the fields behind the "splat"(not my sproc) are ImmunizationID int, HAReviewID int, ImmunizationMaintID int, ImmunizationOther varchar(50), ImmunizationDate smalldatetime, ImmunizationReasonID int The first two are PK and FK, respectively. The other two ints are linke to the Maint Table where there description is stored. That is what I am stuck on, the INNER JOIN AND the LEFT OUTER JOIN Thanks, SELECT tblHAReviewImmunizations.*, tblMaintItem.ItemDescription, tblMaintItem2.ItemDescription as Reason FROM dbo.tblHAReviewImmunizations INNER JOIN dbo.tblMaintItem ON dbo.tblHAReviewImmunizations.ImmunizationMaintID = dbo.tblMaintItem.ItemID LEFT OUTER JOIN dbo.tblMaintItem as tblMaintItem2 ON dbo.tblHAReviewImmunizations.ImmunizationReasonID = tblMaintItem2.ItemID WHERE HAReviewID = @haReviewID My attempt so far -- public static DataTable GetImmunizations(int haReviewID) { using (var context = McpDataContext.Create()) { var currentImmunizations = from haReviewImmunization in context.tblHAReviewImmunizations where haReviewImmunization.HAReviewID == haReviewID join maintItem in context.tblMaintItems on haReviewImmunization.ImmunizationReasonID equals maintItem.ItemID into g from maintItem in g.DefaultIfEmpty() let Immunization = GetImmunizationNameByID( haReviewImmunization.ImmunizationMaintID) select new { haReviewImmunization.ImmunizationDate, haReviewImmunization.ImmunizationOther, Immunization, Reason = maintItem == null ? " " : maintItem.ItemDescription }; return currentImmunizations.CopyLinqToDataTable(); } } private static string GetImmunizationNameByID(int? immunizationID) { using (var context = McpDataContext.Create()) { var domainName = from maintItem in context.tblMaintItems where maintItem.ItemID == immunizationID select maintItem.ItemDescription; return domainName.SingleOrDefault(); } }

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• How to Implement Overlay blend method using opengles 1.1

  - by Cylon

  Blow is the algorithm of overlay. and i want using it on iphone, but iphone 3g only support opengles 1.1, can not using glsl. can i using blend function or texture combine to implement it. thank you /////////Reference from OpenGL Shading® Language Third Edition /////////// 19.6.12 Overlay OVERLAY first computes the luminance of the base value. If the luminance value is less than 0.5, the blend and base values are multiplied together. If the luminance value is greater than 0.5, a screen operation is performed. The effect is that the base value is mixed with the blend value, rather than being replaced. This allows patterns and colors to overlay the base image, but shadows and highlights in the base image are preserved. A discontinuity occurs where luminance = 0.5. To provide a smooth transition, we actually do a linear blend of the two equations for luminance in the range [0.45,0.55]. float luminance = dot(base, lumCoeff); if (luminance < 0.45) result = 2.0 * blend * base; else if (luminance 0.55) result = white - 2.0 * (white - blend) * (white - base); else { vec4 result1 = 2.0 * blend * base; vec4 result2 = white - 2.0 * (white - blend) * (white - base); result = mix(result1, result2, (luminance - 0.45) * 10.0); }

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• Why ntp settle time toe long?

  - by fercis

  I simply try to set-up NTP to my system. Both server and clients will run on my computer which are linked together with local link. One of them will have the reference clock. Both the server and Client are linux Ubuntu. I install ntp daemon to both sides. In clients, I enter the ip address of the server to /etc/ntp.conf. Everything works fine. However, the setting of the time to correct time in client side takes too long time (around 17 minutes). Is it possible to gather correct time just at startup. I write some code that regularly calls "ntpdate " by system call and the problem is solved but there has to be something that allows me to decrease the poll time of the client to 1-2 minutes. There are some settings as maxpoll - minpoll in ntp.conf, but I couldn't manage to understand their function, because with the best configuration (minpoll 4? 16 seconds?) I also cannot see that client side corrects its time before 10 minutes. In addition, in some cases my client is an embedded system (ARM - IGEP board) and it always opens with an irrelevant date (2-3 years ago). So the time that takes to correct the time should not depend on the time difference also.

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• Servlet Mapping Help - Possible to Avoid Referencing Context Name?

  - by AJ

  Hi all, I am working on a Spring application and trying to get my URL mapping correct. What I would like to have work is the following: http://localhost:8080/idptest -> doesn't work But instead, I have to reference the context name in my URL in order to resolve the mapping: http://localhost:8080/<context_name>/idptest -> works How can I avoid the requirement of referencing the context name in my URL without using a rewrite/proxy engine e.g. Apache? Here is the servlet definition and mapping from my web.xml: <servlet> <servlet-name>idptest</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <init-param> <param-name>contextConfigLocation</param-name> <param-value>/WEB-INF/conf/idptest.xml</param-value> </init-param> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>idptest</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping> Here's the outline of my controller (showing annotations for request mappings): @Controller @RequestMapping("/idptest") public class MyController { @RequestMapping(method=RequestMethod.GET) public String setupForm(Model model){ MyObject someObject = new MyObject(); model.addAttribute("someObject", someObject); return "myform"; } @RequestMapping(method = RequestMethod.POST) public String processSubmit(@ModelAttribute("someObject") MyObject someObject) throws Exception { // POST logic... } } Thanks!

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• How do I grab and use a variables coming back through ValueList from an AJAX call?

  - by Mel

  I'm trying the following code to execute a search and it's not working. On the search.cfm page, the only value coming back is the value I input into the search field (even if I click an autosuggest value, it's not coming back; only the letters I actually type myself come back). <cfform class="titleSearchForm" id="searchForm" action="search.cfm?GameID=#cfautosuggestvalue.GameID#" method="post"> <fieldset> <cfinput type="text" class="titleSearchField" name="TitleName" onChange="form.submit()" autosuggest="cfc:gz.cfcomp.search.AutoSuggestSearch({cfautosuggestvalue})"> <input type="button" class="titleSearchButton" value=" " /> </fieldset> </cfform> Query in CFC: <cfquery name="SearchResult" datasource="myDSN"> SELECT CONCAT(titles.TitleName, ' on ', platforms.PlatformAbbreviation) AS sResult, games.GameID FROM games Inner Join platforms ON games.PlatformID = platforms.PlatformID Inner Join titles ON titles.TitleID = games.TitleID WHERE UCase(titleName) LIKE Ucase('#ARGUMENTS.SearchString#%') ORDER BY titleName ASC; </cfquery> Two things: First of all, I would like to get the GameID back to the page making the AJAX request; I know why it is not coming back: Because I'm only returning sResult var, which does not include the GameID. Is there a way to return the GameID value without displaying it? The second thing: How to I grab a value from the auto-suggest once it is returned? Say I want to grab the GameID, or if I can't do that, the "TitleName" to use that in my query? I tried passing it to the form this way: action="search.cfm?GameID=#cfautosuggestvalue.GameID#" - but that does not work. How do I reference the autosuggestionvalue varaibles for use? Thanks

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• Associating an object with another object for GC clearup

  - by thecoop

  Is there any way of associating an object instance (object A) with a second object (object B) in a generalised way, so that when B gets collected A becomes eligable for collection? The same behaviour that would happen if B had an instance variable pointing to A, but without explicitly changing the class definition of B, and being able to do this in a dynamic way? The same sort of effect could be done by using the Component.Disposed event in a funky way, but I don't want to make B disposable EDIT I'm basically creating a cache of objects that are associated with a single 'root' object, and I don't want the cache to be static, as there can be lots of root objects using different caches, so lots of memory will be used up when a root object is no longer used but the cached objects are still around. So, I want a collection of cached objects to be associated with each 'root' object, without changing the root object definition. Sort of like metadata of an extra object reference attached to each root object instance. That way, each collection will get collected when the root object is collected, and not hang around like they would if a static cache was used.

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• adding Json to mutable array resolves in crash

  - by user2957713

  Hello guys I am new to Xcode/iOS developing I trying to add json data to the mutable array , and it results in app crash :( so far here is my code: if(! [defaults objectForKey:@"Person1"]) [defaults setObject:[PersonsFromSearch objectAtIndex:index] forKey:@"Person1"]; else { NSMutableArray *Array = [[NSMutableArray alloc]init]; id object = [defaults objectForKey:@"Person1"]; Array = [object isKindOfClass:[NSArray class]] ? object : @[object]; [Array addObject:[PersonsFromSearch objectAtIndex:index]];//crash here :(( [Array moveObjectFromIndex:[Array count] toIndex:0]; } Crash Dump: * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFDictionary addObject:]: unrecognized selector sent to instance 0xbf98dc0' what is wrong here ? can you please help me to resolve this issue Array contains this (Json?) { Address = "\U05d3\U05e8\U05da \U05d4\U05e9\U05dc\U05d5\U05dd 53"; CellPhone = "052-3275381"; EMail = "[email protected]"; EnglishPerson = "Yehuda Konfortes"; FaceBookLink = ""; Fax1 = "03-7330703"; Fax2 = ""; FileNAme = "100050.jpg"; HomeEMail = ""; HomeFax = ""; HomePhone1 = ""; HomePhone2 = ""; PersonID = 100050; PersonName = "\U05d9\U05d4\U05d5\U05d3\U05d4 \U05e7\U05d5\U05e0\U05e4\U05d5\U05e8\U05d8\U05e1"; Phone1 = "03-7330733"; Phone2 = ""; ZipCode = ""; }

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• Accessing a Class Member from a First-Class Function

  - by dbyrne

  I have a case class which takes a list of functions: case class A(q:Double, r:Double, s:Double, l:List[(Double)=>Double]) I have over 20 functions defined. Some of these functions have their own parameters, and some of them also use the q, r, and s values from the case class. Two examples are: def f1(w:Double) = (d:Double) => math.sin(d) * w def f2(w:Double, q:Double) = (d:Double) => d * q * w The problem is that I then need to reference q, r, and s twice when instantiating the case class: A(0.5, 1.0, 2.0, List(f1(3.0), f2(4.0, 0.5))) //0.5 is referenced twice I would like to be able to instantiate the class like this: A(0.5, 1.0, 2.0, List(f1(3.0), f2(4.0))) //f2 already knows about q! What is the best technique to accomplish this? Can I define my functions in a trait that the case class extends? EDIT: The real world application has 7 members, not 3. Only a small number of the functions need access to the members. Most of the functions don't care about them.

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• Google Spreadsheet API problem: memory exceeded

  - by Robbert

  Hi guys, Don't know if anyone has experience with the Google Spreadsheets API or the Zend_GData classes but it's worth a go: When I try to insert a value in a 750 row spreadsheet, it takes ages and then throws an error that my memory limit (which is 128 MB!) was exceeded. I also got this when querying all records of this spreadsheet but this I can imaging because it's quite a lot of data. But why does this happen when inserting a row? That's not too complex, is it? Here's the code I used: public function insertIntoSpreadsheet($username, $password, $spreadSheetId, $data = array()) { $service = Zend_Gdata_Spreadsheets::AUTH_SERVICE_NAME; $client = Zend_Gdata_ClientLogin::getHttpClient($username, $password, $service); $client->setConfig(array( 'timeout' => 240 )); $service = new Zend_Gdata_Spreadsheets($client); if (count($data) == 0) { die("No valid data"); } try { $newEntry = $service->insertRow($data, $spreadSheetId); return true; } catch (Exception $e) { return false; } }

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• Why does Microsoft advise against readonly fields with mutable values?

  - by Weeble

  In the Design Guidelines for Developing Class Libraries, Microsoft say: Do not assign instances of mutable types to read-only fields. The objects created using a mutable type can be modified after they are created. For example, arrays and most collections are mutable types while Int32, Uri, and String are immutable types. For fields that hold a mutable reference type, the read-only modifier prevents the field value from being overwritten but does not protect the mutable type from modification. This simply restates the behaviour of readonly without explaining why it's bad to use readonly. The implication appears to be that many people do not understand what "readonly" does and will wrongly expect readonly fields to be deeply immutable. In effect it advises using "readonly" as code documentation indicating deep immutability - despite the fact that the compiler has no way to enforce this - and disallows its use for its normal function: to ensure that the value of the field doesn't change after the object has been constructed. I feel uneasy with this recommendation to use "readonly" to indicate something other than its normal meaning understood by the compiler. I feel that it encourages people to misunderstand the meaning of "readonly", and furthermore to expect it to mean something that the author of the code might not intend. I feel that it precludes using it in places it could be useful - e.g. to show that some relationship between two mutable objects remains unchanged for the lifetime of one of those objects. The notion of assuming that readers do not understand the meaning of "readonly" also appears to be in contradiction to other advice from Microsoft, such as FxCop's "Do not initialize unnecessarily" rule, which assumes readers of your code to be experts in the language and should know that (for example) bool fields are automatically initialised to false, and stops you from providing the redundancy that shows "yes, this has been consciously set to false; I didn't just forget to initialize it". So, first and foremost, why do Microsoft advise against use of readonly for references to mutable types? I'd also be interested to know: Do you follow this Design Guideline in all your code? What do you expect when you see "readonly" in a piece of code you didn't write?

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• Lazarus Pascal - DB Connection - clarification

  - by itsols

  The following code is from the docs here: Program ConnectDB var AConnection : TSQLConnection; Procedure CreateConnection; begin AConnection := TIBConnection.Create(nil); AConnection.Hostname := 'localhost'; AConnection.DatabaseName := '/opt/firebird/examples/employee.fdb'; AConnection.UserName := 'sysdba'; AConnection.Password := 'masterkey'; end; begin CreateConnection; AConnection.Open; if Aconnection.Connected then writeln('Succesful connect!') else writeln('This is not possible, because if the connection failed, ' + 'an exception should be raised, so this code would not ' + 'be executed'); AConnection.Close; AConnection.Free; end. The main body of the code makes sense to me BUT I don't get where TSQLConnection came from. I cannot use CTRL + Space to autocomplete it either, which means my program has no reference to it. I'm trying to connect to Postgres by the way. Can someone please state what TSQLConnection is? Thanks!

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• Using the Proxy pattern with C++ iterators

  - by Billy ONeal

  Hello everyone :) I've got a moderately complex iterator written which wraps the FindXFile apis on Win32. (See previous question) In order to avoid the overhead of constructing an object that essentially duplicates the work of the WIN32_FIND_DATAW structure, I have a proxy object which simply acts as a sort of const reference to the single WIN32_FIND_DATAW which is declared inside the noncopyable innards of the iterator. This is great because Clients do not pay for construction of irrelevant information they will probably not use (most of the time people are only interested in file names), and Clients can get at all the information provided by the FindXFile APIs if they need or want this information. This becomes an issue though because there is only ever a single copy of the object's actual data. Therefore, when the iterator is incrememnted, all of the proxies are invalidated (set to whatever the next file pointed to by the iterator is). I'm concerned if this is a major problem, because I can think of a case where the proxy object would not behave as somebody would expect: std::vector<MyIterator::value_type> files; std::copy(MyIterator("Hello"), MyIterator(), std::back_inserter(files)); because the vector contains nothing but a bunch of invalid proxies at that point. Instead, clients need to do something like: std::vector<std::wstring> filesToSearch; std::transform( DirectoryIterator<FilesOnly>(L"C:\\Windows\\*"), DirectoryIterator<FilesOnly>(), std::back_inserter(filesToSearch), std::mem_fun_ref(&DirectoryIterator<FilesOnly>::value_type::GetFullFileName) ); Seeing this, I can see why somebody might dislike what the standard library designers did with std::vector<bool>. I'm still wondering though: is this a reasonable trade off in order to achieve (1) and (2) above? If not, is there any way to still achieve (1) and (2) without the proxy?

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• Rails - eager load the number of associated records, but not the record themselves.

  - by Max Williams

  I have a page that's taking ages to render out. Half of the time (3 seconds) is spent on a .find call which has a bunch of eager-loaded associations. All i actually need is the number of associated records in each case, to display in a table: i don't need the actual records themselves. Is there a way to just eager load the count? Here's a simplified example: @subjects = Subject.find(:all, :include => [:questions]) In my table, for each row (ie each subject) i just show the values of the subject fields and the number of associated questions for each subject. Can i optimise the above find call to suit these requirements? I thought about using a group field but my full call has a few different associations included, with some second-order associations, so i don't think group by will work. @subjects = Subject.find(:all, :include => [{:questions => :tags}, {:quizzes => :tags}], :order => "subjects.name") :tags in this case is a second-order association, via taggings. Here's my associations in case it's not clear what's going on. Subject has_many :questions has_many :quizzes Question belongs_to :subject has_many :taggings has_many :tags, :through => :taggings Quiz belongs_to :subject has_many :taggings has_many :tags, :through => :taggings Grateful for any advice - max

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• SQL query recursion for a web-like structure

  - by MickeyD

  I have a table here, named "Foo". The data is set up something like this. ID TableReference DataId0 DataId1 DataId2 -- -------------- ------- ------- ------- 1 Prize 3 4 5 2 Prize 4 5 NULL 3 Cash 1 NULL NULL 4 Prize 8 NULL 12 5 Foo 2 3 NULL 6 Cash 8 1 10 7 Foo 5 1 2 Etc. The data is horribly set up, I know, but I didn't set it up that way. :) I'm only dealing with the after effect. I'm trying to come up with a way to essentially "flatten" the table; that is, to display all the data to a point where the table "Foo" does not reference itself. I'm trying to figure out a sql query that I can do to get there. Usually when I deal with recursion, I have (or can establish) parent IDs and set it up that way, but for this table there are seemingly multiple child and parent IDs creating a web-like structure instead of a hierarchy. So I'm at a loss where to even begin to write a sql query for something like this. Note: There is no infinite looping (where one Foo points to another Foo, which points back to the original Foo) from what I've found. Using t-sql. Thanks for any assistance, if at all possible.

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• PHP: Next Available Value in an Array, starting with a non-indexed value

  - by Erik Smith

  I've been stumped on this PHP issue for about a day now. Basically, we have an array of hours formatted in 24-hour format, and an arbitrary value ($hour) (also a 24-hour). The problem is, we need to take $hour, and get the next available value in the array, starting with the value that immediately proceeds $hour. The array might look something like: $goodHours = array('8,9,10,11,12,19,20,21). Then the hour value might be: $hour = 14; So, we need some way to know that 19 is the next best time. Additionally, we might also need to get the second, third, or fourth (etc) available value. The issue seems to be that because 14 isn't a value in the array, there is not index to reference that would let us increment to the next value. To make things simpler, I've taken $goodHours and repeated the values several times just so I don't have to deal with going back to the start (maybe not the best way to do it, but a quick fix). I have a feeling this is something simple I'm missing, but I would be so appreciative if anyone could shed some light. Erik

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• populate textboxs with xml node attributes

  - by Doug

  I have Data.xml: <?xml version="1.0" encoding="utf-8" ?> <data> <album> <slide title="Autum Leaves" description="Leaves from the fall of 1986" source="images/Autumn Leaves.jpg" thumbnail="images/Autumn Leaves_thumb.jpg" /> <slide title="Creek" description="Creek in Alaska" source="images/Creek.jpg" thumbnail="images/Creek_thumb.jpg" /> </album> </data> I'd like to be able to edit the attributes of each Slide node via GridView (that has a "Select" column added.) And so far I have: protected void GridView1_SelectedIndexChanged(object sender, EventArgs e) { int selectedIndex = GridView1.SelectedIndex; LoadXmlData(selectedIndex); } private void LoadXmlData(int selectedIndex) { XmlDocument xmldoc = new XmlDocument(); xmldoc.Load(MapPath(@"..\photo_gallery\Data.xml")); XmlNodeList nodelist = xmldoc.DocumentElement.ChildNodes; XmlNode xmlnode = nodelist.Item(selectedIndex); titleTextBox.Text = xmlnode.Attributes["title"].InnerText; descriptionTextBox.Text = xmlnode.Attributes["description"].InnerText; sourceTextBox.Text = xmlnode.Attributes["source"].InnerText; thumbTextBox.Text = xmlnode.Attributes["thumbnail"].InnerText; The code for LoadXmlData is just a guess on my part - I'm new to working with xml in this way. I'd like have the user to slected the row from the gridview, then populate a set of text boxes with each slide attributed for updating back to the Data.xml file. The error I'm getting is "Object reference not set to an instance of an object" at the line: titleTextBox.Text = xmlnode.Attributes["@title"].InnerText; - so I'm not reaching the attribute "title" of the slide node. Thanks for any ideas you may have.

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• Netlogo: error when putting variable in table, only constants allowe??

  - by Chantal

  Hello, Currently I am working on a Netlogo program where I need to use nodes and links for vehicle routing problem. (links are called streets in the program) Here I have some practical problems of how to input variable linkspeed in a table with another node. Constants like 200 etc are fine. Online I found some examples where variables are used, but I do not know why I keep getting the following error: Expected a constant. (or why netlogo expects a constant) Here is the relevant piece of code: extensions [table] streets-own [linkspeed linktoll] nodes-own [netw] ;; In another piece of code linkspeed is assigned successfully to the links to cheapcalc ;; start conditions set costs very high 300000 ;; state 3 unsearched state 2 searching state 1 searched (for later purposes) ask nodes [ set i 0 set j count nodes set netw table:make while [i < j][ table:put netw (i) [3000000 3] set i (i + 1)]] set i 0 let k 0 ask node 35 ;; here i use node 35 as an example. ;; node 35 is connected to node 34, 36, 20 and 50 [table:put netw (35) [0 1] ;; node need to search costs to travel to itself ;; putting constants is ok. while [i < j] [ask my-links [ask both-ends [if (who != 35) [set color blue ;; set temp ([linkspeed] of street 35 who) ;; here my real goal is to put this in stat of i. but i is easier than linkspeed. table:put netw (who) [ i 2 ] ] ] ] set i (i + 1)] ] ;; next node for later, no it is just repetition of the same. end I hope somebody knows what is going on... Kind regards, Chantal

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• Are MEF's ComposableParts contracts instance-based?

  - by Dave

  I didn't really know how to phrase the title of my questions, so my apologies in advance. I read through parts of the MEF documentation to try to find the answer to my question, but couldn't find it. I'm using ImportMany to allow MEF to create multiple instances of a specific plugin. That plugin Imports several parts, and within calls to a specific instance, it wants these Imports to be singletons. However, what I don't want is for all instances of this plugin to use the same singleton. For example, let's say my application ImportManys Blender appliances. Every time I ask for one, I want a different Blender. However, each Blender Imports a ControlPanel. I want each Blender to have its own ControlPanel. To make things a little more interesting, each Blender can load BlendPrograms, which are also contained within their own assemblies, and MEF takes care of this loading. A BlendProgram might need to access the ControlPanel to get the speed, but I want to ensure that it is accessing the correct ControlPanel (i.e. the one that is associated with the Blender that is associated with the program!) This diagram might clear things up a little bit: As the note shows, I believe that the confusion could come from an inherently-poor design. The BlendProgram shouldn't touch the ControlPanel directly, and instead perhaps the BlendProgram should get the speed via the Blender, which will then delegate the request to its ControlPanel. If this is the case, then I assume the BlendProgram needs to have a reference to a specific Blender. In order to do this, is the right way to leverage MEF and use an ImportingConstructor for BlendProgram, i.e. [ImportingConstructor] public class BlendProgram : IBlendProgram { public BlendProgram( Blender blender) {} } And if this is the case, how do I know that MEF will use the intended Blender plugin?

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