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• Cepstral Analysis for pitch detection

  - by Ohmu

  Hi! I'm looking to extract pitches from a sound signal. Someone on IRC just explain to me how taking a double FFT achieves this. Specifically: take FFT take log of square of absolute value (can be done with lookup table) take another FFT take absolute value I am attempting this using vDSP I can't understand how I didn't come across this technique earlier. I did a lot of hunting and asking questions; several weeks worth. More to the point, I can't understand why I didn't think of it. I am attempting to achieve this with vDSP library. it looks as though it has functions to handle all of these tasks. However, I'm wondering about the accuracy of the final result. I have previously used a technique which scours the frequency bins of a single FFT for local maxima. when it encounters one, it uses a cunning technique (the change in phase since the last FFT) to more accurately place the actual peak within the bin. I am worried that this precision will be lost with this technique I'm presenting here. I guess the technique could be used after the second FFT to get the fundamental accurately. But it kind of looks like the information is lost in step 2. as this is a potentially tricky process, could someone with some experience just look over what I'm doing and check it for sanity? also, I've heard there is an alternative technique involving fitting a quadratic over neighbouring bins. Is this of comparable accuracy? if so, I would favour it, as it doesn't involve remembering bin phases. so questions: does this approach makes sense? Can it be improved? I'm a bit worried about And the log square component; there seems to be a vDSP function to do exactly that: vDSP_vdbcon however, there is no indication it precalculates a log-table -- I assume it doesn't, as the FFT function requires an explicit pre-calculation function to be called and passed into it. and this function doesn't. Is there some danger of harmonics being picked up? is there any cunning way of making vDSP pull out the maxima, biggest first? Can anyone point me towards some research or literature on this technique? the main question: is it accurate enough? Can the accuracy be improved? I have just been told by an expert that the accuracy IS INDEED not sufficient. Is this the end of the line? Pi PS I get SO annoyed (npi) when I want to create tags, but cannot. :| I have suggested to the maintainers that SO keep track of attempted tags, but I'm sure I was ignored. we need tags for vDSP, accelerate framework, cepstral analysis

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• C#: System.Lazy&lt;T&gt; and the Singleton Design Pattern

  - by James Michael Hare

  So we've all coded a Singleton at one time or another.  It's a really simple pattern and can be a slightly more elegant alternative to global variables.  Make no mistake, Singletons can be abused and are often over-used -- but occasionally you find a Singleton is the most elegant solution. For those of you not familiar with a Singleton, the basic Design Pattern is that a Singleton class is one where there is only ever one instance of the class created.  This means that constructors must be private to avoid users creating their own instances, and a static property (or method in languages without properties) is defined that returns a single static instance. 1: public class Singleton 2: { 3: // the single instance is defined in a static field 4: private static readonly Singleton _instance = new Singleton(); 5:  6: // constructor private so users can't instantiate on their own 7: private Singleton() 8: { 9: } 10:  11: // read-only property that returns the static field 12: public static Singleton Instance 13: { 14: get 15: { 16: return _instance; 17: } 18: } 19: } This is the most basic singleton, notice the key features: Static readonly field that contains the one and only instance. Constructor is private so it can only be called by the class itself. Static property that returns the single instance. Looks like it satisfies, right?  There's just one (potential) problem.  C# gives you no guarantee of when the static field _instance will be created.  This is because the C# standard simply states that classes (which are marked in the IL as BeforeFieldInit) can have their static fields initialized any time before the field is accessed.  This means that they may be initialized on first use, they may be initialized at some other time before, you can't be sure when. So what if you want to guarantee your instance is truly lazy.  That is, that it is only created on first call to Instance?  Well, there's a few ways to do this.  First we'll show the old ways, and then talk about how .Net 4.0's new System.Lazy<T> type can help make the lazy-Singleton cleaner. Obviously, we could take on the lazy construction ourselves, but being that our Singleton may be accessed by many different threads, we'd need to lock it down. 1: public class LazySingleton1 2: { 3: // lock for thread-safety laziness 4: private static readonly object _mutex = new object(); 5:  6: // static field to hold single instance 7: private static LazySingleton1 _instance = null; 8:  9: // property that does some locking and then creates on first call 10: public static LazySingleton1 Instance 11: { 12: get 13: { 14: if (_instance == null) 15: { 16: lock (_mutex) 17: { 18: if (_instance == null) 19: { 20: _instance = new LazySingleton1(); 21: } 22: } 23: } 24:  25: return _instance; 26: } 27: } 28:  29: private LazySingleton1() 30: { 31: } 32: } This is a standard double-check algorithm so that you don't lock if the instance has already been created.  However, because it's possible two threads can go through the first if at the same time the first time back in, you need to check again after the lock is acquired to avoid creating two instances. Pretty straightforward, but ugly as all heck.  Well, you could also take advantage of the C# standard's BeforeFieldInit and define your class with a static constructor.  It need not have a body, just the presence of the static constructor will remove the BeforeFieldInit attribute on the class and guarantee that no fields are initialized until the first static field, property, or method is called.   1: public class LazySingleton2 2: { 3: // because of the static constructor, this won't get created until first use 4: private static readonly LazySingleton2 _instance = new LazySingleton2(); 5:  6: // Returns the singleton instance using lazy-instantiation 7: public static LazySingleton2 Instance 8: { 9: get { return _instance; } 10: } 11:  12: // private to prevent direct instantiation 13: private LazySingleton2() 14: { 15: } 16:  17: // removes BeforeFieldInit on class so static fields not 18: // initialized before they are used 19: static LazySingleton2() 20: { 21: } 22: } Now, while this works perfectly, I hate it.  Why?  Because it's relying on a non-obvious trick of the IL to guarantee laziness.  Just looking at this code, you'd have no idea that it's doing what it's doing.  Worse yet, you may decide that the empty static constructor serves no purpose and delete it (which removes your lazy guarantee).  Worse-worse yet, they may alter the rules around BeforeFieldInit in the future which could change this. So, what do I propose instead?  .Net 4.0 adds the System.Lazy type which guarantees thread-safe lazy-construction.  Using System.Lazy<T>, we get: 1: public class LazySingleton3 2: { 3: // static holder for instance, need to use lambda to construct since constructor private 4: private static readonly Lazy<LazySingleton3> _instance 5: = new Lazy<LazySingleton3>(() => new LazySingleton3()); 6:  7: // private to prevent direct instantiation. 8: private LazySingleton3() 9: { 10: } 11:  12: // accessor for instance 13: public static LazySingleton3 Instance 14: { 15: get 16: { 17: return _instance.Value; 18: } 19: } 20: } Note, you need your lambda to call the private constructor as Lazy's default constructor can only call public constructors of the type passed in (which we can't have by definition of a Singleton).  But, because the lambda is defined inside our type, it has access to the private members so it's perfect. Note how the Lazy<T> makes it obvious what you're doing (lazy construction), instead of relying on an IL generation side-effect.  This way, it's more maintainable.  Lazy<T> has many other uses as well, obviously, but I really love how elegant and readable it makes the lazy Singleton.

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• Enabling Http caching and compression in IIS 7 for asp.net websites

  - by anil.kasalanati

  Caching – There are 2 ways to set Http caching 1-      Use Max age property 2-      Expires header. Doing the changes via IIS Console – 1.       Select the website for which you want to enable caching and then select Http Responses in the features tab       2.       Select the Expires webcontent and on changing the After setting you can generate the max age property for the cache control    3.       Following is the screenshot of the headers   Then you can use some tool like fiddler and see 302 response coming from the server. Doing it web.config way – We can add static content section in the system.webserver section <system.webServer>   <staticContent>             <clientCache cacheControlMode="UseMaxAge" cacheControlMaxAge="365.00:00:00" />   </staticContent> Compression - By default static compression is enabled on IIS 7.0 but the only thing which falls under that category is CSS but this is not enough for most of the websites using lots of javascript.  If you just thought by enabling dynamic compression would fix this then you are wrong so please follow following steps –   In some machines the dynamic compression is not enabled and following are the steps to enable it – Open server manager Roles > Web Server (IIS) Role Services (scroll down) > Add Role Services Add desired role (Web Server > Performance > Dynamic Content Compression) Next, Install, Wait…Done!   ?  Roles > Web Server (IIS) ?  Role Services (scroll down) > Add Role Services     Add desired role (Web Server > Performance > Dynamic Content Compression)     Next, Install, Wait…Done!     Enable  - ?  Open server manager ?  Roles > Web Server (IIS) > Internet Information Services (IIS) Manager   Next pane: Sites > Default Web Site > Your Web Site Main pane: IIS > Compression         Then comes the custom configuration for encrypting javascript resources. The problem is that the compression in IIS 7 completely works on the mime types and by default there is a mismatch in the mime types Go to following location C:\Windows\System32\inetsrv\config Open applicationHost.config The mimemap is as follows  <mimeMap fileExtension=".js" mimeType="application/javascript" />   So the section in the staticTypes should be changed          <add mimeType="application/javascript" enabled="true" />     Doing the web.config way –   We can add following section in the system.webserver section <system.webServer> <urlCompression doDynamicCompression="false"  doStaticCompression="true"/> More Information/References – ·         http://weblogs.asp.net/owscott/archive/2009/02/22/iis-7-compression-good-bad-how-much.aspx ·         http://www.west-wind.com/weblog/posts/98538.aspx  

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• What functionality does dynamic typing allow?

  - by Justin984

  I've been using python for a few days now and I think I understand the difference between dynamic and static typing. What I don't understand is under what circumstances it would be preferred. It is flexible and readable, but at the expense of more runtime checks and additional required unit testing. Aside from non-functional criteria like flexibility and readability, what reasons are there to choose dynamic typing? What can I do with dynamic typing that isn't possible otherwise? What specific code example can you think of that illustrates a concrete advantage of dynamic typing?

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• Are there any empirical studies on the effect of different languages on software quality?

  - by jgre

  The proponents of functional programming languages assert that functional programming makes it easier to reason about code. Those in favor of statically typed languages say that their compilers catch enough errors to make up for the additional complexity of type systems. But everything I read on these topics is based on rational argument, not on empirical data. Are there any empirical studies on what effects the different categories of programming languages have on defect rates or other quality metrics? (The answers to this question seem to indicate that there are no such studies, at least not for the dynamic vs. static debate)

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• best practice for last-modified and created dates

  - by drewbenn

  I have a website with a handful (currently 3; I anticipate about a dozen when it's complete) of static html pages. I'd like to include "created" and "last-modified" dates in the pages for the benefit of visitors who arrive a week or a month or a few years from now. I expect anyone who cares to be viewing the source, so I could do: <!-- created yyyy-mm-dd, last-modified yyyy-mm-dd --> but I'd like to use something more standard (and elegant). I've found one reference to last modified (but only a mention in the text, not an actual code reference, so I'm not positive how to properly implement it) but not created. Is there a proper way to display both (or at least one) of these dates?

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• Types of semantic bugs, logic errors [closed]

  - by C-Otto

  I am a PhD student and currently focus on automatically finding instances of new types of bugs in (Java) programs that cannot be found by existing tools like FindBugs. The existing tool currently is used to prove/disprove termination of (Java) programs. I have some ideas (see below), but I could need more input from you (experienced programmers, potential users of my tool). What kind of bugs do you wish to find? What types of bugs exist and might be suitable for my analysis? One strength of the approach I use is detailled information about the heap. So in contrast to FindBugs, I can work with knowledge of the form "variable x and variable y are disjoint on the heap" or "variable z is not cyclic". It is also possible to see if a method might have side effects (and if so, which variables may/may not be affected by it). Example 1: Vacuous call: Graph graphOne = createGraph(); Graph graphTwo = createGraph(); Node source = graphTwo.getRootNode(); for (Node n : graphOne.getNodes()) { if (areConnected(source, n)) { graphTwo.addNode(n); } } Imagine createGraph() creates a fresh graph, so that graphOne and graphTwo are disjoint on the heap. Then, because source is taken from graphTwo instead of graphOne, the call to areConnected always returns false. In this situation I could find out that the call areConnected is useless (because it does not have any side effect and the return value always is false) which helps finding the real bug (taking source from the wrong graph). For this the information that x and y are disjoint (because graphOne and graphTwo are disjoint) is crucial. This bug is related to calling x.equals(y) where x and y are objects of different classes. In this scenario, most implementations of equals() always return false, which most likely is not the intended result. FindBugs already finds this bug (hardcoded to equals(), semantics of implementation is not checked). Example 2: Useless code: someCode(); while (something()) { yetMoreSomething(); } moreCode(); In the case that the loop (so the code in something() and yetMoreSomething()) does not modify anything visible outside the loop, it does not make sense to run this code - the program has the same behaviour as someCode(); moreCode() (i.e., without the loop). To find this out, one needs detailled information about the side effects of the (possibly useless) code. If I can prove that the code does not have any side effect that can be observed afterwards (in the example: in moreCode() or later), then the code indeed is useless. Of course, here Input/Output of any form must be seen as a side effect, so that a System.out.println(...) is not considered useless. Example 3: Ignored return value: Instead of x = foo(); and making use of x, the method is called without storing the result: foo();. If the method does not have any side effect, its invocation is useless and can be dropped. Most likely, the bug here is that the returned value should have been used. Here, too, detailled information about side effects are needed. Can you think of similar types of bugs that might be detected (only) with detailled information about the heap, side effects, semantics of called methods, ...? Did you encounter bugs related to the ones shown below in "real life"? By the way, the tool is AProVE and Java related publications can be found on my homepage. Thanks a lot, Carsten

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• PASS Summit 2012: keynote and Mobile BI announcements #sqlpass

  - by Marco Russo (SQLBI)

  Today at PASS Summit 2012 there have been several announcements during the keynote. Moreover, other news have not been highlighted in the keynote but are equally if not more important for the BI community. Let’s start from the big news in the keynote (other details on SQL Server Blog): Hekaton: this is the codename for in-memory OLTP technology that will appear (I suppose) in the next release of the SQL Server relational engine. The improvement in performance and scalability is impressive and it enables new scenarios. I’m curious to see whether it can be used also to improve ETL performance and how it differs from using SSD technology. Updates on Columnstore: In the next major release of SQL Server the columnstore indexes will be updatable and it will be possible to create a clustered index with Columnstore index. This is really a great news for near real-time reporting needs! Polybase: in 2013 it will debut SQL Server 2012 Parallel Data Warehouse (PDW), which will include the Polybase technology. By using Polybase a single T-SQL query will run queries across relational data and Hadoop data. A single query language for both. Sounds really interesting for using BigData in a more integrated way with existing relational databases. And, of course, to load a data warehouse using BigData, which is the ultimate goal that we all BI Pro have, right? SQL Server 2012 SP1: the Service Pack 1 for SQL Server 2012 is available now and it enable the use of PowerPivot for SharePoint and Power View on a SharePoint 2013 installation with Excel 2013. Power View works with Multidimensional cube: the long-awaited feature of being able to use PowerPivot with Multidimensional cubes has been shown by Amir Netz in an amazing demonstration during the keynote. The interesting thing is that the data model behind was based on a many-to-many relationship (something that is not fully supported by Power View with Tabular models). Another interesting aspect is that it is Analysis Services 2012 that supports DAX queries run on a Multidimensional model, enabling the use of any future tool generating DAX queries on top of a Multidimensional model. There are still no info about availability by now, but this is *not* included in SQL Server 2012 SP1. So what about Mobile BI? Well, even if not announced during the keynote, there is a dedicated session on this topic and there are very important news in this area: iOS, Android and Microsoft mobile platforms: the commitment is to get data exploration and visualization capabilities working within June 2013. This should impact at least Power View and SharePoint/Excel Services. This is the type of UI experience we are all waiting for, in order to satisfy the requests coming from users and customers. The important news here is that native applications will be available for both iOS and Windows 8 so it seems that Android will be supported initially only through the web. Unfortunately we haven’t seen any demo, so it’s not clear what will be the offline navigation experience (and whether there will be one). But at least we know that Microsoft is working on native applications in this area. I’m not too surprised that HTML5 is not the magic bullet for all the platforms. The next PASS Business Analytics conference in 2013 seems a good place to see this in action, even if I hope we don’t have to wait other six months before seeing some demo of native BI applications on mobile platforms! Viewing Reporting Services reports on iPad is supported starting with SQL Server 2012 SP1, which has been released today. This is another good reason to install SP1 on SQL Server 2012. If you are at PASS Summit 2012, come and join me, Alberto Ferrari and Chris Webb at our book signing event tomorrow, Thursday 8 2012, at the bookstore between 12:00pm and 12:30pm, or follow one of our sessions!

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• An Object reference is required for the non-static field

  - by Muhammad Akhtar

  I have make my existing method to static method to get access in javascript, like.. [WebMethod(EnableSession = true), ScriptMethod()] public static void Build(String ID) { Control releaseControl = LoadControl("~/Controls/MyControl.ascx"); //An Object reference is required for the non-static field, mthod or property // 'System.Web.UI.TemplateControl.LoadControl(string)' plc.Controls.Add(releaseControl); // where plc is place holder control //object reference is required for the nonstatic field, method, or property '_Default.pl' } When I build I am getting error and I have posted these in comments below each line before converted it to static method, it working perfectly. Please suggest me the solution of my issue. Thanks

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• Static factory pattern with EJB3/JBoss

  - by purecharger

  I'm fairly new to EJBs and full blown application servers like JBoss, having written and worked with special purpose standalone Java applications for most of my career, with limited use of JEE. I'm wondering about the best way to adapt a commonly used design pattern to EJB3 and JBoss: the static factory pattern. In fact this is Item #1 in Joshua Bloch's Effective Java book (2nd edition) I'm currently working with the following factory: public class CredentialsProcessorFactory { private static final Log log = LogFactory.getLog(CredentialsProcessorFactory.class); private static Map<CredentialsType, CredentialsProcessor> PROCESSORS = new HashMap<CredentialsType, CredentialsProcessor>(); static { PROCESSORS.put(CredentialsType.CSV, new CSVCredentialsProcessor()); } private CredentialsProcessorFactory() {} public static CredentialsProcessor getProcessor(CredentialsType type) { CredentialsProcessor p = PROCESSORS.get(type); if(p == null) throw new IllegalArgumentException("No CredentialsProcessor registered for type " + type.toString()); return p; } However, in the implementation classes of CredentialsProcessor, I require injected resources such as a PersistenceContext, so I have made the CredentialsProcessor interface a @Local interface, and each of the impl's marked with @Stateless. Now I can look them up in JNDI and use the injected resources. But now I have a disconnect because I am not using the factory anymore. My first thought was to change the getProcessor(CredentialsType) method to do a JNDI lookup and return the SLSB instance that is required, but then I need to configure and pass the proper qualified JNDI name. Before I go down that path, I wanted to do more research on accepted practices. How is this design pattern treated in EJB3 / JEE?

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• Can't define static abstract string property

  - by goombaloon

  I've run into an interesting problem and am looking for some suggestions on how best to handle this... I have an abstract class that contains a static method that accepts a static string that I would like to define as an abstract property. Problem is that C# doesn't doesn't support the following (see the ConfigurationSectionName and Current properties): public abstract class ProviderConfiguration : ConfigurationSection { private const string _defaultProviderPropertyName = "defaultProvider"; private const string _providersPropertyName = "providers"; protected static string ConfigurationSectionName { get; } public static Configuration Current { get { return Configuration)ConfigurationManager.GetSection(ConfigurationSectionName); } } } I suppose one way to handle this would be to make ConfigurationSectionName NOT abstract and then create a new definition of ConfigurationSectionName in the derived classes, but that feels pretty hackish. Any suggestions would be most welcome. Gratias!!!

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• Java (Tomcat): how to configure a cookieless subdomain to serve static content

  - by Webinator

  One of the tip given by both Google and Yahoo! to speed up webpages loading is to configure a cookieless subdomain to server static content. How do you configure a "cookieless subdomain" using Tomcat in standalone mode (this question is not about how to use Apache to serve static content in a cookieless-way, but about how to do it in Tomcat-standalone mode)? Note that I don't care about filters supporting If-Modified-Since nor care about filters supporting gzipping: the static content I'm serving is forever cacheable (or its name will change) and it is already compressed data (so gzip would only slow down the transfer). Do I need two different Tomcat webapps? (one "cookiefull" and one "cookieless") Do I need two different servlets? (as of now I've got only one dispatcher/controller servlet). Why would a "regular" link to, say, a static image be called in a cookiefull way when it would be on the same domain as the main webapp and then be called in a "cookie-less" way when it is on a subdomain? I don't understand exactly what is going on: is it the browser that decides to append or not cookies to the query? If so, why would it not append the cookies to a static query on a "cookieless" subdomain. Any example as to what is going on behind the scene is most welcome :)

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• PowerMock Mockito static methods

  - by anergy

  Do we need to mock all static methods of a class when using PowerMock (with Mockito)? I mean, suppose we have: class MockMe { public static MockMe getInstance(){ //return new Instance via complex process; } public static List<X> anotherStaticMethod(){ // does xyz } } My question, if I need to mock getInstance method, is it necessary to mock "anotherStaticMethod" as well? PowerMock version:1.3, Mockito version:1.8

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• defining asmx webservice class objects as static

  - by Usama Khalil

  Hi, is it better to declare Webservice class object instances as static as the .asmx webservice classes have only static methods. what i want is that i declare and instantiate webservice asmx class as static in aspx Page Behind Class. and on every event call on that page i could perform operation against webservice methods. is it beneficial in terms of performance? Thanks Usama

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• C# Generic Static Constructor

  - by Seattle Leonard

  Will a static constructor on a generic class be run for every type you pass into the generic parameter such as this: class SomeGenericClass<T> { static List<T> _someList; static SomeGenericClass() { _someList = new List<T>(); } } Are there any draw backs to using this approach?

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• Using singleton instead of a global static instance

  - by Farstucker

  I ran into a problem today and a friend recommended I use a global static instance or more elegantly a singleton pattern. I spent a few hours reading about singletons but a few things still escape me. Background: What Im trying to accomplish is creating an instance of an API and use this one instance in all my classes (as opposed to making a new connection, etc). There seems to be about 100 ways of creating a singleton but with some help from yoda I found some thread safe examples. ..so given the following code: public sealed class Singleton { public static Singleton Instance { get; private set; } private Singleton() { APIClass api = new APIClass(); //Can this be done? } static Singleton() { Instance = new Singleton(); } } How/Where would you instantiate the this new class and how should it be called from a separate class? EDIT: I realize the Singleton class can be called with something like Singleton obj1 = Singleton.Instance(); but would I be able to access the methods within the APIs Class (ie. obj1.Start)? (not that I need to, just asking) EDIT #2: I might have been a bit premature in checking the answer but I do have one small thing that is still causing me problems. The API is launching just fine, unfortunately Im able to launch two instances? New Code public sealed class SingletonAPI { public static SingletonAPI Instance { get; private set; } private SingletonAPI() {} static SingletonAPI() { Instance = new SingletonAPI(); } // API method: public void Start() { API myAPI = new API();} } but if I try to do something like this... SingletonAPI api = SingletonAPI.Instance; api.Start(); SingletonAPI api2 = SingletonAPI.Instance; // This was just for testing. api2.Start(); I get an error saying that I cannot start more than one instance.

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• Ruby on Rails - Static page as start page

  - by meetraghu28

  Hello! I am developing an app in RoR which has static and dynamic parts. The static portion is placed in the public/ folder of the app. Now if i have an index.html in my public folder then i will not be able to use the routes configured in my routes.rb The default configurations like map.connect /:controller/:action will not be usable if i have an index.html. So i removed the index html. Now i have a static page startpage.html in my public/ folder which has to be the starting page of the app. And the i have links in it for other static/dynamic pages. The RoR app is hosted in apache and i tried to configure the Virtual Host configuration by adding the DirectoryIndex param so that when ever a request comes for the site it will direct it to the startpage.html but still it takes me to the default controller that i have specified in routes.rb with map.root I dont want to add a dummy controller and action and create a view which has the startpage and configure routes.rb to use it as the root. What i am looking to do here is Basically startpage.html should be my first page in the app served as a static page from the public/ folder. This will then have links to other pages and controllers/actions Here i am not able to apache to redirect to the html page instead of passing on the control to rails application. Directory listing is also enabled by using Options Indexes but still no change. Any pointers anyone?

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• Filtering code elements when analyzing source code.

  - by Martin

  Hi everybody, Currently I am making a survey about source code analysis and the thing that puzzles me greatly is what is it that project managers and developers would like to filter when analyzing source code (especially when applying OOP metrics - e.g. skpping insignificant methods and classes during analysis or filtering context-based elements according to the type of project). If you have any suggestions based on yout experience with code analysis I will greatly appreciate if you can share some ideas about filtering of elements. Thanks, Martin

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• Java: Cipher package (encrypt and decrypt). invalid key error

  - by noinflection

  Hello folks, i am doing a class with static methods to encrypt and decrypt a message using javax.crypto. I have 2 static methods that use ecipher and dcipher in order to do what they are supossed to do i need to initialize some variables (which are static also). But when i try to use it i get InvalidKeyException with the parameters i give to ecipher.init(...). I can't find why. Here is the code: private static byte[] raw = {-31, 17, 7, -34, 59, -61, -60, -16, 26, 87, -35, 114, 0, -53, 99, -116, -82, -122, 68, 47, -3, -17, -21, -82, -50, 126, 119, -106, -119, -5, 109, 98}; private static SecretKeySpec skeySpec; private static Cipher ecipher; private static Cipher dcipher; static { try { skeySpec = new SecretKeySpec(raw, "AES"); // Instantiate the cipher ecipher = Cipher.getInstance("AES"); dcipher = Cipher.getInstance("AES"); ecipher.init(Cipher.ENCRYPT_MODE, skeySpec); dcipher.init(Cipher.DECRYPT_MODE, skeySpec); } catch (NoSuchAlgorithmException e) { throw new UnhandledException("No existe el algoritmo deseado", e); } catch (NoSuchPaddingException e) { throw new UnhandledException("No existe el padding deseado", e); } catch (InvalidKeyException e) { throw new UnhandledException("Clave invalida", e); } }

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• Java Static Methods

  - by KP65

  Hello, I am wondering when to use static methods? Say If i have a class with a few getters and setters, a method or two, and i want those methods only to be invokable on an instance object of the class. Does this mean i should use a static method? e.g Obj x = new Obj(); x.someMethod or Obj.someMethod (is this the static way?) I'm rather confused!

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• C# 4.0: casting dynamic to static

  - by Kevin Won

  This is an offshoot question that's related to another I asked here. I'm splitting it off because it's really a sub-question: I'm having difficulties casting an object of type dynamic to another (known) static type. I have an ironPython script that is doing this: import clr clr.AddReference("System") from System import * def GetBclUri(): return Uri("http://google.com") note that it's simply newing up a BCL System.Uri type and returning it. So I know the static type of the returned object. now over in C# land, I'm newing up the script hosting stuff and calling this getter to return the Uri object: dynamic uri = scriptEngine.GetBclUri(); System.Uri u = uri as System.Uri; // casts the dynamic to static fine Works no problem. I now can use the strongly typed Uri object as if it was originally instantiated statically. however.... Now I want to define my own C# class that will be newed up in dynamic-land just like I did with the Uri. My simple C# class: namespace Entity { public class TestPy // stupid simple test class of my own { public string DoSomething(string something) { return something; } } } Now in Python, new up an object of this type and return it: sys.path.append(r'C:..path here...') clr.AddReferenceToFile("entity.dll") import Entity.TestPy def GetTest(): return Entity.TestPy(); // the C# class then in C# call the getter: dynamic test = scriptEngine.GetTest(); Entity.TestPy t = test as Entity.TestPy; // t==null!!! here, the cast does not work. Note that the 'test' object (dynamic) is valid--I can call the DoSomething()--it just won't cast to the known static type string s = test.DoSomething("asdf"); // dynamic object works fine so I'm perplexed. the BCL type System.Uri will cast from a dynamic type to the correct static one, but my own type won't. There's obviously something I'm not getting about this...

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• Why aren't static const floats allowed?

  - by Jon Cage

  I have a class which is essentially just holds a bunch of constant definitions used through my application. For some reason though, longs compile but floats do not: class MY_CONSTS { public : static const long LONG_CONST = 1; // Compiles static const float FLOAT_CONST = 0.001f; // C2864 }; Gives the following error: 1>c:\projects\myproject\Constant_definitions.h(71) : error C2864: 'MY_CONSTS::FLOAT_CONST' : only static const integral data members can be initialized within a class Am I missing something?

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• Calling method on category included from iPhone static library causes NSInvalidArgumentException

  - by Corey Floyd

  I have created a static library to house some of my code like categories. I have a category for UIViews in "UIView-Extensions.h" named Extensions. In this category I have a method called: - (void)fadeOutWithDelay:(CGFloat)delay duration:(CGFloat)duration; Calling this method works fine on the simulator on Debug configuration. However, if try to run the app on the device I get a NSInvalidArgumentException: [UIView fadeOutWithDelay:duration:]: unrecognized selector sent to instance 0x1912b0 *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[UIView fadeOutWithDelay:duration:]: unrecognized selector sent to instance 0x1912b0 It seems for some reason UIView-Extensions.h is not being included in the device builds. What I have checked/tried I did try to include another category for NSString, and had the same issue. Other files, like whole classes and functions work fine. It is an issue that only happens with categories. I did a clean all targets, which did not fix the problem. I checked the static library project, the categories are included in the target's "copy headers" and "compile sources" groups. The static library is included in the main projects "link binary with library" group. Another project I have added the static library to works just fine. I deleted and re-added the static library with no luck -ObjC linker flag is set Any ideas? nm output libFJSCodeDebug.a(UIView-Extensions.o): 000004d4 t -[UIView(Extensions) changeColor:withDelay:duration:] 00000000 t -[UIView(Extensions) fadeInWithDelay:duration:] 000000dc t -[UIView(Extensions) fadeOutWithDelay:duration:] 00000abc t -[UIView(Extensions) firstResponder] 000006b0 t -[UIView(Extensions) hasSubviewOfClass:] 00000870 t -[UIView(Extensions) hasSubviewOfClass:thatContainsPoint:] 000005cc t -[UIView(Extensions) rotate:] 000002d8 t -[UIView(Extensions) shrinkToSize:withDelay:duration:] 000001b8 t -[UIView(Extensions) translateToFrame:delay:duration:] U _CGAffineTransformRotate 000004a8 t _CGPointMake U _CGRectContainsPoint U _NSLog U _OBJC_CLASS_$_UIColor U _OBJC_CLASS_$_UIView U ___CFConstantStringClassReference U ___addsf3vfp U ___divdf3vfp U ___divsf3vfp U ___extendsfdf2vfp U ___muldf3vfp U ___truncdfsf2vfp U _objc_enumerationMutation U _objc_msgSend U _objc_msgSend_stret U dyld_stub_binding_helper

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• Issue with deserialization of a static property in .Net

  - by Punit Singhi

  I have a class called Test which has four public properties and one of them is static. the problem is after deserialization the static property contains null value. i have debugged the code and found that at server side it contains the value which is a collection , but at client side it becomes null after deserialization. i know static members doesn't serialize and deserialize so obviously it should contain the value.

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• NullPointerException with static variables

  - by tomekK

  I just hit very strange (to me) behaviour of java. I have following classes: public abstract class Unit { public static final Unit KM = KMUnit.INSTANCE; public static final Unit METERS = MeterUnit.INSTANCE; protected Unit() { } public abstract double getValueInUnit(double value, Unit unit); protected abstract double getValueInMeters(double value); } And: public class KMUnit extends Unit { public static final Unit INSTANCE = new KMUnit(); private KMUnit() { } //here are abstract methods overriden } public class MeterUnit extends Unit { public static final Unit INSTANCE = new MeterUnit(); private MeterUnit() { } ///abstract methods overriden } And my test case: public class TestMetricUnits extends TestCase { @Test public void testConversion() { System.out.println("Unit.METERS: " + Unit.METERS); System.out.println("Unit.KM: " + Unit.KM); double meters = Unit.KM.getValueInUnit(102.11, Unit.METERS); assertEquals(0.10211, meters, 0.00001); } } 1) MKUnit and MeterUnit are both singletons initialized statically, so during class loading. Constructors are private, so they can't be initialized anywhere else. 2) Unit class contains static final references to MKUnit.INSTANCE and MeterUnit.INSTANCE I would expect that: KMUnit class is loaded and instance is created. MeterUnit class is loaded and instance is created. Unit class is loaded and both KM and METERS variable are initialized, they are final so they cant be changed. But when I run my test case in console with maven my result is: T E S T S Running de.audi.echargingstations.tests.TestMetricUnits Unit.METERS: m Unit.KM: null Tests run: 3, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 0.089 sec <<< FAILURE! - in de.audi.echargingstations.tests.TestMetricUnits testConversion(de.audi.echargingstations.tests.TestMetricUnits) Time elapsed: 0.011 sec <<< ERROR! java.lang.NullPointerException: null at de.audi.echargingstations.tests.TestMetricUnits.testConversion(TestMetricUnits.java:29) Results : Tests in error: TestMetricUnits.testConversion:29 NullPointer And the funny part is that, when I run this test from eclipse via JUnit runner everything is fine, I have no NullPointerException and in console I have: Unit.METERS: m Unit.KM: km So the question is: what can be the reason that KM variable in Unit is null (and in the same time METERS is not null)

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