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• Why is the 'if' statement considered evil?

  - by Vadim

  I just came from Simple Design and Testing Conference. In one of the session we were talking about evil keywords in programming languages. Corey Haines, who proposed the subject, was convinced that if statement is absolute evil. His alternative was to create functions with predicates. Can you please explain to me why if is evil. I understand that you can write very ugly code abusing if. But I don't believe that it's that bad.

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• Tokenize problem in Java with separator ". "

  - by user112976

  I need to split a text using the separator ". ". For example I want this string : Washington is the U.S Capital. Barack is living there. To be cut into two parts: Washington is the U.S Capital. Barack is living there. Here is my code : // Initialize the tokenizer StringTokenizer tokenizer = new StringTokenizer("Washington is the U.S Capital. Barack is living there.", ". "); while (tokenizer.hasMoreTokens()) { System.out.println(tokenizer.nextToken()); } And the output is unfortunately : Washington is the U S Capital Barack is living there Can someone explain what's going on?

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• Copy constructor demo (crashing... case 2)

  - by AKN

  Please have a glance at this program: class CopyCon { public: char *name; CopyCon() { name = new char[20]; name = "Hai";//_tcscpy(name,"Hai"); } CopyCon(const CopyCon &objCopyCon) { name = new char[_tcslen(objCopyCon.name)+1]; _tcscpy(name,objCopyCon.name); } ~CopyCon() { if( name != NULL ) { delete[] name; name = NULL; } } }; int main() { CopyCon obj1; CopyCon obj2(obj1); cout<<obj1.name<<endl; cout<<obj2.name<<endl; } This program crashes on execution. Error: "Expression: _BLOCK_TYPE_IS_VALID(pHead-nBlockUse)" If I assign "Hai" to name using aasignment operator, its crashing. Where as when I use string func _tcscpy to assign "Hai" to name, its working perfectly. Can some one explain why so?

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• CORBA Naming Service returns incorrect location of a registered object

  - by dave-keiture

  Hi experts, I have a simple setup with several objects registered at orbd. Remote client initializes connection to the ORB and tries to resolve a reference to the Naming Serice (IDL:omg.org/CosNaming/NamingContextExt:1.0). So far it's all fine - ORB returns giop.iiop.host/giop.iiop.port pair. When reference to the Naming Service is resolved, client tries to resolve_str() one of the registered objects. This time, Naming Service returns completely different pair giop.iiop.host/giop.iiop.port for the object (not the host/port of a Naming Service) - I don't know anything about them. When client tries to call a method on a resolved object, it fails, as the host/port pair is not configured in the firewall. Could you please explain, why it's happening? Thanks in advance!

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• ajax parameter to send correctly a variable to a specified url

  - by kawtousse

  I am trying to send data to a servlet from a js file but the servlet never received the parameter. so this is what I have: function showProject(prj) { xmlhttp=GetXmlHttpObject(); if (xmlhttp==null) { alert ("Browser does not support HTTP Request"); return; } var url="ServletxmlGenerator"; idprj = prj.options[prj.selectedIndex].value; //alert(idprj); url=url+"?idprj="+idprj; xmlhttp.onreadystatechange=stateChanged; xmlhttp.open("GET",url,true); xmlhttp.send(null); } and to capture th request it is with: public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String projectcode=request.getParameter("idprj"); System.out.println("++++projectCode:=" +projectcode); the output is like: ++++projectCode:=null Can any one explain it to me it seems to be correct but i didnot find the error.Thinks

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• Spring bean's DESTROY-METHOD attribute [does not work for me]

  - by EugeneP

  Can get work the attribute "destroy-method". First, even if I type non-existing method name into "destroy-method" attribute, Spring initialization completes fine (already strange!). Next, when a bean has a "prototype" scope, then I suppose it must be destroyed before the application is closed. That not happens, it is simply never called in my case. Though, after extracting this bean I can call this method explicitly and it does its job. Could you explain why this method is never called in my Spring 2.5 case? p.s. The method exists, it is public and has no arguments.

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• No whitespace between a cast and a namespace operator?

  - by Pod

  Hello. Could anyone please explain the following line of code, found on http://docs.openttd.org/ai__cargo_8cpp_source.html return (AICargo::TownEffect)::CargoSpec::Get(cargo_type)->town_effect; If this line was: return (AICargo::TownEffect) ::CargoSpec::Get(cargo_type)->town_effect; (note the space between TownEffect) and the ::) then I would understand it fine. However there is no whitespace in that document*, which would mean (AICargo::TownEffect) is the left operand of the :: operator. How does this code work/compile? Or are the two things equivilent due to some obscure C++ rule? *It's the same in the cpp file as well.

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• Single HTML Table from multiple MySQL tables

  - by David Chouinard

  Hi! I've been struggling for a while with this one; I'll try to explain it here as simply as possible. Consider this MySQL table: +----------+-----------+---------+--------+ |status_id |session_id |pilot_id |present | +----------+-----------+---------+--------+ |1 |61 |901 |1 | |2 |63 |901 |1 | |3 |62 |901 |0 | |4 |62 |902 |1 | |5 |63 |903 |1 | +----------+-----------+---------+--------+ Both session_id and pilot_id are foreign keys making reference to a primary key in another table. The same pilot_id can be associated with different session_id, but every pilot_id-session_id combination is unique. I need to make an HTML table (in PHP) that would display the data like this: +----------+---------+---------+---------+ | |61 |62 |63 | +----------+---------+---------+---------+ |901 |X | |X | |902 | |X | | |903 | | |X | +----------+---------+---------+---------+ Hence, rows are pilot_id and columns are session_id. When a pilot_id-session_id combination has a present value of 1, the corresponding cell should be checked. (ie. when the row-combination is zero or the combination does not exist in the MySQL table, nothing should appear in the HTML table) Phew. Any ideas? Thanks!

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• Use the [Serializable] attribute or subclassing from MarshalByRefObject?

  - by Theo Lenndorff

  I'd like to use an object across AppDomains. For this I can use the [Serializeable] attribute: [Serializable] class MyClass { public string GetSomeString() { return "someString" } } Or subclass from MarshalByRefObject: class MyClass: MarshalByRefObject { public string GetSomeString() { return "someString" } } In both cases I can use the class like this: AppDomain appDomain = AppDomain.CreateDomain("AppDomain"); MyClass myObject = (MyClass)appDomain.CreateInstanceAndUnwrap( typeof(MyClass).Assembly.FullName, typeof(MyClass).FullName); Console.WriteLine(myObject.GetSomeString()); Why do both approaches seem to have the same effect? What is the difference in both approaches? When should I favor the one approach over the other? EDIT: At the surface I know that there are differences between both mechanisms, but if someone jumped out of a bush and asked me the question I couldn't give him a proper answer. The questions are quite open questions. I hoped that someone can explain it better than I could do.

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• set variables in an MVC application?

  - by Melissa

  I am trying to learn about the Orchard MVC application. I see the following code but cannot understand what it is doing. Can someone explain what this: User.As<UserPart>().Record.UserName = value; means? public class UserEditViewModel { [Required] public string UserName { get { return User.As<UserPart>().Record.UserName; } set { User.As<UserPart>().Record.UserName = value; } } [Required] public string Email { get { return User.As<UserPart>().Record.Email; } set { User.As<UserPart>().Record.Email = value; } } public IContent User { get; set; } }

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• Different results when applying function to equal values

  - by Johannes Stiehler

  I'm just digging a bit into Haskell and I started by trying to compute the Phi-Coefficient of two words in a text. However, I ran into some very strange behaviour that I cannot explain. After stripping everything down, I ended up with this code to reproduce the problem: let sumTup = (sumTuples°concat) frequencyLists let sumFixTup = (138, 136, 17, 204) putStrLn (show ((138, 136, 17, 204) == sumTup)) putStrLn (show (phi sumTup)) putStrLn (show (phi sumFixTup)) This outputs: True NaN 0.4574206676616167 So although the sumTupand sumFixTup show as equal, they behave differently when passed to phi. The definition of phi is: phi (a, b, c, d) = let dividend = fromIntegral(a * d - b * c) divisor = sqrt(fromIntegral((a + b) * (c + d) * (a + c) * (b + d))) in dividend / divisor

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• iOS CollectionView with horizontal paging instead of vertical scrolling

  - by Nico Griffioen

  I'm working on a project for a client. It's an iPad pdf reader. The client wants a collection view, but instead of scrolling vertically, he wants it to use a page control. It's pretty hard to explain, but what I basically want is all the PDFs on the device in a grid, like on the iBooks app. When that grid overflows, I want to use a page control to display the extra elements on a second page (like in the weather app). My thoughts on this were: - Create a page control with one page. - On that page, create a UICollectionView. - If the number of elements is greater than 9 add a page to the page control and add another UICollectionView, until there are enough pages to display all elements. However, this seems horribly inefficient, so my question is if there's a better way to do this.

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• Why Eventmachine Defer slower than Ruby Thread?

  - by allenwei

  I have two scripts which using mechanize to fetch google index page. I assuming Eventmachine will faster than ruby thread, but not. Eventmachine code cost "0.24s user 0.08s system 2% cpu 12.682 total" Ruby Thread code cost "0.22s user 0.08s system 5% cpu 5.167 total " Am I use eventmachine in wrong way? Who can explain it to me, thanks! 1 Eventmachine require 'rubygems' require 'mechanize' require 'eventmachine' trap("INT") {EM.stop} EM.run do num = 0 operation = proc { agent = Mechanize.new sleep 1 agent.get("http://google.com").body.to_s.size } callback = proc { |result| sleep 1 puts result num+=1 EM.stop if num == 9 } 10.times do EventMachine.defer operation, callback end end 2 Ruby Thread require 'rubygems' require 'mechanize' threads = [] 10.times do threads << Thread.new do agent = Mechanize.new sleep 1 puts agent.get("http://google.com").body.to_s.size sleep 1 end end threads.each do |aThread| aThread.join end

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• TypeError: Python thinks that I passed a function 2 arguments but I only passed it 1

  - by slhck

  I work on something in Seattle Repy which is a restricted subset of Python. Anyway, I wanted to implement my own Queue that derives from a list: class Queue(list): job_count = 0 def __init__(self): list.__init__(self) def appendleft(item): item.creation_time = getruntime() item.current_count = self.job_count self.insert(0, item) def pop(): item = self.pop() item.pop_time = getruntime() return item Now I call this in my main server, where I use my own Job class to pass Jobs to the Queue: mycontext['queue'] = Queue() # ... job = Job(str(ip), message) mycontext['queue'].appendleft(job) The last line raises the following exception: Exception (with type 'exceptions.TypeError'): appendleft() takes exactly 1 argument (2 given) I'm relatively new to Python, so could anyone explain to me why it would think that I gave appendleft() two arguments when there obviously was only one?

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• Python sys.argv lists and indexes

  - by Fred Gerbig

  In the below code I understand that sys.argv uses lists, however I am not clear on how the index's are used here. def main(): if len(sys.argv) >= 2: name = sys.argv[1] else: name = 'World' print 'Hello', name if __name__ == '__main__': main() If I change name = sys.argv[1] to name = sys.argv[0] and type something for an argument it returns: Hello C:\Documents and Settings\fred\My Documents\Downloads\google-python-exercises \google-python-exercises\hello.py Which kind of make sense. Can someone explain how the 2 is used here: if len(sys.argv) >= 2: And how the 1 is used here: name = sys.argv[1]

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• SQL to return dates that fall in period and range

  - by Nate

  Hey stackers, I’ve been grinding my head on this for a while… My goal is to return all dates that fall between a start and end date and have a certain period as a factor, from the start date. (hard to explain) For example… Start Date: Nov 20, 1987; End Date: Jan 01, 1988; Period: 10 days; I want these dates: Nov 20, 1987; Nov 30, 1987; Dec 10, 1987; Dec 20, 1987; Dec 30, 1987; I already have a date table with all dates from 1900 to 2099. The period could be by days, months or years. Any ideas? Let me know if you need more info.

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• Problem with usercontrol scaling when added at run-time in .Net, WinForms

  - by Jules

  First here's the steps to replicate, then I'll explain what the problem is: (1) Add a usercontrol to a form in the construtor, after the InitializeComponent call. (2) Run the form. (3) Click a button to increase the form font size. All the controls within the usercontrol scale perfectly but the usercontrol itself doesn't. It's width and height are increased by way too much. To correct the problem, the usercontrol must be added before the InitializeComponent call. If it wasn't possible for me to add the usercontrol before InitializeComponent, is there any way for me to correct the scaling?

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• Would dynamically created JavaScript files be cached?

  - by venksster

  So my application uses a LOT of js files. thats a lot of http requests. I decided to combine them dynamically at the server in packs of 3-4 files clubbed by functionality. My client side request is: ...script type="text/javascript" src="http://mydomain.com/core-js.php" ... My server side does: --core-js.php-- header("Content-type: application/x-javascript"); include_once('file1.js'); include_once('file2.js'); include_once('file3.js'); include_once('file4.js'); I am setting a far future expire header on core-js.php. My question is, would core-js.php be cached at the client side? If it would be, could someone please explain how? Thanks!

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• Office Interop addins installer?

  - by jimbojw

  I have three C# Solutions in Visual Stuido 2008, one each for Word, Excel and PowerPoint using interop to hook various events. In each Solution, I have exactly one class, the one created by default when using File - New - Project - Visual C# - Office - 2007. Now that I have my addins working properly, it's time to create an installer. I understand that I may also have to distribute the PIAs. I would like my installer to register itself such that it can be uninstalled via the normal Add/Remove Programs mechanism. My organization is somewhat standardized around WiX for creating installers, but I'm open to any suggestions. How do I produce an MSI or EXE capable of installing my addins? GUI/wizard for the installer is not necessary. I'm happy to RTFM - so far all the tutorials I've found only explain how to create the project and do some of the coding. Maybe I'm using the wrong search terms? Thanks in advance for any help!

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• Limitation of Attachment size when using SMTP

  - by Gas Gemba

  Hi, I wrote a C++ program to send a mail using SMTP. But when I attach any files I notices that a single file's size always is limited to 808 bytes. As an example if I send a text file with 10 KBs, when I download the attachment it has only text worth 808 bytes. If the large file is a zip file, it gets corrupted in unzipping obviously due to CRC failure. I used a MAPI library to send larger files without a problem. Is this a network limitation of SMTP? Can someone please explain why this is happening?? Thank You!!!

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• Image Processing, joining the small images to form the main image

  - by n0idea

  Good morning everyone, Actually I'm having a small issue in image processing and I'm in need of some help. First of all, let me explain what i want to do, i have an image that was split into 4 other small images. I currently have like 6 small images that i need to figure out which ones are part of the real image. Second, what i currently know is that that i should compare these images edges or last column with the first column of the other image. I'm not sure yet what exactly should be done, anyone is able to put me on the same tracks, with some detailed hints and how to compare the edges of 2 images. Some links and example codes will be help full. One more thing, how am i able to read .Raw images using java, c# or python ?

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• how does gwt work or rather how gwt loads the code into the app.html file

  - by Pero

  i would like to know what the rootPanel (which is in the entryClass) exactly is and how gwt loads the java code into the appname.html file via rootpanel. what happens there exactly? where is the connection between the rootpanel and the html file. i could not find any side which explains this process in a detail. the only thing i know i that all the created panels are div-elements. it would be very helpfulf if somebody could explain it or send some good links to websites which are explaining this issue. thx!

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• Weird SQL Server 2005 Collation difference between varchar() and nvarchar()

  - by richardtallent

  Can someone please explain this: SELECT CASE WHEN CAST('iX' AS nvarchar(20)) > CAST('-X' AS nvarchar(20)) THEN 1 ELSE 0 END, CASE WHEN CAST('iX' AS varchar(20)) > CAST('-X' AS varchar(20)) THEN 1 ELSE 0 END Results: 0 1 SELECT CASE WHEN CAST('i' AS nvarchar(20)) > CAST('-' AS nvarchar(20)) THEN 1 ELSE 0 END, CASE WHEN CAST('i' AS varchar(20)) > CAST('-' AS varchar(20)) THEN 1 ELSE 0 END Results: 1 1 On the first query, the nvarchar() result is not what I'm expecting, and yet removing the X make the nvarchar() sort happen as expected. (My original queries used the '' and N'' literal syntax to distinguish varchar() and nvarchar() rather than CAST() and got the same result.) Collation setting for the database is SQL_Latin1_General_CP1_CI_AS.

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• DOM and Javascript

  - by Bob Smith

  I let a user reconfigure the location of a set of rows in a table by giving them ability to move them up and down. The changes are done by swapping nodes in the DOM. After the user has moved rows around, when I do a view source, I see the HTML in the original state (before the user made any changes). Can someone explain why that is? My understanding was when we do any DOM operations, the underlying HTML will be changed as well. EDIT: Does that mean on the server side, when attempt to get the state after user's changes, I will be able to get what I need? I am using C#/ASP.NET. Could it be because this is a HTML table (not ASP.NET Server control), that it's not maintaining the state of the changes?

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• Problem with "scopes" of variables in try catch blocks in Java

  - by devoured elysium

  Could anyone explain me why in the last lines, br is not recognized as variable? I've even tried putting br in the try clause, setting it as final, etc. Does this have anything to do with Java not support closures? I am 99% confident similar code would work in C#. private void loadCommands(String fileName) { try { final BufferedReader br = new BufferedReader(new FileReader(fileName)); while (br.ready()) { actionList.add(CommandFactory.GetCommandFromText(this, br.readLine())); } } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { if (br != null) br.close(); //<-- This gives error. It doesn't // know the br variable. } } Thanks

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