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• C++ Thread Safe Integer

  - by Paul Ridgway

  Hello everyone, I have currently created a C++ class for a thread safe integer which simply stores an integer privately and has public get a set functions which use a boost::mutex to ensure that only one change at a time can be applied to the integer. Is this the most efficient way to do it, I have been informed that mutexes are quite resource intensive? The class is used a lot, very rapidly so it could well be a bottleneck... Googleing C++ Thread Safe Integer returns unclear views and oppinions on the thread safety of integer operations on different architectures. Some say that a 32bit int on a 32bit arch is safe, but 64 on 32 isn't due to 'alignment' Others say it is compiler/OS specific (which I don't doubt). I am using Ubuntu 9.10 on 32 bit machines, some have dual cores and so threads may be executed simultaneously on different cores in some cases and I am using GCC 4.4's g++ compiler. Thanks in advance...

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• Project Euler #163 understanding

  - by Paul

  I spent quite a long time searching for a solution to this problem. I drew tons of cross-hatched triangles, counted the triangles in simple cases, and searched for some sort of pattern. Unfortunately, I hit the wall. I'm pretty sure my programming/math skills did not meet the prereq for this problem. So I found a solution online in order to gain access to the forums. I didn't understand most of the methods at all, and some just seemed too complicated. Can anyone give me an understanding of this problem? One of the methods, found here: http://www.math.uni-bielefeld.de/~sillke/SEQUENCES/grid-triangles (Problem C) allowed for a single function to be used. How did they come up with that solution? At this point, I'd really just like to understand some of the concepts behind this interesting problem. I know looking up the solution was not part of the Euler spirit, but I'm fairly sure I would not have solved this problem anyhow.

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• handling activity destruction in multithreaded android app

  - by Jayesh

  Hi, I have a multithreded app where background threads are used to load data over network or from disk/db. Every once in a while user will perform some action e.g. fetch news over network, which will spawn a background AsyncTask, but for some reason user will quit the app (press back button so that activity gets destroyed). In most such scenarios, I make appropriate checks in the background thread after it returns from n/w i/o, so that it won't crash by accessing members of the activity that is destroyed by now. However some corner cases are left where crashes happen, because the background thread would access some member of activity that is now null. Do other Android developers have some generic/recommended framework to handle such scenarios? These are the times when I wish android would have guaranteed termination of all threads when activity destroys (in the same way that regular linux process cleans up when it's quit)... but I guess Android devs had good reasons for not exposing process lifetimes through the api.

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• Unit testing huge applications - Proven methodologies?

  - by NLV

  Hello members I've been working in windows forms applications and ASP.Net applications for the past 10 months. I've always wondered how to perform proper unit testing on the complete application in a robust manner covering all the scenarios. I've the following questions regarding them - What are the standard mechanisms in performing unit testing and writing test cases? Does the methodologies change based on the application nature such as Windows Forms, Web applications etc? What is the best approach to make sure we cover all the scenarios? Any popular books on this? Popular tools for performing unit testing?

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• SQL select all items of an owner from an item-to-owner table

  - by kdobrev

  I have a table bike_to_owner. I would like to select current items owned by a specific user. Table structure is CREATE TABLE IF NOT EXISTS `bike_to_owner` ( `bike_id` int(10) unsigned NOT NULL, `user_id` int(10) unsigned NOT NULL, `last_change_date` date NOT NULL, PRIMARY KEY (`bike_id`,`user_id`,`last_change_date`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci; In the profile page of the user I would like to display all his/her current possessions. I wrote this statement: SELECT `bike_id`,`user_id`,max(last_change_date) FROM `bike_to_owner` WHERE `user_id` = 3 group by `last_change_date` but i'm not quite sure it works correctly in all cases. Can you please verify this is correct and if not suggest me something better. Using php/mysql. Thanks in advance!

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• jQuery resizable() dynamic maxWidth option

  - by Vitaliy Isikov

  I have 3 columns that are resizable. When one is made wider, the one to it's left is made smaller. Essentially there are only 2 handles. Left col and Mid col. So when Mid col is made thinner, Right col expands accordingly. All three of them are contained with a 900px parent div, so the sum of all three is always 900. They have max and min widths set statically. My issue is that if you take the left handle and move it all the way to the right you're still able to use the right handle and expand the mid col past the edge of the parent div. I thought of a way to solve that issue by writing up a function that checks the widths of the columns and then subtracts left and right columns from the parent div width, I called it mWid. This leaves me with the number I want to set as the maxWidth for Mid col. Now the issue is that mWid is not gettings updated for here "maxWidth: mWid" Here is what the function for the right handle looks like: $(function() { $("#midResizable").resizable({ handles: 'e', containment: '#container', maxWidth: mWid, // gets set once, but doesn't update! WHY? minWidth: 195, resize: function(event, ui) { contWidth = $('#container').width() newWidth = $(this).width() leftWidth = $('#leftResizable').width() rightWidth = $('#rightResizable').width() $("#rightResizable").css("width", (contWidth-15)-(newWidth)-(leftWidth)+"px"); checkWid() } }); }); function checkWid() { rightWidth = $('#rightResizable').width() leftWidth = $('#leftResizable').width() contWidth = $('#container').width() mWid = (contWidth-15)-(rightWidth)-(leftWidth) }

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• Prototype and jQuery concatenation failure

  - by Corey Hart

  I found something strange when trying to concatenate prototype and jQuery. It seems as though when concatenated, the $ jquery reference doesn't get overwritten by prototype. I've built two test cases to single this out, and it's failing in Chrome8 and FF 3.6. Test Case 1 - Without Concatenation jQuery and Prototype are loaded separately with different script tags. jQuery is loaded first, Prototype second. Test Case 2 - With Concatenation jQuery and Prototype are concatenated into a single file, and loaded with a single script tag. jQuery is first in the script, and prototype is added second. These should act identically, but the second test is throwing errors because the $ function in prototype doesn't overwrite the $ jquery reference. Did I set these up wrong, or are browsers rendering javascript differently when it's all in the same file?

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• why do we have to send the const " type " reference instead of just the types name to the constructo

  - by hamza

  i m trying to make a simple program ( & yes , it is a homework ) that can generate Dates , & like most of normal people : i made my Class attributes private , i tried to send the same type that i m working on to the constructor but the complier have not accept it , i did some research & i found out that in cases like that people generously send a const "type" reference to the constructor witch meant to me that have not understand OOP well so why do we have to send the const " type " reference instead of just the types name to the constructor ? & please give me some links or websites for beginners PS : sorry for my English

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• Python - react to custom keyboard interrupt

  - by flixic

  Hello. I am writing python chatbot that displays output through console. Every half second it asks server for updates, and responds to message. In the console I can see chat log. This is sufficient in most cases, however, sometimes I want to interrupt normal workflow and write custom chat answer myself. I would love to be able to press a button (or combination) that would switch to "custom reply mode". What is the best way to do that, or achieve similar result? Thanks a lot!

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• Instance where embedded C++ compilers don't support multiple inheritance?

  - by Nathan

  I read a bit about a previous attempt to make a C++ standard for embedded platforms where they specifically said multiple inheritance was bad and thus not supported. From what I understand, this was never implemented as a mainstream thing and most embedded C++ compilers support most standard C++ constructs. Are there cases where a compiler on a current embedded platform (i.e. something not more than a few years old) absolutely does not support multiple inheritance? I don't really want to do multiple inheritance in a sense where I have a child with two full implementations of a class. What I am most interested in is inheriting from a single implementation of a class and then also inheriting one or more pure virtual classes as interfaces only. This is roughly equivalent to Java/.Net where I can extend only one class but implement as many interfaces as I need. In C++ this is all done through multiple inheritance rather than being able to specifically define an interface and declare a class implements it.

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• my first shader in WebGL

  - by Diego

  Hello, I am writing my first shader in WebGL. I was wondering if the GLSL language has any way to evaluate if an attribute or a uniform is null. According to the specs it does not support to do something like if (attributeX) { dothis(); } else{ dothat(): } And I think it would be a waste to write a bool attribute for each of these cases would be a waste. Another question: what happen during rendering when you don't pass along the uniforms or attribs to the shader? Thanks!

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• win7 + vc7.1 + mfc = stackoverflow

  - by fogbit

  Hello! I've moved my vc7.1 project from WInXP to Win7. After rebuilding i got stackoverflow error in function _malloc_dbg when i start the program. "Unhandled exception at 0x0051bf0f in XXX.exe: 0xC00000FD: Stack overflow." Call stack: msvcr71d.dll!_malloc_dbg(unsigned int nSize=140, int nBlockUse=2, const char * szFileName=0x10267784, int nLine=163) msvcr71d.dll!_calloc_dbg(unsigned int nNum=1, unsigned int nSize=140, int nBlockUse=2, const char * szFileName=0x10267784, int nLine=163) msvcr71d.dll!_mtinit() msvcr71d.dll!_CRTDLL_INIT(void * hDllHandle=0x10200000, unsigned long dwReason=1, void * lpreserved=0x0018fd24) I tried to set up different stacksizes in project options (from 10 to 100 mbytes), in all cases i got this error. How can i fix this?

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• Bookmarkabale ajax calls with MVC routing

  - by devzero

  I have a page with a menu that uses JQuery AJAX calls to populate the page with. To reflect any changes I update the URL with a #... instead of ?... or /... So an URL that originally reads : htpp://localhost/pages/index/id=1 would look like : http://localhost/#pages/index/id=1. If a user bookmarks this, and later comes back to the page, I wonder if it's possible to use the second URL in my route decoding, or if I have to load it blank, then use the same JS/Ajax to populate the page? In my mind it is problematic to use Ajax in these cases if a user copies the link and mails it to a friend with JavaScript disabled. edit#1: Fixed some spelling.

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• ASP.NET MVC: What is the correct way to redirect to pages/actions in MVC?

  - by Mark Redman

  I am fairly new to MVC but not sure exactly which Redirect... replaces the standard redirect used in WebForms ie the standard Response.Redirect() For instance, I need to redirect to other pages in a couple of scenarios: 1) WHen the user logs out (Forms signout in Action) I want to redirect to a login page 2) In a Controller or base Controller event eg Initialze, I want to redirect to another page (AbsoluteRootUrl + Controller + Action) It seems that multiple redirects get called in some cases which causes errors, something to do with the fact a page is already being redirected? How can cancel the current request and just redirect?

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• PHP eval() code in between <?php ?> from database

  - by kr1zmo

  Some of you may be annoyed with this question, and claim it's unsafe blah blah. I want to be able to put php into the database and run it. I have to do this because I store page layouts in the database and each our different for each other, however in some cases I want to use dynamic content for some of the pages. assume $query_from_db is the string returned from the database. php should only eval() the code in between <?php and ?> $query_from_db = '<div> <?php //php to run function dosomething() { //bleh } ?> </div> '; php echo eval($query_from_db);

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• ActiveRecord Create (not !) Throwing Exception on Validation

  - by myferalprofessor

  So I'm using ActiveRecord model validations to validate a form in a RESTful application. I have a create action that does: @association = Association.new and the receiving end of the form creates a data hash of attributes from the form parameters to save to the database using: @association = user.associations.create(data) I want to simply render the create action if validation fails. The problem is that the .create (not !) method is throwing an exception in cases where the model validation fails. Example: validates_format_of :url, :with => /(^$)|(^(http|https):\/\/[a-z0-9]+([\-\.]{1}[a-z0-9]+)*\.[a-z]{2,5}(([0-9]{1,5})?\/.*)?$)/ix, :message => "Your url doesn't seem valid." in the model produces: ActiveRecord::RecordInvalid Exception: Validation failed: Url Your url doesn't seem valid. I thought .create! is supposed throw an exception whereas .create is not. Am I missing something here? Ruby 1.8.7 patchlevel 173 & rails 2.3.3

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• Is there a way to let NetBeans work with Amazon-ec2 disk space?

  - by khelll

  Hello, I'm sick of using vim to develop on some far Amazon-ec2 machine. I'm wondering if there is any way to Use NetBeans on my laptop to develop on and run the code on that machine. Basically I want a way to let NetBeans operate on an external disk space that I connect to using SSH, In my case I'm using Mac OS X 10.6.3 locally and the external disk space is located on some Amazon-ec2 machine. Any ideas? Or solution for such cases when a developer needs to code on some external machine and use a good IDE? Cheers,

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• convert string to dict using list comprehension in python

  - by Pavel

  I have came across this problem a few times and can't seem to figure out a simple solution. Say I have a string string = "a=0 b=1 c=3" I want to convert that into a dictionary with a, b and c being the key and 0, 1, and 3 being their respective values (converted to int). Obviously I can do this: list = string.split() dic = {} for entry in list: key, val = entry.split('=') dic[key] = int(val) But I don't really like that for loop, It seems so simple that you should be able to convert it to some sort of list comprehension expression. And that works for slightly simpler cases where the val can be a string. dic = dict([entry.split('=') for entry in list]) However, I need to convert val to an int on the fly and doing something like this is syntactically incorrect. dic = dict([[entry[0], int(entry[1])] for entry.split('=') in list]) So my question is: is there a way to eliminate the for loop using list comprehension? If not, is there some built in python method that will do that for me?

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• Is there a browser-agnostic way to detect client-side script errors with Watin?

  - by Michael

  We're using WatiN to test our web portals. During the course of an E2E test, we'll occasionally see client-side script errors on the IE status bar. I'd like to chain a handler onto the script error event and record the error for later analysis and bug filing. Problem is, I don't know that there's a global script error event or how to chain into it. And if there's not a browser-agnostic way to accomplish this, I can create MyIE and MyFF subclasses but then this becomes two browser-specific questions. In essence, I'm thinking of something like this entirely made-up call: browser.ScriptEngine.SetCustomErrorHandler(LogScriptingError); ... where LogScriptErrors is my code that does the obvious. Many of our client-side scripting errors don't necessarily prevent the test from continuing (a pretty UI element didn't animate, for example, but the underlying form is still submittable), so I'd like to log the error and forge ahead in most cases.

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• Displaying Fields (and/instead of Properties) in a PropertyGrid

  - by Jenk

  I'd like to use a PropertyGrid to manipulate the data on some objects, however these objects don't have properties, they have fields. Thus a property grid doesn't display them (high five MS!) Before anyone posts "just use properties": I can't at the moment.. these objects are DTOs and are used to send data to a VB6 Interop dll, thus all the parameters for the method calls are "ref" parameters (high five MS!), and C# won't compile if you use a property instead of a field or variable (high five MS!). No, I am not going to create local variables for every property on any given object. There many, many fields, and many, many test cases that would need updating, as well as the production code it self, and this post/question may be the path of least resistance. :)

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• This is a great job opportunity!!! [closed]

  - by Stuart Gordon

  ASP.NET MVC Web Developer / London / £450pd / £25-£50,000pa / Interested contact [email protected] ! As a web developer within the engineering department, you will work with a team of enthusiastic developers building a new ASP.NET MVC platform for online products utilising exciting cutting edge technologies and methodologies (elements of Agile, Scrum, Lean, Kanban and XP) as well as developing new stand-alone web products that conform to W3C standards. Key Responsibilities and Objectives: Develop ASP.NET MVC websites utilising Frameworks and enterprise search technology. Develop and expand content management and delivery solutions. Help maintain and extend existing products. Formulate ideas and visions for new products and services. Be a proactive part of the development team and provide support and assistance to others when required. Qualification/Experience Required: The ideal candidate will have a web development background and be educated to degree level in a Computer Science/IT related course plus ASP.NET MVC experience. The successful candidate needs to be able to demonstrate commercial experience in all or most of the following skills: Essential: ASP.NET MVC with C# (Visual Studio), Castle, nHibernate, XHTML and JavaScript. Experience of Test Driven Development (TDD) using tools such as NUnit. Preferable: Experience of Continuous Integration (TeamCity and MSBuild), SQL Server (T-SQL), experience of source control such as Subversion (plus TortioseSVN), JQuery. Learn: Fluent NHibernate, S#arp Architecture, Spark (View engine), Behaviour Driven Design (BDD) using MSpec. Furthermore, you will possess good working knowledge of W3C web standards, web usability, web accessibility and understand the basics of search engine optimisation (SEO). You will also be a quick learner, have good communication skills and be a self-motivated and organised individual.

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• How do I find iTunes library folder on Mac and Windows?

  - by Boris

  I made an application that parse the iTunes library to retrieve its content. It works fine in most cases but if a user moved his library somewhere else than the default iTunes folder (see: http://lifehacker.com/238296/ultranewb--how-to-move-your-itunes-library-to-an-external-drive), then I need a way to find this path. On Mac, I was looking into ~/Library/Preferences/com.apple.iTunes.plist. There is a setting called "alis:1:iTunes Library Location" but it contains several parameters all concatenated and converted to hexadecimal. On Windows, I found this file "C:\Documents and Settings\\Application Data\Apple Computer\iTunes\iTunesPrefs.xml" that contains a setting "iTunes Library XML Location:1" but this one is encoded. Any help would be greatly appreciated. Thanks!

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• Common "truisms" needing correction the most

  - by Charles Bretana

  In addition to "I never met a man I didn't like", Will Rogers had another great little ditty I've always remembered. It went: "It's not what you don't know that'll hurt you, it's what you do know that ain't so." We all know or subscribe to many IT "truisms" that mostly have a strong basis in fact, in something in our professional careers, something we learned from others, lessons learned the hard way by ourselves, or by others who came before us. Unfortuntely, as these truisms spread throughout the community, the details—why they came about and the caveats that affect when they apply—tend to not spread along with them. We all have a tendency to look for, and latch on to, small "rules" or principles that we can use to avoid doing a complete exhaustive analysis for every decision. But even though they are correct much of the time, when we sometimes misapply them, we pay a penalty that could be avoided by understooding the details behind them. For example, when user-defined functions were first introduced in SQL Server it became "common knowledge" within a year or so that they had extremely bad performance (because it required a re-compilation for each use) and should be avoided. This "trusim" still increases many database developers' aversion to using UDFs, even though Microsoft's introduction of InLine UDFs, which do not suffer from this issue at all, mitigates this issue substantially. In recent years I have run into numerous DBAs who still believe you should "never" use UDFs, because of this. What other common not-so-"trusims" do you know, which many developers believe, that are not quite as universally true as is commonly understood, and which the developer community would benefit from being better educated about? Please include why it was "true" to start off with, and under what circumstances it's not true. Limit responses to issues that are technical, where the "common" application of a "rule or principle" is in fact correct most of the time, or was correct back when it was first elucidated, but—in the edge cases, or because of not understanding the principle thoroughly, because technology has changed since it first spread, or applying the rule today without understanding the details behind the rule—can easily backfire or cause the opposite of the intended effect.

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• How to get the Zoom Levels and Lat and Long values of the Map when Zoom in/out.

  - by ChandraSekhar

  I am implement an application based on the MapKit using iphone sdk.I just now a method to get the event when we drag, zoom in/out on the map. The method is as like this (void)mapView:(MKMapView *)mapView regionDidChangeAnimated:(BOOL)animated Now I need to get the following bullets. 1.TopLeft's and Bottom Right's Latitude and longitude values. 2.Center of the Map. 3.zoom level. Please give me suggessions to solve the above 3 use cases. Thanks in Advance, Sekhar Bethalam.

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• Is there any reason why someone would want to create an Core Data model programmatically?

  - by mystify

  I wonder in which cases it would be good to make an NSManagedObjectModel completely programmatically, with NSEntityDescription instances and all this stuff. I'm that kind of person who prefers to code programmatically, rejecting Interface Builder. But when it comes to Core Data, I have a hard time figuring out why I should kill my time NOT using the nice Xcode Data Modeler tool. And since data models are stuck to a given state (except when you want to do some ugly migration operations where thinks probably go wrong and users get mad, really mad), I see no big sense in a data model that's made programmatically for the purpose of changing it all the time. Did I miss something?

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