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  • return Queryable<T> or List<T> in a Repository<T>

    - by Danny Chen
    Currently I'm building an windows application using sqlite. In the data base there is a table say User, and in my code there is a Repository<User> and a UserManager. I think it's a very common design. In the repository there is a List method: //Repository<User> class public List<User> List(where, orderby, topN parameters and etc) { //query and return } This brings a problem, if I want to do something complex in UserManager.cs: //UserManager.cs public List<User> ListUsersWithBankAccounts() { var userRep = new UserRepository(); var bankRep = new BankAccountRepository(); var result = //do something complex, say "I want the users live in NY //and have at least two bank accounts in the system } You can see, returning List<User> brings performance issue, becuase the query is executed earlier than expected. Now I need to change it to something like a IQueryable<T>: //Repository<User> class public TableQuery<User> List(where, orderby, topN parameters and etc) { //query and return } TableQuery<T> is part of the sqlite driver, which is almost equals to IQueryable<T> in EF, which provides a query and won't execute it immediately. But now the problem is: in UserManager.cs, it doesn't know what is a TableQuery<T>, I need to add new reference and import namespaces like using SQLite.Query in the business layer project. It really brings bad code feeling. Why should my business layer know the details of the database? why should the business layer know what's SQLite? What's the correct design then?

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  • Android CursorAdapters, ListViews and background threads

    - by MattC
    This application I've been working on has databases with multiple megabytes of data to sift through. A lot of the activities are just ListViews descending through various levels of data within the databases until we reach "documents", which is just HTML to be pulled from the DB(s) and displayed on the phone. The issue I am having is that some of these activities need to have the ability to search through the databases by capturing keystrokes and re-running the query with a "like %blah%" in it. This works reasonably quickly except when the user is first loading the data and when the user first enters a keystroke. I am using a ResourceCursorAdapter and I am generating the cursor in a background thread, but in order to do a listAdapter.changeCursor(), I have to use a Handler to post it to the main UI thread. This particular call is then freezing the UI thread just long enough to bring up the dreaded ANR dialog. I'm curious how I can offload this to a background thread totally so the user interface remains responsive and we don't have ANR dialogs popping up. Just for full disclosure, I was originally returning an ArrayList of custom model objects and using an ArrayAdapter, but (understandably) the customer pointed out it was bad memory-manangement and I wasn't happy with the performance anyways. I'd really like to avoid a solution where I'm generating huge lists of objects and then doing a listAdapter.notifyDataSetChanged/Invalidated() Here is the code in question: private Runnable filterDrugListRunnable = new Runnable() { public void run() { if (filterLock.tryLock() == false) return; cur = ActivityUtils.getIndexItemCursor(DrugListActivity.this); if (cur == null || forceRefresh == true) { cur = docDb.getItemCursor(selectedIndex.getIndexId(), filter); ActivityUtils.setIndexItemCursor(DrugListActivity.this, cur); forceRefresh = false; } updateHandler.post(new Runnable() { public void run() { listAdapter.changeCursor(cur); } }); filterLock.unlock(); updateHandler.post(hideProgressRunnable); updateHandler.post(updateListRunnable); } };

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  • [Apache] Creating rewrite rules for multiple urls in the same folder

    - by DavidYell
    I have been asked by our client to convert a site we created into SEO friendly url format. I've managed to crack a small way into this, but have hit a problem with having the same urls in the same folder. I am trying to rewrite the following urls, /review/index.php?cid=intercasino /review/submit.php?cid=intercasino /review/index.php?cid=intercasino&page=2#reviews I would like to get them to, /review/intercasino /submit-review/intercasino /review/intercasino/2#reviews I've almost got it working using the following rule, RewriteRule (submit-review)/(.*)$ review/submit.php?cid=$2 [L] RewriteRule (^review)/(.*) review/index.php?cid=$2 The problem, you may already see, is that /submit-review rewrites to /review, which in turn gets rewritten to index.php, thus my review submission page is lost in place of my index page. I figured that putting [L] would prevent the second rule being called, but it seems that it rewrites both urls in two seperate passes. I've also tried [QSE], and [S=1] I would rather not have to move my files into different folders to get the rewriting to work, as that just seems too much like bad practise. If anyone could give me some pointers on how to differentiate between these similar urls that would be great! Thanks (Ref: http://httpd.apache.org/docs/2.0/mod/mod_rewrite.html)

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  • .NET binary serialization conditionally without ISerializable

    - by SillyWhy
    I got 2 classes, for example: public class A { private B b; ... } public class B { ... } I need to serialize an object A using BinaryFormatter. When remoting it shall include the field b, but not when serialize to file. Here is what I added: [Serializable] public class A : MarshalByRefObject { private B b; [OnSerializing] private void OnSerializing(StreamingContext context) { if (context.State == StreamingContextStates.File) { this.b = null; } } ... } [Serializable] public class B : MarshalByRefObject { ... } I think this is a bad design because if another class C also contains B, in class C we must add the duplicate OnSerializing() logic as in A. Class B should decide what to do, not class A or C. I don't want to use ISerializable interface because there are too many variables in class B have to be added to SerializationInfo. I can create a SerializationSurrogate for class B, which perform nothing in GetObjectData() & SetObjectData(), then use it when serializing to file. However the same maintenance issue because whoever modify class B can't notice what going to happen during serialization & the existence of SerializationSurrogate. Is there a better alternative?

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  • Why are a visual studio project's command-line settings stored per user? Is it OK to check-in (and

    - by DanO
    We're creating an application that understands some command-line parameters. There are some default's we would like to supply on the command-line when debugging, and these are easily set in the project settings as explained here. The thing is visual studio stores these settings in a *.csproj.user file, and the default settings for integrated source control do not check-in *.user files. We would like to just have these default command-line parameters in everyone's IDE when debugging this project. Often (but not always) when visual studio guides you into doing things a certain way it is for good reason. We probably don't want to just check-in someone's .csproj.user file... right? This question is has a few parts: Why does Visual Studio store this particular setting per user? Is there a way to alter this behavior? - Would doing so bring bad juju? Under these circumstances is it OK to check-in and share a .user file? Is there a better way to accomplish what we are trying to do here? Thank you -

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  • casting vs using the 'as' keyword in the CLR

    - by Frank V
    I'm learning about design patterns and because of that I've ended using a lot of interfaces. One of my "goals" is to program to an interface, not an implementation. What I've found is that I'm doing a lot of casting or object type conversion. What I'd like to know is if there is a difference between these two methods of conversion: public interface IMyInterface { void AMethod(); } public class MyClass : IMyInterface { public void AMethod() { //Do work } // other helper methods.... } public class Implementation { IMyInterface _MyObj; MyClass _myCls1; MyClass _myCls2; public Implementation() { _MyObj = new MyClass(); // What is the difference here: _myCls1 = (MyClass)_MyObj; _myCls2 = (_MyObj as MyClass); } } If there is a difference, is there a cost difference or how does this affect my program? Hopefully this makes sense. Sorry for the bad example; it is all I could think of... Update: What is "in general" the preferred method? (I had a question similar to this posted in the 'answers'. I moved it up here at the suggestion of Michael Haren. Also, I want to thank everyone who's provided insight and perspective on my question.

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  • Can knowing C actually hurt the code you write in higher level languages?

    - by Jurily
    The question seems settled, beaten to death even. Smart people have said smart things on the subject. To be a really good programmer, you need to know C. Or do you? I was enlightened twice this week. The first one made me realize that my assumptions don't go further than my knowledge behind them, and given the complexity of software running on my machine, that's almost non-existent. But what really drove it home was this Slashdot comment: The end result is that I notice the many naive ways in which traditional C "bare metal" programmers assume that higher level languages are implemented. They make bad "optimization" decisions in projects they influence, because they have no idea how a compiler works or how different a good runtime system may be from the naive macro-assembler model they understand. Then it hit me: C is just one more abstraction, like all others. Even the CPU itself is only an abstraction! I've just never seen it break, because I don't have the tools to measure it. I'm confused. Has my mind been mutilated beyond recovery, like Dijkstra said about BASIC? Am I living in a constant state of premature optimization? Is there hope for me, now that I realized I know nothing about anything? Is there anything to know, even? And why is it so fascinating, that everything I've written in the last five years might have been fundamentally wrong? To sum it up: is there any value in knowing more than the API docs tell me? EDIT: Made CW. Of course this also means now you must post examples of the interpreter/runtime optimizing better than we do :)

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  • Passing a Variable into jQuery AJAX

    - by Scott
    I'm stuck in a rut. I hope some one can help. Basically, I am building an AJAX mobile web app with jQuery. I am able to parse a specific XML file just fine, but I want the option to parse other XML files based on the link they were clicked on and load them on the fly into the same DIV or UL. So: click on Link1, loads XML1 click on Link2, loads XML2 I would like to be able to do this all client side, so no PHP (or is that a bad idea?). This the jquery code I've been using: $(document).ready(function() { $("a.load_ajax").click(loadAjax()); function loadAjax() { var fileID = get('?lineID='); var dataID = "xml/" + fileID + ".xml" $.ajax({ type: "GET", url: dataID, dataType: "xml", success: parseXml }); function parseXml(xml) { $(xml).find("train").each(function() { $("ul#ajax-output").append('<li>' + $(this).find("time").text() + '</li>'); }); } } }); Its just not working at all. I have been passing the variable using GET in the url. So the link in the HTML goes to /?lineID=SBD_to_Union and it should load the XML file called SBD_to_Union.xml Making sense to anyone? I'd appreciate some help.

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  • Why is passing a string literal into a char* argument only sometimes a compiler error?

    - by Brian Postow
    I'm working in a C, and C++ program. We used to be compiling without the make-strings-writable option. But that was getting a bunch of warnings, so I turned it off. Then I got a whole bunch of errors of the form "Cannot convert const char* to char* in argmuent 3 of function foo". So, I went through and made a whole lot of changes to fix those. However, today, the program CRASHED because the literal "" was getting passed into a function that was expecting a char*, and was setting the 0th character to 0. It wasn't doing anything bad, just trying to edit a constant, and crashing. My question is, why wasn't that a compiler error? In case it matters, this was on a mac compiled with gcc-4.0. EDIT: added code: char * host = FindArgDefault("EMailLinkHost", ""); stripCRLF(linkHost, '\n'); where: char *FindArgDefault(char *argName, char *defVal) {// simplified char * val = defVal; return(val); } and void stripCRLF(char *str, char delim) { char *p, *q; for (p = q = str; *p; ++p) { if (*p == 0xd || *p == 0xa) { if (p[1] == (*p ^ 7)) ++p; if (delim == -1) *p = delim; } *q++ = *p; } *q = 0; // DIES HERE } This compiled and ran until it tried to set *q to 0...

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  • If a table has two xml columns, will inserting records be a lot slower?

    - by Lieven Cardoen
    Is it a bad thing to have two xml columns in one table? + How much slower are these xml columns in terms of updating/inserting/reading data? In profiler this kind of insert normally takes 0 ms, but sometimes it goes up to 160ms: declare @p8 xml set @p8=convert(xml,N'<interactions><interaction correct="false" score="0" id="0" gapid="0" x="61" y="225"><feedback/><element id="0" position="0" elementtype="1"><asset/></element></interaction><interaction correct="false" score="0" id="1" gapid="1" x="64" y="250"><feedback/><element id="0" position="0" elementtype="1"><asset/></element></interaction><interaction correct="false" score="0" id="2" gapid="2" x="131" y="250"><feedback/><element id="0" position="0" elementtype="1"><asset/></element></interaction></interactions>') declare @p14 xml set @p14=convert(xml,N'<contentinteractions/>') exec sp_executesql N'INSERT INTO [dbo].[PackageSessionNodes]([dbo].[PackageSessionNodes].[PackageSessionId], [dbo].[PackageSessionNodes].[TreeNodeId],[dbo].[PackageSessionNodes].[Duration], [dbo].[PackageSessionNodes].[Score],[dbo].[PackageSessionNodes].[ScoreMax], [dbo].[PackageSessionNodes].[Interactions],[dbo].[PackageSessionNodes].[BrainTeaser], [dbo].[PackageSessionNodes].[DateCreated], [dbo].[PackageSessionNodes].[CompletionStatus], [dbo].[PackageSessionNodes].[ReducedScore], [dbo].[PackageSessionNodes].[ReducedScoreMax], [dbo].[PackageSessionNodes].[ContentInteractions]) VALUES (@ins_dboPackageSessionNodesPackageSessionId, @ins_dboPackageSessionNodesTreeNodeId, @ins_dboPackageSessionNodesDuration, @ins_dboPackageSessionNodesScore, @ins_dboPackageSessionNodesScoreMax, @ins_dboPackageSessionNodesInteractions, @ins_dboPackageSessionNodesBrainTeaser, @ins_dboPackageSessionNodesDateCreated, @ins_dboPackageSessionNodesCompletionStatus, @ins_dboPackageSessionNodesReducedScore, @ins_dboPackageSessionNodesReducedScoreMax, @ins_dboPackageSessionNodesContentInteractions) ; SELECT SCOPE_IDENTITY() as new_id This is the table: CREATE TABLE [dbo].[PackageSessionNodes]( [PackageSessionNodeId] [int] IDENTITY(1,1) NOT NULL, [PackageSessionId] [int] NOT NULL, [TreeNodeId] [int] NOT NULL, [Duration] [int] NULL, [Score] [float] NOT NULL, [ScoreMax] [float] NOT NULL, [Interactions] [xml] NOT NULL, [BrainTeaser] [bit] NOT NULL, [DateCreated] [datetime] NULL, [CompletionStatus] [int] NOT NULL, [ReducedScore] [float] NOT NULL, [ReducedScoreMax] [float] NOT NULL, [ContentInteractions] [xml] NOT NULL, CONSTRAINT [PK_PackageSessionNodes] PRIMARY KEY CLUSTERED ( [PackageSessionNodeId] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO ALTER TABLE [dbo].[PackageSessionNodes] WITH CHECK ADD CONSTRAINT [FK_PackageSessionNodes_PackageSessions] FOREIGN KEY([PackageSessionId]) REFERENCES [dbo].[PackageSessions] ([PackageSessionId]) ON UPDATE CASCADE ON DELETE CASCADE GO ALTER TABLE [dbo].[PackageSessionNodes] CHECK CONSTRAINT [FK_PackageSessionNodes_PackageSessions] GO ALTER TABLE [dbo].[PackageSessionNodes] WITH CHECK ADD CONSTRAINT [FK_PackageSessionNodes_TreeNodes] FOREIGN KEY([TreeNodeId]) REFERENCES [dbo].[TreeNodes] ([TreeNodeId]) GO ALTER TABLE [dbo].[PackageSessionNodes] CHECK CONSTRAINT [FK_PackageSessionNodes_TreeNodes] GO ALTER TABLE [dbo].[PackageSessionNodes] ADD CONSTRAINT [DF_PackageSessionNodes_Score] DEFAULT ((-1)) FOR [Score] GO ALTER TABLE [dbo].[PackageSessionNodes] ADD CONSTRAINT [DF_PackageSessionNodes_ScoreMax] DEFAULT ((-1)) FOR [ScoreMax] GO ALTER TABLE [dbo].[PackageSessionNodes] ADD CONSTRAINT [DF_PackageSessionNodes_DateCreated] DEFAULT (getdate()) FOR [DateCreated] GO ALTER TABLE [dbo].[PackageSessionNodes] ADD CONSTRAINT [DF_PackageSessionNodes_ReducedScore] DEFAULT ((-1)) FOR [ReducedScore] GO ALTER TABLE [dbo].[PackageSessionNodes] ADD CONSTRAINT [DF_PackageSessionNodes_ReducedScoreMax] DEFAULT ((-1)) FOR [ReducedScoreMax] GO

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  • What are the general strategies for the server of an FPS multiplayer game to update its clients?

    - by Hooray Im Helping
    A friend and I were having a discussion about how a FPS server updates the clients connected to it. We watched a video of a guy cheating in Battlefield: Bad Company 2 and saw how it highlighted the position of enemies on the screen and it got us thinking. His contention was that the server only updates the client with information that is immediately relevant to the client. I.e. the server won't send information about enemy players if they are too far away from the client or out of the client's line of sight for reasons of efficiency. He was unsure though - he brought up the example of someone hiding behind a rock, not able to see anyone. If the player were suddenly to pop up where he had three players in his line of sight, there would be a 50ms delay before they were rendered on his screen while the server transmitted the necessary information. My contention was the opposite: that the server sends the client all the information about every player and lets the client sort out what is allowed and what isn't. I figured it would actually be less expensive computationally for the server to just send everything to the client and let the client do the heavy lifting, so to speak. I also figured this is how cheat programs work - they intercept the server packets, get the location of enemies, then show them on the client's view. So the question: What are some general policies or strategies a modern first person shooter server employs to keep its clients updated?

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  • Visual SourceSafe (VSS): "Access to file (filename) denied" error

    - by tk-421
    Hi, can anybody help with the above SourceSafe error? I've spent hours trying to find a fix. I've also Googled the heck out of it but couldn't find a scenario matching mine, because in my case only a few files (not all) are affected. Here's what I found: only a few files in my project generate this error other files in the same directory (for example, App_Code has one of the problem files) work fine I've tried checking out from both the VSS client and Visual Studio another developer can check out the main problem file without any problems This sounds like a permission issue for my user, right? However: I found the location of one of the problem files in VSS's data directory (using VSS's naming format, as in 'fddaaaaa.a') and checked its permissions; everything looks fine and its permissions match those of other files I can check out successfully I can see no differences in the file properties between working and non-working files What else can I check? Has anyone encountered this problem before and found a solution? Thanks. P.S.: SourceGear, svn or git are not options, unfortunately. P.P.S.: Tried unsuccessfully to add tag "sourcesafe." EDIT: Hey Paddy, I tried to click 'add comment' to respond to your comment, but I'm getting a javascript error when loading this page in IE8 ("jquery undefined," etc.) so this isn't working. This is when checking out files, and yes, I've obliterated my local copy more times than I can remember. ;) EDIT 2: Thanks for the responses, guys (again I can't 'add comment' due to jQuery not loading, maybe blocked as discussed in Meta). If the problem was caused by antivirus or a bad disk, would other users still be able to check out the file(s)? That's the case here, which makes me think it's a permission issue specific to my account. However I've looked at the permissions and they match both other users' settings and settings on other files which I can check out.

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  • Showing Loading screen during REST service request in android app ?

    - by sat
    Currently here is what I am following, As soon as my app is launched, I have to send a request for REST service, It will take little time , so I thought of showing loading screen, In onCreate() of my Activity , first thing will be to show loading screen(progress dialog) , And I kick off the background Activity using AsyncTask , i.e. requesting for REST service and onPostexecute() I close the dialog and then I do setContentView(myxml); and update the UI . Can this approach be improved ? Problem which I faced was , Sometimes , Garbage collector may start(due to various reasons) and my app hangs at loading screen forever , because of Garbage collector , even request for REST service is not sent and because of it some wake up call comes and rest is disaster and Force close. But sometimes even ForceClose doesnot come fast , may be because of GC. so I cannot even go back and stuck in loading screen. Only thing which I can do at that point is to come back HOME. After that If I come back to my app its still loading , so definitely this approach seems to be a bad design. Whats the right approach ?

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  • Creating android app Database with big amount of data

    - by Thomas
    Hi all, The database of my application need to be filled with a lot of data, so during onCreate(), it's not only some create table sql instructions, there is a lot of inserts. The solution I chose is to store all this instructions in a sql file located in res/raw and which is loaded with Resources.openRawResource(id). It works well but I face to encoding issue, I have some accentuated caharacters in the sql file which appears bad in my application. This my code to do this : public String getFileContent(Resources resources, int rawId) throws IOException { InputStream is = resources.openRawResource(rawId); int size = is.available(); // Read the entire asset into a local byte buffer. byte[] buffer = new byte[size]; is.read(buffer); is.close(); // Convert the buffer into a string. return new String(buffer); } public void onCreate(SQLiteDatabase db) { try { // get file content String sqlCode = getFileContent(mCtx.getResources(), R.raw.db_create); // execute code for (String sqlStatements : sqlCode.split(";")) { db.execSQL(sqlStatements); } Log.v("Creating database done."); } catch (IOException e) { // Should never happen! Log.e("Error reading sql file " + e.getMessage(), e); throw new RuntimeException(e); } catch (SQLException e) { Log.e("Error executing sql code " + e.getMessage(), e); throw new RuntimeException(e); } The solution I found to avoid this is to load the sql instructions from a huge static final string instead of a file, and all accentutated characters appears well. But Isn't there a more elegant way to load sql instructions than a big static final String attribute with all sql instructions ? Thanks in advance Thomas

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  • Kohana 3, problem with m2m data adding

    - by Marek
    Hello I posted this on official forum but with no result. I am getting :Undefined index: enrollment error when trying to save data. My pivot model: class Model_Enrollment extends ORM { protected $_belongs_to = array('page' => array(), 'menugroup' => array()); } Model_Page protected $_has_many = array('templates' => array(), 'menugroups' => array('through' => 'enrollment')); Model_Menugroup protected $_has_many = array('menuitems' => array(), 'pages' => array('through' => 'enrollment')); //Overriden save() method in Model_Menugroup: public function save() { if (empty($this->created)) { $this->created = time(); } parent::save(); $this->reload(); if (! $this->is_global) { if (! empty($this->groupOwnerPagesId) { $page = ORM::factory('page'); foreach($this->groupOwnerPagesId as $id) { $this->add('enrollment', $page->find($id)); } } } } I did: I corrected table names in pivot model by changing them to singular I even now using the same name for pivot table / model = enrollment. The same as in tutorial. Just in case So the pivot table has name 'enrollment' and has 2 columns: page_id , menugroup_id I tried to add pk in pivot table, but it changed nothing I tried to add/remove db relation between pages/menugroups and pivot table (InnoDB) but with no luck I tried save all data in controller, but with the same bad result:( I am still getting the same error: Undefined index: enrollment in ORM line: $columns = array($this-_has_many[$alias]['foreign_key'], $this-_has_many[$alias]['far_key']); Could somebody tell me, what can be else wrong? I have no other ideas:( Kind regards

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  • Repeated host lookups failing in urllib2

    - by reve_etrange
    I have code which issues many HTTP GET requests using Python's urllib2, in several threads, writing the responses into files (one per thread). During execution, it looks like many of the host lookups fail (causing a name or service unknown error, see appended error log for an example). Is this due to a flaky DNS service? Is it bad practice to rely on DNS caching, if the host name isn't changing? I.e. should a single lookup's result be passed into the urlopen? Exception in thread Thread-16: Traceback (most recent call last): File "/usr/lib/python2.6/threading.py", line 532, in __bootstrap_inner self.run() File "/home/da/local/bin/ThreadedDownloader.py", line 61, in run page = urllib2.urlopen(url) # get the page File "/usr/lib/python2.6/urllib2.py", line 126, in urlopen return _opener.open(url, data, timeout) File "/usr/lib/python2.6/urllib2.py", line 391, in open response = self._open(req, data) File "/usr/lib/python2.6/urllib2.py", line 409, in _open '_open', req) File "/usr/lib/python2.6/urllib2.py", line 369, in _call_chain result = func(*args) File "/usr/lib/python2.6/urllib2.py", line 1170, in http_open return self.do_open(httplib.HTTPConnection, req) File "/usr/lib/python2.6/urllib2.py", line 1145, in do_open raise URLError(err) URLError: <urlopen error [Errno -2] Name or service not known>

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  • Does Function pointer make the program slow?

    - by drigoSkalWalker
    Hi guys. I read about function pointers in C And everyone said that will make my program run slow. Is it true? I made a program to check it. And I got the same results on both cases. (mesure the time.) So, is it bad to use fuction pointer? Thanks in advance. To response for some guys. I said 'run slow' for the time that I have compared on a loop. like this. int end = 1000; int i = 0; while (i < end) { fp = func; fp (); } When you execute this, i got the same time if I execute this. while (i < end) { func (); } So I think that function pointer have no difference of time and it don't make a program run slow as many people said.

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  • Why I can't get all UDP packets?

    - by Jack
    My program use UdpClient to try to receive 27 responses from 27 hosts. The size of the response is 10KB. My broadband incoming bandwidth is 150KB/s. The 27 responses are sent from the hosts almost at the same time and for every 10 secs. However, I can only receive 8 - 17 responses each time. The number of responses that I can receive is quite dynamic but within the range. Can anyone tell me why? why can't I receive all? I understand UDP is not reliable. but I tried receiving 5 - 10 responses at the same time, it worked. I guess the network links are not so bad. The code is very simple. ON the 27 hosts, I just use UdpClient to send 10KB to my machine. On my machine, I have one UdpClient receive datagrams. Each time I get a data, I create a thread to handle it (basically handling it means just print out "I received 10KB", but it runs in a thread). listener = new UDPListener(Port); listener.Start(); while (true) { try { UDPContext context = listener.Accept(); ThreadPool.QueueUserWorkItem(new WaitCallback(HandleMessage), context); } catch (Exception) { } } If I reduce the size of the response down to 3KB, the case gets much better that roughly 25 responses can be received. Any more idea? UDP buffer problems???

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  • How do I call +class methods in Objective C without referencing the class?

    - by TimM
    I have a series of "policy" objects which I thought would be convenient to implement as class methods on a set of policy classes. I have specified a protocol for this, and created classes to conform to (just one shown below) @protocol Counter +(NSInteger) countFor: (Model *)model; @end @interface CurrentListCounter : NSObject <Counter> +(NSInteger) countFor: (Model *)model; @end I then have an array of the classes that conform to this protocol (like CurrentListCounter does) +(NSArray *) availableCounters { return [[[NSArray alloc] initWithObjects: [CurrentListCounter class],[AllListsCounter class], nil] autorelease]; } Notice how I am using the classes like objects (and this might be my problem - in Smalltalk classes are objects like everything else - I'm not sure if they are in Objective-C?) My exact problem is when I want to call the method when I take one of the policy objects out of the array: id<Counter> counter = [[MyModel availableCounters] objectAtIndex: self.index]; return [counter countFor: self]; I get a warning on the return statement - it says -countFor: not found in protocol (so its assuming its an instance method where I want to call a class method). However as the objects in my array are instances of class, they are now like instance methods (or conceptually they should be). Is there a magic way to call class methods? Or is this just a bad idea and I should just create instances of my policy objects (and not use class methods)?

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  • Correct way to switch between UIView with ARC. My way leads to memory leaks :( (iOS)

    - by Andrei Golubev
    i use xcode 4.4 with ARC on.. I have dynamically created UIViews in the ViewController.m: UIView*myviews[10]; Then in the - (void)viewDidLoad function i fill each of it with pictures i need myviews[viewIndex] = [[UIView alloc]initWithFrame:myrec]; UIImage *testImg; UIImageView * testImgView; testImg = [UIImage imageNamed:[NSString stringWithFormat:@"imgarray%d.png", viewIndex]; testImgView.image = testImg; viewindex++; So all seems to be fine, when i want to jump from one view to another i do with two buttons next: [self.view addSubview:views[viewIndex]]; CATransition *animation = [CATransition animation]; [animation setDelegate:self]; [animation setDuration:1.0f]; [animation setType:@"rippleEffect"]; [animation setSubtype:kCATransitionFromTop]; //[animation setTimingFunction:[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut]]; [self.view.layer addAnimation:animation forKey:@"transitionViewAnimation"]; Nothing seems to be bad, but the memory consumption grows with huge speed when i switch between views.. and then i get low memory warning or sometimes application will just crash. I have tried to use UIViewController array and was switching between the controllers: nothing changes, the memory low warning is what i end up with.. Maybe i need to clean the memory somehow? But how? ARC does not allow to use release and so on.. last what i have tried (sorry, maybe not very professional) before to add new subview is this NSArray *viewsToRemove = [self.view subviews]; for (UIView *views in viewsToRemove) { [views removeFromSuperview]; } But this does not help either.. Please don't judge too strong, i am still new to iOS and Objective-c..

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  • Cannot change font size /type in plots

    - by Sameet Nabar
    I recently had to re-install my operating system (Ubuntu). The only thing I did differently is that I installed Matlab on a separate partition, not the main Ubuntu partition. After re-installing, the fonts in my plots are no longer configurable. For example, if I ask the title font to be bold, it doesn't happen. I ran the sample code below on my computer and then on my colleague's computer and the 2 results are attached. This cannot be a problem with the code; rather in the settings of Matlab. Could somebody please tell me what settings I need to change? Thanks in advance for your help. Regards, Sameet. x1=-pi:.1:pi; x2=-pi:pi/10:pi; y1=sin(x1); y2=tan(sin(x2)) - sin(tan(x2)); [AX,H1,H2]=plotyy(x1,y1,x2,y2); xlabel ('Time (hh:mm)'); ylabel (AX(1), 'Plot1'); ylabel (AX(2), 'Plot2'); axes(AX(2)) set(H1,'linestyle','none','marker','.'); set(H2,'linestyle','none','marker','.'); title('Plot Title','FontWeight','bold'); set(gcf, 'Visible', 'off'); [legh, objh] = legend([H1 H2],'Plot1', 'Plot2','location','Best'); set(legend,'FontSize',8); print -dpng Trial.png; Bad image: http://imageshack.us/photo/my-images/708/trial1u.png/ Good image: http://imageshack.us/photo/my-images/87/trial2.png/

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  • How expensive is a context switch? Is it better to implement a manual task switch than to rely on OS

    - by Vilx-
    The title says it all. Imagine I have two (three, four, whatever) tasks that have to run in parallel. Now, the easy way to do this would be to create separate threads and forget about it. But on a plain old single-core CPU that would mean a lot of context switching - and we all know that context switching is big, bad, slow, and generally simply Evil. It should be avoided, right? On that note, if I'm writing the software from ground up anyway, I could go the extra mile and implement my own task-switching. Split each task in parts, save the state inbetween, and then switch among them within a single thread. Or, if I detect that there are multiple CPU cores, I could just give each task to a separate thread and all would be well. The second solution does have the advantage of adapting to the number of available CPU cores, but will the manual task-switch really be faster than the one in the OS core? Especially if I'm trying to make the whole thing generic with a TaskManager and an ITask, etc?

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  • Why do people keep parsing HTML using regex? [closed]

    - by polygenelubricants
    As much as I love regular expressions, it's obvious to me that it's not the best tool for parsing HTML, especially given the numerous good HTML parsers out there. And yet there are numerous questions on stackoverflow that attempts to parse HTML using regex. And people would always point out what a bad idea that is in the comments. And the accepted answer would often have a disclaimer how this isn't really the ideal way of doing things. But based on the constant flow of questions, it still seems that people keep parsing HTML using regex, despite the perceived difficulty in reading and maintaining it (and that's putting correctness aside for now). So my question is: why? Is it because it's easy to learn? Is it because it's faster? Is it because it's the industry standard? Is it because there are already so many reusable regexes to build from? Is it because 100% correctness is never really the objective? (90% good enough?) etc... I'd also like to hear from the downvoters why they did so. Is it because: There's absolutely nothing wrong with using regex to parse HTML and asking "Why?" is just dumb? The premise of the question is flawed because the people who are using regex to parse HTML is such a small minority?

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  • Casting pointer to object to void * in C++

    - by JB
    I've been reading StackOverflow too much and started doubting all the code I've ever written, I keep thinking "Is that undefined behavour?" even in code that has been working for ages. So my question - Is it safe and well defined behavour to cast a pointer to an object (In this case abstract interface classes) to a void* and then later on cast them back to the original class and call method using them? I'm fully aware that the code that does this is probably awful. I wouldn't even consider writing it like this now (this is old code which I don't really want to change), so I'm not looking for a discussion of better ways to do this. I already know how to write it better if I ever did this again. But if it's actually broken to rely on this in C++ then I'll have to look at changing the code, if it's merely awful code then changing it won't be a priority. I would have had no doubts about something this simple a year or two ago but as my understanding of C++ increases I actually find I have more and more worries about code being safe under the standards even if it works perfectly well. Perhaps reading too much stack overflow is a bad thing for productivity sometimes :P

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  • Is it acceptable to wrap PHP library functions solely to change the names?

    - by Carson Myers
    I'm going to be starting a fairly large PHP application this summer, on which I'll be the sole developer (so I don't have any coding conventions to conform to aside from my own). PHP 5.3 is a decent language IMO, despite the stupid namespace token. But one thing that has always bothered me about it is the standard library and its lack of a naming convention. So I'm curious, would it be seriously bad practice to wrap some of the most common standard library functions in my own functions/classes to make the names a little better? I suppose it could also add or modify some functionality in some cases, although at the moment I don't have any examples (I figure I will find ways to make them OO or make them work a little differently while I am working). If you saw a PHP developer do this, would you think "Man, this is one shoddy developer?" Additionally, I don't know much (or anything) about if/how PHP is optimized, and I know that usually PHP performace doesn't matter. But would doing something like this have a noticeable impact on the performance of my application?

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