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• MySQL Integer vs DateTime index

  - by David Kuridža

  Let me start by saying I have looked at many similar questions asked, but all of them relate to Timestamp and DateTime field type without indexing. At least that is my understanding. As we all know, there are certain advantages when it comes to DateTime. Putting them aside for a minute, and assuming table's engine is InnoDB with 10+ million records, which query would perform faster when criteria is based on: DateTime with index int with index In other words, it is better to store date and time as DateTime or UNIX timestamp in int? Keep in mind there is no need for any built-in MySQL functions to be used.

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• About first-,second- and third-class value

  - by forest58

  First-class value can be passed as an argument returned from a subroutine assigned into a variable. Second-class value just can be passed as an argument. Third-class value even can't be passed as an argument. Why should these things defined like that? As I understand, "can be passed as an argument" means it can be pushed into the runtime stack;"can be assigned into a variable" means it can be moved into a different location of the memory; "can be returned from a subroutine" almost has the same meaning of "can be assigned into a variable" since the returned value always be put into a known address, so first class value is totally "movable" or "dynamic",second class value is half "movable" , and third class value is just "static", such as labels in C/C++ which just can be addressed by goto statement, and you can't do nothing with that address except "goto" .Does My understanding make any sense? or what do these three kinds of values mean exactly?

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• Is Learning the win32 API Worthwhile?

  - by kronoz

  I was certain that somebody would have specifically asked this question, but from what I can see no-one has (there's been a question about learning win32 but that doesn't cover whether it's worthwhile doing so). I am very interested in gaining a deeper understanding of all the systems I use (I mostly program in C#, at least professionally), so I wondered, very simply - is learning win32 worthwhile, or is it overkill? Am I wasting my time? Is the knowledge I'd gain worth the effort? Similar / related questions on StackOverflow: Does it still make sense to learn low level WinAPI programming? How relevant is Win32 programming to modern professionals?

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• Explicit constructor still has default values even though a default constructor is not invoked.

  - by Phoenix

  According to my understanding a default constructor initializes the state of the object to default values, so if i provide an explicit no-arg public constructor like this then how are the values of d and e still getting initialized to zero because in this case the default constructor is not invoked. public class B extends A{ private int d; private int e; public B() { System.out.println(d); System.out.println(e); } } EDIT:: The only thing default constructor does is call to super() then how come if i have a explicitly mentioned a constructor here and A has a protected variable say c which is initialized to 17 in its constructor. Should I not be explicitly calling super() to be able to see that change since I'm using my own constructor ? Why is B still getting the value of 17 through inheritance ?

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• Rails 3 ActiveRecord group_by sort by count

  - by Craig

  The following view code generates a series of links with totals (as expected): <% @jobs.group_by(&:employer_name).sort.each do |employer, jobs| %> <%= link_to employer, jobs_path() %> <%= "(#{jobs.length})" %> <% end %> However, when I refactor the view's code and move the logic to a helper, the code doesn't work as expect. view: <%= employer_filter(@jobs_clone) %> helper: def employer_filter(jobs) jobs.group_by(&:employer_name).sort.each do |employer,jobs| link_to employer, jobs_path() end end The following output is generated: <Job:0x10342e628>#<Job:0x10342e588>#<Job:0x10342e2e0>Employer A#<Job:0x10342e1c8>Employer B#<Job:0x10342e0d8>Employer C#<Job:0x10342ded0>Employer D# What am I not understanding? At first blush, the code seems to be equivalent.

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• Android sql creating database once

  - by semajhan

  One thing i'm not understanding is how to create the database and data just once in an android application. I extend SQLiteOpenHelper and use a DataHelper class that to manipulate data. Now, I have addEvent() and updateEvent() within the DataHelper class. I create an instance of DataHelper in my Activity and addEvent() a couple of times to insert data. Well, now I don't know how to just do that once. If I restart the app, its just going to "addEvent()" again and so the data is being reset every time. Sorry for the probably really REALLY noob question. The only solution I found was not using the DataHelper class and just adding data "manually" within the onCreate() method in SQLiteOpenHelper.

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• Using ManagementClass.Getinstances() from IronPython

  - by Leo Bontemps

  I have an IronPython script that looks for current running processes using WMI. The code looks like this: import clr clr.AddReference('System.Management') from System.Management import ManagementClass from System import Array mc = ManagementClass('Win32_Processes') procs = mc.GetInstances() That last line where I call the GetInstances() method raises the following error: Traceback (most recent call first): File "<stdin>", line 1, in <module> SystemError: Not Found I am not understanding what's not being found?!? I believe that I may need to pass an instance of ManagementOperationObserver and of EnumerationOptions to GetInstance() however, I don't understand why that is, since the method with the signature Getinstance() is available in ManagementClass.

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• If I had to create a server farm what should I do? (how others companies work?)

  - by Michel

  I have a business idea but this is not really my field so I'm trying to understand what I'm really dealing with. I have a general understanding of how a web farm works, I'm a web developer and I understand the technology behind it, but I'm curious to know specifically how a web farm is set up and which professionals are involved. Things to consider probably are the hardware, the power supply, the software managment, the cooling system and if possible the usage of green technology/power recycling. Basically, can you explain me how a web hosting company is structured and how it works? A big question, I know, but from what I already read here about the subject a lot of you know this stuff. Thanks for your time guys!

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• How messages flows between computers connected with Internet or LAN ?

  - by Praveen

  Hi All, I have been doing Windows programming in .Net since last two years. Now I am shifting to web programming so I just stuck in understanding the fundamentals of web programming, after googling I came to StackOverflow to learn from all of you great guys. My confusion is about how messages flow between systems in distributed enviornment ? I mean suppose I want to send a message "Hello" to a system connected to LAN or Internet, then what will be the steps taken to send the message. Second thing is suppose my system is "A" and I wana send message to system "B" which is connected via a wire, so how the message flows on wire and how system "B" reads it from the wire ? Please someone explain me in a layman terms. Thank you all in advance.

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• Post data with jQuery to ASP.net, am I doing this secure enough?

  - by Wim Haanstra

  For a website I am building, I am using jQuery to post data to Generic Handlers I created for this purpose. Because you need to be logged in, to do most post actions (like 'rate a picture'), I am currently using the following technique: User visits page Page determines if user is logged in On Page_Load the page fills a hidden field with an encrypted string, which contains several needed variables, like User ID, Picture ID (of the picture they are currently viewing), the DateTime when the page was rendered. When the user clicks a "I like this picture"-button, I do a $.ajax post to my Generic Handler, with the encrypted string and the value whether or not they liked the picture. The Generic Handler decrypts the supplied encrypted string and takes a look at the DateTime to determine if it was not too long ago When everything works out, the vote is submitted to the database. In my understanding this is a pretty secure way to handle a situation like this. But maybe I am missing a very important point here. Any advice would be very welcome.

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• Response Time is different for mulitiple execution of the application with the same request Performa

  - by sivananda

  My java application functionality is to provide reference data (basically loads lots of data from xml files into hashmap) and hence we request for one such data from the hashmap based on a id and we have such multiple has map for different set of business data. The problem is that when i tried executing the java application for the same request multiple times, the response times are different like 31ms, 48ms, 72ms, 120ms, 63ms etc. hence there is a considerable gap between the min and max time taken for the execution to complete. Ideally, i would expect the response times to be like, 63ms, 65ms, 61ms, 70ms, 61ms, but in my case the variation of the response time for the same request is varying hugely. I had used a opensource profile to understand if there is any extra execution of the methods or memory leak, but as per my understanding there was no problem. Please let me know what could be the reasons and how can i address this problem.

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• What is a Custom Class?

  - by John Saunders

  Many questions here on SO ask about custom classes. I, on the other hand, have no idea what they're talking about. "Custom class" seems to mean the same thing I mean when I say "class". What did I miss, back in the '80s, that keeps me from understanding? I know that it's possible to purchase a packaged system - for Accounting, ERP, or something like that. You can then customize it, or add "custom code" to make the package do things that are specific to your business. But that doesn't describe the process used in writing a .NET program. In this case, the entire purpose of the .NET Framework is to allow us to write our own code. There is nothing useful out of the box.

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• requireJS : How to structure Javascript for an entire site?

  - by pagewil

  I have 3000+ lines of javascript that I need to get into a sensible/maintainable structure. I have chosen to use requireJS as it has been recommend to me by a few people. I have a bunch of variables that are used throughout the application and need to be available everywhere. I also have a bunch of functions that need to be available everywhere. Apart from these two dependencies most of the code can be divided off into their own modules. I am having trouble understanding how to manage my main variables so that if one module of code makes changes to the variables the rest of the JS modules will see that change. I think I need to see a few examples that demonstrate how requireJS is intended to work on a larger scale that the examples in the documentation. If anyone is an experienced requireJS user I would love the hear your tips!

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• Java how does Key Event Handling Mechanism(KeyListeners notified) work ?

  - by Carbonizer

  How does application/JVM know which classes if implemented key handling interfaces ? Does it use java Reflections or does it check all the classes for methods ? How can a application or executing JVM understanding to deliver the user event or call the specific methods on a class that implemented the keylistener interface. Does it look at all the classes if those methods are implemented or how does it know which classes implmented keylistener interface ? If you dont implement the keylistener Interface for a class but still implmentation all its methods. Do the class still process the user event occurred ?

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• How can I load an MP3 or similar music file for display and anaysis in wxWdigets?

  - by Jon Cage

  I'm developing a GUI in wxPython which allows a user to generate sequences of colours for some toys I'm building. Part of the program needs to load an MP3 (and potentially other formats further down the line) and display it to the user. That shuold be sufficient to get started but later I'd like to add features like identifying beats and some crude frequency analysis. Is there any simple way of loading / understanding an MP3's contents to display a plot of it's amplitudes to the screen using wxWidgets? I later intend to port to C++/wxWidgets for speed and to avoid having to distribute wxPython.

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• OpenGL ES perspective projection

  - by TimeManx

  I'm having a hard time understanding how glFrustum & gluPerspective work. I understand the concept of perspective projection but the functions aren't behaving how I expect them to. For example, if I set the frustum this way glFrustumf(0, 10, 0, 10, 1, 100) and have a rectangle at points 0, 0, 1, 0, 10, 1, 10, 10, 1, 10, 0, 1 then the rectangle is drawn with its left edge at -5 & right edge at 5, so the left half of the rectangle isn't visible. And if x is translated, I'd expect y to be too. But that doesn't happen either. In whatever examples I've seen, the coordinates for the projection matrix are taken as glFrustumf(-10, 10, -10, 10, 1, 100) but either way, whatever part is shown should be dependent on the rectangle's coordinates, right?

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• Python Class Variables Question

  - by zyq524

  I have some doubt about python's class variables. As my understanding, if I define a class variable, which is declared outside the init() function, this variable will create only once as a static variable in C++. This seems right for some python types, for instance, dict and list type, but for those base type, e.g. int,float, is not the same. For example: class A: dict1={} list1=list() int1=3 def add_stuff(self, k, v): self.dict1[k]=v self.list1.append(k) self.int1=k def print_stuff(self): print self.dict1,self.list1,self.int1 a1 = A() a1.add_stuff(1, 2) a1.print_stuff() a2=A() a2.print_stuff() The output is: {1: 2} [1] 1 {1: 2} [1] 3 I understand the results of dict1 and list1, but why does int1 behavior different?

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• C# Possible to partial class "program" class for a console application?

  - by JL

  I was wondering if its possible to change the default "program" class that gets created for any console application to a partial class. I want to do this because I want better organisation rather than have all methods in 1 file categorized by region. It would make more sense for me to have certain method categories sitting in separate files. My understanding of a partial class is that it is a class definition in multiple files that during a compile merges the class files into 1 class unit. I could be wrong, or there could be a better way for me to achieve better organisational structure. Any suggestions would help, and thanks

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• MVC Helper Extension issue

  - by BeCool

  Hi, I need to implement a HtmlHelper extension in my MVC project simply just to output some string but ONLY in the DEBUG mode, not in REALEASE. My first attempt would be: [Conditional("DEBUG")] public static string TestStringForDebugOnly(this HtmlHelper helper, string testString) { return testString; } But obviously that would give a compile error: "The Conditional attribute is not valid because its return type is not void." So my understanding is once you set [Condition] attribute, it doesnt allow to return anything? why? What is other way to implement this kind of function? anyone help would be much appreciated. Thanks!

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• recommend a server side technology for gwt (beginner)

  - by user486503

  hi all ! I am developing a gwt project and am looking for an appropriate server side technology. it should support be open source and support user login (and not using openID...) with password recovery etc it seems that the de-facto standard would be spring + hibernate. however, I am unfamiliar with neither of them and understand that the learning curve (especially for spring) is very high. gwt was quite easy to learn using GOOG's excellent online tutorials but the spring equivalent seem to impose lots of configuration files and deeper understanding of its internals. so I am looking for a simpler server side technology to deploy my gwt app. I am definitely prepared to learn a new framework if necessary but not something that would take me 2 months just to understand the fundamentals... any ideas...?

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• CruiseControl.NET, Visual Studio & SubVersion

  - by Ian

  Hi All, I am setting up a Continuous Integration server. I have one issue that doesn't seem to be mentioned in the tutorials. I have a ASP.net Web Application that I need to compile and them publish. My Problem is that I seem to be able to compile the app but when I attempt to use a buildPublisher this copies every thing including .svn files & folders and ms CS files. I am using an MSBuild task to compile my source. I tried setting my MSBuild Output Directory to directory but this didn't seem to have any effect. What am I not understanding? Thanks

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• PHP MySQL Insert Data

  - by happyCoding25

  Hello, Im trying to insert data into a table in MySQL. I found/modified some code from w3Schools and still couldn't get it working. Heres what I have so far: <?php $rusername=$_POST['username']; $rname=$_POST['name']; $remail=$_POST['emailadr']; $rpassword=$_POST['pass']; $rconfirmpassword=$_POST['cpass']; if ($rpassword==$rconfirmpassword) { $con = mysql_connect("host","user","password"); if (!$con) { die('Could not connect: ' . mysql_error()); } mysql_select_db("mydbname ", $con); } mysql_query("INSERT INTO members (id, username, password) VALUES ('4', $rusername, $rpassword)"); ?> Did I mistype something? To my understanding "members" is the name of the table. If anyone knows whats wrong I appreciate the help. Thanks

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• jquery - how is multiple selection working in this example?

  - by hatorade

  The relevant snippet of HTML: <span class="a"> <div class="fieldname">Question 1</div> <input type="text" value="" name="q1" /> </span> The relevant jQuery: $.each($('.a'), function(){ $thisField = $('.fieldname', $(this)); }); What exactly is being set to $thisField? If my understanding of multiple selectors in jQuery is correct, it should be grabbing the outer <span> element AND the inner <div> element. But for some reason, if I use $thisField.prepend("hi"); it ends up putting hi right before the text Question 1, but not before <div>. I thought multiple selectors would grab both elements, and that prepend() adds hi to the beginning of BOTH elements, not just the <div>

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• NHibernate: References still being eagerly selected after specifying AddJoin

  - by cbp

  I have a query which is something like this: Session.CreateSQLQuery( @"SELECT f.*, b.*, z.* FROM Foo f LEFT OUTER JOIN Bar b ON b.Id = f.BarId LEFT OUTER JOIN Zar z ON z.Id = b.ZarId" ) .AddEntity("f", typeof(Foo)) .AddJoin("b", "f.BarId") .AddJoin("z", "f.ZarId") .List<Foo>(); The problem is that I am still getting hundreds of SELECT requests made to the Zar table, even though I have specified that Zar should be joined. As far as I am aware the only relationship is Foo-Bar-Zar, i.e. the reference to Zar is not occurring anywhere else. Is my understanding of AddJoin correct? What could be going wrong? List item

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• Question marks in Java generics.

  - by gnucom

  I tried to make sure this wasn't a duplicate post, sorry if I was blind. This is a small snippet of code taken from some of the examples that accompany the Stanford Parser. I've been developing in Java for about 4 years, but have never had a very strong understanding of what this style of code is supposed to indicate. List<? extends HasWord> wordList = toke.tokenize(); I'm not worried about the details of the code. What I'm confusing about is what exactly the generic expression is supposed to convey, in English. Can someone explain this to me? Thanks!

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