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• My Core Animation block isn't working like I'd expect

  - by Alex Reynolds

  I have a UIView called activityView, which contains two subviews activityIndicator and cancelOperationsButton. These views are embedded in a XIB and wired up to my view controller. I have two methods that deal with activating (showing) and deactivating (hiding) these two subviews: - (void) enableActivityIndicator { [activityIndicator startAnimating]; [cancelOperationsButton setHidden:NO]; } - (void) disableActivityIndicator { [activityIndicator stopAnimating]; [cancelOperationsButton setHidden:YES]; } By themselves, these two methods work fine. To give this a bit of polish, I'd like to add an animation that fades these subviews in and out: - (void) enableActivityIndicator { [activityIndicator startAnimating]; [cancelOperationsButton setHidden:NO]; [UIView beginAnimations:@"fadeIn" context:nil]; [UIView setAnimationDelay:0.0f]; [UIView setAnimationDuration:1.0f]; [UIView setAnimationCurve:UIViewAnimationCurveEaseIn]; activityView.alpha = 1.0f; [UIView commitAnimations]; } - (void) disableActivityIndicator { [UIView beginAnimations:@"fadeOut" context:nil]; [UIView setAnimationDelay:0.0f]; [UIView setAnimationDuration:1.0f]; [UIView setAnimationCurve:UIViewAnimationCurveEaseOut]; activityView.alpha = 0.0f; [UIView commitAnimations]; [activityIndicator stopAnimating]; [cancelOperationsButton setHidden:YES]; } But the animations are not working — the subviews just show up or disappear without the parent view's alpha property having an effect on transparency. How should I write these methods to get the fade-in, fade-out effect I am after?

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• Return enum instead of bool from function for clarity ?

  - by Moe Sisko

  This is similar to : http://stackoverflow.com/questions/2908876/net-bool-vs-enum-as-a-method-parameter but concerns returning a bool from a function in some situations. e.g. Function which returns bool : public bool Poll() { bool isFinished = false; // do something, then determine if finished or not. return isFinished; } Used like this : while (!Poll()) { // do stuff during wait. } Its not obvious from the calling context what the bool returned from Poll() means. It might be clearer in some ways if the "Poll" function was renamed "IsFinished()", but the method does a bit of work, and (IMO) would not really reflect what the function actually does. Names like "IsFinished" also seem more appropriate for properties. Another option might be to rename it to something like : "PollAndReturnIsFinished" but this doesn't feel right either. So an option might be to return an enum. e.g : public enum Status { Running, Finished } public Status Poll() { Status status = Status.Running; // do something, then determine if finished or not. return status; } Called like this : while (Poll() == Status.Running) { // do stuff during wait. } But this feels like overkill. Any ideas ?

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• C#: Is it possible to use expressions or functions as keys in a dictionary?

  - by Svish

  Would it work to use Expression<Func<T>> or Func<T> as keys in a dictionary? For example to cache the result of heavy calculations. For example, changing my very basic cache from a different question of mine a bit: public static class Cache<T> { // Alternatively using Expression<Func<T>> instead private static Dictionary<Func<T>, T> cache; static Cache() { cache = new Dictionary<Func<T>, T>(); } public static T GetResult(Func<T> f) { if (cache.ContainsKey(f)) return cache[f]; return cache[f] = f(); } } Would this even work? Edit: After a quick test, it seems like it actually works. But I discovered that it could probably be more generic, since it would now be one cache per return type... not sure how to change it so that wouldn't happen though... hmm Edit 2: Noo, wait... it actually doesn't. Well, for regular methods it does. But not for lambdas. They get various random method names even if they look the same. Oh well c",)

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• MSIE8 compatibility mode not rendering dynamically created table

  - by KristoferA - Huagati.com

  A bit weird... ...if running in IE8 quirks mode, the table added by the following code doesn't render. Can anyone tell me why, because it is not obvious to me..? <html xmlns="http://www.w3.org/1999/xhtml"> <head> <script> function AddTable() { var table = document.createElement('table'); var row = document.createElement('tr'); table.appendChild(row); var cell = document.createElement('td'); cell.innerHTML='abc'; row.appendChild(cell); var divContainer = document.getElementById('divContainer'); divContainer.appendChild(table); } </script> </head> <body> <div id='divContainer'> </div> <input type='button' value='add table' onclick='javascript:AddTable()' /> </body> </html>

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• Google App Engine Needs Index Error

  - by Andrew Johnson

  I am currently getting a needs index error on my app engine app: http://www.gaiagps.com/wiki/home. I believe this index should have been created automatically by my index.yaml file (see below). Googling a bit, I think I just need to wait for my index to be built. Is this correct, or do I need to do something manually? Is there some sort of index-building queue? My tables are very, very small right now. EDIT: I added the line "indexes:" to my app.yaml, and now app engine reports the index is building, so I think this is fixed. It's weird that this file was wrong considering I've never touched it. indexes: # AUTOGENERATED # This index.yaml is automatically updated whenever the dev_appserver # detects that a new type of query is run. If you want to manage the # index.yaml file manually, remove the above marker line (the line # saying "# AUTOGENERATED"). If you want to manage some indexes # manually, move them above the marker line. The index.yaml file is # automatically uploaded to the admin console when you next deploy # your application using appcfg.py. - kind: Revision properties: - name: name - name: created The app works on my dev server, but not in production. However, on my dev console, I have noticed this error (EDIT: THIS ERROR IS GONE NOW THAT I ADDED indexes: to the app.yaml file above): ERROR 2009-10-18 04:46:51,908 dev_appserver_index.py:176] Error parsing /gaiagps.com/index.yaml: 'NoneType' object is not callable in "<string>", line 13, column 3: - kind: Revision ^

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• asp.net mvc: What is the correct way to return html from controller to refresh select list?

  - by Mark Redman

  Hi, I am new to ASP.NET MVC, particularly ajax operations. I have a form with a jquery dialog for adding items to a drop-down list. This posts to the controller action. If nothing (ie void method) is returned from the Controller Action the page returns having updated the database, but obviously there no chnage to the form. What would be the best practice in updating the drop down list with the added id/value and selecting the item. I think my options are: 1) Construct and return the html manually that makes up the new <select> tag [this would be easy enough and work, but seems like I am missing something] 2) Use some kind of "helper" to construct the new html [This seems to make sense] 3) Only return the id/value and add this to the list and select the item [This seems like an overkill considering the item needs to be placed in the correct order etc] 4) Use some kind of Partial View [Does this mean creating additional forms within ascx controls? not sure how this would effect submitting the main form its on? Also unless this is reusable by passing in parameters(not sure how thats done) maybe 2 is the option?] UPDATE: Having looked around a bit, it seems that generating html withing the controller is not a good idea. I have seen other posts that render partialviews to strings which I guess is what I need and separates concerns (since the html bits are in the ascx). Any comments on whether that is good practice.

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• How to display my server's current response time to an average user

  - by Jason

  Sorry, I'm not really sure of the right way to ask this one so bear with me... We have a web application that runs on a set of servers at a data center (not in our offices) We want to be able to somehow 'advertise' to our clients/users that the availability or response time of our servers has met a standard throughout the day. I am being asked to come up with a standard metric that we can easily advertise on our login screen that shows current "standard response time" checked every x minutes. My thinking is that I need to capture something like the results of a traceroute from a server (either in our office, amazon, etc..) to one of the data center servers and come up with a Red/Yellow/Green type of a notifier for the login screen to let the user know that our tests are responding normally and if they are having delay issues it could be their network or connection to the internet. We have lots of clients in rural areas that have poor connectivity and we are trying to let them know any slowness might be on their end, not ours. I've got the LAMP stack to work with, but this could also be some other system all together as long as it can update the main server with the results. I already have pingdom reports that are available, but that's a bit more than people want to read sometimes. Any ideas on what I can do?

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• Help understanding linux/tcp.h

  - by Chris

  I'm learning to use raw sockets, and im trying to prase out the tcp header data, but i can't seem to figure out what res1, ece, and cwr are. Through my networking book and google i know what the rest stand for, but can't seem to find anything on those three. Below is the tcphdr struct in my includes area. Ive commented the parts a bit as i was figureing out what they stood for. struct tcphdr { __be16 source; __be16 dest; __be32 seq; __be32 ack_seq; #if defined(__LITTLE_ENDIAN_BITFIELD) _u16 res1:4, doff:4,//tcp header length fin:1,//final syn:1,//synchronization rst:1,//reset psh:1,//push ack:1,//ack urg:1,// urge ece:1, cwr:1; #elif defined(_BIG_ENDIAN_BITFIELD) __u16 doff:4,//tcp header length res1:4, cwr:1, ece:1, urg:1,//urge ack:1,//ack psh:1,//push rst:1,//reset syn:1,//synchronization fin:1;//final #else #error "Adjust your defines" #endif __be16 window; __sum16 check; __be16 urg_ptr; };

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• How to estimate tomcat server requirements?

  - by Daniil

  We have a brand new webapp written that runs on Tomcat. So far, only one client is using it through the day. They run about 180 unique logins a day. Not really a lot IMO. Now, we managed to sell it to a brand new client who likes and wants to roll it out to 50,000 clients. How many of them will login at the same time - no idea. But I need to do the whole thing - allocate, create, config and maintain. OK - last is simple(errrr). The application runs off of Tomcat 5.5 on Gentoo (I'm thinking to upgrade to Tomcat 6) with MSSQL & mySQL behind. I do realize that a more enterprise ready application would be a better fit, but that's not an option at the moment. Since I've never done this before, I'm a bit lost. Can someone advice on how to go about estimating the equipment requirements for this client? Tomcat does have clustering, so that I can do. MS SQL - I'm sure they have something too. I'm thinking to stick it behind LVS (which we do use at the moment for something else too). Any help from people who deal with these details is greatly appreciated!

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• ODBC and NLS_LANG

  - by Michael S.

  Let's say that I've created two different program executables, e.g. in C++. For some reason, the two programs internals representation of text are different from each other. Let's say the first program is using text representation A and the other text representation B. It could be a specific 8-bit ANSI codepage, Unicode/UTF-8 or Unicode/UTF-16 or whatever. Now each program want to communicate text (add/retrieve data) to/from the same database table on a (database) server. Each program communicates with the database through ODBC. So the programs do not know what database system they they are communicating with. In this specific case through the database is actually a Oracle RDMS database and the database server administrator has setup the database to use UTF-8. On the system on which the programs are running an appropriate ODBC driver is available, so that the programs can connect through ODBC. Each program will treat and convert from the ODBC data type SQL_C_CHAR to its internal text representation appropriately. I assume that the programs cannot do no other than to assume a specific encoding returned for SQL_C_CHAR text. If not the programs has to be told which encoding that is. For Oracle, I know that the NLS_LANG environment variable can be used on the client. I assume it affects the ODBC driver (related to SQL_C_CHAR) to convert from a specific encoding (as given by NLS_LANG) to the internal encoding of the database (in this example UTF-8) and vice-versa. If the machine running my programs are having a NLS_LANG this setting will affect the byte sequences returned for SQL_C_CHAR so my programs cannot suddenly assume a specific encoding for the text returned via SQL_C_CHAR. Is it possible to setup the ODBC connection (preferably programmatically at runtime), so that it takes care of text conversions appropriately for the two programs, i.e. from/to representation to/from UTF-8 and from/to representation B to/from UTF-8? Regards, /Michael PS. As the programs are connecting through ODBC I don't think it would be nice that they should now anything about NLS_LANG as this is a Orcacle specific environment variable.

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• List<object>.RemoveAll - How to create an appropriate Predicate

  - by CJM

  This is a bit of noob question - I'm still fairly new to C# and generics and completely new to predicates, delegates and lamda expressions... I have a class 'Enquiries' which contains a generic list of another class called 'Vehicles'. I'm building up the code to add/edit/delete Vehicles from the parent Enquiry. And at the moment, I'm specifically looking at deletions. From what I've read so far, it appears that I can use Vehicles.RemoveAll() to delete an item with a particular VehicleID or all items with a particular EnquiryID. My problem is understanding how to feed .RemoveAll the right predicate - the examples I have seen are too simplistic (or perhaps I am too simplistic given my lack of knowledge of predicates, delegates and lambda expressions). So if I had a List<Of Vehicle> Vehicles where each Vehicle had an EnquiryID, how would I use Vehicles.RemoveAll() to remove all vehicles for a given EnquiryID? I understand there are several approaches to this so I'd be keen to hear the differences between approaches - as much as I need to get something working, this is also a learning exercise. As an supplementary question, is a Generic list the best repository for these objects? My first inclination was towards a Collection, but it appears I am out of date. Certainly Generics seem to be preferred, but I'm curious as to other alternatives. Thanks

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• GPIB connection to external device using MATLAB

  - by hkf

  Is there a way to establish a GPIB connection using MATLAB without the instrument control Tool box? (I don't have it). Also is there a way for MATLAB to know what the external device's RS232 parameter values are ( Baud rate, stop bit etc..). For the RS232 connection I have the following code: % This function is meant to send commands to Potentiostat Model 263A. % A run includes turning the cell on, reading current for time t1, turning % the cell off, waiting for time t2. % t1 is the duration [secs] for which the Potentiostat must run (cell is on) % t2 is the duration [secs] to on after off % n is the number of runs % port is the serial port name such as COM1 function [s] = Potentiostat_control(t1,t2,n) port = input('type port name such as COM1', 's') s = serial(port); set(s,'BaudRate', 9600, 'DataBits', 8, 'Parity', 'even', 'StopBits', 2 ,'Terminator', 'CR/LF'); fopen(s) %fprintf(s,'RS232?') disp(['Total runs requested = ' num2str(n)]) disp('i denotes number of runs executed so far..'); for i=1:n i %data1 = query(s, '*IDN?') fprintf(s,'%s','CELL 1'); % sends the command 'CELL 1' %fprintf(s,'%s','READI'); pause(t1); fprintf(s,'%s','CELL 0'); %fprintf(s,'%s','CLEAR'); pause(t2); end fclose(s)

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• Can't install do_mysql gem?

  - by maccy1

  I'm trying to install the do_mysql on my Snow Leopord system Macbook Pro 13", but I keep getting this error: n216-160:~ myself$ sudo gem1.9 install do_mysql Password: Building native extensions. This could take a while... ERROR: Error installing do_mysql: ERROR: Failed to build gem native extension. /opt/local/bin/ruby1.9 extconf.rb checking for mysql_query() in -lmysqlclient... no *** extconf.rb failed *** Could not create Makefile due to some reason, probably lack of necessary libraries and/or headers. Check the mkmf.log file for more details. You may need configuration options. Provided configuration options: --with-opt-dir --without-opt-dir --with-opt-include --without-opt-include=${opt-dir}/include --with-opt-lib --without-opt-lib=${opt-dir}/lib --with-make-prog --without-make-prog --srcdir=. --curdir --ruby=/opt/local/bin/ruby1.9 --with-mysql-config --without-mysql-config --with-mysql-dir --without-mysql-dir --with-mysql-include --without-mysql-include=${mysql-dir}/include --with-mysql-lib --without-mysql-lib=${mysql-dir}/lib --with-mysqlclientlib --without-mysqlclientlib Gem files will remain installed in /opt/local/lib/ruby1.9/gems/1.9.1/gems/do_mysql-0.10.0 for inspection. Results logged to /opt/local/lib/ruby1.9/gems/1.9.1/gems/do_mysql-0.10.0/ext/do_mysql_ext/gem_make.out n216-160:~ myself$ I have no idea why. I also reinstalled my verison of MySQL with the MySQL 5.4.3 beta, 64-bit as others suggested but no dice. Does anyone have any idea what is wrong?

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• Port Win32 DLL hook to Linux

  - by peachykeen

  I have a program (NWShader) which hooks into a second program's OpenGL calls (NWN) to do post-processing effects and whatnot. NWShader was originally built for Windows, generally modern versions (win32), and uses both DLL exports (to get Windows to load it and grab some OpenGL functions) and Detours (to hook into other functions). I'm using the trick where Win will look in the current directory for any DLLs before checking the sysdir, so it loads mine. I have on DLL that redirects with this method: #pragma comment(linker, "/export:oldFunc=nwshader.newFunc) To send them to a different named function in my own DLL. I then do any processing and call the original function from the system DLL. I need to port NWShader to Linux (NWN exists in both flavors). As far as I can tell, what I need to make is a shared library (.so file). If this is preloaded before the NWN executable (I found a shell script to handle this), my functions will be called. The only problem is I need to call the original function (I would use various DLL dynamic loading methods for this, I think) and need to be able to do Detour-like hooking of internal functions. At the moment I'm building on Ubuntu 9.10 x64 (with the 32-bit compiler flags). I haven't been able to find much on Google to help with this, but I don't know exactly what the *nix community refers to it as. I can code C++, but I'm more used to Windows. Being OpenGL, the only part the needs modified to be compatible with Linux is the hooking code and the calls. Is there a simple and easy way to do this, or will it involve recreating Detours and dynamically loading the original function addresses?

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• Git as mercurial client? Why no git-hg?

  - by aapeli

  This is a question that's been bothering me for a while. I've done my homework and checked stackoverflow and found at least these two topics about my question: Git for Mercurial like git-svn and Git interoperability with a Mercurial repository I've done some serious googling to solve this issue, but so far with no luck. I've also read the Git Internals book, and the Mercurial Definitive Behind the Scenes to try to figure this out. I'm still a bit puzzled why I haven't been able to find any suitable git-hg type of a tool. From my perspective hg-svn is one of the main features, why I've chosen to use git over mercurial also at work. It allows me to use a workflow I like, and nobody else needs to bother, if they don't care. I just don't see the point in using the intermediate hg repo to convert back and forth, as suggested in one of the chains. So anyway, from what I've read hg and git seem very similar in conceptual design. There are differences under the hood, but none of those should prevent creating a git client for hg. As it seems to me, remote tracking branches and octopus merges make git even more powerful than hg is. So, the real question, is there any real reason why git-hg does not exist (or at least is very hard to find)? Is there some animosity from git users (and developers) towards their hg counterparts that has caused the lack of the git-hg tool? Do any of you have any plans to develop something like this, and go public with it? I could volunteer (although with very feeble C-skills) to participate to get this done. I just don't possess the full knowledge to start this up myself. Could this be the tool to end all DVCS wars for good?

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• Where does IE store the ASP.NET_SessionId cookie?

  - by scherand

  I am a bit baffled here; using IE7, ASP.NET 2.0 and Cassini (the VS built-in web server; although the same thing seems to be true for "real" applications deployed in IIS) I am looking for the session-id-cookie. My test page shows a session id (by printing out Session.SessionId) and Response.Cookies.Keys contains ASP.NET_SessionId. So far so good. But I cannot find the cookie in IEs cookie-store! Nor does "remove all cookies" reset the session (as it does in FF)... So where - I am tempted to write that four letter word - does IE store that bloody cookie? Or am I missing something? By the way there is no hidden field with a session id either, as far as I can see. If I check in FF there is a cookie called ASP.NET_SessionId as I would expect. And as mentioned above deleting that cookie does start a new session; as I would expect. Can anybody imagine what is happening here?

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• A new method of supporting FOSS?

  - by James

  I have been kicking an idea around for sometime and wondered if something of it's nature hadn't already been invented. The premise is a website that integrates code management, project/team management, and micro-transactions. Donations, in and of themselves, are a sporadic, and unreliable method of supporting developers. Furthermore most free software that accepts donations is started by programmers ,be it to learn, because of a hobby, or because they saw a niche that needed to be filled. There is no method in place of of saying "hay, the FOSS community needs this kind of software, will someone develop it, and accept donations!?" Programmers should be programming, not busy begging for money. Basically the idea is people can go to the site in question, and start a project or make a request. Anyone signed up with the site can start a request. Each member account is free to support or "upvote" a project request. Requests and the associated number of votes let programmers in the community know the needs of the community. When a project is started a request for developers can be put forth. Developers have a ranking based on commits to other projects. The project founder can send invites to known Developers, or accept invites from members based on developer ranking. Once the project has at least one team-member, an objectives sheet or "draft" can be put out, listing design, goals, and features. The founding member and each team-member may contribute to this sheet. Each "milestone", or "Feature" is represented by an article. An article is any unit of a draft that can be voted on by The Project Founder, Team-members, and contributors...which brings me to the next half of this idea. --Microtransactions-- People signed up with this hypothetical website can purchase credits which then can be transfered to projects they would like to support. Anyone who transfers credits to a project is known as a contributor to that project. At anytime a Founder, or the lead team-member may submit an article, or a design (multiple articles) for consideration. All team-members, as well as the Founder, can vote once for each article freely. Contributors may vote yes or no on a number of articles (independent of any given meeting where a particular design or article is considered) equal to the number of credits they have placed into a contributors fund for that particular project. A contributors fund is a proxy between a sites credit account, and a projects credit account. It is sort of like a promise to contribute, instead of an actual contribution. Contributers may place constraints on particular articles such that if those constraints (a yes or no vote) are satisfied then a manually specified amount of credits is automatically transfered to the project account. This allows a project to develop based on the needs of those who may (in the future) financially rely on the project. --- Code commits & milestones --- When a team-member makes a commit, they may specify if it's a minor commit, a bug fix, a compatibility patch (i.e. for a new platform), or a milestone (an article voted on previously). People signed up with the website, may download the updated project and test it to see if the programmer's assertion is true about the commit. A report may then be filed on a small form, giving a one or two paragraphs, and a positive or negative confirmation of the programmer's goal for that particular commit. After all milestones for a particular draft are complete, a new draft is submitted for voting. Also funds may withdrawn by each team-member based on the proportion of commits and milestones confirmed (fulfilled the stated purpose) for each programmer. --- voting --- Members, contributor, and non-contributor, may make priority requests for particular articles of a draft. The project founder may or may not opt to fill those requests based on the volume of upvotes. A fulfilled priority request means that any team-member that makes a community-confirmed commit for an article is, when all articles for the draft are fulfilled, granted a portion of project credits in proportion to the average priority of all the articles he committed. ---- Notes --- While this is horribly prone to design-by-committee the one saving grace is that the lead team-member may place constraints on a draft such that some, or ALL articles must be voted yes. Commits may not begin until a draft satisfying said constraints is approved. What does SO think, is this idea feasible? Does anyone see major problems with this? Is there any insights, or improvements that could be made?

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• Sql Exception: Error converting data type numeric to numeric

  - by Lucifer

  Hello We have a very strange issue with a database that has been moved from staging to production. The first time the database was moved it was by detaching, copying and reattaching, the second time we tried restoring from a backup of the staging. Both SQL Servers are the same version of MS SQL 2008, running on 64 bit hardware. The code accessing the database is the same build, built using the .net 2.0 framework. Here is the error message and some of the stack trace: Exception Details: System.Data.SqlClient.SqlException: Error converting data type numeric to numeric. Stack Trace: [SqlException (0x80131904): Error converting data type numeric to numeric.] System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection) +1953274 System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) +4849707 System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) +194 System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) +2392 System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString) +204 System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async) +954 System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result) +162 System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(DbAsyncResult result, String methodName, Boolean sendToPipe) +175 System.Data.SqlClient.SqlCommand.ExecuteNonQuery() +137 Version Information: Microsoft .NET Framework Version:2.0.50727.4200; ASP.NET Version:2.0.50727.4016

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• Practical rules for premature optimization

  - by DougW

  It seems that the phrase "Premature Optimization" is the buzz-word of the day. For some reason, iphone programmers in particular seem to think of avoiding premature optimization as a pro-active goal, rather than the natural result of simply avoiding distraction. The problem is, the term is beginning to be applied more and more to cases that are completely inappropriate. For example, I've seen a growing number of people say not to worry about the complexity of an algorithm, because that's premature optimization (eg http://stackoverflow.com/questions/2190275/help-sorting-an-nsarray-across-two-properties-with-nssortdescriptor/2191720#2191720). Frankly, I think this is just laziness, and appalling to disciplined computer science. But it has occurred to me that maybe considering the complexity and performance of algorithms is going the way of assembly loop unrolling, and other optimization techniques that are now considered unnecessary. What do you think? Are we at the point now where deciding between an O(n^n) and O(n!) complexity algorithm is irrelevant? What about O(n) vs O(n*n)? What do you consider "premature optimization"? What practical rules do you use to consciously or unconsciously avoid it? This is a bit vague, but I'm curious to hear other peoples' opinions on the topic.

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• Get the signed/unsigned variant of an integer template parameter without explicit traits

  - by Blair Holloway

  I am looking to define a template class whose template parameter will always be an integer type. The class will contain two members, one of type T, and the other as the unsigned variant of type T -- i.e. if T == int, then T_Unsigned == unsigned int. My first instinct was to do this: template <typename T> class Range { typedef unsigned T T_Unsigned; // does not compile public: Range(T min, T_Unsigned range); private: T m_min; T_Unsigned m_range; }; But it doesn't work. I then thought about using partial template specialization, like so: template <typename T> struct UnsignedType {}; // deliberately empty template <> struct UnsignedType<int> { typedef unsigned int Type; }; template <typename T> class Range { typedef UnsignedType<T>::Type T_Unsigned; /* ... */ }; This works, so long as you partially specialize UnsignedType for every integer type. It's a little bit of additional copy-paste work (slash judicious use of macros), but serviceable. However, I'm now curious - is there another way of determining the signed-ness of an integer type, and/or using the unsigned variant of a type, without having to manually define a Traits class per-type? Or is this the only way to do it?

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• Editing a .class file directly, playing around with opcodes

  - by echox

  Hi, today I just tried to play a little bit around with the opcodes in compiled java class file. After inserting iinc 1,1 the java virtual machine responds with: Exception in thread "main" java.lang.ClassFormatError: Truncated class file at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClassCond(ClassLoader.java:632) at java.lang.ClassLoader.defineClass(ClassLoader.java:616) at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141) at java.net.URLClassLoader.defineClass(URLClassLoader.java:283) at java.net.URLClassLoader.access$000(URLClassLoader.java:58) at java.net.URLClassLoader$1.run(URLClassLoader.java:197) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:190) at java.lang.ClassLoader.loadClass(ClassLoader.java:307) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:248) Could not find the main class: Test. Program will exit. This is my example source code: public class Test { public static void main(String[] args) { int i = 5; i++; i++; i++; System.out.println("Number: " + i + "\n"); } } The opcode for an increment is 0x84 + 2 bytes for operands. There's only one section in the resulting class file, which contains 0x84: [..] 8401 0184 0101 8401 01[..] So I would translate this as: iinc 1,1 iinc 1,1 iinc 1,1 corresponding to my i++; i++; i++; I then tried to append just 840101 to increment the variable once more, but that didn't work and resulted in the ClassFormatError. Is there anything like a checksum for the class file? I looked up the format of a classfile in http://java.sun.com/docs/books/jvms/second_edition/html/ClassFile.doc.html but could not find anything which points out to some kind of bytes_of_classfile or something. I also don't understand why the error is "Truncated Class File", because I did append something :-) I know its not a good idea to edit class files directly, but I'm just interested on the VM internals here.

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• Using Silverlight for Views in ASP.Net MVC - a bad idea?

  - by bplus

  I'm currently writing a small application for use internally at my office. I started out teaching myself some MVC (I've been a C# dev for 3 years). One of the main requirements is editable grids - I quickly realised that silverlight (i have zero silverlight experience) could be a big help in this. I've managed to create a proof of concept of getting MVC and silverlight to talk back an forth by combining these two techniques: Creating a Rest API using MVC MVC SilverLight I also got some help on stackoverflow: silverlight-grids-mvc-http-post Essentially all I'm doing is embedding a silver light object in a view. Serializing the Model data as JSON and passing it to silverlight(using intit params written into the response). The silverlight object can post data back to the controller as JSON. So far this seems like it could work quite well. However I am a bit concerned that I could be painting myself into a corner with this approach, as in I don't have much experience with either technology so I'm worried I'm going get hit with something further down the line that I won't be able to work around. Has anybody else tried doing this? Any advice would be much appreciated!

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• Using a function with variable argument strings

  - by wrongusername

  I was playing around a bit with functions with variable arguments, and decided to make a function to create vectors with the arguments. My function for creating an int vector worked... vector<int> makeIntVector(int numArgs, ...) { va_list listPointer; va_start(listPointer, numArgs); vector<int> made; for(int a = 0; a < numArgs; a++) made.push_back(va_arg(listPointer, int)); va_end(listPointer); return made; } but not my function for creating a string vector: vector<string> makeStringVector(int numArgs, string something, ...) { va_list listPointer; va_start(listPointer, something); vector<string> made; for(int a = 0; a < numArgs; a++) made.push_back(va_arg(listPointer, string)); va_end(listPointer); return made; } which crashes the program. What am I doing wrong?

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• Do you like Twisted?

  - by Luca

  I use Python Twisted for web development, and I don't like it? I know async programming is a great idea, I know there are may async web servers now, I know it's the only way to solve some problems you'd have with threads but I don't like. The problem is that, you're forced to program in a twisted way. So, the architecture you have in mind, very often have to be modified to fit the way twisted works. The architecture have to follow the technology, I don't think this is good. When we use callback in javascript, we don't have too many difficulties: things are usually simpler, we use a callback in response to an Ajax call. But in a server web app things are, very often, a bit more complex. Writing chain of callbacks don't seem to me a wonderful way of programming. The code is not simple, and so it is difficult to understand and to maintain. Writing twisted code we very often lost the linear intuitive idea of the algorithm we wanted to implement, especially when things grow in complexity. What's your point of view?

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• Any teams out there using TypeMock? Is it worth the hefty price tag?

  - by dferraro

  Hi, I hope this question is not 'controversial' - I'm just basically asking - has anyone here purchased TypeMock and been happy (or unhappy) with the results? We are a small dev shop of only 12 developers including the 2 dev managers. We've been using NMock so far but there are limitations. I have done research and started playing with TypeMock and I love it. It's super clean syntax and lets you basically mock everything, which is great for legacy code. The problem is - how do I justify to my boss spending 800-1200$ per license for an API which has 4-5 competitors that are completly free? 800-1200$ is how much Infragistrics or Telerik cost per license - and there sure as hell isn't 4-5 open source comparable UI frameworks... Which is why I find it a bit overpriced, albeit an awesome library... Any opinions / experiences are greatly appreciated. EDIT: after finding MOQ I thought I fell in love - until I found out that it's not fully supported in VB.NET because VB lacks lambda sub routines =(. Is anyone using MOQ for VB.NET? The problem is we are a mixed shop - we use C# for our CRM development and VB for everything else. Any guidence is greatly appreciated again

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