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How do I daemonize an arbitrary script in unix?

- by dreeves

I'd like a daemonizer that can turn an arbitrary, generic script or command into a daemon. There are two common cases I'd like to deal with: I have a script that should run forever. If it ever dies (or on reboot), restart it. Don't let there ever be two copies running at once (detect if a copy is already running and don't launch it in that case). I have a simple script or command line command that I'd like to keep executing repeatedly forever (with a short pause between runs). Again, don't allow two copies of the script to ever be running at once. Of course it's trivial to write a "while(true)" loop around the script in case 2 and then apply a solution for case 1, but a more general solution will just solve case 2 directly since that applies to the script in case 1 as well (you may just want a shorter or no pause if the script is not intended to ever die (of course if the script really does never die then the pause doesn't actually matter)). Note that the solution should not involve, say, adding file-locking code or PID recording to the existing scripts. More specifically, I'd like a program "daemonize" that I can run like % daemonize myscript arg1 arg2 or, for example, % daemonize 'echo `date` >> /tmp/times.txt' which would keep a growing list of dates appended to times.txt. (Note that if the argument(s) to daemonize is a script that runs forever as in case 1 above, then daemonize will still do the right thing, restarting it when necessary.) I could then put a command like above in my .login and/or cron it hourly or minutely (depending on how worried I was about it dying unexpectedly). NB: The daemonize script will need to remember the command string it is daemonizing so that if the same command string is daemonized again it does not launch a second copy. Also, the solution should ideally work on both OS X and linux but solutions for one or the other are welcome. (If I'm thinking of this all wrong or there are quick-and-dirty partial solutions, I'd love to hear that too.)

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Need help getting buttons to work...

- by Mike Droid

I am trying to get my first button to update a display number in my view when clicked. This view will have several buttons and "outputs" displayed. After reading examples and Q's here, I finally put something together that runs, but my first button is still not working; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.ship_layout); mSwitcher = (TextSwitcher) findViewById(R.id.eng_val); } private TextSwitcher mSwitcher; // Will be connected with the buttons via XML void onClick(View v){ switch (v.getId()) { case R.id.engplus: engcounter++; updateCounter(); break; case R.id.engneg: engcounter--; updateCounter(); break; } } private void updateCounter() { mSwitcher.setText(String.valueOf(engcounter)); } The .xml for this button is; <TextSwitcher android:id="@+id/eng_val" android:visibility="visible" android:paddingTop="9px" android:paddingLeft="50px" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_below="@+id/build" android:layout_toRightOf="@+id/engeq" android:textColor="#DD00ff00" android:textSize="24sp"/> This is within a Relative Layout that appears otherwise OK. When I had set the view to have a TextView with the number set as a string , the number displayed, but I could not figure out how to update the text with a numerical field. That may be my real problem. I have gone through many examples generally referenced from the dev. site (UI, Common Tasks, various samples), and I am still not seeing the connection here... Again, this is simply a try at getting variables to respond to buttons and update on the view. So, a few Q's for anyone that can help; 1) Is there any easier way of doing this (ie. send numerical value to View) ? 2) Why isn't my TextSwitcher displaying the number? 3) Should I be using a TextSwitcher here? 4) Any examples of this you can point me to?

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JSON to display text -- Freezes UI

- by Adam Storr

Hi everyone, I currently have a very simple view which displays info from a JSON feed. The problem I'm facing is the few second pause I encounter once I press this tab. How can I make this view load instantly and then have the label.text areas load after? Preferable with an activity indicator? Should I use threads? Thanks in advance! Code: - (NSString *)stringWithUrl:(NSURL *)url { NSURLRequest *urlRequest = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadRevalidatingCacheData timeoutInterval:30]; NSData *urlData; NSURLResponse *response; NSError *error; urlData = [NSURLConnection sendSynchronousRequest:urlRequest returningResponse:&response error:&error]; return [[NSString alloc] initWithData:urlData encoding:NSUTF8StringEncoding]; } - (id)objectWithUrl:(NSURL *)url { SBJsonParser *jsonParser = [SBJsonParser new]; NSString *jsonString = [self stringWithUrl:url]; return [jsonParser objectWithString:jsonString error:NULL]; } - (NSDictionary *)downloadStats { id response = [self objectWithUrl:[NSURL URLWithString:@"http://www.example.com/JSON"]]; NSDictionary *feed = (NSDictionary *)response; return feed; [feed release]; } - (void)viewDidLoad { [super viewDidLoad]; [GlobalStatsScrollView setScrollEnabled:YES]; [GlobalStatsScrollView setContentSize:CGSizeMake(320, 360)]; } - (void)viewWillAppear:(BOOL)animated { NSLog(@"View appears"); // Download JSON Feed NSDictionary *feed = [self downloadStats]; totalproduced.text = [feed valueForKey:@"Produced"]; totalno.text = [feed valueForKey:@"Total"]; mostcommon.text = [feed valueForKey:@"Most Common"]; }

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How to make 2 incompatible types, but with the same members, interchangeable?

- by Quigrim

Yesterday 2 of the guys on our team came to me with an uncommon problem. We are using a third-party component in one of our winforms applications. All the code has already been written against it. They then wanted to incorporate another third-party component, by the same vender, into our application. To their delight they found that the second component had the exact same public members as the first. But to their dismay, the 2 components have completely separate inheritance hierarchies, and implement no common interfaces. Makes you wonder... Well, makes me wonder. An example of the problem: public class ThirdPartyClass1 { public string Name { get { return "ThirdPartyClass1"; } } public void DoThirdPartyStuff () { Console.WriteLine ("ThirdPartyClass1 is doing its thing."); } } public class ThirdPartyClass2 { public string Name { get { return "ThirdPartyClass2"; } } public void DoThirdPartyStuff () { Console.WriteLine ("ThirdPartyClass2 is doing its thing."); } } Gladly they felt copying and pasting the code they wrote for the first component was not the correct answer. So they were thinking of assigning the component instant into an object reference and then modifying the code to do conditional casts after checking what type it was. But that is arguably even uglier than the copy and paste approach. So they then asked me if I can write some reflection code to access the properties and call the methods off the two different object types since we know what they are, and they are exactly the same. But my first thought was that there goes the elegance. I figure there has to be a better, graceful solution to this problem.

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Globally define parts of virtualhost definition to reduce redundancy

- by user1428900

I have setup an apache server and this apache server points to a bunch of virtualhosts. The definition of the virtualhosts are as follows, <VirtualHost *:80> ServerName <url> RewriteEngine on ReWriteCond %{SERVER_PORT} !^443$ RewriteRule ^/(.*) https://%{HTTP_HOST}/$1 [NC,R,L] # Enable client-side caching of resources ExpiresActive On ExpiresByType image/png "now plus 48 hours" ExpiresByType image/jpeg "now plus 48 hours" ExpiresByType image/gif "now plus 48 hours" ExpiresByType application/javascript "now plus 48 hours" ExpiresByType application/x-javascript "now plus 48 hours" ExpiresByType text/javascript "now plus 48 hours" ExpiresByType text/css "now plus 48 hours" </VirtualHost> . . . <VirtualHost *:80> ServerName <url> RewriteEngine on ReWriteCond %{SERVER_PORT} !^443$ RewriteRule ^/(.*) https://%{HTTP_HOST}/$1 [NC,R,L] # Enable client-side caching of resources ExpiresActive On ExpiresByType image/png "now plus 48 hours" ExpiresByType image/jpeg "now plus 48 hours" ExpiresByType image/gif "now plus 48 hours" ExpiresByType application/javascript "now plus 48 hours" ExpiresByType application/x-javascript "now plus 48 hours" ExpiresByType text/javascript "now plus 48 hours" ExpiresByType text/css "now plus 48 hours" </VirtualHost> I have a ton of virtual host definitions similar to the examples shown above. Since, most of the definitions other than the ServerName are the same, I was wondering if there was a way to define these common definitions globally. I am new to apache configuration and I felt that as the number of virtualhost definitions increase my configuration file becomes longer and redundant.

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Is there a standard SQL Table design for overriding 'big picture' default values with lower level de

- by RichardHowells

Here's an example. Suppose we are trying to calculate a service charge. Say sales in the USA attract a 10 dollar charge, sales in the UK attract a 20 dollar charge So far it's easy - we are starting to imagine a table that lists charges by country. Now lets assume that Alaska and Hawaii are treated as special cases they are both 15 dollars That suggests a table with states, Alaska and Hawaii are charged at 15, but presumably we need 48 (redundant) rows all saying 10. This gives us a maintainance problem, our user only wants to type 10 once NOT 48 times. It does not sit well with the UK either. The UK does not have states. Suppose we throw in another couple of cross cutting rules. If you order by phone there is a 10% supplement on the charge. If you order via the web there is a 10% discount. But for some reason best known to the owners of the business the web/phone supplement/discount are not applied in Hawaii. It seems to me that this is quite a common kind of problem and there is probably a well known arrangement of tables to store the data. Most cases get handled by broad brush answers, but there are some very detailed low level variations that give rise to a huge number of theoretical combinations, most of which are not used.

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jQuery: serializing array returns empty string

- by John Smith

I did not forget to add name attributes as is a common problem and yet my serialized form is returning an empty string. What am I doing wrong? HTML/javascript: <head> <script src="http://ajax.googleapis.com/ajax/libs/jquery/2.1.0/jquery.min.js"></script> <script> $( document ).ready( function() { $('#word_form').submit(function(e) { e.preventDefault(); console.log($(this).serialize()); //returns an empty string }); }); </script> </head> <body> <div id="wrapper"> <form name="word_form" id="word_form" method="POST"> <input type="image" name="thumbsUp" id="thumb1" value="1" src="http://upload.wikimedia.org/wikipedia/commons/8/87/Symbol_thumbs_up.svg" style="width:50px;height:50px;"> <input type="image" name="thumbsDown" id="thumb2" value="2" src="http://upload.wikimedia.org/wikipedia/commons/8/84/Symbol_thumbs_down.svg" style="width:50px;height:50px;"> </form> </div> </body> Thanks!

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Organizing development teams

- by Patrick

A long time ago, when my company was much smaller, dividing the development work over teams was quite easy: the 'application' team developed the applications-specific logic, often requiring a deep insight of specific industry problems) the 'generic' team developed the parts that were common/generic for all applications (user interface related stuff, database access, low-level Windows stuff, ...) Over the years the boundaries between the teams have become fuzzy: the 'application' teams often write application-specific functionality with a 'generic' part, so instead of asking the 'generic' team to write that part for them, they write it themselves to speed up the developments; then donate it to the 'generic' team the 'generic' team's focus seems to be more 'maintenance oriented'. All of the 'very generic' code has already been written, so no new developments are needed in it, but instead they continuously have to support all the functionality donated by the application teams. All this seems to indicate that it's not a good idea anymore to have this split in teams. Maybe the 'generic' team should evolve into a 'software quality' team (defining and guarding the rules for writing good quality software), or into a 'software deployment' team (defining how software should be deployed, installed, ...). How do you split up the work in different teams if you have different applications? everybody can write generic code and donates it to a central 'generic' team? everybody can write generic code, but nobody 'manages' this generic code (everybody is the owner) generic code is written by a 'generic' team only and the applications have to wait until the 'generic' team delivers the generic part (via a library, via a DLL) there is no overlap in code between the different applications some other way? Notice that thee advantage of having the mix (allowing everybody to write everywhere in the code) is that: code is written in a more flexible way it's easier to debug the code since you can easily step into the 'generic' code in the debugger But the big (and maybe only) disadvantage is that this generic code may become nobody's responsibility if there is no clear team that manages it anymore. What is your vision?

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Best way and problems when using ajax tabs with an MVC PHP project

- by Jonathan

Hi, I'm building an IMDB.com like website using PHP/jQuery and a MVC approach (no OOP). I have an index.php base controller to 'rule them all' :), a controllers folder with all the controllers, a models folder and a view folder. In some pages of the website I have tabbed navigation, when the visitor clicks on one of those tabs to get more information, jQuery gets that data using the $.post or $.get method and shows it on the tab container, obviously without refreshing the page. The problem is that those pages loaded by ajax are also generated using controllers, models, and views, and the things are getting a bit complicated for someone like me ( = 'no experience'). To dynamically get the data I some times need to include a model twice, include an include in an include in an include, send information multiple times, connect with the database again, and all sort of things like that and I'm sure there is a better and prettier way to do this. I'm searching for the best approach and common methods for this. I have no experience working with a big project like this. This is a personal project so I have full control and every answer is welcome. Thanks!!!

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Why does Perl lose foreign characters on Windows; can this be fixed (if so, how)?

- by Alex R

Note below how ã changes to a. NOTE2: Before you blame this on CMD.EXE and Windows pipe weirdness, see Experiment 2 below which gets a similar problem using File::Find. The particular problem I'm trying to fix involves working with image files stored on a local drive, and manipulating the file names which may contain foreign characters. The two experiments shown below are intermediate debugging steps. The ã character is common in latin languages. e.g. http://pt.wikipedia.org/wiki/Cão Experiment 1 Experiment 2 To get around my particular problem, I tried using File::Find instead of piped input. The issue actually gets worse: Debugging update: I tried some of the tricks listed at http://perldoc.perl.org/perlunicode.html, e.g. use utf8, use feature 'unicode_strings', etc, to no avail. Environment and Version Info The OS is Windows 7, 64-bit. The Perl is: This is perl 5, version 12, subversion 2 (v5.12.2) built for MSWin32-x64-multi-thread (with 8 registered patches, see perl -V for more detail) Copyright 1987-2010, Larry Wall Binary build 1202 [293621] provided by ActiveState http://www.ActiveState.com Built Sep 6 2010 22:53:42

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Has inheritance become bad?

- by mafutrct

Personally, I think inheritance is a great tool, that, when applied reasonably, can greatly simplify code. However, I seems to me that many modern tools dislike inheritance. Let's take a simple example: Serialize a class to XML. As soon as inheritance is involved, this can easily turn into a mess. Especially if you're trying to serialize a derived class using the base class serializer. Sure, we can work around that. Something like a KnownType attribute and stuff. Besides being an itch in your code that you have to remember to update every time you add a derived class, that fails, too, if you receive a class from outside your scope that was not known at compile time. (Okay, in some cases you can still work around that, for instance using the NetDataContract serializer in .NET. Surely a certain advancement.) In any case, the basic principle still exists: Serialization and inheritance don't mix well. Considering the huge list of programming strategies that became possible and even common in the past decade, I feel tempted to say that inheritance should be avoided in areas that relate to serialization (in particular remoting and databases). Does that make sense? Or am messing things up? How do you handle inheritance and serialization?

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When to use basic types (Integer, String), and when to write a new class?

- by belgarat

Stackoverflow users: A lot of things can be represented in programs by using the basic types, or we can create a new class for it. Example: A social security number can be a number, string or its own object. (Other common examples: Phone numbers, names, zip codes, user id, order id and other id's.) My question is: When should the basic types be used, and when should we write ourselves a new class? I see that when you need to add behavior, you'll want to create a class (example, social security number parsing, validation, formatting, etc). But is this the only criteria? I have come across cases where many of these things are represented as java Integers and/or Strings. We loose the benefit of type-checking, and I have often seen bugs caused by parameters being mixed in calls to function(Intever, Integer, Integer, Integer). On the other hand, some programmers are opposed to over-designing by creating classes for "eveything". Obviously, the answer is "it depends". But, what do you think, and what do you normally do?

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custom sorting or ordering a table without resorting the whole shebang

- by fuugus

for ten years we've been using the same custom sorting on our tables, i'm wondering if there is another solution which involves fewer updates, especially since today we'd like to have a replication/publication date and would'nt like to have our replication replicate unnecessary entries. i had a look into nested sets, but it does'nt seem to do the job for us. base table: id | a_sort ---+------- 1 10 2 20 3 30 after inserting insert into table (a_sort) values(15) an entry at the second position. id | a_sort ---+------- 1 10 2 20 3 30 4 15 ordering the table with select * from table order by a_sort and resorting all the a_sort entries, updating at least id=(2,3,4) will of course produce the desired output id | a_sort ---+------- 1 10 4 20 2 30 3 40 the column names, the column count, datatypes, a possible join, possible triggers or the way the resorting is done is/are irrelevant to the problem. also we've found some pretty neat ways to do this task fast. only; how the heck can we reduce the updates in the db to 1 or 2 max. seems like an awfully common problem. the captain obvious in me thougth once "use an a_sort float(53), insert using a fixed value of ordervaluefirstentry+abs(ordervaluefirstentry-ordervaluenextentry)/2".. but this would only allow around 1040 "in between" entries - so never resorting seems a bit problematic ;)

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Is it a wise decision to go from dev to third line/Tier 3 dev support?

- by dotnetdev

Hi, I am an experienced, mid-level developer. However, I recently spotted a job for a company which is small but has a lot of emphasis on training(beyond the basic technical training, but also mentoring, leadership training, etc). The role is 3rd line so still very technical. It's in app support so it's post implementation development rather than pure out-and-out development like I do now (or don't, as the senior devs do all of the interesting work). However, and this is the question - is this sort of career move common? Also, wouldn't a tech support role be a big shock to the system because I've never dealt with customers? I therefore think it's a bad move? Working in dev, I am used to the lack of customer contact and it is all filtered through by my manager. But in tech support, contacting customers/rude customers could be scary. I don't mind fixing other people's mistakes (better than me making mistakes!) and doing post-implementation dev for production systems (will give me a lot of discipline), and I do get bored sitting in the same place looking/talking to the same people in suits (I work in a corporate environment). The company puts A LOT of emphasis on training and prospects, which I don't get in the current (big) company I work at. Any advice on how to handle tech support is appreciated! Thanks

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How to combine two rows and calculate the time difference between two timestamp values in MySQL?

- by Nadar

I have a situation that I'm sure is quite common and it's really bothering me that I can't figure out how to do it or what to search for to find a relevant example/solution. I'm relatively new to MySQL (have been using MSSQL and PostgreSQL earlier) and every approach I can think of is blocked by some feature lacking in MySQL. I have a "log" table that simply lists many different events with their timestamp (stored as datetime type). There's lots of data and columns in the table not relevant to this problem, so lets say we have a simple table like this: CREATE TABLE log ( id INT NOT NULL AUTO_INCREMENT, name VARCHAR(16), ts DATETIME NOT NULL, eventtype VARCHAR(25), PRIMARY KEY (id) ) Let's say that some rows have an eventtype = 'start' and others have an eventtype = 'stop'. What I want to do is to somehow couple each "startrow" with each "stoprow" and find the time difference between the two (and then sum the durations per each name, but that's not where the problem lies). Each "start" event should have a corresponding "stop" event occuring at some stage later then the "start" event, but because of problems/bugs/crashed with the data collector it could be that some are missing. In that case I would like to disregard the event without a "partner". That means that given the data: foo, 2010-06-10 19:45, start foo, 2010-06-10 19:47, start foo, 2010-06-10 20:13, stop ..I would like to just disregard the 19:45 start event and not just get two result rows both using the 20:13 stop event as the stop time. I've tried to join the table with itself in different ways, but the key problems for me seems to be to find a way to correctly identify the corresponding "stop" event to the "start" event for the given "name". The problem is exactly the same as you would have if you had table with employees stamping in and out of work and wanted to find out how much they actually were at work. I'm sure there must be well known solutions to this, but I can't seem to find them...

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Detailstext in TableView from Coredata Iphone

- by user554867

Hey, that is my first question here at stackoverflow. Let me try to be specific as I can. The project is as follows: I am trying to parse an xml file in an iphone app, which works already. I am saving the parsed data into the CoreData of the Iphone. So far so good: I have two elements of the xml file which I want to show in the tableview as the text and the detailtext. Now the strange behaviour occurs: If I take the data of the Core Data and trying to visualize them in the tableview, then both elements are displayed in seperate cells and not as detailtext of the element. If I am just taking a constant string for the detailtext, then it works, but if I am trying to take for every cell a specific element from the Core Data then it is shown seperately in the tableview. I googled a lot, reading here and there. I dont know which code I should show because I dont have a clue where exactly the mistake could be. Maybe someone can answer that immediately because it is a stupid mistake somewhere, which is common. Thanks for your help.

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Linq to SQL Intersect help needed

- by mohang

Hi, I have tried various suggestions given in SO. I still did not get the answers needed. Kindly help me. I appreciate your help. I have two sets. I need help to get the linq to sql intersection done. I have two sets. IQueryable<BusinessEntity> firstSet = from ent in all entities where ... // Code to get the first set. IQueryable<BusinessEntity> secondSet = from ent in all entities where... // Code to get the second set. Now I want the intersection, that is common elements of these sets. I have tried various ways including the following and I did not get the result I wanted. Please help me to get the right result. var commonEntities = (from ent1 in firstSet from ent2 in secondSet where ent1.BusinessEntityId == ent2.BusinessEntityId select ent1);

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Applying a function that may fail to all values in a list

- by Egwor

I want to apply a function f to a list of values, however function f might randomly fail (it is in effect making a call out to a service in the cloud). I thought I'd want to use something like map, but I want to apply the function to all elements in the list and afterwards, I want to know which ones failed and which were successful. Currently I am wrapping the response objects of the function f with an error pair which I could then effectively unzip afterwards i.e. something like g : (a->b) -> a -> [ b, errorBoolean] f : a-> b and then to run the code ... map g (xs) Is there a better way to do this? The other alternative approach was to iterate over the values in the array and then return a pair of arrays, one which listed the successful values and one which listed the failures. To me, this seems to be something that ought to be fairly common. Alternatively I could return some special value. What's the best practice in dealing with this??

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Designers, Expression or SharePoint Designer, and real source control

- by David Lively

I'm trying desperately to move from VSS to a real source control system. Options include TFS and SVN. My designers need to keep their ability to modify source files and instantly preview their changes in a browser without having to commit their changes. Using FPSE with VSS, this works flawlessly, since saving a file causes the copy in the working folder on the dev server to be updated, so they can just save and refresh their browser which is pointed at the dev server. The site in question consists of 350k+ lines of classic ASP code and some new ASP.NET MVC. They only need to be able to modify views within the MVC code, not C#. Though Expression includes a version of Cassini for local debugging, Cassini does not support classic ASP. Surely someone has solved this problem before. It can't be necessary to install IIS on each designer's machine (this is absolutely untenable). I need a way to have a common working folder on a dev webserver updated whenever someone saves a file locally, just like using FPSE. I'd rather not write an FPSE proxy that knows how to talk to TFS/SVN. Any suggestions? (I know I've asked this question in the past, but I haven't yet found a solution.)

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Find and Replace using Perl for a dynamic url based on wordpress post

- by user1068544

How do you find the following div using perl. The url and image location will consistently change based on the post url, so i need to use a wild card. I must use a regular expression because I am limited in what i can use due to the software i am using. http://community.autoblogged.com/entries/344640-common-search-and-replace-patterns <div class="tweetmeme_button" style="float: right; margin-left: 10px;"> <a href="http://api.tweetmeme.com/share?url=http%3A%2F%2Fjumpinblack.com%2F2011%2F11%2F25%2Fdrake-and-rick-ross-you-only-live-once-ep-mixtape-2011-download%2F"><br /> <img src="http://api.tweetmeme.com/imagebutton.gif?url=http%3A%2F%2Fjumpinblack.com%2F2011%2F11%2F25%2Fdrake-and-rick-ross-you-only-live-once-ep-mixtape-2011-download%2F&source=jumpinblack1&style=compact&b=2" height="61" width="50" /><br /> </a> </div> I tried using <div class="tweetmeme_button" style="float: right; margin-left: 10px;">.*<\/div>

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In C/C++,how to link dynamic link lib which compiled in GCC/G++ in MS VStudio?

- by coanor

These days, I use Flex & Bison generated some codes to develop a SQL-parser alike tools, these code can't compiled silently(may be this another topic) in VS2005,but GCC/G++ works well, then I compiled these code with mingw in dll(in windows xp), and then linked these function facades in VS2005, but it seems can't link the dll during linking. Does MS VS2005 recognize the dll which compiled using mingw on windows? Is there anything I need to do additional? For example, adding something in the include-file that declare the exported APIs? Does any one can give some advices? The condition is, as in VS2005, if you want to export some APIs, you may show a *.def file to tell nmake which API you want to export, and then you may create a(or some) *.h file to declare somthing about these APIs(adding some stdcall alike prefix as a call protocal) and some data-type definition. But with GCC/G++, you do not need to do such boring things, just use [ar], you can get these APIs, so my *.h file do not add call protocol and no *.def, just like common function declaration. After *.dll generated, add the *.h file and [mv] generated *.dll in VS2005 project directory, then set the linking *.dll in project setting. Does these steps generated my Question? BTW, I found and tested VC6-compiled dll can be linked with mingw in Windows XP, but the reverse can't work. Anyway, forgive my poor English, and thanks for your concern.

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How to change a recursive function for count files and catalogues?

- by user661999

<?php function scan_dir($dirname) { $file_count = 0 ; $dir_count = 0 ; $dir = opendir($dirname); while (($file = readdir($dir)) !== false) { if($file != "." && $file != "..") { if(is_file($dirname."/".$file)) ++$file_count; if(is_dir($dirname."/".$file)) { ++ $dir_count; scan_dir($dirname."/".$file); } } } closedir($dir); echo "There are $dir_count catalogues and $file_count files.<br>"; } $dirname = "/home/user/path"; scan_dir($dirname); ?> Hello, I have a recursive function for count files and catalogues. It returns result for each catalogue. But I need a common result. How to change the script? It returns : There are 0 catalogues and 3 files. There are 0 catalogues and 1 files. There are 2 catalogues and 14 files. I want: There are 2 catalogues and 18 files.

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Is inheritance bad nowadays?

- by mafutrct

Personally, I think inheritance is a great tool, that, when applied reasonably, can greatly simplify code. However, I seems to me that many modern tools dislike inheritance. Let's take a simple example: Serialize a class to XML. As soon as inheritance is involved, this can easily turn into a mess. Especially if you're trying to serialize a derived class using the base class serializer. Sure, we can work around that. Something like a KnownType attribute and stuff. Besides being an itch in your code that you have to remember to update every time you add a derived class, that fails, too, if you receive a class from outside your scope that was not known at compile time. (Okay, in some cases you can still work around that, for instance using the NetDataContract serializer in .NET. Surely a certain advancement.) In any case, the basic principle still exists: Serialization and inheritance don't mix well. Considering the huge list of programming strategies that became possible and even common in the past decade, I feel tempted to say that inheritance should be avoided in areas that relate to serialization (in particular remoting and databases). Does that make sense? Or am messing things up? How do you handle inheritance and serialization?

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How can I compare the performance of log() and fp division in C++?

- by Ventzi Zhechev

Hi, I’m using a log-based class in C++ to store very small floating-point values (as the values otherwise go beyond the scope of double). As I’m performing a large number of multiplications, this has the added benefit of converting the multiplications to sums. However, at a certain point in my algorithm, I need to divide a standard double value by an integer value and than do a *= to a log-based value. I have overloaded the *= operator for my log-based class and the right-hand side value is first converted to a log-based value by running log() and than added to the left-hand side value. Thus the operations actually performed are floating-point division, log() and floating-point summation. My question whether it would be faster to first convert the denominator to a log-based value, which would replace the floating-point division with floating-point subtraction, yielding the following chain of operations: twice log(), floating-point subtraction, floating-point summation. In the end, this boils down to whether floating-point division is faster or slower than log(). I suspect that a common answer would be that this is compiler and architecture dependent, so I’ll say that I use gcc 4.2 from Apple on darwin 10.3.0. Still, I hope to get an answer with a general remark on the speed of these two operators and/or an idea on how to measure the difference myself, as there might be more going on here, e.g. executing the constructors that do the type conversion etc. Cheers!

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Objective C - creating concrete class instances from base class depending upon type

- by indiantroy

Just to give a real world example, say the base class is Vehicle and concrete classes are TwoWheeler and FourWheeler. Now the type of the vehicle - TwoWheeler or FourWheeler, is decided by the base class Vehicle. When I create an instance of TwoWheeler/FourWheeler using alloc-init method, it calls the super implementation like below to set the value of common properties defined in the Vehicle class and out of these properties one of them is type that actually decides if the type is TwoWheeler or FourWheeler. if (self = [super initWithDictionary:dict]){ [self setOtherAttributes:dict]; return self; } Now when I get a collection of vehicles some of them could be TwoWheeler and others will be FourWheeler. Hence I cannot directly create an instance of TwoWheeler or FourWheeler like this Vehicle *v = [[TwoWheeler alloc] initWithDictionary:dict]; Is there any way I can create an instance of base class and once I know the type, create an instance of child class depending upon type and return it. With the current implementation, it would result in infinite loop because I call super implementation from concrete class. What would be the perfect design to handle this scenario when I don't know which concrete class should be instantiated beforehand?

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