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  • lock file so that it cannot be deleted

    - by JoeCool
    I'm working with two independent c/c++ applications on Windows where one of them constantly updates an image on disk (from a webcam) and the other reads that image for processing. This works fine and dandy 99.99% of the time, but every once in a while the reader app is in the middle of reading the image when the writer deletes it to refresh it with a new one. The obvious solution to me seems to be to have the reader put some sort of a lock on the file so that the writer can see that it can't delete it and thus spin-lock on it until it can delete and update. Is there anyway to do this? Or is there another simple design pattern I can use to get the same sort of constant image refreshing between two programs? Thanks, -Robert

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  • Vectorizing sums of different diagonals in a matrix

    - by reve_etrange
    I want to vectorize the following MATLAB code. I think it must be simple but I'm finding it confusing nevertheless. r = some constant less than m or n [m,n] = size(C); S = zeros(m-r,n-r); for i=1:m-r for j=1:n-r S(i,j) = sum(diag(C(i:i+r-1,j:j+r-1))); end end The code calculates a table of scores, S, for a dynamic programming algorithm, from another score table, C. The diagonal summing is to generate scores for individual pieces of the data used to generate C, for all possible pieces (of size r). Thanks in advance for any answers! Sorry if this one should be obvious...

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  • How can I work around the fact that in C++, sin(3.14159265) is not 0?

    - by Adam Doyle
    In C++, const double Pi = 3.14159265; cout << sin(Pi); // displays: 3.58979e-009 it SHOULD display the number zero I understand this is because Pi is being approximated, but is there any way I can have a value of Pi hardcoded into my program that will return 0 for sin(Pi)? (a different constant maybe?) In case you're wondering what I'm trying to do: I'm converting polar to rectangular, and while there are some printf() tricks I can do to print it as "0.00", it still doesn't consistently return decent values (in some cases I get "-0.00") The lines that require sin and cosine are: x = r*sin(theta); y = r*cos(theta); BTW: My Rectangular - Polar is working fine... it's just the Polar - Rectangular Thanks! edit: I'm looking for a workaround so that I can print sin(some multiple of Pi) as a nice round number to the console (ideally without a thousand if-statements)

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  • PHPDelicious - Fail to Connect to Delicious

    - by Meander365
    phpdelicious (http://www.phpdelicious.com/) is a wrapper class for pulling in your delicious bookmarks using php. But I can't get it to work. Here's my code - my index.php: <?php require('php-delicious.inc.php'); define('DELICIOUS_USER', 'my-user-name-here'); define('DELICIOUS_PASS', 'my-password-here'); $oDelicious = new PhpDelicious(DELICIOUS_USER, DELICIOUS_PASS); ?> <?php if ($aPosts = $oDelicious->GetAllPosts()) { foreach ($aPosts as $aPost) { echo '<a href="'.$aPost['url'].'">'.$aPost['desc'].'</a>'; echo $aPost['notes']; echo $aPost['updated']; } } else { echo $oDelicious->LastErrorString(); } ?> But I get this error : Notice: Use of undefined constant CACHE_PATH - assumed 'CACHE_PATH' in C:\wamp\www\testing\cache.inc.php on line 44 Connection to del.icio.us failed. Any ideas?

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  • Cannot get mysql gem to work in Snow Leopard, unable to setup ruby on rails environment

    - by user325020
    I am having some serious problems, however this seems to be a common thing. I have Snow Leopard 10.6.3 and here are my other version info: MySQL mysql Ver 14.14 Distrib 5.1.46, for apple-darwin10.2.0 (i386) using readline 5.1 gem 1.3.6 ruby 1.8.7 (2009-06-08 patchlevel 173) [universal-darwin10.0] My problem is that no matter what I do to try and install the mysql gem, i still get the error every time i do rake db:migrate uninitialized constant MysqlCompat::MysqlRes I have installed the mysql gem based on instructions around the web that say to use export ARCHFLAGS="-arch i386 -arch x86_64" ; sudo gem install --no-rdoc --no-ri mysql -- -v 2.7 --with-mysql-dir=/usr/local --with-mysql-config=/usr/local/mysql/bin/mysql_config This DOES work, as it gives this output: Building native extensions. This could take a while... Successfully installed mysql-2.8.1 1 gem installed Any help would be greatly appreciated

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  • Distance from a point to a polygon

    - by clwen
    I am trying to determine the distance from a point to a polygon in 2D space. The point can be inside or outside the polygon; The polygon can be convex or concave. If the point is within the polygon or outside the polygon with a distance smaller than a user-defined constant d, the procedure should return True; False otherwise. I have found a similar question: Distance from a point to a polyhedron or to a polygon. However, the space is 2D in my case and the polygon can be concave, so it's somehow different from that one. I suppose there should be a method simpler than offsetting the polygon by d and determining it's inside or outside the polygon. Any algorithm, code, or hints for me to google around would be appreciated.

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  • maths: motion depending on time

    - by clamp
    hello, i have a mathematical problem: i have a function where the only parameter is the current time. the return should be a position which is used to place an object on a certain place. int position(int time) { int x = 0; //TODO implement x depending on time return x; } so basically the function is called every frame to put the object in motion. the motion should look like this (this is the actual question): a linear motion for time A, the object moves at constant speed no motion for time B, the object is stopped repeat at 1. thanks!

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  • How can my CGI program access non-browseable files?

    - by Zerobu
    I was wondering if it was possible to read a text file that was located in a directory called "/home/user/files" I wanted to read it from my cgi-bin which is located in /home/user/cgi-bi/ Below is my code, #!/usr/bin/perl use strict; use CGI; #Virtual Directory #Steffan Harris eval { use constant PASSWORD => 'perl'; use constant UPLOAD_DIR => '/home/sharris2/files'; sub mapToFile { print chdir UPLOAD_DIR; } #This function will list all files in a directory. sub listDirectoryFiles { chdir UPLOAD_DIR; my @files = <*>; mapToFile; print<<LIST; <h2>Current Files</h2> <ul> LIST if(!$files[0]) { print" </ul>\n<em>No files in directory</em>"; } foreach(@files) { print" <li>$_</li>"; } print " </ul>\n"; } #This function generates a 404 Not Found error sub generate404 { print<<RESPONSE; Status: 404 Not Found Content-Type: text/html <html> <head><title>404 Not Found</title></head> <body> <p> <h1>404 - Not Found</h1> </p> The requested URL <b>$ENV{"HTTP_HOST"}$ENV{"REQUEST_URI"}</b> was not found on the server. </body> </html> RESPONSE exit; } #This function checks the path info to see if it matches a file in the UPLOAD_DIR directory, If it does not, then it returns a 404 error sub checkExsistence { if($ENV{"PATH_INFO"}) { chdir UPLOAD_DIR; my @files = <*>; if(!$files[0] and $ENV{"PATH_INFO"} eq "/") { return; } foreach(@files) { if($ENV{"PATH_INFO"} eq "/".$_ || $ENV{"PATH_INFO"} eq "/") { print "yes"; return; } } generate404; } } sub checkPassword { my ($password, $cgi); $cgi = new CGI; $password = $cgi->param('passwd'); unless($password eq PASSWORD) { print<<RESPONSE; Status: 200 OK Content-Type: text/html <html> <head> <title>Incorrect Password</title> </head> <body> <h1>Invalid password entered.</h1> <h3><a href="/~sharris2/cgi-bin/files/">Go Back</a></h3> </body> RESPONSE exit; } } sub upLoadFile { checkPassword; my ($uploadfile, $cgi); $cgi = new CGI; $uploadfile = $cgi->upload('uploadfile'); chdir UPLOAD_DIR; $uploadfile or die "Did not receive a file to upload"; open my $FILE, '>', UPLOAD_DIR."/$uploadfile" or die "$!"; while(<$uploadfile>) { print $FILE $_; } } #Start of main part of program my $cgi = new CGI; if(!$ENV{"PATH_INFO"}) { print $cgi->redirect('/~sharris2/cgi-bin/files/'); } checkExsistence; if($ENV{"REQUEST_METHOD"} eq "POST") { upLoadFile; } print <<"HEADERS"; Status: 200 OK Content-Type: text/html HEADERS print <<"HTML"; <html> <head> <title>Virtual Directory</title> </head> <body> HTML listDirectoryFiles; print<<HTML; <h2>Upload a new file</h2> <form method = "POST" enctype = "multipart/form-data" action = "/~sharris2/cgi-bin/files/" /> File:<input type = "file" name="uploadfile"/> <p>Password: <input type = "password" name ="passwd"/></p> <p><input type = "submit" value= "Submit File" /></p> </form> </body> </html> HTML };

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  • Assigning an @Annotation enum a value

    - by h2g2java
    I created enum Restrictions{ none, enumeration, fractionDigits, length, maxExclusive, maxInclusive, maxLength, minExclusive, minInclusive, minLength, pattern, totalDigits, whiteSpace; public Restrictions setValue(int value){ this.value = value; return this; } public int value; } So that I could happily do something like this, which is perfectly legal syntax. Restrictions r1 = Restrictions.maxLength.setValue(64); The reason being is, I am using enum to restrict the type of restriction that could be used, and be able to assign a value to that restriction. However, my actual motivation is to use that restriction in an @annotation. @Retention(RetentionPolicy.RUNTIME) @Target({ElementType.TYPE, ElementType.FIELD, ElementType.METHOD}) public @interface Presentable { Restrictions[] restrictions() default Restrictions.none; } So that, I intended to do this: @Presentable(restrictions=Restrictions.maxLength.setValue(64)) public String userName; to which, the compiler croaks The value for annotation enum attribute must be an enum constant expression. Is there a way to accomplish what I wish to accomplish

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  • long integer problem

    - by hopefulLLl
    hello friends,, m a beginner at c language.. m using turbo c ++ compiler 16 bit. nw the max answer obtained by me is aaround 32000.. nw if i want a number larger that that then i use long int.. if i execute the following programme.. #include <stdio.h> void main() { long int x; x=40000; printf("%d", x); } then i get error that constant value is long in function main().. kindly tell me how to get an answer more that 32000 by getting rid of this error! thnx..

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  • Thread vs ThreadPool - .Net 2.0

    - by NLV
    Hello I'm not able to understand the difference between Thread vs ThreadPool. Consider i've to manipulate 50,000 records using threads. In case of threads i need to either predefine no of threads or no of records per threads. Either of them has to be constant. In case of threadpool we dont need to set any of them theoretically. But practically we need to assign the number of records per thread, because the no of threads may grow extremely large if the input no of records is huge. Any insights on this?

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  • ruby in 100 minutes good_morning method issue

    - by user2525947
    I have been doing the Ruby in 100 minutes on the JumpStart labs website, and encountered a problem during part 5. I was asked to create a good_morning method that would print out a greeting such as 'Happy Monday, it's the 130 day of 2013'. Here is my current program: class PersonalChef def good_morning today = Date.today.strftime("%A") day_of_year = Date.today.yday puts "Happy#{today}! It is the #{day_of_year} day of year." return self end def make_toast(color) puts " Making your toast #{color}!" return self end def make_milkshake(flavor) puts " Making a #{flavor} milkshake!" return self end def make_eggs(quantity) puts " Making you #{quantity} eggs!" return self end end when I try to run the program load on irb( 'personal_chef.rb', frank = PersonalChef.new, frank.make_milkshake('chocolate'), etc, everything works fine until I try to type frank.good_morning into irb, which gives the following error message: NameError: uninitialized constant PersonalChef :: Date from personal_chef.rb:5: in good_morning from (irb):3 from /bin/irb:12:in '' Any help or information to help me solve this issue would be greatly appreciated. Thanks for your time!

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  • mmap() for large file I/O?

    - by Boatzart
    I'm creating a utility in C++ to be run on Linux which can convert videos to a proprietary format. The video frames are very large (up to 16 megapixels), and we need to be able to seek directly to exact frame numbers, so our file format uses libz to compress each frame individually, and append the compressed data onto a file. Once all frames are finished being written, a journal which includes meta data for each frame (including their file offsets and sizes) is written to the end of the file. I'm currently using ifstream and ofstream to do the file i/o, but I am looking to optimize as much as possible. I've heard that mmap() can increase performance in a lot of cases, and I'm wondering if mine is one of them. Our files will be in the tens to hundreds of gigabytes, and although writing will always be done sequentially, random access reads should be done in constant time. Any thoughts as to whether I should investigate this further, and if so does anyone have any tips for things to look out for? Thanks!

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  • The best way to assign an immutable instance to a Collection in Java

    - by Ali
    Today I was reading through some Hibernate code and I encounter something interesting. There is a class called CollectionHelper that defines the following constant varibale: public final class CollectionHelper { public static final List EMPTY_LIST = Collections.unmodifiableList( new ArrayList(0 ) ; public static final Collection EMPTY_COLLECTION = Collections.unmodifiableCollection(new ArrayList(0) ); public static final Map EMPTY_MAP = Collections.unmodifiableMap( new HashMap(0) ); They have used these constants to initialize collections with immutable instances. Why they didn't simply use the Collections.EMPTY_LIST for initializing lists? Is there a benefit in using the following method?

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  • Optional read from STDIN in C

    - by Yuval A
    My application is basically a shell which expects an input of type cmd [x], where cmd is constant and x is optional. So cmd 1 is legal as well as cmd by itself - then I assume a default parameter for x. I am doing this: char cmd[64]; scanf("%s", cmd); int arg; scanf("%d", &arg); // but this should be optional How can I read the integer parameter, and set it to a default if none is currently available in the prompt? I do not want the prompt to wait for additional input if it was not given in the original command. I tried several versions using fgetc() and getchar() and comparing them to EOF but to no avail. Each version I tried ends up waiting on that optional integer parameter.

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  • mod,prime -> inverse possible

    - by Piet
    Hi all. I was wondering if one can do the following: We have: X is a product of N-primes, thus I assume unique. C is a constant. We can assure that C is a number that is part of the N-primes or not. Whichever will work best. Thus: X mod C = Z We have Z and C and we know that X was a product of N-primes, where N is restricted lets say first 100 primes. Is there anyway we can get back X?

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  • FFmpeg bitrate issue.

    - by user329840
    I'm dealing with a very big issue about bit rate , ffmpeg provide the -b option for the bit rate and for adjustment it provide -minrate and -maxrate, -bufsize but it don't work proper. If i'm giving 256kbps at -b option , when the trans-coding finishes , it provide the 380kbps. How can we achieve the constant bit rate using ffmpeg. If their is +-10Kb it's adjustable. but the video bit rate always exceed by 50-100 kbps. I'm using following command ffmpeg -i "demo.avs" -vcodec libx264 -s 320x240 -aspect 4:3 -r 15 -b 256kb \ -minrate 200kb -maxrate 280kb -bufsize 256kb -acodec libmp3lame -ac 2 \ -ar 22050 -ab 64kb -y "output.mp4" When trans-coding is done, the Media Info show overall bit rate 440kb (it should be 320kb). Is their something wrong in the command. Or i have to use some other parameter? Plz provide your suggestion its very important.

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  • Plural to Singular conversion trouble in Rails Migrations?

    - by Earlz
    Hi, I'm a beginner at Ruby On Rails and am trying to get a migration to work with the name Priorities So, here is the code I use in my migration: class Priorities < ActiveRecord::Migration def self.up create_table :priorities do |t| t.column :name, :string, :null => false, :limit => 32 end Priority.create :name => "Critical" Priority.create :name => "Major" Priority.create :name => "Minor" end def self.down drop_table :priorities end end This results in the following error though: NOTICE: CREATE TABLE will create implicit sequence "priorities_id_seq" for serial column "priorities.id" NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "priorities_pkey" for table "priorities" rake aborted! An error has occurred, this and all later migrations canceled: uninitialized constant Priorities::Priority Is this some problem with turning ies to y for converting something plural to singular?

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  • Get a list of documents from Mongo DB

    - by Andrei Neagu
    Hello, I want to do something like this: List<int> fff = new List<int>(); fff.Add(1); fff.Add(2); fff.Add(5); Mongo m = new Mongo(); m.Connect(); var dataBase = m.GetDatabase("database"); var collection = dataBase.GetCollection("coll"); IMongoQuery queryable = collection.AsQueryable(); MongoQueryProvider prov = new MongoQueryProvider(collection); var query = new MongoQuery(prov); var ffppp = from p221 in query where fff.Contains((int)p221["oid"]) select p221; This throws this error : The method 'Contains' could not be converted into a constant. I saw that mongo has an operator $in. Does any one know how can I use it from c#? (http://www.mongodb.org/display/DOCS/Advanced+Queries) Thanks

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  • How does Rails find models and controllers? How can I get it to load more models?

    - by David
    I'm trying to create a non-ActiveRecord model in app/models/gamestate.rb. Then inside my controller (PlayController) I should be able to do GameState.new, right? No go: NameError (uninitialized constant PlayController::GameState): app/controllers/play_controller.rb:23:in `play' (at least in the development environment) But! If I do have a model called app/models/play.rb, then it's automatically loaded and I can do Play.new. So my question is: how does Rails know which classes to load? What sort of name mangling does it do to get from play#action to PlayController to app/controllers/play_controller.rb to app/models/play.rb? It seems awfully fragile, but maybe a better understanding of how this works would help. And finally, how can I get it to load app/models/gamestate.rb?

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  • Use a template parameter in a preprocessor directive?

    - by Ranju V
    Is it possible to use a non-type constant template parameter in a preprocessor directive? Here's what I have in mind: template <int DING> struct Foo { enum { DOO = DING }; }; template <typename T> struct Blah { void DoIt() { #if (T::Doo & 0x010) // somecode here #endif } }; When I try this with something like Blah<Foo<0xFFFF>>, VC++ 2010 complains something about unmatched parentheses in the line where we are trying to use "#if". I am guessing the preprocessor doesn't really know anything about templates and this sort of thing just isn't in its domain. What say? Thanks!

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  • MySQL or SQL Server

    - by user203708
    I'm creating an application that I want to run on either MySQL or SQL Server (not both at the same time) I've created two PHP classes DatabaseMySQL and DatabaseSQLSVR and I'd like my application to know which database class to use based on a constant set up at install. define(DB_TYPE, "mysql"); // or "sqlsrv" I'm trying to think of the best way to handle this. My thought is to do an "if else" wherever I instantiate the database: $db = (DB_TYPE == "mysql") ? new DatabaseMySQL : new DatabaseSQLSVR; I know there has to be a better way of doing this though. Suppose I want to add a third database type later; I'll have to go and redo all my code. Yuk!! Any help would be much appreciated. Thank

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  • Which jsPerf-test should I consider as standard for checking the performance of javascript template-engines

    - by bhargav
    I am on a search for a javascript template engine that has good performance when used in large js applications and is also very suitable for mobile applications. So I have gone through the various jsPerf-tests for these. There seems to be a lot which show different results and it is confusing to find out which is the standard test. Can some one guide me a standard jsPerf that I can refer to and that should also include following templates dust, underscore, hogan, mustache, handlebars. From what I have observed dot.js is a constant performer with good rendering speed, but is it mature enough for larger applications ? What is this "with" and "no with" that is shown in the jspref tests? Can some one explain. In all the tests I have seen popular templates like mustache, handlebars, dust, hogan,etc seems to be behind performance than other templates, so why people are using them leaving out the top performers,is it because of maturity of these template engines? Thanks in advance

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  • Division to the nearest 1 decimal place without floating point math?

    - by John Sheares
    I am having some speed issues with my C# program and identified that this percentage calculation is causing a slow down. The calculation is simply n/d * 100. Both the numerator and denominator can be any integer number. The numerator can never be greater than the denominator and is never negative. Therefore, the result is always from 0-100. Right now, this is done by simply using floating point math and is somewhat slow, since it's being calculated tens of millions of times. I really don't need anything more accurate than to the nearest 0.1 percent. And, I just use this calculated value to see if it's bigger than a fixed constant value. I am thinking that everything should be kept as an integer, so the range with 0.1 accuracy would be 0-1000. Is there some way to calculate this percentage without floating point math?

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  • How to manipulate a gridview in asp.net when the columns in the gridview are generated during runtim

    - by Nandini
    Hi guys, In my application,i have a gridview in which columns are created at runtime.Actually these columns are created when i am entering data in a database table. My gridview is like this:- Description | Column1 | Column2 | Column3 | ...... |....... |......... Input volt | 55 | 56 | 553 |........ Output volt | 656 | 45 | 67 | where Column1,Column2,column3 may vary during runtime.i need to enter values to these columns during runtime.But i cant bind these columns because these are created during runtime. The first column "Description" will not change.It will remain constant.For each description,there will be values for each column.At last these data will be saved to the database.How to add columns in the gridview during runtime?

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