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• Can I Import an updated structure into a MySQL table without losing its current content?

  - by Udi Wertheimer

  We use MySQL tables to which we add new fields from time to time as our product evolves. I'm looking for a way to export the structure of the table from one copy of the db, to another, without erasing the contents of the table I'm importing to. For example say I have copies A and B of a table, and I add fields X,Y,Z to table A. Is there a way to copy the changed structure (fields X,Y,Z) to table B while keeping its content intact? I tried to use mysqldump, but it seems I can only copy the whole table with its content, overriding the old one, or I can use the "-d" flag to avoid copying data (dumping structure only), but this will create an empty table when imported, again overriding old data. Is there any way to do what I need with mysqldump, or some other tool?

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• C++ Forward declaration for virtual function

  - by Gokul

  Hi, I have a class hierarchy and i am writing a virtual function in it. Say there are three classes class A { virtual A* test(); }; ( File A.h ) class B : public A { virtual C* test(); }; ( File B.h ) class C : public A {}; ( File C.h ) Now is it possible for me to avoid including C.h in B.h, by doing some kind of forward declaration saying that C is a sub-class of A? Thanks, Gokul.

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• Python: Hack to call a method on an object that isn't of its class

  - by cool-RR

  Assume you define a class, which has a method which does some complicated processing: class A(object): def my_method(self): # Some complicated processing is done here return self And now you want to use that method on some object from another class entirely. Like, you want to do A.my_method(7). This is what you'd get: TypeError: unbound method my_method() must be called with A instance as first argument (got int instance instead). Now, is there any possibility to hack things so you could call that method on 7? I'd want to avoid moving the function or rewriting it. (Note that the method's logic does depend on self.) One note: I know that some people will want to say, "You're doing it wrong! You're abusing Python! You shouldn't do it!" So yes, I know, this is a terrible terrible thing I want to do. I'm asking if someone knows how to do it, not how to preach to me that I shouldn't do it.

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• How can I load an MP3 or similar music file for display and analysis in wxWidgets?

  - by Jon Cage

  I'm developing a GUI in wxPython which allows a user to generate sequences of colours for some toys I'm building. Part of the program needs to load an MP3 (and potentially other formats further down the line) and display it to the user. That should be sufficient to get started but later I'd like to add features like identifying beats and some crude frequency analysis. Is there any simple way of loading / understanding an MP3's contents to display a plot of its amplitudes to the screen using wxWidgets? I later intend to port to C++/wxWidgets for speed and to avoid having to distribute wxPython.

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• Fast exchange of data between unmanaged code and managed code

  - by vizcaynot

  Hello: Without using p/invoke, from a C++/CLI I have succeeded in integrating various methods of a DLL library from a third party built in C. One of these methods retrieves information from a database and stores it in different structures. The C++/CLI program I wrote reads those structures and stores them in a List<, which is then returned to the corresponding reading and use of an application programmed completely in C#. I understand that the double handling of data (first, filling in several structures and then, filling all of these structures into a list<) may generate an unnecessary overload, at which point I wish C++/CLI had the keyword "yield". Depending on the above scenario, do you have recommendations to avoid or reduce this overload? Thanks.

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• Invisible Delimiter for Strings in HTML

  - by noah

  I need a way to identify certain strings in HTML markup. I know what the strings are, but it is possible that they could be substrings of other strings in the document. To find them, I output a special delimiter character (currently using \032). On page load, we go through the HTML and record the location of the strings, and remove the delimiter. Unfortunately, most browsers show the delimiter character until we can find and remove them all. I'd like to avoid that if possible. Is there a character or string that will be preserved in the HTML content (so a comment wont work) but wont be visible to the user? It also needs to be something that is fairly unlikely to appear next to a string, so something like &nbsp; wouldn't work either. EDIT: Sorry, I forgot to mention that the strings will be in attributes, so any sort of tag wont work.

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• Python __setattr__ and __getattr__ for global scope?

  - by KT

  Suppose I need to create my own small DSL that would use Python to describe a certain data structure. E.g. I'd like to be able to write something like f(x) = some_stuff(a,b,c) and have Python, instead of complaining about undeclared identifiers or attempting to invoke the function some_stuff, convert it to a literal expression for my further convenience. It is possible to get a reasonable approximation to this by creating a class with properly redefined __getattr__ and __setattr__ methods and use it as follows: e = Expression() e.f[e.x] = e.some_stuff(e.a, e.b, e.c) It would be cool though, if it were possible to get rid of the annoying "e." prefixes and maybe even avoid the use of []. So I was wondering, is it possible to somehow temporarily "redefine" global name lookups and assignments? On a related note, maybe there are good packages for easily achieving such "quoting" functionality for Python expressions?

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• Inheritance vs specific types in Financial Modelling for cashflows

  - by BlueTrin

  Hello, I have to program some financial applications where I have to represent a schedule of flows. The flows can be of 3 types: - fee flow (just a lump payment at some date) - floating rate flow (the flow is dependant of an interest rate to be determined at a later date) - fixed rate flow (the flow is dependant of an interest rate determined when the deal is done) I need to keep the whole information and I need to represent a schedule of these flows. Originally I wanted to use inheritance and create three classes FeeFlow, FloatingFlow, FixedFlow all inheriting from ICashFlow and implement some method GetFlowType() returning an enum then I could dynamic_cast the object to the correct type. That would allow me to have only one vector to represent my schedule. What do you think of this design, should I rather use three vectors vector, vector and vector to avoid the dynamic casts ?

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• Get ANSI-colored output from external command

  - by German Rumm

  I am writing a small script for watchr that runs my PHP unit tests. Current script runs tests using system() and displays them colored. I am trying to add libnotify functionality, but for that I need to parse the output and match against regexp, so that notification will either display green or red. system() doesn't return output, %x does return, but puts p doesn't display colors, which I need to quickly see which test failed. One option would be to run tests twice - once for display in terminal window, and second time for checking which notification to show, but I would rather avoid it.

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• access custom group

  - by Carlos

  I have my Access 2007 database configured to use "Custom" groups in the navigation pane. I've grouped all my tables in a way that makes sense. However, whenever I update a link table, it loses its grouping. I have not been able to find a way to avoid this. Since it seems to be unavoidable, I'd like to simply have a macro that adds the table back to the right group programatically. I have not found any examples on how to do this. Any suggestions?

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• RewriteRule and php download counter

  - by rcourtna

  (1) I have a site that serves up MP3 files: http://domain/files/1234567890.mp3 (2) I have a php script that tracks file download counts: http://domain/modules/download_counter.php?file=/files/1234567890.mp3 After download_counter.php records the download, it redirects to the original file: Header("Location: $FQDN_url"); (3) I'd like all my public links to be presented as the direct file urls from (1). I'm trying to use Apache to redirect the requests to download_counter.php: RewriteRule ^files/(.+\.mp3)$ /modules/download_counter.php?file=/files/$1 [L] I'm currently stuck on (3), as it results in a redirect loop, since download_counter.php simply redirects the request back to the original file (rather than streaming the file contents). I'm also motivated to use download_counter.php as is (without modifying it's redirect behaviour). This is because the script is part of a larger CMS module, and I'd like to avoid complicating my upgrade path. Perhaps there is no solution to my problem (other than modifying the download_counter script). WDYT?

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• Limit scope of #define

  - by Ujjwal Singh

  What is the correct strategy to limit the scope of #define and avoid unwarrented token collisions. In the following configuration: Main.c # include "Utility_1.h" # include "Utility_2.h" VOID Utility() // Was written without knowing of: Utility_1 & Utility_2 { const UINT ZERO = 0; } VOID Main() { ... } // Collision; for Line:5 Compiler does not indicate what replaced Utility_1.h # define ZERO "Zero" # define ONE "One" BOOL Utility_1(); Utility_2.h # define ZERO '0' # define ONE '1' BOOL Utility_2(); Utility_2.c # include "Utility_2.h" BOOL Utility_2() { // Using: ZERO & ONE } //Collision: Character Literal replaced with String {Edit} Note: This is supposed to be a generic quesition so do not limit yourself to enum or other defined types. i.e. What to do when: I MUST USE #define Please comment on my proposed solution below.. _

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• Client / Server application for Video BroadCasting on LAN

  - by jbl

  I m much of a newbie to client/server applications and networking.I am currently starting up a project in which we are planning to create an application or something like a website accessible only to clients in that LAN network.We want the server to upload videos so that the clients can view them whenever they want.Also the clients can upload videos.Also we want some kind of registration to provide authentication to avoid bogus videos.Also additional features that can be added on later like comment section,ratings,Groups etc. Basically what we want is to build mini-youtube but with one major difference , we want the application to be LAN based. This is the idea behind the project.But we dont know where to start from as we are new to this stuff and also we have like 1 year to work on the project.Please guide me as to what all softwares i'll be needing to get this working !

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• Cookie is setting twice (duplicated)

  - by Erik Larsson

  I'm new to cookies, and im trying to set a cookie where to store the referrer (the org ref). But when i try this function: function do_it_cookie() { // Check if cookie exists if (isset($_COOKIE['ref'])) { // It dose exist, do nothing or anything... } else { setcookie ('ref', $_SERVER['HTTP_REFERER'], time() + 60, '/'); header ("Location: http://www.nyttforetag.com/mind-your-own-business/"); } } I want to store the cookie on the user computer for 30 days, if the return i want to know the initial refereeing url. But when i use this and lets say i go to another page in my site and then go back to the homepage its sets a new cookie with the exact same name and with the ref of the previous page. Is there away to avoid this?

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• Why does C++ linking use virtually no CPU?

  - by John

  On a native C++ project, linking right now can take a minute or two, yet during this time CPU drops from 100% during compilation to virtually zero. Does this mean linking is primarily a disk activity? If so, is this the main area an SSD would make big changes? But, why aren't all my OBJ files (or as many as possible) kept in RAM after compilation to avoid this? With 4Gb of RAM I should be able to save a lot of disk access and make it CPU-bound again, no?

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• Are PDO prepared statements sufficient to prevent SQL injection?

  - by Mark Biek

  Let's say I have code like this: $dbh = new PDO("blahblah"); $stmt = $dbh->prepare('SELECT * FROM users where username = :username'); $stmt->execute( array(':username' => $_REQUEST['username']) ); The PDO documentation says The parameters to prepared statements don't need to be quoted; the driver handles it for you. Is that truly all I need to do to avoid SQL injections? Is it really that easy? You can assume MySQL if it makes a difference. Also, I'm really only curious about the use of prepared statements against SQL injection. In this context, I don't care about XSS or other possible vulnerabilities.

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• mod_rewrite: remove trailing slash (only one!)

  - by tshabalala

  Hello. I use mod_rewrite/.htaccess for pretty URLs. I'm using this condition/rule to eliminate trailing slashes (or rather: rewrite to the non-trailing-slash-URL, by a 301 redirect; I'm doing this to avoid duplicate content and because I like URLs with no trailing slashes better): RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteCond %{HTTP_HOST} !^\.localhost$ [NC] RewriteRule ^(.+)/$ http://%{HTTP_HOST}/$1 [R=301,L] Working well so far. Only drawback: it also forwards "multiple-trailing-slash"-URLs to non-trailing-slash-URLs. Example: http://example.tld/foo/bar////// forwards to http://example.tld/foo/bar while I only want http://example.tld/foo/bar/ to forward to http://example.tld/foo/bar. So, is it possible to only eliminate trailing slashes if it's actually just one trailing slash? Sorry if this is a somewhat annoying or weird question! Thanks.

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• Inline function and calling cost in C

  - by Eonil

  I'm making a vector/matrix library. (GCC, ARM NEON, iPhone) typedef struct{ float v[4]; } Vector; typedef struct{ Vector v[4]; } Matrix; I passed struct data as pointer to avoid performance degrade from data copying when calling function. So I thought designed function like this: void makeTranslation(const Vector* factor, Matrix* restrict result); But, if function is inline, is there any reason to pass values as pointer for performance? Do those variables copied too? How about register and caches? inline Matrix makeTranslation(Vector factor) __attribute__ ((always_inline)); How do you think about calling costs of each cases?

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• Side effects of reordering columns in PostgreSQL

  - by Summer

  I sometimes re-order the columns in my Postgres DB. Since Postgres can only add columns at the end of tables, I end up re-ordering by adding new columns at the end of the table, setting them equal to existing columns, and then dropping the original columns. My question is: what does PostgreSQL do with the memory that's freed by dropped columns? Does it automatically re-use the memory, so a single record consumes the same amount of space as it did beforehand? But that would require a re-write of the whole table, so to avoid that, does it just keep a bunch of blank space around in each record? Thanks! ~S

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• Updating Activity UI from Different Activity Method?

  - by stormin986

  I have a tab widget where one of the tabs is a chat-type feature. I want to update the chat data at an interval (variable depending on whether the chat tab is active or not). The best approach seemed to be using an AsyncTask in my main TabActivity class, as that would avoid any issues of the chat activity being destroyed while in the background, while an AsyncTask was running. I wanted to ensure that the Activity isn't destroyed and recreated, thus causing my AsyncTask to be unable to modify the actual active Activity's data. However, now that my AsyncTask is in the TabActivity activity, I don't have a direct way to call my Chat's ListAdapter notifyDataSetChanged() from my onPostExecute() method anymore. Is there a way to get a reference to a given Tab's current Activity from the TabHost/TabActivity? Or, alternatively, can I assume my chat activity will never be destroyed as a child activity of the TabActivity activity (well, never destroyed while the TabActivity is active at least), and then just put the AsyncTask in the Chat Activity?

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• cd Terminal at a given directory after running a Python script?

  - by Dave Everitt

  I'm working on a simple Python script that can use subprocess and/or os to execute some commands, which is working fine. However, when the script exits I'd like to cd the actual Terminal (in this case OS X) so on exit, the new files are ready to use in the directory where the have been created. All the following (subprocess.Popen, os.system, os.chdir) can do what I want from within the script (i.e. they execute stuff in the target directory) but on exit leave the Terminal at the script's own directory, not the target directory. I'd like to avoid writing a shell script to temporary file just to achieve this, if this is at all possible anyway?

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• MySQL foreign key constraints, cascade delete

  - by Cudos

  Hello. I want to use foreign keys to keep the integrity and avoid orphans (I already use innoDB). How do I make a SQL statment that DELETE ON CASCADE? Secondly, that using DELETE ON CASCADE. E.g. if I delete a category then it would delete products related to that category even though there are other categories related to those products. The pivot table "categories_products" creates a many-to-many relationship between the two other tables. categories - id (INT) - name (VARCHAR 255) products - id - name - price categories_products - categories_id - products_id

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• Best Practices for a Web App Staging Server (on a budget)

  - by fig-gnuton

  I'd like to set up a staging server for a Rails app. I use git & github, Cap, and have a VPS with Apache/Passenger. I'm curious as to the best practices for a staging setup, as far as both the configuration of the staging server as well as the processes for interacting with it. I do know it should be as identical to the production server as possible, but restricting public access to it will limit that, so tips on securing it only for my use would also be great. Another specific question would be whether I could just create a virtual host on the VPS, so that the staging server could reside alongside the production one. I have a feeling there may be reasons to avoid this, though.

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• Is window.location.href = 'some_page.html' followed by search engines?

  - by Arkaaito

  Currently our website uses links to allow the user to change their locale. The problem with this is that you get a lot of random outlinks from each page on the site to... the same page, in other languages. When a search engine traverses this, it gets an excessively complex view of the site. We were going to change it to a form post to avoid this. However, it seems to me that we should just be able to change it to an onclick="window.location.href='change_my_language.php'" rather than an href="change_my_language.php". Am I right? Or do the major search engines scan for and follow this sort of thing nowadays?

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• Show friendly message on ASP.NET Ajax error

  - by balexandre

  You all know how annoying is this: I do have a log system and the correct error is well explicit there, but I want to give a better message to the user. I keep trying several ways but I'm using Telerik components and well jQuery and I ended up using both ASP.NET Ajax methods and jQuery, so I use function pageLoad() { try { var manager = Sys.WebForms.PageRequestManager.getInstance(); manager.add_endRequest(endRequest); manager.add_beginRequest(OnBeginRequest); manager } catch (err) { alert(err); } } as well $(document).ready(function() { ... } that alert(err) is never fired even upon OnClick events what's the best approach to avoid this message errors and provide a cleaner way? all this happens in <asp:UpdatePanel> as I use that when I didn't know better (3 years ago!) and I really don't want to mess up and build all again from scratch :( Any help is greatly appreciated Updated with more error windows after volpav solution

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