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  • Is there any reason to use C instead of C++ for embedded development?

    - by Piotr Czapla
    Question I have two compilers on my hardware C++ and C89 I'm thinking about using C++ with classes but without polymorphism (to avoid vtables). The main reasons I’d like to use C++ are: I prefer to use “inline” functions instead of macro definitions. I’d like to use namespaces as I prefixes clutter the code. I see C++ a bit type safer mainly because of templates, and verbose casting. I really like overloaded functions and constructors (used for automatic casting). Do you see any reason to stick with C89 when developing for very limited hardware (4kb of RAM)? Conclusion Thank you for your answers, they were really helpful! I though the subject through and I will stick with C mainly because: It is easier to predict actual code in C and this is really important if you have only 4kb of ram. My team consists of C developers mainly so advance features of C++ won't be frequently used. I've found a way to inline functions in my C compiler (C89). It is hard to accept one answer as you provided so many good answers. Unfortunately I can't create a wiki and accept it so I will choose one answer that made me think most.

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  • DRYing up Rails Views with Nested Resources

    - by viatropos
    What is your solution to the problem if you have a model that is both not-nested and nested, such as products: a "Product" can belong_to say an "Event", and a Product can also just be independent. This means I can have routes like this: map.resources :products # /products map.resources :events do |event| event.resources :products # /events/1/products end How do you handle that in your views properly? Note: this is for an admin panel. I want to be able to have a "Create Event" page, with a side panel for creating tickets (Product), forms, and checking who's rsvp'd. So you'd click on the "Event Tickets" side panel button, and it'd take you to /events/my-new-event/tickets. But there's also a root "Products" tab for the admin panel, which could list tickets and other random products. The 'tickets' and 'products' views look 90% the same, but the tickets will have some info about the event it belongs to. It seems like I'd have to have views like this: products/index.haml products/show.haml events/products/index.haml events/products/show.haml But that doesn't seem DRY. Or I could have conditionals checking to see if the product had an Event (@product.event.nil?), but then the views would be hard to understand. How do you deal with these situations? Thanks so much.

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  • Counting down to zero in contrast to counting up to length - 1

    - by Helper Method
    Is it recommended to count in small loops (where possible) down from length - 1 to zero instead of counting up to length - 1? 1.) Counting down for (int i = a.length - 1; i >= 0; i--) { if (a[i] == key) return i; } 2.) Counting up for (int i = 0; i < a.length; i++) { if (a[i] == key) return i; } The first one is slightly faster that the second one (because comparing to zero is faster) but is a little more error-prone in my opinion. Besides, the first one could maybe not be optimized by future improvements of the JVM. Any ideas on that?

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  • Working with multiple input and output files in Python

    - by Morlock
    I need to open multiple files (2 input and 2 output files), do complex manipulations on the lines from input files and then append results at the end of 2 output files. I am currently using the following approach: in_1 = open(input_1) in_2 = open(input_2) out_1 = open(output_1, "w") out_2 = open(output_2, "w") # Read one line from each 'in_' file # Do many operations on the DNA sequences included in the input files # Append one line to each 'out_' file in_1.close() in_2.close() out_1.close() out_2.close() The files are huge (each potentially approaching 1Go, that is why I am reading through these input files one at a time. I am guessing that this is not a very Pythonic way to do things. :) Would using the following form good? with open("file1") as f1: with open("file2") as f2: # etc. If yes, could I do it while avoiding the highly indented code that would result? Thanks for the insights!

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  • What ways are there for cleaning an R environment from objects?

    - by Tal Galili
    I know I can use ls() and rm() to see and remove objects that exist in my environment. However, when dealing with "old" .RData file, one needs to sometimes pick an environment a part to find what to keep and what to leave out. What I would like to do, is to have a GUI like interface to allow me to see the objects, sort them (for example, by there size), and remove the ones I don't need (for example, by a check-box interface). Since I imagine such a system is not currently implemented in R, what ways do exist? What do you use for cleaning old .RData files? Thanks, Tal

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  • Increasing your efficiency during programming

    - by Tom
    Yeah, yeah, I know, it is a little bit of offtopic, but let's try. So, I want to increase my efficiency during my programming as much as possible to programme as fast and sensibly as possiblle. What do you do before starting coding? Drink a lot of coffee, energy drinks? Do you listen to music during programming or you keep quite? Share your ideas.

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  • Fast read of certain bytes of multiple files in C/C++

    - by Alejandro Cámara
    I've been searching in the web about this question and although there are many similar questions about read/write in C/C++, I haven't found about this specific task. I want to be able to read from multiple files (256x256 files) only sizeof(double) bytes located in a certain position of each file. Right now my solution is, for each file: Open the file (read, binary mode): fstream fTest("current_file", ios_base::out | ios_base::binary); Seek the position I want to read: fTest.seekg(position*sizeof(test_value), ios_base::beg); Read the bytes: fTest.read((char *) &(output[i][j]), sizeof(test_value)); And close the file: fTest.close(); This takes about 350 ms to run inside a for{ for {} } structure with 256x256 iterations (one for each file). Q: Do you think there is a better way to implement this operation? How would you do it?

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  • [MySQL/PHP] Avoid using RAND()

    - by Andrew Ellis
    So... I have never had a need to do a random SELECT on a MySQL DB until this project I'm working on. After researching it seems the general populous says that using RAND() is a bad idea. I found an article that explains how to do another type of random select. Basically, if I want to select 5 random elements, I should do the following (I'm using the Kohana framework here)? If not, what is a better solution? Thanks, Andrew <?php final class Offers extends Model { /** * Loads a random set of offers. * * @param integer $limit * @return array */ public function random_offers($limit = 5) { // Find the highest offer_id $sql = ' SELECT MAX(offer_id) AS max_offer_id FROM offers '; $max_offer_id = DB::query(Database::SELECT, $sql) ->execute($this->_db) ->get('max_offer_id'); // Check to make sure we're not trying to load more offers // than there really is... if ($max_offer_id < $limit) { $limit = $max_offer_id; } $used = array(); $ids = ''; for ($i = 0; $i < $limit; ) { $rand = mt_rand(1, $max_offer_id); if (!isset($used[$rand])) { // Flag the ID as used $used[$rand] = TRUE; // Set the ID if ($i > 0) $ids .= ','; $ids .= $rand; ++$i; } } $sql = ' SELECT offer_id, offer_name FROM offers WHERE offer_id IN(:ids) '; $offers = DB::query(Database::SELECT, $sql) ->param(':ids', $ids) ->as_object(); ->execute($this->_db); return $offers; } }

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  • Where to store selected language on multilingual site: session/cookies or url?

    - by tig
    I have a site that has all its content translated to multiple languages and has no accounts (to set prefered language there). I can detect preferred language using Accept-Language, ip or anything else. I have 3 ways to store user language selection: Detect language and store it in cookie/session and allow switching language (and also store it in cookie/session) Use detected language if there is no language specified in url, and show links to url with different language Use default site language and show links to other languages Storing langage in url can be of any type: different domain, subdomain, or somewhere in url I think about first case as it allows me to send one url to anyone and it will be presented to them in their preferred language. But another opinion is that different language means different data, so it must have different link.

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  • What are the virtues of using XML comments in .NET?

    - by Michal Czardybon
    I can't understand the virtues of using XML comments. I know they can be converted into nice documentation external to the code, but the same can be achieved with the much more concise DOxygen syntax. In my opinion the XML comments are wrong, because: They obfuscate the comments and the code in general. (They are more difficult to read by humans). Less code can be viewed on a single screen, because "summary" and "/summary" take additional lines. They suggest that all method parameters have to be commented, whereas 90% of them are obvious and SHOULD be left not commented. The only problem I have with this is that my point of view seems to be in minority. Why?

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  • Choosing between instance methods and separate functions?

    - by StackedCrooked
    Adding functionality to a class can be done by adding a method or by defining a function that takes an object as its first parameter. Most programmers that I know would choose for the solution of adding a instance method. However, I sometimes prefer to create a separate function. For example, in the example code below Area and Diagonal are defined as separate functions instead of methods. I find it better this way because I think these functions provide enhancements rather than core functionality. Is this considered a good/bad practice? If the answer is "it depends", then what are the rules for deciding between adding method or defining a separate function? class Rect { public: Rect(int x, int y, int w, int h) : mX(x), mY(y), mWidth(w), mHeight(h) { } int x() const { return mX; } int y() const { return mY; } int width() const { return mWidth; } int height() const { return mHeight; } private: int mX, mY, mWidth, mHeight; }; int Area(const Rect & inRect) { return inRect.width() * inRect.height(); } float Diagonal(const Rect & inRect) { return std::sqrt(std::pow(static_cast<float>(inRect.width()), 2) + std::pow(static_cast<float>(inRect.height()), 2)); }

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  • Reverse search in Hibernate Search

    - by Javi
    Hello, I'm using Hibernate Search (which uses Lucene) for searching some Data I have indexed in a directory. It works fine but I need to do a reverse search. By reverse search I mean that I have a list of queries stored in my database I need to check which one of these queries match with a Data object each time Data Object is created. I need it to alert the user when a Data Object matches with a Query he has created. So I need to index this single Data Object which has just been created and see which queries of my list has this object as a result. I've seen Lucene MemoryIndex Class to create an index in memory so I can do something like this example for every query in a list (though iterating in a Java list of queries would not be very efficient): //Iterating over my list<Query> MemoryIndex index = new MemoryIndex(); //Add all fields index.addField("myField", "myFieldData", analyzer); ... QueryParser parser = new QueryParser("myField", analyzer); float score = index.search(query); if (score > 0.0f) { System.out.println("it's a match"); } else { System.out.println("no match found"); } The problem here is that this Data Class has several Hibernate Search Annotations @Field,@IndexedEmbedded,... which indicated how fields should be indexed, so when I invoke index() method on the FullTextEntityManager instance it uses this information to index the object in the directory. Is there a similar way to index it in memory using this information? Is there a more efficient way of doing this reverse search? Thanks

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  • What is the Proper approach for Constructing a PhysicalAddress object from Byte Array

    - by Paul Farry
    I'm trying to understand what the correct approach for a constructor that accepts a Byte Array with regard to how it stores it's data (specifically with PhysicalAddress) I have an array of 6 bytes (theAddress) that is constructed once. I have a source array of 18bytes (theAddresses) that is loaded from a TCP Connection. I then copy the 6bytes from theAddress+offset into theAddress and construct the PhysicalAddress from it. Problem is that the PhysicalAddress just stores the Reference to the array that was passed in. Therefore if you subsequently check the addresses they only ever point to the last address that was copied in. When I took a look inside the PhysicalAddress with reflector it's easy to see what's going on. public PhysicalAddress(byte[] address) { this.changed = true; this.address = address; } Now I know this can be solved by creating theAddress array on each pass, but I wanted to find out what really is the best practice for this. Should the constructor of an object that accepts a byte array create it's own private Variable for holding the data and copy it from the original Should it just hold the reference to what was passed in. Should I just created theAddress on each pass in the loop

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  • What is the proper way to code a read-while loop in Scala?

    - by ARKBAN
    What is the "proper" of writing the standard read-while loop in Scala? By proper I mean written in a Scala-like way as opposed to a Java-like way. Here is the code I have in Java: MessageDigest md = MessageDigest.getInstance( "MD5" ); InputStream input = new FileInputStream( "file" ); byte[] buffer = new byte[1024]; int readLen; while( ( readLen = input.read( buffer ) ) != -1 ) md.update( buffer, 0, readLen ); return md.digest(); Here is the code I have in Scala: val md = MessageDigest.getInstance( hashInfo.algorithm ) val input = new FileInputStream( "file" ) val buffer = new Array[ Byte ]( 1024 ) var readLen = 0 while( readLen != -1 ) { readLen = input.read( buffer ) if( readLen != -1 ) md.update( buffer, 0, readLen ) } md.digest The Scala code is correct and works, but feels very un-Scala-ish. For one it is a literal translation of the Java code, taking advantage of none of the advantages of Scala. Further it is actually longer than the Java code! I really feel like I'm missing something, but I can't figure out what. I'm fairly new to Scala, and so I'm asking the question to avoid falling into the pitfall of writing Java-style code in Scala. I'm more interested in the Scala way to solve this kind of problem than in any specific helper method that might be provided by the Scala API to hash a file. (I apologize in advance for my ad hoc Scala adjectives throughout this question.)

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  • Manipulating the address of a variable to store a smaller type?

    - by Sidnicious
    This is what I get for pampering myself with high-level programming languages. I have a function which writes a 32-bit value to a buffer, and a uint64_t on the stack. Is the following code a sane way to store it? uint64_t size = 0; // ... getBytes((uint32_t*)&size+0x1); I'm assuming that this would be the canonical, safe style: uint64_t size = 0; // ... uint32_t smallSize; getBytes(&smallSize); size = smallSize;

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  • Should non-English member names be changed to English?

    - by M.A. Hanin
    Situation: Automatically generated memebers, such as MenuStrip items, have their (automatically generated) names based on the text entered when the item was created. My most common situation is creating a menu-strip and adding menu-items by entering their text (using the graphical designer). Since my GUI is in Hebrew, all these members have a name which contains a Hebrew string. Something like "(hebrew-text)ToolStripItem". When I create event handlers, the event handlers "inherit" the hebrew text: "(hebrew-text)ToolStripMenuItem_Click". This actually works well, IntelliSense has no problem with Hebrew text, and so does the compiler. The question is: should I change these names (or prevent them from being created in the first place)? What are the possible consequences of keeping those names?

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  • How often to run getWritableDatabase() and getReadableDatabase()?

    - by jawonlee
    I'm writing a Service, a Content Provider, and one or more apps. The Service writes new data to the Content Provider's SQLite database every 5 minutes or so plus at user input, and is intended to run pretty much forever in the background. The app, when running, will display data pulled from the Content Provider, and will be refreshed whenever the Service puts more data into the Content Provider's database. Given that the Service only inserts into the database once every five minutes, when is the right time to call SQLiteOpenHelper's getWritableDatabase() / getReadableDatabase()? Is it on the onCreate() of the Content Provider, or should I run it every time there is an insert() and close it at the end of insert()? The data being inserted every 5 minutes will contain multiple inserts.

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  • What is the best way to store site configuration data?

    - by DaveDev
    I have a question about storing site configuration data. We have a platform for web applications. The idea is that different clients can have their data hosted and displayed on their own site which sits on top of this platform. Each site has a configuration which determines which panels relevant to the client appear on which pages. The system was originally designed to keep all the configuration data for each site in a database. When the site is loaded all the configuration data is loaded into a SiteConfiguration object, and the clients panels are generated based on the content of this object. This works, but I find it very difficult to work with to apply change requests or add new sites because there is so much data to sift through and it's difficult maintain a mental model of the site and its configuration. Recently I've been tasked with developing a subset of some of the sites to be generated as PDF documents for printing. I decided to take a different approach to how I would define the configuration in that instead of storing configuration data in the database, I wrote XML files to contain the data. I find it much easier to work with because instead of reading meaningless rows of data which are related to other meaningless rows of data, I have meaningful documents with semantic, readable information with the relationships defined by visually understandable element nesting. So now with these 2 approaches to storing site configuration data, I'd like to get the opinions of people more experienced in dealing with this issue on dealing with these two approaches. What is the best way of storing site configuration data? Is there a better way than the two ways I outlined here? note: StackOverflow is telling me the question appears to be subjective and is likely to be closed. I'm not trying to be subjective. I'd like to know how best to approach this issue next time and if people with industry experience on this could provide some input.

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  • Rank Source Control Options-VSS vs CVS vs none vs your own hell

    - by Roman A. Taycher
    It seems like a lot of people here and on many programmer wikis/blogs/ect. elsewhere really dislike VSS. A lot of people also have a serious dislike for cvs. In many places I have heard a lot of differing opinions on whether or not using VSS or cvs is better or worse then using no source control, please rate the worst and explain why!!!!! you rated them this way. Feel free to throw in your own horrible system in the rankings. If you feel it depends on the circumstances try to explain the some of the different scenarios which lead to different rankings. (note:I see a lot of discussion of what is better but little of what is worse.) second note: while both answers are nice I'm looking less for good replacements and more for a comparison of which is worse and more importantly why!

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  • Passing arguments and values from HTML to jQuery (events)

    - by Jaroslav Moravec
    What is the practice to pass arguments from HTML to jQuery events function. For example getting id of row from db: <tr class="jq_killMe" id="thisItemId-id"> ... </tr> and jQuery: $(".jq_killMe").click(function () { var tmp = $(this).attr('id).split("-"); var id = tmp[0] // ... } What's the best practise, if I want to pass more than one argument? Is it better not to use jQuery? For example: <tr onclick="killMe('id')"> ... </tr> I didn't find the answer on my question, I will be glad even for links. Thanks. Edit (pre solution) So you suggested two methods to do that: Add custom attributes to element (XHTML) Use attribute ID and parse it by regex Attribute data-* attributes in HTML5 Use hidden children elements I like first solution, but... I would like to (I have to (employer)) produce valid code. Here is a nice question and answers: http://stackoverflow.com/questions/994856/so-what-if-custom-html-attributes-arent-valid-xhtml And the second is not so pretty as the first, but valid. So the compromise is... The third is the solution for future, but here is a lot of CMS where we have to use XHTML or HTML4. (And HTML5 is the long process)

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  • Best way for user authentication on JavaEE 6 using JSF 2.0?

    - by ngeek
    I'm wondering what the current state of art recommendation is regarding user authentication for a web application making use of JSF 2.0 (and if any components do exist) and JEE6 core mechanisms (login/check permissions/logouts) with user information hold in a JPA entity. The Sun tutorial is a bit sparse on this (only handles servlets). This is without making use of a whole other framework, like Spring-Security (acegi), or Seam, but trying to stick hopefully with the new Java EE 6 platform (web profile) if possible. Thanks, Niko

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