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• Cross-platform and language (de)serialization

  - by fwgx

  I'm looking for a way to serialize a bunch of C++ structs in the most convenient way so that the serialization is portable across C++ and Java (at a minimum) and across 32bit/64bit, big/little endian platforms. The structures to be serialized just contain data, i.e. they're pure data objects with no state or behavior. The idea being that we serialize the structs into an octet blob that we can store in a database "generically" and be read out later on. Thus avoiding changing the database whenever a struct changes and also avoiding assigning each data member to a field - i.e. we only want one table to hold everything "generically" as a binary blob. This should make less work for developers and require less changes when structures change. I've looked at boost.serialize but don't think there's a way to enable compatibility with Java. And likewise for inheriting Serializable in Java. If there is a way to do it by starting with an IDL file that would be best as we already have IDL files that describe the structures. Cheers in advance!

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• Looking for a good dev environment for OSGi bundles

  - by Riduidel

  Hi, I'm currently investigating in the field of dev environment for OSGi bundles. My goal is to find a way to develop, test and debug with ease the bundles I'll be coding. Besides, I have some "cultural" requirements. I want to be able to use java continuous integration servers (typically, Hudson) As a consequence of that first requirement, I want to have a repeatable, one-click build process. My typical tool for that is maven. And finally, being long-term Eclipse user, and having the m2eclipse at hand to merge my eclipse env with my maven one, I obviously want to be able to test and debug with that IDE. So far, here are the infos I know I can use (and have already tested) maven-bundle-plugin, maven-ipojo-plugin which both offer clean packaging facilities I have tested maven pax (and eclipse pax) and am not really satisfied with both : maven pax generates a very heavy project, where adding dependencies is very error-prone (the maven pax:import-bundle command line, with all its arguments, is a hell per se) I have taken a look at Karaf, which seems to have some nice direct maven provisionning, but I don't know how to integrate it with my Eclipse, besides using the traditionnal JPDA bridge. However, it seems to be more production-oriented than dev-oriented, and as such may require heavy configuration to fit my need (although the reading of its user manual doesn't revedal that). Have you got any ideas ? Some maven/eclipse plugins ?

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• parameter error in my Facebook app

  - by Robert

  I have written a small app and put it on facebook. I got an application ID and secret. Then I wrote the following script to access my app (just as told on the facebook page). <?php require './src/facebook.php'; $facebook = new Facebook(array( 'appId' => 'xxxx', 'secret' => 'xxxx', 'cookie' => true, // enable optional cookie support )); try { $me = $facebook->api('/me'); } catch (FacebookApiException $e) { error_log($e); } if ($facebook->getSession()) { echo '<a href="' . $facebook->getLogoutUrl() . '">Logout</a>'; } else { echo '<a href="' . $facebook->getLoginUrl() . '">Login</a>'; } ?> Then I started running this script. It prompted me with the login link, then took me to the facebook login page. However, after I enter my facebook login details, I get this error page: Error. API Error Code: 100 API Error Description: Invalid parameter Error Message: next is not owned by the application. Could anyone help me a little bit please, I am really confused here about what's going on.

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• lightweight webserver to integrate on client end.

  - by Gopal

  Hi ,... I need to create a python module that will be installed on end-user machines. One of the scripts in that module should be able to receive http POSTS (usually with some JSON formatted data in the body) and then pass on that data to an appropriate python script. I can think of two ways to do this: a) Open a listening server socket on port 80, wait for that http request to come in, parse it and then pass that data to another python script depending on the url that arrived. This method will not require the end-user to install a webserver. End user only has to install the python module. b) Have a mini-webserver installed along with the python module. The webserver will do the same job as [a] via CGI without me requiring to write the CGI functionality. But then the user will have to install the web-server (ie., the hassle of yet another install). Would like to avoid that if possible. IF [b] is the easier option, what is the smallest simplest webserver there is (preferably one that can be packaged as part of the python module itself so that it does not have to be separately installed). Must be opensource of course. regards Gopal

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• Submit WordPress form programmatically

  - by songdogtech

  How can I let a user access a WordPress protected page with a URL that will submit the password in the form below? I want to be able to let a user get to a password protected WordPress page without needing to type the password, so when they go to the page, the password is submitted by a POST URL on page load. This not intended to be secure in any respect; I'll need to hardcode the password in the URL and the PHP. It's just for simplicity for the user, and once they're in, the cookie will let them in for 10 more days. I will select the particular user with separate PHP function that determines their IP or WordPress login status. I used Wireshark to find the POST string: post_password=mypassword&Submit=Submit but using this URL mydomain.com/wp-pass.php?post_password=mypassword&Submit=Submit gives me a blank page. This is the form: <form action="http://mydomain.com/wp-pass.php" method="post"> Password: <input name="post_password" type="password" size="20" /> <input type="submit" name="Submit" value="Submit" /></form> This is wp-pass.php: <?php require( dirname(__FILE__) . '/wp-load.php'); if ( get_magic_quotes_gpc() ) $_POST['post_password'] = stripslashes($_POST['post_password']); setcookie('wp-postpass_' . COOKIEHASH, $_POST['post_password'], time() + 864000, COOKIEPATH); wp_safe_redirect(wp_get_referer()); ?> What am I doing wrong? Or is there a better way to let a user into a password protected page automatically?

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• Pass a data.frame column name to a function

  - by Kevin Middleton

  I'm trying to write a function to accept a data.frame (x) and a column from it. The function performs some calculations on x and later returns another data.frame. I'm stuck on the best-practices method to pass the column name to the function. The two minimal examples fun1 and fun2 below produce the desired result, being able to perform operations on x$column, using max() as an example. However, both rely on the seemingly (at least to me) inelegant (1) call to substitute() and possibly eval() and (2) the need to pass the column name as a character vector. fun1 <- function(x, column){ do.call("max", list(substitute(x[a], list(a = column)))) } fun2 <- function(x, column){ max(eval((substitute(x[a], list(a = column))))) } df <- data.frame(A = 1:20, B = rnorm(10)) fun1(df, "B") fun2(df, "B") I would like to be able to call the function as fun(df, B), for example. Other options I have considered but have not tried: Pass column as an integer of the column number. I think this would avoid substitute(). Ideally, the function could accept either. with(x, get(column)), but, even if it works, I think this would still require substitute Make use of formula() and match.call(), neither of which I have much experience with. Subquestion: Is do.call() preferred over eval()? Thanks, Kevin

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• Data Mappers, Models and Images

  - by James

  Hi, I've seen and read plenty of blog posts and forum topics talking about and giving examples of Data Mapper / Model implementations in PHP, but I've not seen any that also deal with saving files/images. I'm currently working on a Zend Framework based project and I'm doing some image manipulation in the model (which is being passed a file path), and then I'm leaving it to the mapper to save that file to the appropriate location - is this common practise? But then, how do you deal with creating say 3 different size images from the one passed in? At the moment I have a "setImage($path_to_tmp_name)" which checks the image type, resizes and then saves back to the original filename. A call to "getImagePath()" then returns the current file path which the data mapper can use and then change with a call to "setImagePath($path)" once it's saved it to the appropriate location, say "/content/my_images". Does this sound practical to you? Also, how would you deal with getting the URL to that image? Do you see that as being something that the model should be providing? It seems to me like that model should worry about where the images are being stored or ultimately how they're accessed through a browser and so I'm inclined to put that in the ini file and just pass the URL prefix to the view through the controller. Does that sound reasonable? I'm using GD for image manipulation - not that that's of any relevance. UPDATE: I've been wondering if the image resizing should be done in the model at all. The model could require that it's provided a "main" image and a "thumb" image, both of certain dimensions. I've thought about creating a "getImageSpecs()" function in the model that would return something that defines the required sizes, then a separate image manipulation class could carry out the resizing and (perhaps in the controller?) and just pass the final paths in to the model using something like "setImagePaths($images)". Any thoughts much appreciated :) James.

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• Problem with Zend Project

  - by Fincha

  Hello, i write a script and it works perfectly, on my local server. I have uploaded it on my server and now I getting this Problem Parse error: syntax error, unexpected '{' in /homepages/46/d319011794/htdocs/suche/public/index.php on line 18 an here is my index.php <?php error_reporting(E_ALL || E_STRICT); define('APPLICATION_PATH', realpath(dirname(__FILE__)) . '/../application'); set_include_path( APPLICATION_PATH . '/../library' . PATH_SEPARATOR . '../application/models' . PATH_SEPARATOR . get_include_path() ); require_once 'Zend/Loader.php'; Zend_Loader::registerAutoload(); new App_Connect(); try { //Line 18 require '../application/bootstrap.php'; } catch(Exception $exception) { echo "<html><body>Fehler beim bootstraping"; if(defined('APPLICATION_ENVIROMENT') && APPLICATION_EVIROMENT != 'production') { echo "<br><br>" . $exception->getMessage() . "<br>" . "<div align='left'>Stack Trace: " . "<pre> " . $exception->getTraceAsString() . "</pre></div>"; } echo "</body></html>"; exit(1); } Zend_Controller_Front::getInstance()->dispatch(); This is a Zend Project... so may be some one know what to do...

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• Python: Memory usage and optimization when modifying lists

  - by xApple

  The problem My concern is the following: I am storing a relativity large dataset in a classical python list and in order to process the data I must iterate over the list several times, perform some operations on the elements, and often pop an item out of the list. It seems that deleting one item out of a Python list costs O(N) since Python has to copy all the items above the element at hand down one place. Furthermore, since the number of items to delete is approximately proportional to the number of elements in the list this results in an O(N^2) algorithm. I am hoping to find a solution that is cost effective (time and memory-wise). I have studied what I could find on the internet and have summarized my different options below. Which one is the best candidate ? Keeping a local index: while processingdata: index = 0 while index < len(somelist): item = somelist[index] dosomestuff(item) if somecondition(item): del somelist[index] else: index += 1 This is the original solution I came up with. Not only is this not very elegant, but I am hoping there is better way to do it that remains time and memory efficient. Walking the list backwards: while processingdata: for i in xrange(len(somelist) - 1, -1, -1): dosomestuff(item) if somecondition(somelist, i): somelist.pop(i) This avoids incrementing an index variable but ultimately has the same cost as the original version. It also breaks the logic of dosomestuff(item) that wishes to process them in the same order as they appear in the original list. Making a new list: while processingdata: for i, item in enumerate(somelist): dosomestuff(item) newlist = [] for item in somelist: if somecondition(item): newlist.append(item) somelist = newlist gc.collect() This is a very naive strategy for eliminating elements from a list and requires lots of memory since an almost full copy of the list must be made. Using list comprehensions: while processingdata: for i, item in enumerate(somelist): dosomestuff(item) somelist[:] = [x for x in somelist if somecondition(x)] This is very elegant but under-the-cover it walks the whole list one more time and must copy most of the elements in it. My intuition is that this operation probably costs more than the original del statement at least memory wise. Keep in mind that somelist can be huge and that any solution that will iterate through it only once per run will probably always win. Using the filter function: while processingdata: for i, item in enumerate(somelist): dosomestuff(item) somelist = filter(lambda x: not subtle_condition(x), somelist) This also creates a new list occupying lots of RAM. Using the itertools' filter function: from itertools import ifilterfalse while processingdata: for item in itertools.ifilterfalse(somecondtion, somelist): dosomestuff(item) This version of the filter call does not create a new list but will not call dosomestuff on every item breaking the logic of the algorithm. I am including this example only for the purpose of creating an exhaustive list. Moving items up the list while walking while processingdata: index = 0 for item in somelist: dosomestuff(item) if not somecondition(item): somelist[index] = item index += 1 del somelist[index:] This is a subtle method that seems cost effective. I think it will move each item (or the pointer to each item ?) exactly once resulting in an O(N) algorithm. Finally, I hope Python will be intelligent enough to resize the list at the end without allocating memory for a new copy of the list. Not sure though. Abandoning Python lists: class Doubly_Linked_List: def __init__(self): self.first = None self.last = None self.n = 0 def __len__(self): return self.n def __iter__(self): return DLLIter(self) def iterator(self): return self.__iter__() def append(self, x): x = DLLElement(x) x.next = None if self.last is None: x.prev = None self.last = x self.first = x self.n = 1 else: x.prev = self.last x.prev.next = x self.last = x self.n += 1 class DLLElement: def __init__(self, x): self.next = None self.data = x self.prev = None class DLLIter: etc... This type of object resembles a python list in a limited way. However, deletion of an element is guaranteed O(1). I would not like to go here since this would require massive amounts of code refactoring almost everywhere.

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• Keyboard for programming

  - by exhuma

  This may seem a bit a tangential topic. It's not directly related to actual code, but is important for our line of work nevertheless. Over the years, I've switched keyboards a few times. All of them had slightly different key layouts. And I'm not talking about the language/locale layout, but the physical layout! Why not the locale layout? Well, quite frankly, that's easy to change via software. I personally have a German keyboard but have it set to the UK layout. Why? It's quite hard to find different layouts in the shops where I live. Even ordering is not always easy in the shops. So that leaves me with Internet shops. But I prefer to "test" my keyboards before buying. The most notable changes are: Mangled "Home Key Block" I've seen this first on a Logitech keyboard, but it may have originated elsewhere. Shape of the "Enter" key I've seen three different cases so far: Two lines high, wider at the top Two lines high, wider at the bottom One line high Shape of the Backspace button I've seen two types so far: One "character" wide Two "characters" wide OS Keys For Macs, you have the Option and Command buttons, for Windows you have the Windows and Context Menu buttons. Cherry even produced a Linux keyboard once (unfortunately I cannot find many details except news results). I assume a dedicated Linux keyboard would sport a Compose key and had the SysRq always labelled as well (note that some standard layouts do this already). Obviously... .. all these differences entail that some keys have to be moved around the board a lot. Which means, if you are used to one and have to work on another one, you happen to hit the wrong keys quite often. As it happens, this is much more annoying for programmers as it is for people who write texts. Mainly because the keys which are moved around are special character keys, often used in programming. Often these hardware layouts depend also indirectly on where you buy the keyboards. Honestly, I haven't seen a keyboard with a one-line "Enter" key in Germany, nor Luxembourg. I may just have missed it but that's how it looks to me at least. A survey I've seen some attempts at surveys in the style "which keyboard is best for programming". But they all - in my opinion - are not using comparable sets. So I was wondering if it was possible to concoct a survey taking the above criteria into account. But ignoring key dimensions that one would be a bit overkill I guess ;) From what I can see there are the following types of physical layout: Backspace: 2-characters wide Enter: 2-Lines, wider top Backspace: 2-characters wide Enter: 1-Line Backspace: 1-character wide Enter: 2-Lines, wider bottom Then there are the other possible permutations (home-key block, os-keys), which in total makes for quite a large list of categories. Now, I wonder... Would anyone be interested in such a survey? I personally would. Because I am looking for the perfect fit for me. If yes, then I could really use the help of anyone here to propose some models to include in the survey. Once I have some models for each category (I'd say at least 3 per category) I could go ahead and write up a survey, put it on-line and let the it collect data for a while. What do you think?

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• Dependency injection and factory

  - by legenden

  Trying to figure out how to best handle the following scenario: Assume a RequestContext class which has a dependency to an external service, such as: public class RequestContext : IRequestContext { private readonly ServiceFactory<IWeatherService> _weatherService; public RequestContext(ServiceFactory<IWeatherService> weatherService, UserLocation location, string query) { _weatherService = weatherService; ... What sort of dependency should I require in the class that will ultimately instantiate RequestContext? It could be ServiceFactory<IWeatherService>, but that doesn't seem right, or I could create an IRequestContextFactory for it along the lines of: public class RequestContextFactory : IRequestContextFactory { private readonly ServiceFactory<IWeatherService> _weatherService; public RequestContextFactory(ServiceFactory<IWeatherService> weatherService) { _weatherService = weatherService; } public RequestContext Create(UserLocation location, string query) { return new RequestContext(_weatherService, location, query); } } And then pass the IRequestContextFactory through constructor injection. This seems like a good way to do it, but the problem with this approach is that I think it hinders discoverability (devs must know about the factory and implement it, which is not really apparent). Is there a better/more discoverable way that I'm missing?

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• How to make a mapped field inherited from a superclass transient in JPA?

  - by Russ Hayward

  I have a legacy schema that cannot be changed. I am using a base class for the common features and it contains an embedded object. There is a field that is normally mapped in the embedded object that needs to be in the persistence id for only one (of many) subclasses. I have made a new id class that includes it but then I get the error that the field is mapped twice. Here is some example code that is much simplified to maintain the sanity of the reader: @MappedSuperclass class BaseClass { @Embedded private Data data; } @Entity class SubClass extends BaseClass { @EmbeddedId private SubClassId id; } @Embeddable class Data { private int location; private String name; } @Embeddable class SubClassId { private int thingy; private int location; } I have tried @AttributeOverride but I can only get it to rename the field. I have tried to set it to updatable = false, insertable = false but this did not seem to work when used in the @AttributeOverride annotation. See answer below for the solution to this issue. I realise I could change the base class but I really do not want to split up the embedded object to separate the shared field as it would make the surrounding code more complex and require some ugly wrapping code. I could also redesign the whole system for this corner case but I would really rather not. I am using Hibernate as my JPA provider.

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• Why isn't my algorithm for find the biggest and smallest inputs working?

  - by Matt Ellen

  I have started a new job, and with it comes a new language: Ironpython. Thankfully a good language :D Before starting I got to grips with Python on the whole, but that was only a week's worth of learning. Now I'm writing actual code. I've been charged with writing an algorithm that finds the best input parameter to collect data with. The basic algorithm is (as I've been instructed): Set the input parameter to a good guess Start collecting data When data is available stop collecting find the highest point If the point before this (i.e. for the previous parameter value) was higher and the point before that was lower then we've found the max otherwise the input parameter is increased by the initial guess. goto 2 If the max is found then the min needs to be found. To do this the algorithm carries on increasing the input, but by 1/10 of the max, until the current point is greater than the previous point and the point before that is also greater. Once the min is found then the algorithm stops. Currently I have a simplified data generator outputting the sin of the input, so that I know that the min value should be PI and the max value should be PI/2 The main Python code looks like this (don't worry, this is just for my edification, I don't write real code like this): import sys sys.path.append(r"F:\Programming Source\C#\PythonHelp\PythonHelp\bin\Debug") import clr clr.AddReferenceToFile("PythonHelpClasses.dll") import PythonHelpClasses from PHCStruct import Helper from System import Math helper = Helper() def run(): b = PythonHelpClasses.Executor() a = PythonHelpClasses.HasAnEvent() b.Input = 0.0 helper.__init__() def AnEventHandler(e): b.Stop() h = helper h.lastLastVal, h.lastVal, h.currentVal = h.lastVal, h.currentVal, e.Number if h.lastLastVal < h.lastVal and h.currentVal < h.lastVal and h.NotPast90: h.NotPast90 = False h.bestInput = h.lastInput inputInc = 0.0 if h.NotPast90: inputInc = Math.PI/10.0 else: inputInc = h.bestInput/10.0 if h.lastLastVal > h.lastVal and h.currentVal > h.lastVal and h.NotPast180: h.NotPast180 = False if h.NotPast180: h.lastInput, b.Input = b.Input, b.Input + inputInc b.Start(a) else: print "Best input:", h.bestInput print "Last input:", h.lastInput b.Stop() a.AnEvent += AnEventHandler b.Start(a) PHCStruct.py: class Helper(): def __init__(self): self.currentVal = 0 self.lastVal = 0 self.lastLastVal = 0 self.NotPast90 = True self.NotPast180 = True self.bestInput = 0 self.lastInput = 0 PythonHelpClasses has two small classes I wrote in C# before I realised how to do it in Ironpython. Executor runs a delegate asynchronously while it's running member is true. The important code: public void Start(HasAnEvent hae) { running = true; RunDelegate r = new RunDelegate(hae.UpdateNumber); AsyncCallback ac = new AsyncCallback(UpdateDone); IAsyncResult ar = r.BeginInvoke(Input, ac, null); } public void Stop() { running = false; } public void UpdateDone(IAsyncResult ar) { RunDelegate r = (RunDelegate)((AsyncResult)ar).AsyncDelegate; r.EndInvoke(ar); if (running) { AsyncCallback ac = new AsyncCallback(UpdateDone); IAsyncResult ar2 = r.BeginInvoke(Input, ac, null); } } HasAnEvent has a function that generates the sin of its input and fires an event with that result as its argument. i.e.: public void UpdateNumber(double val) { AnEventArgs e = new AnEventArgs(Math.Sin(val)); System.Threading.Thread.Sleep(1000); if (null != AnEvent) { AnEvent(e); } } The sleep is in there just to slow things down a bit. The problem I am getting is that the algorithm is not coming up with the best input being PI/2 and the final input being PI, but I can't see why. Also the best and final inputs are different each time I run the programme. Can anyone see why? Also when the algorithm terminates the best and final inputs are printed to the screen multiple times, not just once. Can someone explain why?

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• I need to run a PHP script via command line but this happens.

  - by user355367

  I need to run a scrip via command line but the files necessary for me to run it require me to be in the directory of the script. But I cannot do it for every command line i need to run. Their are over five thousand. Could someone tell me how to either format the list easily or add something to the format that would make it run. I have something like this.... php /path/to/the/script/01240/script.php php /path/to/the/script/03770/script.php php /path/to/the/script/02110/script.php php /path/to/the/script/02380/script.php php /path/to/the/script/03220/script.php php /path/to/the/script/02340/script.php php /path/to/the/script/03720/script.php php /path/to/the/script/03460/script.php php /path/to/the/script/0180/script.php php /path/to/the/script/02000/script.php php /path/to/the/script/01830/script.php php /path/to/the/script/0980/script.php php /path/to/the/script/0400/script.php php /path/to/the/script/02750/script.php php /path/to/the/script/0760/script.php php /path/to/the/script/02690/script.php ..... and it goes on for 5000 more lines.

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• How to override the default init.tcl

  - by Sean Murphy

  I'm working on a project where I want to make use of TCL as the command interpreter. I have a working c library object which I can load from within the tcl shell but my problem is finding a way to automatically do this while starting a tclsh. Essentially my ultimate goal is to be able to run a script and have it load my library and run some initial startup tcl code before dropping me back to the tclsh command prompt in interactive mode. e.g. tclsh -f myscript.tcl --then-switch-to-interactive or EXPORT TCLINIT=myscript.tcl tclsh The basic goal is to avoid having to distribute tclsh but rather rely in local user installations of tcl. All I would like to distribute is my library, a startup script and a shell command to launch the tclsh with the library preloaded. I've tried using the environment variables TCLINIT and TCL_LIBRARY but they seem to have no effect. The only workable solutions I've found so far are to add "source myscript.tcl" to either the end of /usr/share/tcltk/tcl8.5.init.tcl or ~/.tclshrc However both of these "solutions" are non perfect as they require modification of the default users workspace. It strikes me that there must be a way to handle this in TCL, but my research so far hasn't yielded anything. Does anyone have any suggestions?

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• Calling PHP functions within HEREDOC strings

  - by Doug Kavendek

  In PHP, the HEREDOC string declarations are really useful for outputting a block of html. You can have it parse in variables just by prefixing them with $, but for more complicated syntax (like $var[2][3]), you have to put your expression inside {} braces. In PHP 5, it is possible to actually make function calls within {} braces inside a HEREDOC string, but you have to go through a bit of work. The function name itself has to be stored in a variable, and you have to call it like it is a dynamically-named function. For example: $fn = 'testfunction'; function testfunction() { return 'ok'; } $string = <<< heredoc plain text and now a function: {$fn()} heredoc; As you can see, this is a bit more messy than just: $string = <<< heredoc plain text and now a function: {testfunction()} heredoc; There are other ways besides the first code example, such as breaking out of the HEREDOC to call the function, or reversing the issue and doing something like: ?> <!-- directly outputting html and only breaking into php for the function --> plain text and now a function: <?PHP print testfunction(); ?> The latter has the disadvantage that the output is directly put into the output stream (unless I'm using output buffering), which might not be what I want. So, the essence of my question is: is there a more elegant way to approach this? Edit based on responses: It certainly does seem like some kind of template engine would make my life much easier, but it would require me basically invert my usual PHP style. Not that that's a bad thing, but it explains my inertia.. I'm up for figuring out ways to make life easier though, so I'm looking into templates now.

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• Images in database vs file system

  - by Jesse

  We have a project coming up where we will be building a whole backend CMS system that will power our entire extranet and intranet with one package. The question I have been trying to find an answer to is which is better: storing images in the database (SQL Server 2005) so we may have integrity, single replication plan, etc OR storing on the file system? One issue we have is that we have multiple servers load balanced that require to have the same data at all times. As of now we have SQL replication taking care of that but file replication seems to be a little tougher. Another concern we have is that we would like to have multiple resolutions of the same image, we are not sure if creating and storing each version on the file system would be best or maybe dynamically pulling and creating the resolution image we would like upon request. Our concerns are the with the following: Data integrity Data replication Multiple resolutions Speed of database vs file system Overhead load of database vs file system Data management and backup Does anyone have a similar situation or have any input on what would be recommended? Thanks in advance for the help!

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• Ways to gain a deeper understanding of programming concepts?

  - by MrPlow

  I'm a marketer and have been messing around in PHP/MySQL for years. Recently (the last several months) I've been making my own scripts/programs in Python and I've really enjoyed the whole problem solving process. I've read(skimmed) some books and understand the basics of OOP, polymorphism, etc.. I have a general interest in AI and Natural Language in particular but it seems these things require a masters in Computer Science. My knowledge of math is poor. The last class I took was calculus, and I've forgotten the majority of it. Basically I'm looking for things to learn that will help me think in a more analytic way, and maybe see solutions where I didn't before. Improving my ability to program in Python would be nice too. I don't need to learn a specific language or something for employment, just enjoyment. Although my work often involves web development so some utility would be nice. I don't like learning concepts by just reading them. I need to apply them, even if the examples are contrived. A recommendation of a couple good books or other resources would be nice. :) Apologies if this is too vague/misplaced...

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• Optimizing processing and management of large Java data arrays

  - by mikera

  I'm writing some pretty CPU-intensive, concurrent numerical code that will process large amounts of data stored in Java arrays (e.g. lots of double[100000]s). Some of the algorithms might run millions of times over several days so getting maximum steady-state performance is a high priority. In essence, each algorithm is a Java object that has an method API something like: public double[] runMyAlgorithm(double[] inputData); or alternatively a reference could be passed to the array to store the output data: public runMyAlgorithm(double[] inputData, double[] outputData); Given this requirement, I'm trying to determine the optimal strategy for allocating / managing array space. Frequently the algorithms will need large amounts of temporary storage space. They will also take large arrays as input and create large arrays as output. Among the options I am considering are: Always allocate new arrays as local variables whenever they are needed (e.g. new double[100000]). Probably the simplest approach, but will produce a lot of garbage. Pre-allocate temporary arrays and store them as final fields in the algorithm object - big downside would be that this would mean that only one thread could run the algorithm at any one time. Keep pre-allocated temporary arrays in ThreadLocal storage, so that a thread can use a fixed amount of temporary array space whenever it needs it. ThreadLocal would be required since multiple threads will be running the same algorithm simultaneously. Pass around lots of arrays as parameters (including the temporary arrays for the algorithm to use). Not good since it will make the algorithm API extremely ugly if the caller has to be responsible for providing temporary array space.... Allocate extremely large arrays (e.g. double[10000000]) but also provide the algorithm with offsets into the array so that different threads will use a different area of the array independently. Will obviously require some code to manage the offsets and allocation of the array ranges. Any thoughts on which approach would be best (and why)?

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• Visual Studio: How to attach a debugger dynamically to a specific process

  - by Jeff Cyr

  I am building an internal dev tool to manage different processes commonly used in our development environment. The tool show the list the monitored processes, indicate their running state and allow to start or stop each process. I'd like to add the functionality of attaching a debugger to a monitored process from my tool instead of going in 'Debug-Attach to process' in visual studio and finding the process. My goal is to have something like Debugger.Launch() that would show a list of the available visual studio. I can't use Debugger.Launch() because it lauches the debugger on the process that make the call. I would need something like Debugger.Launch(processId). Does anyone know how to acheive this functionality? A solution could be to implement a command in each monitored process to call Debugger.Launch() when the command is received from the monitoring tool, but I would prefer something that does not require to modify the code of the monitored processes. Side question: When using Debugger.Launch(), instances of Visual Studio that already have a debugger attached are not listed. Visual Studio is not limited to one attached debugger, you can attach on multiple process when using 'Debug - Attach to process'. Anyone know how to bypass this limitation when using Debugger.Launch() or an alternative?

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• Javascript Closures - What are the negatives?

  - by vol7ron

  Question: There seem to be many benefits to Closures, but what are the negatives (memory leakage? obfuscation problems? bandwidth increasage?)? Additionally, is my understanding of Closures correct? Finally, once closures are created, can they be destroyed? I've been reading a little bit about Javascript Closures. I hope someone a little more knowledgeable will guide my assertions, correcting me where wrong. Benefits of Closures: Encapsulate the variables to a local scope, by using an internal function. The anonymity of the function is insignificant. What I've found helpful is to do some basic testing, regarding local/global scope: <script type="text/javascript"> var global_text = ""; var global_count = 0; var global_num1 = 10; var global_num2 = 20; var global_num3 = 30; function outerFunc() { var local_count = local_count || 0; alert("global_num1: " + global_num1); // global_num1: undefined var global_num1 = global_num1 || 0; alert("global_num1: " + global_num1); // global_num1: 0 alert("global_num2: " + global_num2); // global_num2: 20 global_num2 = global_num2 || 0; // (notice) no definition with 'var' alert("global_num2: " + global_num2); // global_num2: 20 global_num2 = 0; alert("local_count: " + local_count); // local_count: 0 function output() { global_num3++; alert("local_count: " + local_count + "\n" + "global_count: " + global_count + "\n" + "global_text: " + global_text ); local_count++; } local_count++; global_count++; return output; } var myFunc = outerFunc(); myFunc(); /* Outputs: ********************** * local_count: 1 * global_count: 1 * global_text: **********************/ global_text = "global"; myFunc(); /* Outputs: ********************** * local_count: 2 * global_count: 1 * global_text: global **********************/ var local_count = 100; myFunc(); /* Outputs: ********************** * local_count: 3 * global_count: 1 * global_text: global **********************/ alert("global_num1: " + global_num1); // global_num1: 10 alert("global_num2: " + global_num2); // global_num2: 0 alert("global_num3: " + global_num3); // global_num3: 33 </script> Interesting things I took out of it: The alerts in outerFunc are only called once, which is when the outerFunc call is assigned to myFunc (myFunc = outerFunc()). This assignment seems to keep the outerFunc open, in what I would like to call a persistent state. Everytime myFunc is called, the return is executed. In this case, the return is the internal function. Something really interesting is the localization that occurs when defining local variables. Notice the difference in the first alert between global_num1 and global_num2, even before the variable is trying to be created, global_num1 is considered undefined because the 'var' was used to signify a local variable to that function. -- This has been talked about before, in the order of operation for the Javascript engine, it's just nice to see this put to work. Globals can still be used, but local variables will override them. Notice before the third myFunc call, a global variable called local_count is created, but it as no effect on the internal function, which has a variable that goes by the same name. Conversely, each function call has the ability to modify global variables, as noticed by global_var3. Post Thoughts: Even though the code is straightforward, it is cluttered by alerts for you guys, so you can plug and play. I know there are other examples of closures, many of which use anonymous functions in combination with looping structures, but I think this is good for a 101-starter course to see the effects. The one thing I'm concerned with is the negative impact closures will have on memory. Because it keeps the function environment open, it is also keeping those variables stored in memory, which may/may not have performance implications, especially regarding DOM traversals and garbage collection. I'm also not sure what kind of role this will play in terms of memory leakage and I'm not sure if the closure can be removed from memory by a simple "delete myFunc;." Hope this helps someone, vol7ron

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• Can I ignore a SIGFPE resulting from division by zero?

  - by Mikeage

  I have a program which deliberately performs a divide by zero (and stores the result in a volatile variable) in order to halt in certain circumstances. However, I'd like to be able to disable this halting, without changing the macro that performs the division by zero. Is there any way to ignore it? I've tried using #include <signal.h> ... int main(void) { signal(SIGFPE, SIG_IGN); ... } but it still dies with the message "Floating point exception (core dumped)". I don't actually use the value, so I don't really care what's assigned to the variable; 0, random, undefined... EDIT: I know this is not the most portable, but it's intended for an embedded device which runs on many different OSes. The default halt action is to divide by zero; other platforms require different tricks to force a watchdog induced reboot (such as an infinite loop with interrupts disabled). For a PC (linux) test environment, I wanted to disable the halt on division by zero without relying on things like assert.

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• Python: Best way to check for Python version in program that uses new language features?

  - by Mark Harrison

  If I have a python script that requires at least a particular version of python, what is the correct way to fail gracefully when an earlier version of python is used to launch the script? How do I get control early enough to issue an error message and exit? For example, I have a program that uses the ternery operator (new in 2.5) and "with" blocks (new in 2.6). I wrote a simple little interpreter-version checker routine which is the first thing the script would call ... except it doesn't get that far. Instead, the script fails during python compilation, before my routines are even called. Thus the user of the script sees some very obscure synax error tracebacks - which pretty much require an expert to deduce that it is simply the case of running the wrong version of python. update I know how to check the version of python. The issue is that some syntax is illegal in older versions of python. Consider this program: import sys if sys.version_info < (2, 4): raise "must use python 2.5 or greater" else: # syntax error in 2.4, ok in 2.5 x = 1 if True else 2 print x When run under 2.4, I want this result $ ~/bin/python2.4 tern.py must use python2.5 or greater and not this result: $ ~/bin/python2.4 tern.py File "tern.py", line 5 x = 1 if True else 2 ^ SyntaxError: invalid syntax (channeling for a coworker)

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• Hiding a button on pushed view and showing it when back to list view

  - by torr

  When I load my list view it has several blog posts and a refresh button on the top left. If I tap on a list item a view is pushed with the contents of that specific post. When this view is pushed in, the refresh button is hidden. But when I tap 'Back' to the parent list view, I'd like the refresh button to show (un-hide) - but it remains hidden. Any idea how to make this work? This is my View: Ext.require(['Ext.data.Store', 'MyApp.model.StreamModel'], function() { Ext.define('MyApp.view.HomeView', { extend: 'Ext.navigation.View', xtype: 'homepanel', requires: [ 'Ext.dataview.List', ], config: { title: 'Home', iconCls: 'home', styleHtmlContent: true, navigationBar: { items: [ { xtype: 'button', iconMask: true, iconCls: 'refresh', align: 'left', action: 'refreshButton', id: 'refreshButtonId' } ] }, items: { title: 'My', xtype: 'list', itemTpl: [ '<div class="post">', ... '</div>' ].join(''), store: new Ext.data.Store({ model: 'MyApp.model.StreamModel', autoLoad: true, storeId: 'stream' }), } } }); }); and my Controller: Ext.define('MyApp.controller.SingleController', { extend: 'Ext.app.Controller', config: { refs: { stream: 'homepanel' }, control: { 'homepanel list': { itemtap: 'showPost' } } }, showPost: function(list, index, element, record) { this.getStream().push({ xtype: 'panel', html: [ '<div class="post">', '</div>' ].join(''), scrollable: 'vertical', styleHtmlContent: true, }); Ext.getCmp('refreshButtonId').hide(); } });

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• Rubygems on Debian: Gems won't load (LoadError)

  - by daswerth

  I've installed the development version of Crunchbang, a linux distro based off Debian. I got Ruby and Rubygems installed, but I can't get the gems I've installed to load. Here is a command-line session: $ ruby -v ruby 1.9.1p378 (2010-01-10 revision 26273) [i486-linux] $ gem env RubyGems Environment: - RUBYGEMS VERSION: 1.3.6 - RUBY VERSION: 1.9.1 (2010-01-10 patchlevel 378) [i486-linux] - INSTALLATION DIRECTORY: /usr/lib/ruby1.9.1/gems/1.9.1 - RUBY EXECUTABLE: /usr/bin/ruby1.9.1 - EXECUTABLE DIRECTORY: /usr/bin - RUBYGEMS PLATFORMS: - ruby - x86-linux - GEM PATHS: - /usr/lib/ruby1.9.1/gems/1.9.1 - /home/corey/.gem/ruby/1.9.1 - GEM CONFIGURATION: - :update_sources => true - :verbose => true - :benchmark => false - :backtrace => false - :bulk_threshold => 1000 - REMOTE SOURCES: - http://rubygems.org/ $ echo $PATH /home/corey/bin:/usr/local/bin:/usr/bin:/bin:/usr/bin/X11:/usr/games:/home/corey/.gem/ruby/1.9.1:/usr/lib/ruby1.9.1/gems/1.9.1 $ gem list -d nokogiri `*** LOCAL GEMS ***` nokogiri (1.4.1) Authors: Aaron Patterson, Mike Dalessio Rubyforge: http://rubyforge.org/projects/nokogiri Homepage: http://nokogiri.org Installed at: /usr/lib/ruby1.9.1/gems/1.9.1 Nokogiri (?) is an HTML, XML, SAX, and Reader parser $ ruby -r rubygems -e "require 'nokogiri'" -e:1:in `require': no such file to load -- nokogiri (LoadError) from -e:1:in `' I've encountered similar problems on Ubuntu before, but they were easy to fix. I can't figure out what's wrong in this particular case, and Google didn't seem to know either. Any help would be greatly appreciated! By the way... this is my first submission to stackoverflow. I hope this question is relevant. :)

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