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• What should be taught in a "Fundamentals of programming" course at university?

  - by Dervin Thunk

  I have started a new question (see here), because I think the topic is of importance in a more general form. The question is now: If you were a professor at a Computer Science Dept. in some university, what would make it into your course? This is a programming course, second term, first year computer science/computer engineering. Remember you have a limited amount of time, and students are of different levels of competence, and some may be scientists, but some will also go on to be programmers in companies of different kinds. You have to cater to all. Bonus: What language? (Although see this question for my current thoughts about this...) Maybe you want to attach a course outline from some university? See here for an even more general question about this. Answer: I can't really summarize this post... I guess it was too subjective. However, it looks like we have to cover the history of computing up to a certain extent, computer architecture (memory, registers, whatever), C, and finally some basic algos and data structures in a problem solving fashion. This will be the bare bones of the course. Thanks all. I will accept the most voted up answer to close the thread, as it should be done.

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• Javascript + PHP $_POST array empty

  - by Peterim

  While trying to send a POST request via xmlhttp.open("POST", "url", true) (javascript) to the server I get an empty $_POST array. Firebug shows that the data is being sent. Here is the data string from Firebug: a=1&q=151a45a150.... But $_POST['q'] returns nothing. The interesting thing is that file_get_contents('php://input') does have my data (the string above), but PHP somehow doesn't recognize it. Tried both $_POST and $_REQUEST, nothing works. Headers being sent: POST /test.php HTTP/1.1 Host: website.com User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2.3) Gecko/20100401 Firefox/3.6.3 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Accept-Language: en-us;q=0.7,en;q=0.3 Accept-Encoding: gzip,deflate Accept-Charset: utf-8;q=0.7,*;q=0.7 Keep-Alive: 115 Connection: keep-alive Referer: http://website.com/ Content-Length: 156 Content-Type: text/plain; charset=UTF-8 Pragma: no-cache Cache-Control: no-cache Thank you for any suggestions.

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• OOP, Interface Design and Encapsulation

  - by Mau

  C# project, but it could be applied to any OO languages. 3 interfaces interacting: public interface IPublicData {} public /* internal */ interface IInternalDataProducer { string GetData(); } public interface IPublicWorker { IPublicData DoWork(); IInternalDataProducer GetInternalProducer(); } public class Engine { Engine(IPublicWorker worker) {} IPublicData Run() { DoSomethingWith(worker.GetInternalProducer().GetData()); return worker.DoWork(); } } Clearly Engine is parametric in the actual worker that does the job. A further source of parametrization is how we produce the 'internal data' via IInternalDataProducer. This implementation requires IInternalDataProducer to be public because it's part of the declaration of the public interface IPublicWorker. However, I'd like it to be internal since it's only used by the engine. A solution is make the IPublicWorker produce the internal data itself, but that's not very elegant since there's only a couple of ways of producing it (while there are many more worker implementations), therefore it's nice to delegate to a couple of separate concrete classes. Moreover, the IInternalDataProducer is used in more places inside the engine, so it's good for the engine to pass around the actual object. I'm looking for elegant ideas/patterns. Cheers :-)

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• Windows Phone 8 Panorama SelectionIndex not changing on swiping through items

  - by Balraj Singh

  I have created Panorama control and binded PanoramaItem from ItemSource. Now when i am changing the selected Panoramaitem by swiping over them the Selected index is always set to -1. I dont know what wrong i am doing while implementation. neither selectionchange event is getting fired. Code: <phone:Panorama Grid.Row="1" Visibility="Visible" x:Name="PnrVwMainNews" ItemsSource="{Binding ParnormaItemsData}" ItemContainerStyle="{StaticResource PanoramaContainerItemStyle}"> <phone:Panorama.ItemTemplate> <DataTemplate> <!-- Panorma Items Template --> <Controls:DynamicContentControl Content="{Binding UsrCntrlDynamic}" /> </DataTemplate> </phone:Panorama.ItemTemplate> </phone:Panorama> PanoramaContainerItemStyle <Style x:Key="PanoramaContainerItemStyle" TargetType="phone:PanoramaItem"> <Setter Property="HorizontalContentAlignment" Value="Stretch" /> <Setter Property="VerticalContentAlignment" Value="Stretch" /> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="phone:PanoramaItem"> <Grid Background="{TemplateBinding Background}" Margin="12,0,0,0"> <Grid.RowDefinitions> <RowDefinition Height="auto" /> <RowDefinition Height="*" /> </Grid.RowDefinitions> <ContentPresenter Content="{TemplateBinding Content}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" Grid.Row="1" VerticalAlignment="{TemplateBinding VerticalContentAlignment}" /> </Grid> </ControlTemplate> </Setter.Value> </Setter> </Style>

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• jQuery - Unchecking checkboxes that act like radio buttons

  - by Cecil

  Hey All, I have the following jQuery code to make my checkboxes act like radio buttons, so that only 1 of the 3 can be checked at a time. <script type="text/javascript" language="javascript"> $(document).ready(function() { $("#testing input:checkbox").change(function(){ var checkname = $(this).attr("name"); $("input:checkbox[name='" + checkname + "']").removeAttr("checked"); this.checked = true; }); }); </script> The checkboxes are layed out like the following: <input type="checkbox" id="testing" name="testing" value="B"> <input type="checkbox" id="testing" name="testing" value="I"> <input type="checkbox" id="testing" name="testing" value="A"> This works exactly how i want it to work, not a problem, except once i click one of the 3, i cant unclick it so that none of them are checked, this is what i want to happen, so along with being only able to click one at a time, im able to uncheck them completely. Any help would be grand :)

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• How do I optimize this postfix expression tree for speed?

  - by Peter Stewart

  Thanks to the help I received in this post: I have a nice, concise recursive function to traverse a tree in postfix order: deque <char*> d; void Node::postfix() { if (left != __nullptr) { left->postfix(); } if (right != __nullptr) { right->postfix(); } d.push_front(cargo); return; }; This is an expression tree. The branch nodes are operators randomly selected from an array, and the leaf nodes are values or the variable 'x', also randomly selected from an array. char *values[10]={"1.0","2.0","3.0","4.0","5.0","6.0","7.0","8.0","9.0","x"}; char *ops[4]={"+","-","*","/"}; As this will be called billions of times during a run of the genetic algorithm of which it is a part, I'd like to optimize it for speed. I have a number of questions on this topic which I will ask in separate postings. The first is: how can I get access to each 'cargo' as it is found. That is: instead of pushing 'cargo' onto a deque, and then processing the deque to get the value, I'd like to start processing it right away. I don't yet know about parallel processing in c++, but this would ideally be done concurrently on two different processors. In python, I'd make the function a generator and access succeeding 'cargo's using .next(). But I'm using c++ to speed up the python implementation. I'm thinking that this kind of tree has been around for a long time, and somebody has probably optimized it already. Any Ideas? Thanks

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• Dealing with multiple generics in a method call

  - by thaBadDawg

  I've been dealing a lot lately with abstract classes that use generics. This is all good and fine because I get a lot of utility out of these classes but now it's making for some rather ugly code down the line. For example: abstract class ClassBase<T> { T Property { get; set; } } class MyClass : ClassBase<string> { OtherClass PropertyDetail { get; set; } } This implementation isn't all that crazy, except when I want to reference the abstract class from a helper class and then I have to make a list of generics just to make reference to the implemented class, like this below. class Helper { void HelpMe<C, T>(object Value) where C : ClassBase<T>, new() { DoWork(); } } This is just a tame example, because I have some method calls where the list of where clauses end up being 5 or 6 lines long to handle all of the generic data. What I'd really like to do is class Helper { void HelpMe<C>(object Value) where C : ClassBase, new() { DoWork(); } } but it obviously won't compile. I want to reference ClassBase without having to pass it a whole array of generic classes to get the function to work, but I don't want to reference the higher level classes because there are a dozen of those. Am I the victim of my own cleverness or is there an avenue that I haven't considered yet?

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• Need help with a simple ASP.NET ModalPopupExtender example

  - by remdao

  I'm new to ASP.NET and I'm trying to get this Ajax ModalPopupExtender working. This is an example i found on the net, but nothing happens when btnpopup is clicked. <%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="ModalTestProject._Default" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" > <head runat="server"> <title>Untitled Page</title> </head> <body> <form id="form1" runat="server"> <asp:scriptmanager id="ScriptManager1" runat="server"> </asp:scriptmanager> <asp:Button ID="btnpopup" runat="server" Text="Button" /> <ajaxToolkit:ModalPopupExtender ID="mpe" runat="server" TargetControlID="btnpopup" PopupControlID="pnlpopup" CancelControlID="btnCancelpopup" EnableViewState="true" DropShadow="true" /> <asp:Panel ID="pnlpopup" runat="server" Width="400px"> test <asp:Button ID="btnCancelpopup" runat="server" Text="Button" /> </asp:Panel> </form> </body> </html>

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• javascript to select text from web page

  - by phil swenson

  I'm trying to write a bookmarklet that grabs any selected text on a web page and sends it to my website. It should (hopefully) work in Chrome, FFX, Safari, and IE. I did a search and found a function, but it doesn't appear to work. Here is the code: <html> <body> <div onClick=getSelText()>Click</div> <div>please select me</div> </body> <script language=javascript> function getSelText(){ var txt = 'nothing'; if (window.getSelection){ txt = "1" + window.getSelection(); } else if (document.getSelection) { txt = "2" + document.getSelection(); } else if (document.selection) { txt = "3" + document.selection.createRange().text; } else return; alert("selected text = " + txt); } </script> </html> when I select the text in the div "please select me" and hit the click div, I just get "selected text = 1" thanks

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• Problem with Boost::Asio for C++

  - by Martin Lauridsen

  Hi there, For my bachelors thesis, I am implementing a distributed version of an algorithm for factoring large integers (finding the prime factorisation). This has applications in e.g. security of the RSA cryptosystem. My vision is, that clients (linux or windows) will download an application and compute some numbers (these are independant, thus suited for parallelization). The numbers (not found very often), will be sent to a master server, to collect these numbers. Once enough numbers have been collected by the master server, it will do the rest of the computation, which cannot be easily parallelized. Anyhow, to the technicalities. I was thinking to use Boost::Asio to do a socket client/server implementation, for the clients communication with the master server. Since I want to compile for both linux and windows, I thought windows would be as good a place to start as any. So I downloaded the Boost library and compiled it, as it said on the Boost Getting Started page: bootstrap .\bjam It all compiled just fine. Then I try to compile one of the tutorial examples, client.cpp, from Asio, found (here.. edit: cant post link because of restrictions). I am using the Visual C++ compiler from Microsoft Visual Studio 2008, like this: cl /EHsc /I D:\Downloads\boost_1_42_0 client.cpp But I get this error: /out:client.exe client.obj LINK : fatal error LNK1104: cannot open file 'libboost_system-vc90-mt-s-1_42.lib' Anyone have any idea what could be wrong, or how I could move forward? I have been trying pretty much all week, to get a simple client/server socket program for c++ working, but with no luck. Serious frustration kicking in. Thank you in advance.

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• Warning: cast increases required alignment

  - by dash-tom-bang

  I'm recently working on this platform for which a legacy codebase issues a large number of "cast increases required alignment to N" warnings, where N is the size of the target of the cast. struct Message { int32_t id; int32_t type; int8_t data[16]; }; int32_t GetMessageInt(const Message& m) { return *reinterpret_cast<int32_t*>(&data[0]); } Hopefully it's obvious that a "real" implementation would be a bit more complex, but the basic point is that I've got data coming from somewhere, I know that it's aligned (because I need the id and type to be aligned), and yet I get the message that the cast is increasing the alignment, in the example case, to 4. Now I know that I can suppress the warning with an argument to the compiler, and I know that I can cast the bit inside the parentheses to void* first, but I don't really want to go through every bit of code that needs this sort of manipulation (there's a lot because we load a lot of data off of disk, and that data comes in as char buffers so that we can easily pointer-advance), but can anyone give me any other thoughts on this problem? I mean, to me it seems like such an important and common option that you wouldn't want to warn, and if there is actually the possibility of doing it wrong then suppressing the warning isn't going to help. Finally, can't the compiler know as I do how the object in question is actually aligned in the structure, so it should be able to not worry about the alignment on that particular object unless it got bumped a byte or two?

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• C# Virtual method call in constructor - how to refactor?

  - by Cristi Diaconescu

  I have an abstract class for database-agnostic cursor actions. Derived from that, there are classes that implement the abstract methods for handling database-specific stuff. The problem is, the base class ctor needs to call an abstract method - when the ctor is called, it needs to initialize the database-specific cursor. I know why this shouldn't be done, I don't need that explanation! This is my first implementation, that obviously doesn't work - it's the textbook "wrong way" of doing it. The overridden method accesses a field from the derived class, which is not yet instantiated: public abstract class CursorReader { private readonly int m_rowCount; protected CursorReader() { m_rowCount = CreateCursor(sqlCmd); //virtual call ! } protected abstract int CreateCursor(string sqlCmd); } public class SqlCursorReader : CursorReader { private SqlConnection m_sqlConnection; public SqlCursorReader(string sqlCmd, SqlConnection sqlConnection) { m_sqlConnection = sqlConnection; //field initialized here } protected override int CreateCursor(string sqlCmd) { //uses not-yet-initialized member *m_sqlConnection* //so this throws a NullReferenceException var cursor = new CustomCursor(sqlCmd, m_sqlConnection); return cursor.Count(); } } I will follow up with an answer on my attempts to fix this...

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• Multiple jQuery.noConflict() instances...

  - by user353816

  I am working with several jQuery scripts that include a MenuFader (http://css-tricks.com/examples/MenuFader/), twitter feed, and timestamp. Additionally I have a couple Mootools scripts that include the Barackslideshow (http://devthought.com/wp-content/moogets/BarackSlideshow/demo.html). And finally I have a scrolling ticker with tooltips taken from the twitter homepage. I originally had a conflict with the Jquery MenuFader and Mootools BarackSlideshow, but easily fixed this issue with the jQuery.noconflict(); and replaced all corresponding $ with jQuery. Unfortunately, after I added the scrolling ticker from Twitter, the Mootools BarackSlideshow and the Jquery MenuFader no longer work. I tried to implement jQuery.noconflict(); then $.noconflict(); then var j = jQuery.noconflict(); and replacing the $ as I did previously, but I cannot get the scripts to play nicely. Any help is greatly appreciated...I have been working on this all day. I am pretty new with javascript, but have managed to get through most problems with a little persistence. Please take a look at the script below: <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.0/jquery.min.js" type="text/javascript"></script> <script src="http://a2.twimg.com/a/1274914417/javascripts/fronts.js" type="text/javascript"></script> <script type="text/javascript"> //<![CDATA[ $( function () { setTimeout(function() { $(".twtr-widget").append($("<div></div>").attr("class", "twtr-fade")); }, 0); (function() { var tabIndex = $("[tabindex]:last").attr("tabIndex"); var setTabIndex = function() { $(this).attr("tabindex", ++tabIndex); } $(".footer-nav a").each(setTabIndex); $(".language-select a").each(setTabIndex); })(); $("#signup_submit").scribe({ event_name: "signup_submit_click", experiment: "ab_signup_button", bucket: "sign_up" }, "www_ab_tests"); $('#signin_menu').isSigninMenu(); new FrontPage().init(); }); //]]>

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• How does one implement storage/retrieval of smart-search/mailbox features?

  - by humble_coder

  Hi All, I have a question regarding implementation of smart-search features. For example, consider something like "smart mailboxes" in various email applications. Let's assume you have your data (emails) stored in a database and, depending on the field for which the query will be created, you present different options to the end user. At the moment let's assume the Subject, Verb, Object approach… For instance, say you have the following: SUBJECTs: message, to_address, from_address, subject, date_received VERBs: contains, does_not_contain, is_equal_to, greater_than, less_than OBJECTs: ??????? Now, in case it isn't clear, I want a table structure (although I'm not opposed to an external XMLesque file of some sort) to store (and later retrieve/present) my criteria for smart searches/mailboxes for later use. As an example, using SVO I could easily store then reconstruct a query for "date between two dates" -- simply use "date greater than" AND "date less than". However, what if, in the same smart search, I wanted a "between" OR'ed with another criterion? You can see that it might get out of hand -- not necessarily in the query creation (as that is rather simplistic), but in the option presentation and storage mechanism. Perhaps I need to think more on a more granular level. Perhaps I need to simply allow the user to select AND or OR for each entry independently instead of making it an ALL OR NOTHING type smart search (i.e. instead of MATCH ALL or MATCH ANY, I need to simply allow them to select -- I just don't want it to turn into a Hydra). Any input would be most appreciated. My apologies if the question is a bit incoherent. It is late, and I my brain is toast. Best.

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• Existentials and Scrap your Boilerplate

  - by finnsson

  I'm writing a XML (de)serializer using Text.XML.Light and Scrap your Boilerplate (at http://github.com/finnsson/Text.XML.Generic) and so far I got working code for "normal" ADTs but I'm stuck at deserializing existentials. I got the existential data type data DataBox where DataBox :: (Show d, Eq d, Data d) => d -> DataBox and I'm trying to get this to compile instance Data DataBox where gfoldl k z (DataBox d) = z DataBox `k` d gunfold k z c = k (z DataBox) -- not OK toConstr (DataBox d) = toConstr d dataTypeOf (DataBox d) = dataTypeOf d but I can't figure out how to implement gunfold for DataBox. The error message is Text/XML/Generic.hs:274:23: Ambiguous type variable `b' in the constraints: `Eq b' arising from a use of `DataBox' at Text/XML/Generic.hs:274:23-29 `Show b' arising from a use of `DataBox' at Text/XML/Generic.hs:274:23-29 `Data b' arising from a use of `k' at Text/XML/Generic.hs:274:18-30 Probable fix: add a type signature that fixes these type variable(s) It's complaining about not being able to figure out the data type of b. I'm also trying to implement dataCast1 and dataCast2 but I think I can live without them (i.e. an incorrect implementation). I guess my questions are: Is it possible to combine existentials with Scrap your Boilerplate? If so: how do you implement gunfold for an existential data type?

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• how to Solve the "Digg" problem in MongoDB

  - by user193116

  A while back,a Digg developer had posted this blog ,"http://about.digg.com/blog/looking-future-cassandra", where the he described one of the issues that were not optimally solved in MySQL. This was cited as one of the reasons for their move to Cassandra. I have been playing with MongoDB and I would like to understand how to implement the MongoDB collections for this problem From the article, the schema for this information in MySQL : CREATE TABLE Diggs ( id INT(11), itemid INT(11), userid INT(11), digdate DATETIME, PRIMARY KEY (id), KEY user (userid), KEY item (itemid) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; CREATE TABLE Friends ( id INT(10) AUTO_INCREMENT, userid INT(10), username VARCHAR(15), friendid INT(10), friendname VARCHAR(15), mutual TINYINT(1), date_created DATETIME, PRIMARY KEY (id), UNIQUE KEY Friend_unique (userid,friendid), KEY Friend_friend (friendid) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; This problem is ubiquitous in social networking scenario implementation. People befriend a lot of people and they in turn digg a lot of things. Quickly showing a user what his/her friends are up to is very critical. I understand that several blogs have since then provided a pure RDBMs solution with indexes for this issue; however I am curious as to how this could be solved in MongoDB.

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• How to specify allowed exceptions in WCF's configuration file?

  - by tucaz

  Hello! I´m building a set of WCF services for internal use through all our applications. For exception handling I created a default fault class so I can return treated message to the caller if its the case or a generic one when I have no clue what happened. Fault contract: [DataContract(Name = "DefaultFault", Namespace = "http://fnac.com.br/api/2010/03")] public class DefaultFault { public DefaultFault(DefaultFaultItem[] items) { if (items == null || items.Length== 0) { throw new ArgumentNullException("items"); } StringBuilder sbItems = new StringBuilder(); for (int i = 0; i Specifying that my method can throw this exception so the consuming client will be aware of it: [OperationContract(Name = "PlaceOrder")] [FaultContract(typeof(DefaultFault))] [WebInvoke(UriTemplate = "/orders", BodyStyle = WebMessageBodyStyle.Bare, ResponseFormat = WebMessageFormat.Json, RequestFormat = WebMessageFormat.Json, Method = "POST")] string PlaceOrder(Order newOrder); Most of time we will use just .NET to .NET communication with usual binds and everything works fine since we are talking the same language. However, as you can see in the service contract declaration I have a WebInvoke attribute (and a webHttp binding) in order to be able to also talk JSON since one of our apps will be built for iPhone and this guy will talk JSON. My problem is that whenever I throw a FaultException and have includeExceptionDetails="false" in the config file the calling client will get a generic HTTP error instead of my custom message. I understand that this is the correct behavior when includeExceptionDetails is turned off, but I think I saw some configuration a long time ago to allow some exceptions/faults to pass through the service boundaries. Is there such thing like this? If not, what do u suggest for my case? Thanks a LOT!

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• Iterate through every node in a XML

  - by Rachel

  Hi I am trying to iterate through every node in a xml, be it the element node, text node or comment. With the below XSL in the very first statement prints the complete xml. How do i copy the very first node in $nodes and call the template process-nodes again removing teh first node in my next iteration? <?xml version='1.0'?> <xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:template match="/"> <xsl:call-template name="process-nodes"> <xsl:with-param name="nodes" select="//node()" as="node()*"/> </xsl:call-template> </xsl:template> <xsl:template name="process-nodes"> <xsl:param name="nodes" as="node()*" /> <xsl:copy-of select="$nodes[1]"/> <xsl:if test="$nodes"> <xsl:call-template name="process-nodes"> <xsl:with-param name="nodes" select="remove($nodes, 1)" /> </xsl:call-template> </xsl:if> </xsl:template> </xsl:stylesheet> Note: I am looking for fixing the issue in this kind of implementation rather than changing the template match to <xsl:template match="@* | node()"> as I need to have some processing which requires this approach. Thanks.

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• Need an Overview of Possibilities for multicolumn programming

  - by Sam

  Hi folks, From source1 and source2 i gather that IE9 will NOT support multi-column css3!! Since it is still the most popular browser (another thing i cannot understand), i am left but no other choice than to use Programming Power to make multi-columns work. Now, I use three divs that float to left, and which are manually filled with text. Please don't laugh i know its stupid! But I would wish to not to have to worry about the columns and just have a one piece of (un-interrupted) text which all goes into only 1 div, and then have a program smart enough to split it up into X equally wide columns. Question: before i start reinvent the wheel, what methods of programming power have you known that tackle this elegantly? Please suggest your best working multi-column layout sources so I can evaluate which option is the best (I will update the below table). Exploring all possibilities 2011 and further, to enable multi column text user experience: Language Author SourceCodeUsage WorksOnAllMajorBrowser? ================================================================================= html manual labour put text manually in separate left-floating divs "Y" // Upside: control! Downside: few changes necessitates to reflow 3 divs manually! CSS3 w3c css3.info/preview/multi-column-layout/ "N" // {-moz-column-count: 3; -webkit-column-count: 3; } Thats all! javascript a list apart will add url soon ? // php ? ? ? //

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• Is it safe to silently catch ClassCastException when searching for a specific value?

  - by finnw

  Suppose I am implementing a sorted collection (simple example - a Set based on a sorted array.) Consider this (incomplete) implementation: import java.util.*; public class SortedArraySet<E> extends AbstractSet<E> { @SuppressWarnings("unchecked") public SortedArraySet(Collection<E> source, Comparator<E> comparator) { this.comparator = (Comparator<Object>) comparator; this.array = source.toArray(); Collections.sort(Arrays.asList(array), this.comparator); } @Override public boolean contains(Object key) { return Collections.binarySearch(Arrays.asList(array), key, comparator) >= 0; } private final Object[] array; private final Comparator<Object> comparator; } Now let's create a set of integers Set<Integer> s = new SortedArraySet<Integer>(Arrays.asList(1, 2, 3), null); And test whether it contains some specific values: System.out.println(s.contains(2)); System.out.println(s.contains(42)); System.out.println(s.contains("42")); The third line above will throw a ClassCastException. Not what I want. I would prefer it to return false (as HashSet does.) I can get this behaviour by catching the exception and returning false: @Override public boolean contains(Object key) { try { return Collections.binarySearch(Arrays.asList(array), key, comparator) >= 0; } catch (ClassCastException e) { return false; } } Assuming the source collection is correctly typed, what could go wrong if I do this?

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• asp.net master page/content page interaction with style sheet

  - by Matt

  Learning how to do a master page in asp.net. Trying to figure out how my style sheet interacts with respects to the master page and content page. I can get HTML tags like body and the style sheet to react. But when I call the ID attribute of a label no styling takes place. What am I missing here as far as interaction? BTW I'm using VS2008 CSS sample: body { height:1200px; width:920px; border-style:solid; border-color:blue; padding:10px 10px 10px 10px; } #toptext1 { position:relative; top:-225px; right:-500px; font-size:22px; font-weight:bold; } From the master page: <body> <form id="form1" runat="server"> <asp:image id="cookNookLogo" ImageUrl="images/Logo.gif" runat="server" AlternateText="CookNook" Width="449px"></asp:image> <p> <asp:Label ID="toptext1" runat="server" Text="Quality Recipes, Hints and Supplies"></asp:Label> </p> From the content page: <%@ Page Language="C#" MasterPageFile="~/CNMasterPage.master" AutoEventWireup="true" CodeFile="Home.aspx.cs" Inherits="Home" Title="Untitled Page" %> <asp:Content ID="Content1" ContentPlaceHolderID="head" Runat="Server"> <link href="App_Themes/cn/cn.css" rel="stylesheet" type="text/css" /> </asp:Content> When I was doing this without a master page it worked so where am I going wrong with the attributes?

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• Java ternary operator and boxing Integer/int?

  - by Markus

  I tripped across a really strange NullPointerException the other day caused by an unexpected type-cast in the ternary operator. Given this (useless exemplary) function: Integer getNumber() { return null; } I was expecting the following two code segments to be exactly identical after compilation: Integer number; if (condition) { number = getNumber(); } else { number = 0; } vs. Integer number = (condition) ? getNumber() : 0; . Turns out, if condition is true, the if-statement works fine, while the ternary opration in the second code segment throws a NullPointerException. It seems as though the ternary operation has decided to type-cast both choices to int before auto-boxing the result back into an Integer!?! In fact, if I explicitly cast the 0 to Integer, the exception goes away. In other words: Integer number = (condition) ? getNumber() : 0; is not the same as: Integer number = (condition) ? getNumber() : (Integer) 0; . So, it seems that there is a byte-code difference between the ternary operator and an equivalent if-else-statement (something I didn't expect). Which raises three questions: Why is there a difference? Is this a bug in the ternary implementation or is there a reason for the type cast? Given there is a difference, is the ternary operation more or less performant than an equivalent if-statement (I know, the difference can't be huge, but still)?

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• To OpenID or not to OpenID? Is it worth it?

  - by Eloff

  Does OpenID improve the user experience? Edit Not to detract from the other comments, but I got one really good reply below that outlined 3 advantages of OpenID in a rational bottom line kind of way. I've also heard some whisperings in other comments that you can get access to some details on the user through OpenID (name? email? what?) and that using that it might even be able to simplify the registration process by not needing to gather as much information. Things that definitely need to be gathered in a checkout process: Full name Email (I'm pretty sure I'll have to ask for these myself) Billing address Shipping address Credit card info There may be a few other things that are interesting from a marketing point of view, but I wouldn't ask the user to manually enter anything not absolutely required during the checkout process. So what's possible in this regard? /Edit (You may have noticed stackoverflow uses OpenID) It seems to me it is easier and faster for the user to simply enter a username and password in a signup form they have to go through anyway. I mean you don't avoid entering a username and password either with OpenID. But you avoid the confusion of choosing a OpenID provider, and the trip out to and back from and external site. With Microsoft making Live ID an OpenID provider (More Info), bringing on several hundred million additional accounts to those provided by Google, Yahoo, and others, this question is more important than ever. I have to require new customers to sign up during the checkout process, and it is absolutely critical that the experience be as easy and smooth as possible, every little bit harder it becomes translates into lost sales. No geek factor outweighs cold hard cash at the end of the day :) OpenID seems like a nice idea, but the implementation is of questionable value. What are the advantages of OpenID and is it really worth it in my scenario described above?

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• Why do Scala maps have poor performance relative to Java?

  - by Mike Hanafey

  I am working on a Scala app that consumes large amounts of CPU time, so performance matters. The prototype of the system was written in Python, and performance was unacceptable. The application does a lot with inserting and manipulating data in maps. Rex Kerr's Thyme was used to look at the performance of updating and retrieving data from maps. Basically "n" random Ints were stored in maps, and retrieved from the maps, with the time relative to java.util.HashMap used as a reference. The full results for a range of "n" are here. Sample (n=100,000) performance relative to java, smaller is worse: Update Read Mutable 16.06% 76.51% Immutable 31.30% 20.68% I do not understand why the scala immutable map beats the scala mutable map in update performance. Using the sizeHint on the mutable map does not help (it appears to be ignored in the tested implementation, 2.10.3). Even more surprisingly the immutable read performance is worse than the mutable read performance, more significantly so with larger maps. The update performance of the scala mutable map is surprisingly bad, relative to both scala immutable and plain Java. What is the explanation?

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• Access Controller Context/ TempData from business objects

  - by thanikkal

  I am trying to build a session/tempdata provider that can be swapped. The default provider will work on top of asp.net mvc and it needed to access the .net mvc TempData from the business object class. I know the tempdata is available through the controller context, but i cant seem to find if that is exposed through HttpContext or something. I dont really want to pass the Controller context as an argument as that would dilute my interface definition since only asp.net based session provider needs this, other (using NoSQL DB etc) doesn't care about Controller Context. To clarify further, adding little more code here. my ISession interface look like this. and when this code goes to production, the session/tempdata is expected to work using NoSql db. But i also like to have another implementation that works on top of asp.net mvc session/tempdata for my dev testing etc. public interface ISession { T GetTempData<T>(string key); void PutTempData<T>(string key, T value); T GetSessiondata<T>(string key); void PutSessiondata<T>(string key, T value); }

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