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  • Is it good practice to initialize array in C/C++?

    - by sand
    I recently encountered a case where I need to compare two files (golden and expected) for verification of test results and even though the data written to both the files were same, the files does not match. On further investigation, I found that there is a structure which contains some integers and a char array of 64 bytes, and not all the bytes of char array were getting used in most of the cases and unused fields from the array contain random data and that was causing the mismatch. This brought me ask the question whether it is good practice to initialize the array in C/C++ as well, as it is done in Java?

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  • undefined method `events' for #<ActiveRecord::Relation:0x4177518> -rails 3.0.3

    - by brg
    I am having this unexplained NoMethodError with undefined method `events' for #. I don't know why since my model association are well defined and the event table has the foreign keys for the user table. I tried using this fix but it failed: Rails 3 ActiveRecord::Relation random associations behavior event.rb class Event < ActiveRecord::Base belongs_to :user attr_accessible :event_name, :Starts_at, :finish, :tracks end user.rb class User < ActiveRecord::Base has_many :events, :dependent = :destroy attr_accessible :name, :event_attributes accepts_nested_attributes_for :events, :allow_destroy = true end schema.rb ActiveRecord::Schema.define(:version = 20101201180355) do create_table "events", :force = true do |t| t.string "event_name" t.string "tracks" t.datetime "starts_at" t.datetime "finish" t.datetime "created_at" t.datetime "updated_at" t.integer "user_id" end end error message NoMethodError in Users#index undefined method `events' for # Extracted source (around line #10): 7: <%= sortable "Tracks" % 8: 10: <% @users.events.each do |event| % 11: <% debugger % 12: 13: <%= event.starts_at % Trace of template inclusion: app/views/users/index.html.erb Rails.root: C:/rails_project1/events_manager Application Trace | Framework Trace | Full Trace app/views/users/_event_user.html.erb:10:in _app_views_users__event_user_html_erb__412443848_34308540_1390678' app/views/users/index.html.erb:7:in_app_views_users_index_html_erb___603337143_34316016_0'

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  • Is it possible to cache all the data in a SQL Server CE database using LinqToSql?

    - by DanM
    I'm using LinqToSql to query a small, simple SQL Server CE database. I've noticed that any operations involving sub-properties are disappointingly slow. For example, if I have a Customer table that is referenced by an Order table, LinqToSql will automatically create an EntitySet<Order> property. This is a nice convenience, allowing me to do things like Customer.Order.Where(o => o.ProductName = "Stopwatch"), but for some reason, SQL Server CE hangs up pretty bad when I try to do stuff like this. One of my queries, which isn't really that complicated takes 3-4 seconds to complete. I can get the speed up to acceptable, even fast, if I just grab the two tables individually and convert them to List<Customer> and List<Order>, then join then manually with my own query, but this is throwing out a lot of what makes LinqToSql so appealing. So, I'm wondering if I can somehow get the whole database into RAM and just query that way, then occasionally save it. Is this possible? How? If not, is there anything else I can do to boost the performance besides resorting to doing all the joins manually? Note: My database in its initial state is about 250K and I don't expect it to grow to more than 1-2Mb. So, loading the data into RAM certainly wouldn't be a problem from a memory point of view. Update Here are the table definitions for the example I used in my question: create table Order ( Id int identity(1, 1) primary key, ProductName ntext null ) create table Customer ( Id int identity(1, 1) primary key, OrderId int null references Order (Id) )

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  • detecting returned errors with $.post

    - by sova
    I'm using $.post to send a query to a JSP which returns some awesome data for me. If the query is malformed, however, the page returns with "error on page" and an HTTP Status of 500 Internal Server Error in jQuery, how can I detect this error so I can tell the user of the failure? runQuery : function () { $.post( admin_stats.runQueryURL, { buster : Math.random, statsQuery: admin_stats.getQuery(), jsp: 'admin_statsQuery' }, admin_stats.handleStatsQuery, "html" ); the returned data is an HTML table which is sufficient for this project at the moment. Also: totally open to criticism if this is ugly or not the way I should be doing things =)

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  • jquery animate() problem (syntax ?)

    - by meo
    $('#somediv').stop(false, true).animate({marginLeft: '-=' + e.width() + 'px'}, options.speed, function(){ options.onNewSlide() }) e.with() returns 640 opctions.speed contains 800 options.onNewSlide() contains a a custom callback function It works fine in firefox. But i debugged it with jquery.lint because it was throwing some random error in IE. lint tells me: When I called animate(...) with your args, an error was thrown! TypeError: c.speed is not a function { message="c.speed is not a function", more...} You passed: [Object { marginLeft="-=640px"}, 800, function()] and it indicates me the line i have posted. I have checked the jquery doc, but my syntax seams ok. Do you know what i am doing wrong? PS: i use jquery 1.4.2 from the google API you can see the error here: http://meodai.ch/slider/ (i know the code is under construction, but still)

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  • C Population Count of unsigned 64-bit integer with a maximum value of 15

    - by BitTwiddler1011
    I use a population count (hamming weight) function intensively in a windows c application and have to optimize it as much as possible in order to boost performance. More than half the cases where I use the function I only need to know the value to a maximum of 15. The software will run on a wide range of processors, both old and new. I already make use of the POPCNT instruction when Intel's SSE4.2 or AMD's SSE4a is present, but would like to optimize the software implementation (used as a fall back if no SSE4 is present) as much as possible. Currently I have the following software implementation of the function: inline int population_count64(unsigned __int64 w) { w -= (w 1) & 0x5555555555555555ULL; w = (w & 0x3333333333333333ULL) + ((w 2) & 0x3333333333333333ULL); w = (w + (w 4)) & 0x0f0f0f0f0f0f0f0fULL; return int(w * 0x0101010101010101ULL) 56; } So to summarize: (1) I would like to know if it is possible to optimize this for the case when I only want to know the value to a maximum of 15. (2) Is there a faster software implementation (for both Intel and AMD CPU's) than the function above?

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  • How can I write a function template for all types with a particular type trait?

    - by TC
    Consider the following example: struct Scanner { template <typename T> T get(); }; template <> string Scanner::get() { return string("string"); } template <> int Scanner::get() { return 10; } int main() { Scanner scanner; string s = scanner.get<string>(); int i = scanner.get<int>(); } The Scanner class is used to extract tokens from some source. The above code works fine, but fails when I try to get other integral types like a char or an unsigned int. The code to read these types is exactly the same as the code to read an int. I could just duplicate the code for all other integral types I'd like to read, but I'd rather define one function template for all integral types. I've tried the following: struct Scanner { template <typename T> typename enable_if<boost::is_integral<T>, T>::type get(); }; Which works like a charm, but I am unsure how to get Scanner::get<string>() to function again. So, how can I write code so that I can do scanner.get<string>() and scanner.get<any integral type>() and have a single definition to read all integral types? Update: bonus question: What if I want to accept more than one range of classes based on some traits? For example: how should I approach this problem if I want to have three get functions that accept (i) integral types (ii) floating point types (iii) strings, respectively.

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  • Hard drive randomly sppeeding up

    - by Glenn Taylor
    Having a weird issue with my hard drive. Running Windows 7 with an I5 processor. At random times the hard drive will start running at top speed and gradually return to normal over the next two minutes or so. Going to Resource Monitor it shows a variety of things with high read or write numbers. Log files NTFS volume log, Windows prefetch, System/user/appdata, and Program data Norton are the usual top ones listed. This just started about three months ago although the computer is about 3 years old. Have run in safe mode with internet over the weekend going to all of my usual sites with no such speed up. Question 1 - what can be causing this? Question 2 - how can I find out where data is being sent(especially if over the net)? Thank you.

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  • O(N log N) Complexity - Similar to linear?

    - by gav
    Hey All, So I think I'm going to get buried for asking such a trivial but I'm a little confused about something. I have implemented quicksort in Java and C and I was doing some basic comparissons. The graph came out as two straight lines, with the C being 4ms faster than the Java counterpart over 100,000 random integers. The code for my tests can be found here; android-benchmarks I wasn't sure what an (n log n) line would look like but I didn't think it would be straight. I just wanted to check that this is the expected result and that I shouldn't try to find an error in my code. I stuck the formula into excel and for base 10 it seems to be a straight line with a kink at the start. Is this because the difference between log(n) and log(n+1) increases linearly? Thanks, Gav

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  • What things can I teach a group of children about programming in one day?

    - by Rich Bradshaw
    I'm running a day for 30 kids aged 11-18 about computer game programming. They have all opted to do it, but they have no experience at all of programming. My main aim is for them to learn a few things: programming is hard/challenging programming is something they can learn to do being a computer games programmer != playing games all day a little more insight into how games actually work I'd thought of splitting them into two groups, of younger/less experience and older/more experience, then doing slightly different things. I'd considered showing them Scratch, Game Maker, before showing them the basics of Python and getting them to write a simple text based game (perhaps something like, computer picks a random number, you have to guess it in as few guesses as possible, computer says higher/lower for each guess). Does anyone have any ideas of things to do/show them/ways to teach them?

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  • Security issues in accepting passwords vs auto generating the password

    - by Vivekanand Poojari
    Hi, I am developing a console application. This application generates a self signed certificate and installs it in the current machine's certificate store. The steps invlolved are :- Generate a certificate Create a pfx file Install the pfx file For these steps i would need a password for protecting the private key and the pfx file. However these passwords are used only during the execution of the exe. Should I auto generate a password using some random number generation algorithm or accept the password as input from the user? What are the security issues involved in both the scenarios ? Thanks Vivekanand

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  • Should I Use GUID or IDENTITY as Thread Number?

    - by user311509
    offerID is the thread # which represents the thread posted. I see in forums posts are represented by random numbers. Is this achieved by IDENTITY? If not, please advice. nvarchar(max) will carry all kind of texts along with HTML tags. CREATE TABLE Offer ( offerID int IDENTITY (4382,15) PRIMARY KEY, memberID int NOT NULL REFERENCES Member(memberID), title nvarchar(200) NOT NULL, thread nvarchar(max) NOT NULL, . . . );

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  • Proper use of use of "cor" function in R

    - by order
    I am interested to know what a proper x (vector matrix or data frame) input looks like. I am currently using the function in two different sorts of matrices. However, I am not sure how R would interpret my data the way I intend. I will explain the types of matrix by example. Type 1 Gene1 Gene2 Gene3 sample1 sample2 Type 2 Sample1 Sample2 Sample3 gene 1 gene 2 gene 3 Are either of these formats valid x parameters? I input both of types of matrices and get some results, but without knowing whether or not this a proper use the function, these are just random numbers. Thank you for your time. I apologize that this isn't more interesting.

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  • Address of array vs. address of array[0] - C language

    - by user324994
    My question is why does the address of an array differ from the address of its first position? I'm trying to write my own malloc, but to start out I'm just allocating a chunk of memory and playing around with the addresses. My code looks roughly like this: #define BUFF_SIZE 1024 static char *mallocbuff; int main(){ mallocbuff = malloc(BUFF_SIZE); printf("The address of mallocbuff is %d\n", &mallocbuff); printf("The address of mallocbuff[0] is %d\n", &mallocbuff[0]); } &mallocbuff is the same address every time I run it. &mallocbuff[0] is some random address every time. I was expecting the addresses to match each other. Can anyone explain why this isn't the case?

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  • Detecting when a process has finished (but not exited)

    - by Egwor
    I have a program that's run in unix (that I have no control over) that when finished prints 'Completed successfully' but does not exit. I want to automatically detect when the process finishes (by checking the output of the command), so that I can kill the process and so that I can proceed do other activities. The complexity comes because I want to be able to run multiples of these scripts concurrently. (One activity I need to do requires the script to be called with various inputs, but each time the script runs it takes a while to return, and so I want to do them in parallel) Has anyone done something similar to this? I could redirect the stderr and stdout output of the command to a temporary file which has a random file name, then tail the file and pipe to grep for the end conditions (I.e. the certain log lines). The problem is, surely tail -f would keep running, and so it would never exit. Should I poll? If so, what's the best approach?

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  • Prevent Apache from answering invalid requests

    - by nickdnk
    I have an Apache web-server that acts as a web front-end for iPhone and iPad applications that communicate by POST and JSON only. Is there any way to prevent Apache from answering requests that are invalid? I can see my error log is filled with attempts to open files such as /admin.php /index.php etc - files that don't exist on my server. I believe this is possible with IIS, but can you do the same thing with Apache? Basically I want the request to appear timed out unless you post exactly the right content to the right file - or at least if you do not request an existing file. This would make the server appear non-existing to everyone but my iPhone users as all communication is SSL and directories are not really guess-able. I did disable the ServerTokens and all that, but I still get File not found etc. when I access the server requesting a random file, which is what these bots do constantly.

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  • Simple integer encryption

    - by tloflin
    Is there a simple algorithm to encrypt integers? That is, a function E(i,k) that accepts an n-bit integer and a key (of any type) and produces another, unrelated n-bit integer that, when fed into a second function D(i,k) (along with the key) produces the original integer? Obviously there are some simple reversible operations you can perform, but they all seem to produce clearly related outputs (e.g. consecutive inputs lead to consecutive outputs). Also, of course, there are cryptographically strong standard algorithms, but they don't produce small enough outputs (e.g. 32-bit). I know any 32-bit cryptography can be brute-forced, but I'm not looking for something cryptographically strong, just something that looks random. Theoretically speaking it should be possible; after all, I could just create a dictionary by randomly pairing every integer. But I was hoping for something a little less memory-intensive.

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  • Having trouble getting GET variables from url.

    - by mchl
    Hey everyone, I'm having trouble with this algorithm to extract the get variables from a url and print them each on a new line like: x=y z=hello etc. but instead it prints a seemingly random section of the url with no newlines to the file. There must be a logic error of some kind but i just can't spot it. for(i_m=0;i_m<len_m;i_m++) { if(var_m[i_m]=='&') { fwrite(var_m+offset_m, 1, amp_m, echo_out); fputc('\n',echo_out); offset_m+=amp_m; amp_m=0; } amp_m++; } any help appreciated.

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  • Reading line by line from a file in C

    - by mh234
    What I am trying to do is print out the contents of a file line by line. I run the program in terminal by doing: ./test testText.txt. When I do this, random characters are printed out but not what is in the file. The text file is located in the same folder as the makefile. What's wrong? #include <stdio.h> FILE *fp; int main(int argc, char *argv[]) { char line[15]; fp = fopen(*argv, "r"); while((fgets(line, 15, fp)) != NULL) { printf(line); printf("\n"); } }

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  • C++/Qt - Memory allocation question

    - by HardCoder1986
    Hello! I recently started investigating Qt for myself and have the following question: Suppose I have some QTreeWidget* widget. At some moment I want to add some items to it and this is done via the following call: QList<QTreeWidgetItem*> items; // Prepare the items QTreeWidgetItem* item1 = new QTreeWidgetItem(...); QTreeWidgetItem* item2 = new QTreeWidgetItem(...); items.append(item1); items.append(item2); widget->addTopLevelItems(items); So far it looks ok, but I don't actually understand who should control the objects' lifetime. I should explain this with an example: Let's say, another function calls widget->clear();. I don't know what happens beneath this call but I do think that memory allocated for item1 and item2 doesn't get disposed here, because their ownage wasn't actually transfered. And, bang, we have a memory leak. The question is the following - does Qt have something to offer for this kind of situation? I could use boost::shared_ptr or any other smart pointer and write something like shared_ptr<QTreeWidgetItem> ptr(new QTreeWidgetItem(...)); items.append(ptr.get()); but I don't know if the Qt itself would try to make explicit delete calls on my pointers (which would be disastrous since I state them as shared_ptr-managed). How would you solve this problem? Maybe everything is evident and I miss something really simple?

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  • How can I make a table move in JavaScript?

    - by Michal Skrzypek
    My problem is that I was creating a simple website the other day and I needed the content to move according to the button pressed. I managed to do so in CSS3, but the solution did not work for IE whatsoever. Therefore I would like to ask if there is a simple solution for that in js? I don't know js at all but I heard what I need is much easier in js than in css. Details: http://i42.tinypic.com/6yl4ia.png I need the table in the picture to move according to the buttons (which are labels to be exact). The visible area is a div. Here's the relevant code (without animation as I was not satisfied with it): body { background-color: #fff; color: #fff; padding:0px; } #bodywrapperfixed { width: 1248px; margin: 0px auto; position: relative; overflow: hidden; height: 730px; } #bodywrapper { display:block; background-color: #fff; width: 1248px; color: #59595B; padding-top:50px; font-family: 'Roboto', sans-serif; position: absolute; top:0px; left:0px; z-index:1; font-size: 60px; height:730px; } #bodywrapper img { width:400px; padding:15px 0px 20px 0px; } #texten { font-family: 'Roboto', sans-serif; font-size: 35px; padding:5px; } #textpl { font-family: 'Roboto', sans-serif; font-size: 25px; padding:5px; } table#linki { width: 110px; border: none; margin-top:15px; } label { display: block; height: 54px; width: 54px; color:#fff; font-family: 'Roboto', sans-serif; font-weight: 300; font-size: 35px; background-color: #117D10; text-align: center; padding:23px; } label:hover { background-color: #004F00; cursor: pointer; } input#pl { position: absolute; top: -9999px; left: -9999px; } input#en { position: absolute; top: -9999px; left: -9999px; } and the relevant HTML: <div id="bodywrapperfixed"> <div id="bodywrapperfloat"> <table id="ramka"> <tr> <td>random text</td> <td><div id="bodywrapper"> <center> <div id="texten"><div style="font-weight:300; display:inline-block;">Introducing the all-in-one entertainment system.</div><div style="font-weight:500; display:inline-block;">&nbsp;For everyone.</div></div> <div id="textpl"><div style="font-weight:300; display:inline-block;">Przedstawiamy zintegrowany system rozrywki.</div><div style="font-weight:500; display:inline-block;">&nbsp;&nbsp;Dla wszystkich.</div></div> <img src="imgs/xboxone.png"> <div id="texten"><div style="font-weight:300; display:inline-block;">Choose your version of the story:</div></div> <div id="textpl"><div style="font-weight:300; display:inline-block;">Wybierz swoja wersja opowiesci:</div></div> <table id="linki"> <tr> <td><label for="en">en</label><input id="en" type="checkbox"></td> <td><label for="pl">pl</label><input id="pl" type="checkbox"></td> </tr></table> </center> </div></td> <td>random text</td> </tr> </table> </div> </div> Here's what it looks like: http://ingame.lh.pl/thinkone/ Please help me.

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  • ODBC - multiple connections from one app to the same data source

    - by Marcin K
    I vaguely remember reading somewhere (in MSDN ODBC documentation?) that one application cannot make more than one connection to a single data source. It seemed to me that I need one connection that all the threads of the application will have to share. I was trying to look this information up, but I can't seem to find it anymore. Does anyone know/remember how this works? It all might become a problem in our app, since some of its threads will dynamically connect to data sources of their choice. I don't want to see random connection errors if two of them will connect at the same time to one source, so I wanted to double check this info.

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  • Flex Filterfunction - Filter by Array of values

    - by Anandh
    How to filter an Arraycollection by "array of values" rather than a single value (simple comparision) , the below code snippet is for filtering by single value now I went into scenario like filter out only price [10,4,1,8] (some random values from the master collection). Is there any better way to do the second code snippet Filter function simple comparision private function filterForTestData(item:Object):Boolean{ if(item.price < slider.value) return true; else return false; } Filter by array of values private function filterForTestData(item:Object,filterBy:Array= [10,4,1,8]):Boolean{ for(randomprice in filterBy) return item.price == randomprice; } [Edited] Apply Filter testData.filterFunction = filterForTestData;

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  • reading partially from sockets

    - by nomad.alien
    I'm having a little test program that sends a lot of udp packets between client-server-client (ping/pong test). The packets are fixed size on each run(last run is max allowable size of udp packet) I'm filling the packets with random data except for the beginning of each packet that contains the packet number. So I'm only interested to see if I receive all the packets back at the client. I'm using sendto() and recvfrom() and I only read the sizeof(packet_number) (which in this case is an int). What happens to the rest of the data? Does it end up in fairyland (gets discarded)? or does the new packet that arrives gets appended to this "old" data? (using linux)

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  • How to achieve jQuery scrolling/overlay effect (video in description)

    - by waffl
    I have two columns. The left column contains text of dynamic lengths. The right column is of fixed height and will contain a set of images selected at random per page load. I am trying to create an effect where while the user scrolls, the Image 2 scrolls above Image 1. When it reaches the top, the Image 1 begins to scroll up until it disappears, then Image 3 comes in and repeats the process. As this is rather confusing, I made a short video describing the desired effect. Video - MP4 I have begun trying to get it working in this jsbin but am at a loss for when the user scrolls back down and also when more images are required. I am thinking my current path is not the right direction. I'm thinking that employing something like jQuery waypoints is more the direction I should be pursuing?

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