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  • reinitialize an object with self.__init__(...)

    - by Kara Jevo
    Could anybody explain whether it is safe to reinitialize an object by calling "self.init(". as shown in the following simplified example? The reason i'm asking is that i couldn't find this method neither in several python books nor in internet. There are some who suggest to list all attributes and set them to initial value one by one. Basically i want to set my object to initial state after it has finished some tasks. class Book(object): def __init__(self,name,author): self.name = name self.author = author self.copies = 5 def reset(self): self.__init__(self.name,self.author) def incrementCopy(self): self.copies += 1 Kite = Book('kite runner','khaled hosseini') print 'initial number of copies:', Kite.copies Kite.incrementCopy() Kite.incrementCopy() Kite.incrementCopy() print '3 copies are added:', Kite.copies Kite.reset() print 'number of copies are reinitialized', Kite.copies initial number of copies: 5 3 copies are added: 8 number of copies are reinitialized 5

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  • When does ref($variable) return 'IO'?

    - by Zaid
    Here's the relevant excerpt from the documentation of the ref function: The value returned depends on the type of thing the reference is a reference to. Builtin types include: SCALAR ARRAY HASH CODE REF GLOB LVALUE FORMAT IO VSTRING Regexp Based on this, I imagined that calling ref on a filehandle would return 'IO'. Surprisingly, it doesn't: use strict; use warnings; open my $fileHandle, '<', 'aValidFile'; close $fileHandle; print ref $fileHandle; # prints 'GLOB', not 'IO' perlref tries to explain why: It isn't possible to create a true reference to an IO handle (filehandle or dirhandle) using the backslash operator. The most you can get is a reference to a typeglob, which is actually a complete symbol table entry [...] However, you can still use type globs and globrefs as though they were IO handles. In what circumstances would ref return 'IO' then?

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  • Int PK inner join Vs Guid PK inner Join on SQL Server. Execution plan.

    - by bigb
    I just did some testing for Int PK join Vs Guid PK. Tables structure and number of records looking like that: Performance of CRUD operations using EF4 are pretty similar in both cases. As we know Int PK has better performance rather than strings. So SQL server execution plan with INNER JOINS are pretty different Here is an execution plan. As i understand according with execution plan from attached image Int join has better performance because it is taking less resources for Clustered index scan and it is go in two ways, am i right? May be some one may explain this execution plan in more details?

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  • Integers in JavaScript

    - by muntoo
    I'm a beginner to Javascript so forgive me if I sound dumb because I learned some Javascript from W3Fools (which are really difficult tutorials - they don't explain anything I want to know, but everything I probably can guess from my experience with C++). I may be switching over to MDN, but if you can recommend any other tutorials, that be great. Anyways, so here's my question: I just read a few lines of this, and apparently: Numbers in JavaScript are "double-precision 64-bit format IEEE 754 values", according to the spec. This has some interesting consequences. There's no such thing as an integer in JavaScript, so you have to be a little careful with your arithmetic if you're used to math in C or Java. I've already seen that there are few of the data types (for variables) I'm used to from C++. But I didn't expect all numbers to automatically be floats. Isn't there any way to use integers, not float? Will a future version of JavaScript support ints?

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  • Difference between static const char* and const char*.

    - by Will MacDonagh
    Could someone please explain the difference in how the 2 snippets of code are handled below? They definitely compile to different assembly code, but I'm trying to understand how the code might act differently. I understand that string literals are thrown into read only memory and are effectively static, but how does that differ from the explicit static below? struct Obj1 { void Foo() { const char* str( "hello" ); } }; and struct Obj2 { void Bar() { static const char* str( "hello" ); } };

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  • CSS: How to affect OTHER elements when a div is hovered

    - by Trufa
    I think this is a very basic question but I not sure how/if it can be done. What I want to do is to is a certain div is hovered, affect the properties of another div. For example, in this simple example when you hover over #cube it changes the background-color but what I that when I hover over #container, #cubeis affected. I don't want to explain further cause I think it might be confusing, but please ask the the question is no clear enough!! Thanks in advance!! jQueriers: abstain yourselves!! only CSS answers :)

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  • Understanding The Convolution Matrix

    - by Ryan Naddy
    I am learning about the Convolution Matrix, and I understand how they work, but I don't understand how to know before hand what the output of a Matrix will look like. For example lets say I want to add a blur to an image, I could guess 10,000+ different combinations of numbers before I get the correct one. I do know though that this formula will give me a blur effect, but I have no idea why. float[] sharpen = new float[] { 1/9f, 1/9f, 1/9f, 1/9f, 1/9f, 1/9f, 1/9f, 1/9f, 1/9f }; Can anyone either explain to me how this works or point me to some article, that explains this? I would like to know before hand what a possible output of the matrix will be without guessing. Basically I would like to know why do we put that number in the filed, and why not some other number?

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  • Manually logging in a user without password

    - by Agos
    Hi everybody; I hope you can help me figure the best way to implement a manual (server-side initiated) login without using the password. Let me explain the workflow: User registers Thank you! An email with an activation link has been sent blablabla (Account now exists but is marked not enabled) User opens email, clicks link (Account is enabled) Thank you! You can now use the site What I'm trying to do is log in the user after he has clicked the email link so he can start using the website right away. I can't use his password since it's encrypted in the DB, is the only option writing a custom authentication backend?

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  • How to use atmosphere-spade-server in combination with atmosphere-pubsub.war

    - by Alfred
    I would like to play with atmosphere-spade-server.jar + pubsub.war. First of I have maven installed, but to be honest Maven is kind of new to me. Could please someone please explain me how to use it correctly. What I have tried Download atmosphere-spade-server + pubsub.war from there site. java -jar atmosphere-spade-server-0.6.0-20100329.142039-1.jar -a atmosphere-pubsub.war curl http://localhost:8080/atmosphere-pubsub/myAtmosphereTopic <html><body><h1>Resource Not> Found</h1></body></html> I would just have a guided tour of how to use Atmosphere.

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  • MVC (model-view-controller) - can it be explained in simple terms?

    - by DVK
    I need to explain to a not-very-technical manager the MVC (model-view-controller) concept and ran into trouble. The problem is that the explanation needs to be on a "your grandma will get it" level - e.g. even the fairly straightforward explanation offered on MVC Wiki page didn't work, at least with my commentary. Does anyone have a reference to a good MVC explanation in simple terms? It would ideally be done with non-techie metaphor examples (e.g. similar to "Decorator pattern is like glasses") - one reason I failed was that all MVC examples I could come up with were development related. I once saw a list of pattern explanations but to the best of my memory MVC was not on it. Thanks!

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  • What are the advantages of a distributed version control for a team that is effectively never distri

    - by Luke CK
    When working remotely, our team only has access to our source code by remote desktop into our office PCs so we never really work in offline mode. Does a distributed version control system like Mercurial or Git still give us advantages over our current centralized Subversion set up? If so, what are they? Are there any drawbacks or pitfalls? I've read in numerous places that shifting to distributed version control requires a change in thinking. Can someone explain what needs to change in this regard?

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  • Django: way to test what class a generic relation content_object is?

    - by bitbutter
    In my project I have a class, NewsItem. Instances of NewsItem act like a wrapper. They can be associated with either an ArtWork instance, or an Announcement instance. Here's how the NewsItem model looks: class NewsItem(models.Model): content_type = models.ForeignKey(ContentType) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey('content_type', 'object_id') date = models.DateTimeField(default=datetime.datetime.now,) class Meta: ordering = ('-date',) def __unicode__(self): return (self.title()) In a template I'm dealing with a NewsItem instance, and would like to output a certain bunch of html it it's 'wrapping' an Artwork instance, and a different bunch of html if it's wrapping an Announcement instance. Could someone explain how I can write a conditional to test for this? My first naive try looked like this: {% if news_item.content_object.type=='Artwork' %}do this{% else %}do that{% endif %}

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  • Grouping DLL's for use in Executable

    - by Peter Turner
    Is there a way to group a bunch of DLL's and still use them at run time (not zipped up). Sorry this question sounds terse and stupid, but I'm not sure what more to ask. I'll explain the situation though: We've had two standalone Windows Applications and now one of our Applications has swelled to such ungainly proportions that the other application cannot run outside of the scope of the first app. We want to maintain some of the encapsulation we had while letting the smaller program in on some of the bigger program's features. There is no problem in running the application, other than we don't want to send out all the 20-30 DLL's that the smaller project has.

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  • Float multiple fixed-width / varible-height boxes into 2 columns

    - by Jeremy H
    I'll try to explain this as best I can. I have multiple divs that are fixed-width but variable height. I want to float these boxes into two columns inside a fixed-width container. What happens when a give them all a float: left value, I get something like this: ######### ######### # box 1 # # box 2 # ######### # ..... # ......... # ..... # ......... ######### ######### ######### # box 3 # # box 4 # # ..... # # ..... # ######### ######### ######### ######### # box 5 # # box 6 # # ..... # ######### # ..... # ######### (The periods are white space) What I really would really like is the top of box 3 to touch the bottom of box 1. Any easy way to acheive this?

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  • javascript and extJs - scope question

    - by ben
    Hi guys, I got a little scope related problem with some js code, maybe somebody can explain to me what I'm making wrong: I'm using extJs and got this snippet: Ext.onReady(function(){ // Form for filter selection var formFilter = new Ext.FormPanel({ // ... items: [ cbGroup = new Ext.form.ComboBox({ fieldLabel: 'Group', store: dsGroups, displayField: 'name', valueField: 'number', emptyText : '- Please choose a group -', listeners:{ 'select': function() { alert(cbGroup.selectedIndex +' '+this.selectedIndex); } } }) ] }); }); The problem: When I access the combobox over 'this' within the listener function, I get the correct result for the selectIndex property. When I access the combobox over it's var name, I allways get the result '-1'. Thank a lot for your help!

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  • Installing XAMPP in Amazon EC2

    - by Woho87
    Hi! Can someone explain to me(not a rocket scientist) all the steps for installing XAMPP for a EC2 instance running Linux? And yes I have look the entire web and found nothing, except this "Deploying a lamp stack" and this "Starting Amazon EC2 with Mac OS X". I found the latter one more useful, but as a said I'm not a rocket scientist. I got stuck in to the latter link where I should edit the file .bash_profile with a text editor. I tried the "vi" in SSH, but why can't I open it on textEditor included in all Macs? Is there any easier way to setting up a XAMPP server for a linux server in EC2?

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  • generic function for extracting values from an array with one particular key in PHP

    - by Sabya
    Is it possible in PHP to extract values from an array with a particular key path and return an array of those values? I'll explain with an example: $user = array ( array( id => 1, email =>'[email protected]', project => array ('project_id' => 222, 'project_name' => 'design') ), array( id => 2, email =>'[email protected]', project => array ('project_id' => 333, 'project_name' => 'design') ) ); /** I have to write a function something like: */ $projectIds = extractValuesWithKey($user, array('project', 'project_id')); print_r($projectIds); Output: Array( [0] => 222, [1] => 333 )

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  • Retain, alloc, properties ... Topic to make your Obj-c life easier !

    - by gotye
    Hey everyone, The more I code, the more I get lost ... so I decided to create a topic entirely dedicated to the memory management for me (and others) not to waste hours understanding obj-c basics ... I'll update it as new questions are asked ! Okay below is some examples : // myArray is property (retain) myArray = otherArray; //myArray isn't a property myArray = otherArray; //myArray is a property (retain) myArray = [[NSArray alloc] init]; //myArray isn't a property myArray = [[NSArray alloc] init]; Could you explain to me what happens in every cases ? And especially the number 3 ;) Thanks for the time. Gotye.

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  • Why calling ISet<dynamic>.Contains() compiles, but throws an exception at runtime?

    - by Andrey Breslav
    Please, help me to explain the following behavior: dynamic d = 1; ISet<dynamic> s = new HashSet<dynamic>(); s.Contains(d); The code compiles with no errors/warnings, but at the last line I get the following exception: Unhandled Exception: Microsoft.CSharp.RuntimeBinder.RuntimeBinderException: 'System.Collections.Generic.ISet<object>' does not contain a definition for 'Contains' at CallSite.Target(Closure , CallSite , ISet`1 , Object ) at System.Dynamic.UpdateDelegates.UpdateAndExecuteVoid2[T0,T1](CallSite site, T0 arg0, T1 arg1) at FormulaToSimulation.Program.Main(String[] args) in As far as I can tell, this is related to dynamic overload resolution, but the strange things are (1) If the type of s is HashSet<dynamic>, no exception occurs. (2) If I use a non-generic interface with a method accepting a dynamic argument, no exception occurs. Thus, it looks like this problem is related particularly with generic interfaces, but I could not find out what exactly causes the problem. Is it a bug in the compiler/typesystem, or legitimate behavior?

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  • What does ER_WARN_FIELD_RESOLVED mean?

    - by VolkerK
    When SHOW WARNINGS after a EXPLAIN EXTENDED shows a Note 1276 Field or reference 'test.foo.bar' of SELECT #2 was resolved in SELECT #1 what exactly does that mean and what impact does it have? In my case it prevents mysql from using what seems to be a perfectly good index. But it's not about fixing that specific query (as it is an irrelevant test). I found http://dev.mysql.com/doc/refman/5.0/en/error-messages-server.html butError: 1276 SQLSTATE: HY000 (ER_WARN_FIELD_RESOLVED) Message: Field or reference '%s%s%s%s%s' of SELECT #%d was resolved in SELECT #%d isn't much of an explaination.

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  • Luasql and SQLite?

    - by OverTheRainbow
    Hello I just got started looking at Lua as an easy way to access the SQLite DLL, but I ran into an error while trying to use the DB-agnostic LuaSQL module: require "luasql.sqlite" module "luasql.sqlite" print("Content-type: Text/html\n") print("Hello!") Note that I'm trying to start from the most basic setup, so only have the following files in the work directory, and sqlite.dll is actually the renamed sqlite3.dll from the LuaForge site: Directory of C:\Temp <DIR> luasql lua5.1.exe lua5.1.dll hello.lua Directory of C:\Temp\luasql sqlite.dll Am I missing some binaries that would explain the error? Thank you. Edit: I renamed the DLL to its original sqlite3.dll and updated the source to reflect this (originally renamed it because that's how it was called in a sample I found). At this point, here's what the code looks like... require "luasql.sqlite3" -- attempt to call field 'sqlite' (a nil value) env = luasql.sqlite() env:close() ... and the error message I'm getting: C:\>lua5.1.exe hello.lua lua5.1.exe: hello.lua:4: attempt to call field 'sqlite' (a nil value)

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  • NASM shift operators

    - by Hudson Worden
    How would you go about doing a bit shift in NASM on a register? I read the manual and it only seems to mention these operators , <<. When I try to use them NASM complains about the shift operator working on scalar values. Can you explain what a scalar value is and give an example of how to use and <<. Also, I thought there were a shr or shl operators. If they do exist can you give an example of how to use them? Thank you for your time.

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  • Request attributes in jsf / icefaces behaves strange (survive request end)

    - by hubertg
    I have the following code in a listener method: FacesContext.getCurrentInstance().getExternalContext().getRequestMap().put("time", new Date()); When a button is clicked the following code is executed System.out.println(FacesContext.getCurrentInstance().getExternalContext().getRequestMap().get("time")); One could except that "time" is null when the listener was not executed while processing the current request, but: it seems like the "time" object survives the request processing. So when "time" has been set sometimes in the past it stays there... can anybody explain this? Thanks.

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  • Is it a good idea to work on header files only, just at the start of the project?

    - by m4design
    To explain my point further, I'm a beginner in programming, and I'm working on a small project. Instead of separating the .cpp file from the header file, I'm implementing the code in the header files, and making one .cpp file for testing. I do this to have less files, hence easier navigation. Then later I'll separate the code as it should be. Will this cause any problems? should I continue doing that? Thanks.

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  • Animated gifs in QMovie

    - by Jason
    I'm displaying an animated gif in my application by creating a QLabel, and setting the movie as a QMovie. The problem I'm having is that when the gif is displayed, any part of the image that stays a constant color throughout the animation shows up as the background color. I hope I'm explaining that clearly. Here's the code I'm using to create the animation if that helps: rewardLabel=new QLabel(); rewardLabel->setCursor(QCursor(Qt::BlankCursor)); rewardLabel->setWindowFlags(Qt::FramelessWindowHint); rewardLabel->hide(); string movieTemp="animations/"+animationFiles[animationIndex]; QString movieFile(movieTemp.c_str()); rewardMovie=new QMovie(movieFile); rewardLabel->setMovie(rewardMovie); Let me know if I need to explain the situation better. Thanks in advance.

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