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• structDelete doesn't effect the shallow copy?

  - by Travis

  I was playing around onError so I tried to create an error using a large xml document object. <cfset variables.XMLByRef = variables.parsedXML.XMLRootElement.XMLChildElement> <cfset structDelete(variables.parsedXML, "XMLRootElement")> <cfset variables.startXMLShortLoop = getTickCount()> <cfloop from = "1" to = "#arrayLen(variables.XMLByRef)#" index = "variables.i"> <cfoutput>#variables.XMLByRef[variables.i].id.xmltext#</cfoutput><br /> </cfloop> <cfset variables.stopXMLShortLoop = getTickCount()> I expected to get an error because I deleted the structure I was referencing. From LiveDocs: Variable Assignment - Creates an additional reference, or alias, to the structure. Any change to the data using one variable name changes the structure that you access using the other variable name. This technique is useful when you want to add a local variable to another scope or otherwise change a variable's scope without deleting the variable from the original scope. instead I got 580df1de-3362-ca9b-b287-47795b6cdc17 25a00498-0f68-6f04-a981-56853c0844ed ... ... ... db49ed8a-0ba6-8644-124a-6d6ebda3aa52 57e57e28-e044-6119-afe2-aebffb549342 Looped 12805 times in 297 milliseconds <cfdump var = "#variables#"> Shows there's nothing in the structure, just parsedXML.xmlRoot.xmlName with the value of XMLRootElement. I also tried <cfset structDelete(variables.parsedXML.XMLRootElement, "XMLChildElement")> as well as structClear for both. More information on deleting from the xml document object. http://help.adobe.com/en_US/ColdFusion/9.0/Developing/WSc3ff6d0ea77859461172e0811cbec22c24-78e3.html Can someone please explain my faulty logic? Thanks.

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• Using static variables for Strings

  - by Vivart

  below content is taken from Best practice: Writing efficient code but i didn't understand why private static String x = "example"; faster than private static final String x ="example"; Can anybody explain this. Using static variables for Strings When you define static fields (also called class fields) of type String, you can increase application speed by using static variables (not final) instead of constants (final). The opposite is true for primitive data types, such as int. For example, you might create a String object as follows: private static final String x = "example"; For this static constant (denoted by the final keyword), each time that you use the constant, a temporary String instance is created. The compiler eliminates "x" and replaces it with the string "example" in the bytecode, so that the BlackBerry® Java® Virtual Machine performs a hash table lookup each time that you reference "x". In contrast, for a static variable (no final keyword), the String is created once. The BlackBerry JVM performs the hash table lookup only when it initializes "x", so access is faster. private static String x = "example"; You can use public constants (that is, final fields), but you must mark variables as private.

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• Why represent shopping carts and order invoices differently in a domain model?

  - by Todd

  I've built some shopping cart systems in the past, but I always designed them such that the final order invoice is just a shopping cart that has been marked as "purchased". All the logic for adding/removing/changing items in a cart is also the logic for the order. All data is stored in the same tables in the database. But it seems this is not the proper way to design an e-commerce site.. Can someone explain the benefit of separating the shopping cart from invoices in the domain model? It seems to me this would lead to a lot of duplicated code, an extra set of tables in the database, and make it harder to maintain in the event the system need to start accommodating more complicated orders (like specifying selected options for an item which may or may not change the price/availability/shipping time of the order). I'm assuming I just haven't seen the light, as every book and other example I see seems to separate these two seemingly similar concerns -- but I can't find any explanation as to the benefit of doing such! It's also the case in the systems that I design that changes are often made after the initial order is confirmed. It's not uncommon for items to be removed, replaced, or added afterwards (but prior to fulfillment).

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• Prototyping Qt/C++ in Python

  - by tstenner

  I want to write a C++ application with Qt, but build a prototype first using Python and then gradually replace the Python code with C++. Is this the right approach, and what tools (bindings, binding generators, IDE) should I use? Ideally, everything should be available in the Ubuntu repositories so I wouldn't have to worry about incompatible or old versions and have everything set up with a simple aptitude install. Is there any comprehensive documentation about this process or do I have to learn every single component, and if yes, which ones? Right now I have multiple choices to make: Qt Creator, because of the nice auto completion and Qt integration. Eclipse, as it offers support for both C++ and Python. Eric (haven't used it yet) Vim PySide as it's working with CMake and Boost.Python, so theoretically it will make replacing python code easier. PyQt as it's more widely used (more support) and is available as a Debian package. Edit: As I will have to deploy the program to various computers, the C++-solution would require 1-5 files (the program and some library files if I'm linking it statically), using Python I'd have to build PyQt/PySide/SIP/whatever on every platform and explain how to install Python and everything else.

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• C++ File manipulation problem

  - by Carlucho

  I am trying to open a file which normally has content, for the purpose of testing i will like to initialize the program without the files being available/existing so then the program should create empty ones, but am having issues implementing it. This is my code originally void loadFiles() { fstream city; city.open("city.txt", ios::in); fstream latitude; latitude.open("lat.txt", ios::in); fstream longitude; longitude.open("lon.txt", ios::in); while(!city.eof()){ city >> cityName; latitude >> lat; longitude >> lon; t.add(cityName, lat, lon); } city.close(); latitude.close(); longitude.close(); } I have tried everything i can think of, ofstream, ifstream, adding ios::out all all its variations. Could anybody explain me what to do in order to fix the problem. Thanks!

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• When I Add <DIV> Bottom Scroll Bar Appears, Even Though It Is Not Greater Than The Page Width

  - by Clay Dempsey

  I have searched for this with no answer. My page loads up perfectly when I load the header, navigation and then center image...all 3 different divs. However I have more I need to add and the div tags change the size of the page even though the css I'm using isn't larger than the page. I have no idea what is happening. Here's the code page where everything is fine: http://www.thehdmgroup.com/midwaymissionary/test.php When I add the below div tag with the below css I get a bottom scrollbar on the page and I don't know why. Can someone please explain it to me? #middleTextBox1 { position: absolute; top:507px; left:172px; width:180px; height:180px; background-color:#411b42; border: 1px solid #434343; padding:10px; color: #FFFFFF; font-size: 10px; font-family: Arial, Helvetica, sans-serif; } <div id="middleTextBox1"> <h3 align="center">Mission:</h3> Words </div> I really have no idea why this is happening, could someone please help me out? Thanks for your time.

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• RequestBuilder timeouts and browser connection limits per domain.

  - by WesleyJohnson

  This is specifically about GWT's RequestBuilder, but should apply to general XHR as well. My company is having me build a near realtime chat application over HTTP. Yes, I do realize there are better ways to do chat aplications, but this is what they want. Eventually we want it working on the iPad/iPhone as well so flash is out, which rules out websockets and comet as well, I think? Anyway, I'm running into issues were I've set GWT's RequestBuilder timeout to 10 seconds and we get very random and sporadic timeouts. We've got error handling and emailing on the server side and never get any errors, which suggests the underlying XHR request that RequestBuilder is built on, never gets to the server and times out after 10 seconds. We're using these request to poll the server for new messages rather often and also for sending new messages to the server and also polling (less frequently) for other parts of application. What I'm afraid of is that we're running into the browsers limit on concurrent connections to the same domain (2 for IE by default?). Now my question is - If I construct a RequestBuilder and call it's send() method and the browser blocks it from sending until one of the 2 connections per domain is free, does the timeout still start while the request is being blocked or will it not start until the browser actually releases the underlying XHR? I hope that's clear, if not please let me know and I'll try to explain more.

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• Perform function in attr() callback?

  - by Jared

  Hello, Not sure if I am doing this correctly or not. Here is my JS: var currentIMG; $( '.leftMenuProductButton' ).hover ( function () { currentIMG = $("#swapImg").attr("src"); var swapIMG = $(this).next(".menuPopup").attr("id"); $("#swapImg").css("opacity", 0).attr("src", productImages[swapIMG], function(){ $("#swapImg").fadeTo("slow", 1); }); }, function () { $("#swapImg").stop().attr("src",currentIMG); }); What I am trying to do is Set a IMG Opacity to 0 (#swapImg), replace it's SRC, then fade it back in. So I am trying to fade it back in using a callback from the attr(). If I am doing this incorrectly, can someone please explain a better way to do this? The reason I am trying to do it in the callback is that I need the fadeTo to only occur after the new image is fully loaded, otherwise it does a bit of a flash. I am using jquery 1.4, and according to http://jquery14.com/day-01/jquery-14 it appears you can do a callback in the attr() method.

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• How can I include DBNull as a value in my strongly typed dataset?

  - by Beska

  I've created a strongly typed dataset (MyDataSet) in my .NET app. For the sake of simplicity, we'll say it has one DataTable (MyDataTable), with one column (MyCol). MyCol has its DataType property set to "System.Int32", and its AllowDBNull property set to "true". I'd like to manually create a new row, and add it to this dataset. I create the row without a problem, with something like: MyDataSet.MyDataTableRow myRow = MySimpleDataSet.MyDataTable.NewItemRow(); Fine. However, when I try to set the value to DBNull: myRow.MyCol = DBNull.Value; I'm told that I can't do it...that it can't cast that to an int. This makes sense, in a way, since I've defined it to be an int...but then how can I get DBNull in there? Am I not supposed to be able to have DBNull in there? Isn't that what the AllowDBNull property is for? I'm obviously missing something fundemental. Can someone help explain what it is? EDIT: I also tried entering "int?" as the DataType, but Visual Studio throws an error when I enter it, saying that "Column requires a valid DataType."

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• NotApplicable marker with display pattern

  - by Jeff Barger

  Ok, so I'm pretty new to Cocoa, especially Bindings, but here's what I'm trying to do. I've got a Core Data model consisting of two entities: Category and Item. Category has a to-many relationship to Item called children, and Item has a relationship to Category called parent. Item has two attributes that Category does not have: quantity and desiredQuantity. What I'd like to do is display the tree in an NSOutlineView with two columns. One column is bound to the name of either the Category or the Item. I want to the second column to display something along the lines of 2 of 5 for the Item rows and nothing at all for the Category rows. When I use a display pattern, the Category rows end up showing of I noticed that if I don't use a display pattern for the second column, and instead just bind its Value to either the quantity or the desiredQuantity, the Category rows show nothing; its only if I try to use the display pattern. How can I make it display nothing for the Category rows and still use the display pattern? Or can I? Edit: I guess I didn't explain what the NotApplicable marker has to do with anything - Category does have properties for quantity and desiredQuantity, but they just return NSNotApplicableMarker.

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• JPA returning null for deleted items from a set

  - by Jon

  This may be related to my question from a few days ago, but I'm not even sure how to explain this part. (It's an entirely different parent-child relationship.) In my interface, I have a set of attributes (Attribute) and valid values (ValidValue) for each one in a one-to-many relationship. In the Spring MVC frontend, I have a page for an administrator to edit these values. Once it's submitted, if any of these fields (as <input> tags) are blank, I remove the ValidValue object like so: Set<ValidValue> existingValues = new HashSet<ValidValue>(attribute.getValidValues()); Set<ValidValue> finalValues = new HashSet<ValidValue>(); for(ValidValue validValue : attribute.getValidValues()) { if(!validValue.getValue().isEmpty()) { finalValues.add(validValue); } } existingValues.removeAll(finalValues); for(ValidValue removedValue : existingValues) { getApplicationDataService().removeValidValue(removedValue); } attribute.setValidValues(finalValues); getApplicationDataService().modifyAttribute(attribute); The problem is that while the database is updated appropriately, the next time I query for the Attribute objects, they're returned with an extra entry in their ValidValue set -- a null, and thus, the next time I iterate through the values to display, it shows an extra blank value in the middle. I've confirmed that this happens at the point of a merge or find, at the point of "Execute query ReadObjectQuery(entity.Attribute). Here's the code I'm using to modify the database (in the ApplicationDataService): public void modifyAttribute(Attribute attribute) { getJpaTemplate().merge(attribute); } public void removeValidValue(ValidValue removedValue) { ValidValue merged = getJpaTemplate().merge(removedValue); getJpaTemplate().remove(merged); } Here are the relevant parts of the entity classes: Entity @Table(name = "attribute") public class Attribute { @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "attribute") private Set<ValidValue> validValues = new HashSet<ValidValue>(0); } @Entity @Table(name = "valid_value") public class ValidValue { @ManyToOne(fetch = FetchType.LAZY) @JoinColumn(name = "attr_id", nullable = false) private Attribute attribute; }

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• problem using the xsl method for-each

  - by joe

  Using XSL I am trying to turn this XML: <book><title>This is a <b>great</b> book</title></book> into this XML: <book>This is a <bold>great</bold> book</book> using this xsl: <xsl:for-each select="book/title/*"> <xsl:choose> <xsl:when test="name() = 'b'"> <bold> <xsl:value-of select="text()"/> </bold> </xsl:when> <xsl:otherwise> <xsl:value-of select="text()"/> </xsl:otherwise> </xsl:choose> </xsl:for-each> but my output is looking like this: <book><bold>great</bold></bold> Can anyone explain why the root text of <title> is getting lost? I believe my for-each select statement may need to be modified but I can't figure out what is should be. Keep in mind that I cannot use an <xsl:template match> because of the complexity of my style sheet. Thanks!

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• What's the correct way to pass parameters from VBScript to COM interface implemented in C#?

  - by nopopem

  I'm trying to expose a fairly simple C# class to COM which should be usable from VBScript (among others). Some objects need to be created via COM calls and will be used in furter calls later on. The definition of the exposed classes and interfaces looks like this: namespace Test { [InterfaceType(ComInterfaceType.InterfaceIsIDispatch)] public interface IComInterface { IFoo CreateFoo(); void UseFoo(int x, IFoo f); } [ClassInterface(ClassInterfaceType.None)] public sealed class CComInterface : IComInterface { public CComInterface() {} public IFoo CreateFoo() { return new Foo(); } public void UseFoo(int x, IFoo f) { f.Bar(); } } [InterfaceType(ComInterfaceType.InterfaceIsIDispatch)] public interface IFoo { void Bar(); } [ClassInterface(ClassInterfaceType.None)] public class Foo : IFoo { internal Foo() {} public void Bar() {} } } The simplest thinkable COM client in VBScript does this: Dim ci Set ci = WScript.CreateObject("Test.CComInterface") Dim foo Set foo = ci.CreateFoo foo.Bar ci.UseFoo 0, foo While the call to Bar succeeds, calling UseFoo fails with "Error 5: invalid procedure call or invalid argument" The generated IDL seems ok to me: dispinterface IComInterface { properties: methods: [id(0x60020003)] IFoo* CreateFoo(); [id(0x60020004)] void UseFoo( [in] long x, [in] IFoo* f); }; The vbs call succeeds when I wrap the second parameter in parentheses like this: ci.UseFoo 0, (foo) As far as I understand (I'm no VBScript expert however) this forces the reference to foo to be passed by value, i.e. a copy of the reference is being made. How can I change the interface so that it can be called with the foo reference directly? Since this will be a public interface used by customers I don't like the idea of having to explain why all the objects created need to be passed back in an extra pair of parentheses...

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• How does SVN store commit time

  - by Salman

  I am working on a project that involves extracting details from a SVN server using SVNKit. My project is already complete and has been working we for a while now. During the testing, I noticed something rather very strange. the Commit Times my extract data seems is alway different from whats there in SVN Logs. I couldnt find any code in my project that could be inducing this difference but now I am looking as to how SVN server stores the Commit time in itself. As we have developer working from different part of the world thus resulting in different timezones, I was thinking that SVN might be storing time after converting them to GMT or timezone of the system on which SVN server is running. But that does not seem to be happening. Instead the times are stored as per the time when the commit was done and in that local timezone itself. I have been unable to find any substantial document on internet to support my theory so far. Can anybody in brief explain as how SVN store the Commit Time for each change? Documentaion links referring to this will be of great help.

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• oracle select query - index on multiple columns

  - by CC

  Hello. I'm working on a sql query, and trying to optimise it, because it takes too long to execute. I have a few select and UNION between. Every select is on the same table but with different condition in WHERE clause. Basically I have allways something like : select * from A where field1 <"toto" and field2 IN (...) UNION select * from A where field1 >"toto2" and field2 =(...) UNION .... I have a index on field1 (it a date field, and field2 is a number). Now, when I do the select and if I put only WHERE field1 <'12/12/2010' it does not use the index. I'm using Toad to see the explain plain and it said: SELECT STAITEMENT Optimiser Mode = CHOOSE TABLE ACCESS FULL It is a huge table, and the index on this column is there. Any idea about this optimiser ? And why it does not uses the index ? Another question is , if I have where clause on field1 and field2 , I have to create only one index, or one index for each field ? Thanks alot.

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• Batch insert mode with hibernate and oracle: seems to be dropping back to slow mode silently

  - by Chris

  I'm trying to get a batch insert working with Hibernate into Oracle, according to what i've read here: http://docs.jboss.org/hibernate/core/3.3/reference/en/html/batch.html , but with my benchmarking it doesn't seem any faster than before. Can anyone suggest a way to prove whether hibernate is using batch mode or not? I hear that there are numerous reasons why it may silently drop into normal mode (eg associations and generated ids) so is there some way to find out why it has gone non-batch? My hibernate.cfg.xml contains this line which i believe is all i need to enable batch mode: <property name="jdbc.batch_size">50</property> My insert code looks like this: List<LogEntry> entries = ..a list of 100 LogEntry data classes... Session sess = sessionFactory.getCurrentSession(); for(LogEntry e : entries) { sess.save(e); } sess.flush(); sess.clear(); My 'logentry' class has no associations, the only interesting field is the id: @Entity @Table(name="log_entries") public class LogEntry { @Id @GeneratedValue public Long id; ..other fields - strings and ints... However, since it is oracle, i believe the @GeneratedValue will use the sequence generator. And i believe that only the 'identity' generator will stop bulk inserts. So if anyone can explain why it isn't running in batch mode, or how i can find out for sure if it is or isn't in batch mode, or find out why hibernate is silently dropping back to slow mode, i'd be most grateful. Thanks

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• How to write these two queries for a simple data warehouse, using ANSI SQL?

  - by morpheous

  I am writing a simple data warehouse that will allow me to query the table to observe periodic (say weekly) changes in data, as well as changes in the change of the data (e.g. week to week change in the weekly sale amount). For the purposes of simplicity, I will present very simplified (almost trivialized) versions of the tables I am using here. The sales data table is a view and has the following structure: CREATE TABLE sales_data ( sales_time date NOT NULL, sales_amt double NOT NULL ) For the purpose of this question. I have left out other fields you would expect to see - like product_id, sales_person_id etc, etc, as they have no direct relevance to this question. AFAICT, the only fields that will be used in the query are the sales_time and the sales_amt fields (unless I am mistaken). I also have a date dimension table with the following structure: CREATE TABLE date_dimension ( id integer NOT NULL, datestamp date NOT NULL, day_part integer NOT NULL, week_part integer NOT NULL, month_part integer NOT NULL, qtr_part integer NOT NULL, year_part integer NOT NULL, ); which partition dates into reporting ranges. I need to write queries that will allow me to do the following: Return the change in week on week sales_amt for a specified period. For example the change between sales today and sales N days ago - where N is a positive integer (N == 7 in this case). Return the change in change of sales_amt for a specified period. For in (1). we calculated the week on week change. Now we want to know how that change is differs from the (week on week) change calculated last week. I am stuck however at this point, as SQL is my weakest skill. I would be grateful if an SQL master can explain how I can write these queries in a DB agnostic way (i.e. using ANSI SQL).

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• How to catch unintentional function interpositioning?

  - by SiegeX

  Reading through my book Expert C Programming, I came across the chapter on function interpositioning and how it can lead to some serious hard to find bugs if done unintentionally. The example given in the book is the following: my_source.c mktemp() { ... } main() { mktemp(); getwd(); } libc mktemp(){ ... } getwd(){ ...; mktemp(); ... } According to the book, what happens in main() is that mktemp() (a standard C library function) is interposed by the implementation in my_source.c. Although having main() call my implementation of mktemp() is intended behavior, having getwd() (another C library function) also call my implementation of mktemp() is not. Apparently, this example was a real life bug that existed in SunOS 4.0.3's version of lpr. The book goes on to explain the fix was to add the keyword static to the definition of mktemp() in my_source.c; although changing the name altogether should have fixed this problem as well. This chapter leaves me with some unresolved questions that I hope you guys could answer: Does GCC have a way to warn about function interposition? We certainly don't ever intend on this happening and I'd like to know about it if it does. Should our software group adopt the practice of putting the keyword static in front of all functions that we don't want to be exposed? Can interposition happen with functions introduced by static libraries? Thanks for the help. EDIT I should note that my question is not just aimed at interposing over standard C library functions, but also functions contained in other libraries, perhaps 3rd party, perhaps ones created in-house. Essentially, I want to catch any instance of interpositioning regardless of where the interposed function resides.

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• Hide All But First Matching Element

  - by Batfan

  I am using jquery to sort through multiple paragraphs. Currently I have it set to show only paragraphs that start with a current letter. But now, I would like to consolidate further. If the text between the paragraph tags has multiple instances, I would like all but the first hidden. This is what I have so far but, it is not working. var letter = '<?php echo(strlen($_GET['letter']) == 1) ? $_GET['letter'] : ''; ?>' function finish(){ jQuery('p').each(function(){ if(jQuery(this).text().substr(0,1).toUpperCase() == letter){ jQuery(this).addClass('current-series'); jQuery(this).html(letter + '<span class="hidden">'+jQuery(this).text().slice(1)+ '</span>'); } else{ jQuery(this).hide();} }) } Update: Sorry guys, I know this is kind of hard to explain. Here's a basic example: The selected letter is B The values returned are: Ball Ball Ball Boy Brain Bat Bat Each of these values is in a paragraph tag. Is there a way to consolidate to this? Ball Boy Brain Bat

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• Silverlight 4, Google Chrome, and HttpWebRequest problem

  - by synergetic

  My Silvrlight 4 application hosted in ASP.NET MVC 2 working fine when used through Internet Explorer 8, both in development server and remote web server (IIS 6.0). However when I try to browse through Google Chrome (version 5.0.375.70) it throws "remote server returned not found" error. The code causing the problem is the following: public class MyWebClient { private HttpWebRequest _request; private Uri _uri; private AsyncOperation _asyncOp; public MyWebClient(Uri uri) { _uri = uri; } public void Start(XElement data) { _asyncOp = AsyncOperationManager.CreateOperation(null); _data = data; _request = (HttpWebRequest)WebRequest.Create(_uri); _request.Method = "POST"; _request.BeginGetRequestStream(new AsyncCallback(BeginRequest), null); } private void BeginRequest(IAsyncResult result) { Stream stream = _request.EndGetRequestStream(result); using (StreamWriter writer = new StreamWriter(stream)) { writer.Write(((XElement)_data).ToString()); } stream.Close(); _request.BeginGetResponse(new AsyncCallback(BeginResponse), null); } private void BeginResponse(IAsyncResult result) { HttpWebResponse response = (HttpWebResponse)_request.EndGetResponse(result); if (response != null) { //process returned data ... } } ... } In short, the above code sends some XML data to web server (to ASP.NET MVC controller) and gets back a processed data. It works when I use Internet Explorer 8. Can someone please explain what is the problem with Google Chrome?

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• Read a text file

  - by Cyprus106

  I have looked everywhere and surprisingly can't find a good solution to this! I've got the following code that is supposed to read a text file and display it's contents. But it's not reading, for some reason. Am I doing something wrong? FTR, I can't use PHP for this. It's gotta be Javascript. var txtFile = new XMLHttpRequest(); txtFile.open("GET", "http://www.mysite.com/todaysTrivia.txt", true); txtFile.send(null); txtFile.onreadystatechange = function() { if (txtFile.readyState == 4) { // Makes sure the document is ready to parse. alert(txtFile.responseText+" - "+txtFile.status); //if (txtFile.status === 200) { // Makes sure it's found the file. var doc = document.getElementById("Trivia-Widget"); if (doc) { doc.innerHTML = txtFile.responseText ; } //} } txtFile.send(null); } Any good ideas what I'm doing wrong? It just keeps givimg me a zero status. EDIT: I guess it would be a good idea to explain why I need this code. It's basically a widget that other folks can put on their own websites that grabs a line of text from my website and displays it on theirs. The problem is that it really can't be server-side since I've got zero control over everyone else's sites that use this.

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• System Calls in windows & Native API?

  - by claws

  Recently I've been using lot of Assembly language in *NIX operating systems. I was wondering about the windows domain. Calling convention in linux: mov $SYS_Call_NUM, %eax mov $param1 , %ebx mov $param2 , %ecx int $0x80 Thats it. That is how we should make a system call in linux. Reference of all system calls in linux: Regarding which $SYS_Call_NUM & which parameters we can use this reference : http://docs.cs.up.ac.za/programming/asm/derick_tut/syscalls.html OFFICIAL Reference : http://kernel.org/doc/man-pages/online/dir_section_2.html Calling convention in Windows: ??? Reference of all system calls in Windows: ??? Unofficial : http://www.metasploit.com/users/opcode/syscalls.html , but how do I use these in assembly unless I know the calling convention. OFFICIAL : ??? If you say, they didn't documented it. Then how is one going to write libc for windows without knowing system calls? How is one gonna do Windows Assembly programming? Atleast in the driver programming one needs to know these. right? Now, whats up with the so called Native API? Is Native API & System calls for windows both are different terms referring to same thing? In order to confirm I compared these from two UNOFFICIAL Sources System Calls: http://www.metasploit.com/users/opcode/syscalls.html Native API: http://undocumented.ntinternals.net/aindex.html My observations: All system calls are beginning with letters Nt where as Native API is consisting of lot of functions which are not beginning with letters Nt. System Call of windows are subset of Native API. System calls are just part of Native API. Can any one confirm this and explain.

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• How to define 2-bit numbers in C, if possible?

  - by Eddy

  For my university process I'm simulating a process called random sequential adsorption. One of the things I have to do involves randomly depositing squares (which cannot overlap) onto a lattice until there is no more room left, repeating the process several times in order to find the average 'jamming' coverage %. Basically I'm performing operations on a large array of integers, of which 3 possible values exist: 0, 1 and 2. The sites marked with '0' are empty, the sites marked with '1' are full. Initially the array is defined like this: int i, j; int n = 1000000000; int array[n][n]; for(j = 0; j < n; j++) { for(i = 0; i < n; i++) { array[i][j] = 0; } } Say I want to deposit 5*5 squares randomly on the array (that cannot overlap), so that the squares are represented by '1's. This would be done by choosing the x and y coordinates randomly and then creating a 5*5 square of '1's with the topleft point of the square starting at that point. I would then mark sites near the square as '2's. These represent the sites that are unavailable since depositing a square at those sites would cause it to overlap an existing square. This process would continue until there is no more room left to deposit squares on the array (basically, no more '0's left on the array) Anyway, to the point. I would like to make this process as efficient as possible, by using bitwise operations. This would be easy if I didn't have to mark sites near the squares. I was wondering whether creating a 2-bit number would be possible, so that I can account for the sites marked with '2'. Sorry if this sounds really complicated, I just wanted to explain why I want to do this.

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• Strange results while measuring delta time on Linux

  - by pachanga

  Folks, could you please explain why I'm getting very strange results from time to time using the the following code: #include <unistd.h> #include <sys/time.h> #include <time.h> #include <stdio.h> int main() { struct timeval start, end; long mtime, seconds, useconds; while(1) { gettimeofday(&start, NULL); usleep(2000); gettimeofday(&end, NULL); seconds = end.tv_sec - start.tv_sec; useconds = end.tv_usec - start.tv_usec; mtime = ((seconds) * 1000 + useconds/1000.0) + 0.5; if(mtime > 10) printf("WTF: %ld\n", mtime); } return 0; } (You can compile and run it with: gcc test.c -o out -lrt && ./out) What I'm experiencing is sporadic big values of mtime variable almost every second or even more often, e.g: $ gcc test.c -o out -lrt && ./out WTF: 14 WTF: 11 WTF: 11 WTF: 11 WTF: 14 WTF: 13 WTF: 13 WTF: 11 WTF: 16 How can this be possible? Is it OS to blame? Does it do too much context switching? But my box is idle( load average: 0.02, 0.02, 0.3). Here is my Linux kernel version: $ uname -a Linux kurluka 2.6.31-21-generic #59-Ubuntu SMP Wed Mar 24 07:28:56 UTC 2010 i686 GNU/Linux

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• Questions on Juval Lowy's IDesign C# Coding Standard

  - by Jan

  We are trying to use the IDesign C# Coding standard. Unfortunately, I found no comprehensive document to explain all the rules that it gives, and also his book does not always help. Here are the open questions that remain for me (from chapter 2, Coding Practices): No. 26: Avoid providing explicit values for enums unless they are integer powers of 2 No. 34: Always explicitly initialize an array of reference types using a for loop No. 50: Avoid events as interface members No. 52: Expose interfaces on class hierarchies No. 73: Do not define method-specific constraints in interfaces No. 74: Do not define constraints in delegates Here's what I think about those: I thought that providing explicit values would be especially useful when adding new enum members at a later point in time. If these members are added between other already existing members, I would provide explicit values to make sure the integer representation of existing members does not change. No idea why I would want to do this. I'd say this totally depends on the logic of my program. I see that there is alternative option of providing "Sink interfaces" (simply providing already all "OnXxxHappened" methods), but what is the reason to prefer one over the other? Unsure what he means here: Could this mean "When implementing an interface explicitly in a non-sealed class, consider providing the implementation in a protected virtual method that can be overridden"? (see Programming .NET Components 2nd Edition, end of chapter “Interfaces and Class Hierarchies”). I suppose this is about providing a "where" clause when using generics, but why is this bad on an interface? I suppose this is about providing a "where" clause when using generics, but why is this bad on a delegate?

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