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  • What is the coolest thing you can do in <10 lines of simple code? Help me inspire beginners!

    - by Tom Ritter
    I'm looking for the coolest thing you can do in a few lines of simple code. I'm sure you can write a Mandelbrot set in Haskell in 15 lines but it's difficult to follow. My goal is to inspire students that programming is cool. We know that programming is cool because you can create anything you imagine - it's the ultimate creative outlet. I want to inspire these beginners and get them over as many early-learning humps as I can. Now, my reasons are selfish. I'm teaching an Intro to Computing course to a group of 60 half-engineering, half business majors; all freshmen. They are the students who came from underprivileged High schools. From my past experience, the group is generally split as follows: a few rock-stars, some who try very hard and kind of get it, the few who try very hard and barely get it, and the few who don't care. I want to reach as many of these groups as effectively as I can. Here's an example of how I'd use a computer program to teach: Here's an example of what I'm looking for: a 1-line VBS script to get your computer to talk to you: CreateObject("sapi.spvoice").Speak InputBox("Enter your text","Talk it") I could use this to demonstrate order of operations. I'd show the code, let them play with it, then explain that There's a lot going on in that line, but the computer can make sense of it, because it knows the rules. Then I'd show them something like this: 4(5*5) / 10 + 9(.25 + .75) And you can see that first I need to do is (5*5). Then I can multiply for 4. And now I've created the Object. Dividing by 10 is the same as calling Speak - I can't Speak before I have an object, and I can't divide before I have 100. Then on the other side I first create an InputBox with some instructions for how to display it. When I hit enter on the input box it evaluates or "returns" whatever I entered. (Hint: 'oooooo' makes a funny sound) So when I say Speak, the right side is what to Speak. And I get that from the InputBox. So when you do several things on a line, like: x = 14 + y; You need to be aware of the order of things. First we add 14 and y. Then we put the result (what it evaluates to, or returns) into x. That's my goal, to have a bunch of these cool examples to demonstrate and teach the class while they have fun. I tried this example on my roommate and while I may not use this as the first lesson, she liked it and learned something. Some cool mathematica programs that make beautiful graphs or shapes that are easy to understand would be good ideas and I'm going to look into those. Here are some complicated actionscript examples but that's a bit too advanced and I can't teach flash. What other ideas do you have?

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  • Getting a Temporary Table Returned from from Dynamic SQL in SQL Server 05, and parsing

    - by gloomy.penguin
    So I was requested to make a few things.... (it is Monday morning and for some reason this whole thing is turning out to be really hard for me to explain so I am just going to try and post a lot of my code; sorry) First, I needed a table: CREATE TABLE TICKET_INFORMATION ( TICKET_INFO_ID INT IDENTITY(1,1) NOT NULL, TICKET_TYPE INT, TARGET_ID INT, TARGET_NAME VARCHAR(100), INFORMATION VARCHAR(MAX), TIME_STAMP DATETIME DEFAULT GETUTCDATE() ) -- insert this row for testing... INSERT INTO TICKET_INFORMATION (TICKET_TYPE, TARGET_ID, TARGET_NAME, INFORMATION) VALUES (1,1,'RT_ID','IF_ID,int=1&IF_ID,int=2&OTHER,varchar(10)=val,ue3&OTHER,varchar(10)=val,ue4') The Information column holds data that needs to be parsed into a table. This is where I am having problems. In the resulting table, Target_Name needs to become a column that holds Target_ID as a value for each row in the resulting table. The string that needs to be parsed is in this format: @var_name1,@var_datatype1=@var_value1&@var_name2,@var_datatype2=@var_value2&@var_name3,@var_datatype3=@var_value3 And what I ultimately need as a result (in a table or table variable): RT_ID IF_ID OTHER 1 1 val,ue3 1 2 val,ue3 1 1 val,ue4 1 2 val,ue4 And I need to be able to join on the result. Initially, I was just going to make this a function that returns a table variable but for some reason I can't figure out how to get it into an actual table variable. Whatever parses the string needs to be able to be used directly in queries so I don't think a stored procedure is really the right thing to be using. This is the code that parses the Information string... it returns in a temporary table. -- create/empty temp table for var_name, var_type and var_value fields if OBJECT_ID('tempdb..#temp') is not null drop table #temp create table #temp (row int identity(1,1), var_name varchar(max), var_type varchar(30), var_value varchar(max)) -- just setting stuff up declare @target_name varchar(max), @target_id varchar(max), @info varchar(max) set @target_name = (select target_name from ticket_information where ticket_info_id = 1) set @target_id = (select target_id from ticket_information where ticket_info_id = 1) set @info = (select information from ticket_information where ticket_info_id = 1) --print @info -- some of these variables are re-used later declare @col_type varchar(20), @query varchar(max), @select as varchar(max) set @query = 'select ' + @target_id + ' as ' + @target_name + ' into #target; ' set @select = 'select * into ##global_temp from #target' declare @var_name varchar(100), @var_type varchar(100), @var_value varchar(100) declare @comma_pos int, @equal_pos int, @amp_pos int set @comma_pos = 1 set @equal_pos = 1 set @amp_pos = 0 -- while loop to parse the string into a table while @amp_pos < len(@info) begin -- get new comma position set @comma_pos = charindex(',',@info,@amp_pos+1) -- get new equal position set @equal_pos = charindex('=',@info,@amp_pos+1) -- set stuff that is going into the table set @var_name = substring(@info,@amp_pos+1,@comma_pos-@amp_pos-1) set @var_type = substring(@info,@comma_pos+1,@equal_pos-@comma_pos-1) -- get new ampersand position set @amp_pos = charindex('&',@info,@amp_pos+1) if @amp_pos=0 or @amp_pos<@equal_pos set @amp_pos = len(@info)+1 -- set last variable for insert into table set @var_value = substring(@info,@equal_pos+1,@amp_pos-@equal_pos-1) -- put stuff into the temp table insert into #temp (var_name, var_type, var_value) values (@var_name, @var_type, @var_value) -- is this a new field? if ((select count(*) from #temp where var_name = (@var_name)) = 1) begin set @query = @query + ' create table #' + @var_name + '_temp (' + @var_name + ' ' + @var_type + '); ' set @select = @select + ', #' + @var_name + '_temp ' end set @query = @query + ' insert into #' + @var_name + '_temp values (''' + @var_value + '''); ' end if OBJECT_ID('tempdb..##global_temp') is not null drop table ##global_temp exec (@query + @select) --select @query --select @select select * from ##global_temp Okay. So, the result I want and need is now in ##global_temp. How do I put all of that into something that can be returned from a function (or something)? Or can I get something more useful returned from the exec statement? In the end, the results of the parsed string need to be in a table that can be joined on and used... Ideally this would have been a view but I guess it can't with all the processing that needs to be done on that information string. Ideas? Thanks!

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  • Compiler issues on VC++ 2008 Express, Seemingly correct code throws errors.

    - by Anthony Clever
    Hi there, I've been trying to get back into coding for a while, so I figured I'd start with some simple SDL, now, without the file i/o, this compiles fine, but when I throw in the stdio code, it starts throwing errors. This I'm not sure about, I don't see any problem with the code itself, however, like I said, I might as well be a newbie, and figured I'd come here to get someone with a little more experience with this type of thing to look at it. I guess my question boils down to: "Why doesn't this compile under Microsoft's Visual C++ 2008 Express?" I've attached the error log at the bottom of the code snippet. Thanks in advance for any help. #include "SDL/SDL.h" #include "stdio.h" int main(int argc, char *argv[]) { FILE *stderr; FILE *stdout; stderr = fopen("stderr", "wb"); stdout = fopen("stdout", "wb"); SDL_Init(SDL_INIT_EVERYTHING); fprintf(stdout, "SDL INITIALIZED SUCCESSFULLY\n"); SDL_Quit(); fprintf(stderr, "SDL QUIT.\n"); fclose(stderr); fclose(stdout); return 0; } /* 1>------ Build started: Project: opengl_crap, Configuration: Debug Win32 ------ 1>Compiling... 1>main.cpp 1>c:\documents and settings\owner\my documents\visual studio 2008\projects\opengl_crap\opengl_crap\main.cpp(6) : error C2090: function returns array 1>c:\documents and settings\owner\my documents\visual studio 2008\projects\opengl_crap\opengl_crap\main.cpp(6) : error C2528: '__iob_func' : pointer to reference is illegal 1>c:\documents and settings\owner\my documents\visual studio 2008\projects\opengl_crap\opengl_crap\main.cpp(6) : error C2556: 'FILE ***__iob_func(void)' : overloaded function differs only by return type from 'FILE *__iob_func(void)' 1> c:\program files\microsoft visual studio 9.0\vc\include\stdio.h(132) : see declaration of '__iob_func' 1>c:\documents and settings\owner\my documents\visual studio 2008\projects\opengl_crap\opengl_crap\main.cpp(7) : error C2090: function returns array 1>c:\documents and settings\owner\my documents\visual studio 2008\projects\opengl_crap\opengl_crap\main.cpp(7) : error C2528: '__iob_func' : pointer to reference is illegal 1>c:\documents and settings\owner\my documents\visual studio 2008\projects\opengl_crap\opengl_crap\main.cpp(9) : error C2440: '=' : cannot convert from 'FILE *' to 'FILE ***' 1> Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast 1>c:\documents and settings\owner\my documents\visual studio 2008\projects\opengl_crap\opengl_crap\main.cpp(10) : error C2440: '=' : cannot convert from 'FILE *' to 'FILE ***' 1> Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast 1>c:\documents and settings\owner\my documents\visual studio 2008\projects\opengl_crap\opengl_crap\main.cpp(13) : error C2664: 'fprintf' : cannot convert parameter 1 from 'FILE ***' to 'FILE *' 1> Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast 1>c:\documents and settings\owner\my documents\visual studio 2008\projects\opengl_crap\opengl_crap\main.cpp(15) : error C2664: 'fprintf' : cannot convert parameter 1 from 'FILE ***' to 'FILE *' 1> Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast 1>c:\documents and settings\owner\my documents\visual studio 2008\projects\opengl_crap\opengl_crap\main.cpp(17) : error C2664: 'fclose' : cannot convert parameter 1 from 'FILE ***' to 'FILE *' 1> Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast 1>c:\documents and settings\owner\my documents\visual studio 2008\projects\opengl_crap\opengl_crap\main.cpp(18) : error C2664: 'fclose' : cannot convert parameter 1 from 'FILE ***' to 'FILE *' 1> Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast 1>Build log was saved at "file://c:\Documents and Settings\Owner\My Documents\Visual Studio 2008\Projects\opengl_crap\opengl_crap\Debug\BuildLog.htm" 1>opengl_crap - 11 error(s), 0 warning(s) ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ========== */

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  • Mysql query help - Alter this mysql query to get these results?

    - by sandeepan-nath
    Please execute the following queries first to set up so that you can help me:- CREATE TABLE IF NOT EXISTS `Tutor_Details` ( `id_tutor` int(10) NOT NULL auto_increment, `firstname` varchar(100) NOT NULL default '', `surname` varchar(155) NOT NULL default '', PRIMARY KEY (`id_tutor`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=41 ; INSERT INTO `Tutor_Details` (`id_tutor`,`firstname`, `surname`) VALUES (1, 'Sandeepan', 'Nath'), (2, 'Bob', 'Cratchit'); CREATE TABLE IF NOT EXISTS `Classes` ( `id_class` int(10) unsigned NOT NULL auto_increment, `id_tutor` int(10) unsigned NOT NULL default '0', `class_name` varchar(255) default NULL, PRIMARY KEY (`id_class`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=229 ; INSERT INTO `Classes` (`id_class`,`class_name`, `id_tutor`) VALUES (1, 'My Class', 1), (2, 'Sandeepan Class', 2); CREATE TABLE IF NOT EXISTS `Tags` ( `id_tag` int(10) unsigned NOT NULL auto_increment, `tag` varchar(255) default NULL, PRIMARY KEY (`id_tag`), UNIQUE KEY `tag` (`tag`), KEY `id_tag` (`id_tag`), KEY `tag_2` (`tag`), KEY `tag_3` (`tag`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=18 ; INSERT INTO `Tags` (`id_tag`, `tag`) VALUES (1, 'Bob'), (6, 'Class'), (2, 'Cratchit'), (4, 'Nath'), (3, 'Sandeepan'), (5, 'My'); CREATE TABLE IF NOT EXISTS `Tutors_Tag_Relations` ( `id_tag` int(10) unsigned NOT NULL default '0', `id_tutor` int(10) default NULL, KEY `Tutors_Tag_Relations` (`id_tag`), KEY `id_tutor` (`id_tutor`), KEY `id_tag` (`id_tag`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; INSERT INTO `Tutors_Tag_Relations` (`id_tag`, `id_tutor`) VALUES (3, 1), (4, 1), (1, 2), (2, 2); CREATE TABLE IF NOT EXISTS `Class_Tag_Relations` ( `id_tag` int(10) unsigned NOT NULL default '0', `id_class` int(10) default NULL, `id_tutor` int(10) NOT NULL, KEY `Class_Tag_Relations` (`id_tag`), KEY `id_class` (`id_class`), KEY `id_tag` (`id_tag`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; INSERT INTO `Class_Tag_Relations` (`id_tag`, `id_class`, `id_tutor`) VALUES (5, 1, 1), (6, 1, 1), (3, 2, 2), (6, 2, 2); In the present system data which I have given , tutor named "Sandeepan Nath" has has created class named "My Class" and tutor named "Bob Cratchit" has created class named "Sandeepan Class". Requirement - To execute a single query with limit on the results to show search results as per AND logic on the search keywords like this:- If "Sandeepan Class" is searched , Tutor Sandeepan Nath's record from Tutor Details table is returned(because "Sandeepan" is the firstname of Sandeepan Nath and Class is present in class name of Sandeepan's class) If "Class" is searched Both the tutors from the Tutor_details table are fetched because Class is present in the name of the class created by both the tutors. Following is what I have so far achieved (PHP Mysql):- <?php $searchTerm1 = "Sandeepan"; $searchTerm2 = "Class"; mysql_select_db("test"); $sql = "SELECT td.* FROM Tutor_Details AS td LEFT JOIN Tutors_Tag_Relations AS ttagrels ON td.id_tutor = ttagrels.id_tutor LEFT JOIN Classes AS wc ON td.id_tutor = wc.id_tutor LEFT JOIN Class_Tag_Relations AS wtagrels ON td.id_tutor = wtagrels.id_tutor LEFT JOIN Tags as t1 on ((t1.id_tag = ttagrels.id_tag) OR (t1.id_tag = wtagrels.id_tag)) LEFT JOIN Tags as t2 on ((t2.id_tag = ttagrels.id_tag) OR (t2.id_tag = wtagrels.id_tag)) where t1.tag LIKE '%".$searchTerm1."%' AND t2.tag LIKE '%".$searchTerm2."%' GROUP BY td.id_tutor LIMIT 10 "; $result = mysql_query($sql); echo $sql; if($result) { while($rec = mysql_fetch_object($result)) $recs[] = $rec; //$rec = mysql_fetch_object($result); echo "<br><br>"; if(is_array($recs)) { foreach($recs as $each) { print_r($each); echo "<br>"; } } } ?> But the results are :- If "Sandeepan Nath" is searched, it does not return any tutor (instead of only Sandeepan's row) If "Sandeepan Class" is searched, it returns Sandeepan's row (instead of Both tutors ) If "Bob Class" is searched, it correctly returns Bob's row If "Bob Cratchit" is searched, it does not return any tutor (instead of only

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  • Which option do you like the most?

    - by spderosso
    I need to show a list of movies ordered by the date they were registered in the system and the amount of comments users have made about them. E.g: Title | Register Date | # of comments Gladiator | 02-01-2010 | 30 Matrix | 01-02-2010 | 20 It is a web application that follows MVC. So, I have the object "Movie", there is a MovieManager interface that is used for retrieving/persisting data to the database and a servlet RecentlyAddedMovies.java that forwards to a .jsp to render the list. I will explain my problem by showing an example of how I am doing another similar task: Showing top ranked movies. Regarding the MovieManager: /** * Returns a collection of the x best-ranked movies * @param x the amount of movies to return * @return A collection of movies * @throws SQLException */ public Collection<Movie> getTopX(int x) throws SQLException; The servlet: public class Top5 extends HttpServlet{ @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { MovieManager movManager = JDBCMovieManager.getInstance(); try { req.setAttribute("movies", movManager.getTopX(5)); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } req.getRequestDispatcher("listMovies.jsp").forward(req, resp); } } And the listMovies.jsp has is some place something like: <c:forEach var="movie" items="${movies}"> ... <c:out value="${movie.title}"/> ... </c:forEach> The difference between the top5 problem and the problem I am trying to solve is that with the top5 thing all the data I needed to show in the view where part of the "Movie" object, so the MovieManager simply returned a Collection of Movies. Now, the MovieManager must retrieve an ordered list of (Movie, # of comments). The Movie object has a collection of Comment associated but of course, it lacks an instance variable with the length of that collection. The following things came into my mind: a) Create a MovieView object or something like that, that is only used by the "View" and "Controller" layer of the MVC which is not part of the "Model" in the sense that is used only for easy retrieval and display of information. This MovieView object will have a title, registerDate and # of Comments so the thing would look something like this: /** * Returns a collection of the x most recently added movies * @param x the amount of movies to return * @return A collection of movies * @throws SQLException */ public Collection<Movie2> getXRecentlyAddedMovies(int x) throws SQLException; The .jsp: <c:forEach var="movie2" items="${movies2}"> ... <c:out value="${movie2.title}"/> <c:out value="${movie2.registerDate}"/> <c:out value="${movie2.noOfComments}"/> ... </c:forEach> b) Add to the Collection the movie has, empty Comments (there is no actual need to retrieve all the comment data from the database) so that the comment's collection.size() will show the number of comments that movie has. (This sounds horrible to me) c) Add to the "Movie" object an instance field noOfComments with the setter and getter that will help with this type of cases even if, looking only from the object point of view, it is a redundant field since it already has a Collection that is ".size()"able . d) Make the MovieManager retrieve some structure like a Map or a Collection of a two component array or something like that that will contain both a Movie object and the associated number of comments and with JSLT iterate over it and show it accordingly.

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  • Why is my code returning a Null Object Refrence error when using WatIn?

    - by Fuzz Evans
    I keep getting a Null Object Refrence Error, but can't tell why. I have a CSV file that contains 100 urls. The file is read into an array called "lines". public partial class Form1 : System.Windows.Forms.Form { string[] lines; public Form1() ... private void ReadLinksIntoMemory() { //this reads the chosen csv file into our "lines" array //and splits on comma's and new lines to create new objects within the array using (StreamReader sr = new StreamReader(@"C:\temp.csv")) { //reads everything in our csv into 1 long line string fileContents = sr.ReadToEnd(); //splits the 1 long line read in into multiple objects of the lines array lines = fileContents.Split(new string[] { ",", Environment.NewLine }, StringSplitOptions.RemoveEmptyEntries); sr.Dispose(); } } The next part is where I get the null object error. When I try to use WatIn to go to the first item in the lines array it says I'm referencing a null object. private void GoToEditLinks() { for (int i = 0; i < lines.Length; i++) { //go to each link sequentially myIE.GoTo(lines[i].ToString()); //sleep so we can make sure the page loads System.Threading.Thread.Sleep(5000); } } When I debug the code it says that the GoTo request calls lines which is null. It seems like I need to declare the array, but don't I need to tell it an exact size to do that? Example: lines = new string[10] I thought I could use the lines.Length to tell it how big to make the array but that didn't work. What is weird to me is I can use the following code without problem: //returns the accurate number of urls that were in the CSV we read in earlier txtbx1.text = lines.Length; //or //this returns the last entry in the csv, as well as the last entry in the array TextBox2.Text = lines[lines.Length - 1]; I am confused why the array clearly has items in it, they can be called to fill a text box, but when I try to call them in my for loop it says its a null reference? UPDATE: By placing my cursor on both calls to lines and pressing f12 I find they both go to the same instance. The thought next is that I am not calling ReadLinksIntoMemory in time, below is my code: private void button1_Click(object sender, EventArgs e) { button1.Enabled = false; ReadLinksIntoMemory(); GoToEditLinks(); button1.Enabled = true; } Unless I'm mistaken the code says that the ReadLinksIntoMemory method must complete before GoToEditLinks can be called? If ReadLinksIntoMemory didn't finish in time I shouldn't be able to fill my text boxes with the lines array length and/or last entry. UPDATE: Stepping into the method GoToEditLinks() I see that lines is null before it calls: myIE.GoTo(lines[i]); but when it hits the goto command the value changes from null to the url it is suppose to go to, but at that same time it gives me the null object error? UPDATE: I added a IsNullOrEmpty check method and lines array passes it without any issue. I'm beginning to think it is an issue with WatIn and the myIE.GoTo command. I think this is the stack trace/call stack? Program.exe!Program.Form1.GoToEditLinks() Line 284 C# Program.exe!Program.Form1.button1_Click(object sender, System.EventArgs e) Line 191 + 0x8 bytes C# [External Code] Program.exe!Program.Program.Main() Line 18 + 0x1d bytes C# [External Code]

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  • Why doesn't my implementation of ElGamal work for long text strings?

    - by angstrom91
    I'm playing with the El Gamal cryptosystem, and my goal is to be able to encipher and decipher long sequences of text. I have come up with a method that works for short sequences, but does not work for long sequences, and I cannot figure out why. El Gamal requires the plaintext to be an integer. I have turned my string into a byte[] using the .getBytes() method for Strings, and then created a BigInteger out of the byte[]. After encryption/decryption, I turn the BigInteger into a byte[] using the .toByteArray() method for BigIntegers, and then create a new String object from the byte[]. This works perfectly when i call ElGamalEncipher with strings up to 129 characters. With 130 or more characters, the output produced from ElGamalDecipher is garbled. Can someone suggest how to solve this issue? Is this an issue with my method of turning the string into a BigInteger? If so, is there a better way to turn my string of text into a BigInteger and back? Below is my encipher/decipher code with a program to demonstrate the problem. import java.math.BigInteger; public class Main { static BigInteger P = new BigInteger("15893293927989454301918026303382412" + "2586402937727056707057089173871237566896685250125642378268385842" + "6917261652781627945428519810052550093673226849059197769795219973" + "9423619267147615314847625134014485225178547696778149706043781174" + "2873134844164791938367765407368476144402513720666965545242487520" + "288928241768306844169"); static BigInteger G = new BigInteger("33234037774370419907086775226926852" + "1714093595439329931523707339920987838600777935381196897157489391" + "8360683761941170467795379762509619438720072694104701372808513985" + "2267495266642743136795903226571831274837537691982486936010899433" + "1742996138863988537349011363534657200181054004755211807985189183" + "22832092343085067869"); static BigInteger R = new BigInteger("72294619754760174015019300613282868" + "7219874058383991405961870844510501809885568825032608592198728334" + "7842806755320938980653857292210955880919036195738252708294945320" + "3969657021169134916999794791553544054426668823852291733234236693" + "4178738081619274342922698767296233937873073756955509269717272907" + "8566607940937442517"); static BigInteger A = new BigInteger("32189274574111378750865973746687106" + "3695160924347574569923113893643975328118502246784387874381928804" + "6865920942258286938666201264395694101012858796521485171319748255" + "4630425677084511454641229993833255506759834486100188932905136959" + "7287419551379203001848457730376230681693887924162381650252270090" + "28296990388507680954"); public static void main(String[] args) { FewChars(); System.out.println(); ManyChars(); } public static void FewChars() { //ElGamalEncipher(String plaintext, BigInteger p, BigInteger g, BigInteger r) BigInteger[] cipherText = ElGamal.ElGamalEncipher("This is a string " + "of 129 characters which works just fine . This is a string " + "of 129 characters which works just fine . This is a s", P, G, R); System.out.println("This is a string of 129 characters which works " + "just fine . This is a string of 129 characters which works " + "just fine . This is a s"); //ElGamalDecipher(BigInteger c, BigInteger d, BigInteger a, BigInteger p) System.out.println("The decrypted text is: " + ElGamal.ElGamalDecipher(cipherText[0], cipherText[1], A, P)); } public static void ManyChars() { //ElGamalEncipher(String plaintext, BigInteger p, BigInteger g, BigInteger r) BigInteger[] cipherText = ElGamal.ElGamalEncipher("This is a string " + "of 130 characters which doesn’t work! This is a string of " + "130 characters which doesn’t work! This is a string of ", P, G, R); System.out.println("This is a string of 130 characters which doesn’t " + "work! This is a string of 130 characters which doesn’t work!" + " This is a string of "); //ElGamalDecipher(BigInteger c, BigInteger d, BigInteger a, BigInteger p) System.out.println("The decrypted text is: " + ElGamal.ElGamalDecipher(cipherText[0], cipherText[1], A, P)); } } import java.math.BigInteger; import java.security.SecureRandom; public class ElGamal { public static BigInteger[] ElGamalEncipher(String plaintext, BigInteger p, BigInteger g, BigInteger r) { // returns a BigInteger[] cipherText // cipherText[0] is c // cipherText[1] is d SecureRandom sr = new SecureRandom(); BigInteger[] cipherText = new BigInteger[2]; BigInteger pText = new BigInteger(plaintext.getBytes()); // 1: select a random integer k such that 1 <= k <= p-2 BigInteger k = new BigInteger(p.bitLength() - 2, sr); // 2: Compute c = g^k(mod p) BigInteger c = g.modPow(k, p); // 3: Compute d= P*r^k = P(g^a)^k(mod p) BigInteger d = pText.multiply(r.modPow(k, p)).mod(p); // C =(c,d) is the ciphertext cipherText[0] = c; cipherText[1] = d; return cipherText; } public static String ElGamalDecipher(BigInteger c, BigInteger d, BigInteger a, BigInteger p) { //returns the plaintext enciphered as (c,d) // 1: use the private key a to compute the least non-negative residue // of an inverse of (c^a)' (mod p) BigInteger z = c.modPow(a, p).modInverse(p); BigInteger P = z.multiply(d).mod(p); byte[] plainTextArray = P.toByteArray(); return new String(plainTextArray); } }

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  • Incremental PCA

    - by smichak
    Hi, Lately, I've been looking into an implementation of an incremental PCA algorithm in python - I couldn't find something that would meet my needs so I did some reading and implemented an algorithm I found in some paper. Here is the module's code - the relevant paper on which it is based is mentioned in the module's documentation. I would appreciate any feedback from people who are interested in this. Micha #!/usr/bin/env python """ Incremental PCA calculation module. Based on P.Hall, D. Marshall and R. Martin "Incremental Eigenalysis for Classification" which appeared in British Machine Vision Conference, volume 1, pages 286-295, September 1998. Principal components are updated sequentially as new observations are introduced. Each new observation (x) is projected on the eigenspace spanned by the current principal components (U) and the residual vector (r = x - U(U.T*x)) is used as a new principal component (U' = [U r]). The new principal components are then rotated by a rotation matrix (R) whose columns are the eigenvectors of the transformed covariance matrix (D=U'.T*C*U) to yield p + 1 principal components. From those, only the first p are selected. """ __author__ = "Micha Kalfon" import numpy as np _ZERO_THRESHOLD = 1e-9 # Everything below this is zero class IPCA(object): """Incremental PCA calculation object. General Parameters: m - Number of variables per observation n - Number of observations p - Dimension to which the data should be reduced """ def __init__(self, m, p): """Creates an incremental PCA object for m-dimensional observations in order to reduce them to a p-dimensional subspace. @param m: Number of variables per observation. @param p: Number of principle components. @return: An IPCA object. """ self._m = float(m) self._n = 0.0 self._p = float(p) self._mean = np.matrix(np.zeros((m , 1), dtype=np.float64)) self._covariance = np.matrix(np.zeros((m, m), dtype=np.float64)) self._eigenvectors = np.matrix(np.zeros((m, p), dtype=np.float64)) self._eigenvalues = np.matrix(np.zeros((1, p), dtype=np.float64)) def update(self, x): """Updates with a new observation vector x. @param x: Next observation as a column vector (m x 1). """ m = self._m n = self._n p = self._p mean = self._mean C = self._covariance U = self._eigenvectors E = self._eigenvalues if type(x) is not np.matrix or x.shape != (m, 1): raise TypeError('Input is not a matrix (%d, 1)' % int(m)) # Update covariance matrix and mean vector and centralize input around # new mean oldmean = mean mean = (n*mean + x) / (n + 1.0) C = (n*C + x*x.T + n*oldmean*oldmean.T - (n+1)*mean*mean.T) / (n + 1.0) x -= mean # Project new input on current p-dimensional subspace and calculate # the normalized residual vector g = U.T*x r = x - (U*g) r = (r / np.linalg.norm(r)) if not _is_zero(r) else np.zeros_like(r) # Extend the transformation matrix with the residual vector and find # the rotation matrix by solving the eigenproblem DR=RE U = np.concatenate((U, r), 1) D = U.T*C*U (E, R) = np.linalg.eigh(D) # Sort eigenvalues and eigenvectors from largest to smallest to get the # rotation matrix R sorter = list(reversed(E.argsort(0))) E = E[sorter] R = R[:,sorter] # Apply the rotation matrix U = U*R # Select only p largest eigenvectors and values and update state self._n += 1.0 self._mean = mean self._covariance = C self._eigenvectors = U[:, 0:p] self._eigenvalues = E[0:p] @property def components(self): """Returns a matrix with the current principal components as columns. """ return self._eigenvectors @property def variances(self): """Returns a list with the appropriate variance along each principal component. """ return self._eigenvalues def _is_zero(x): """Return a boolean indicating whether the given vector is a zero vector up to a threshold. """ return np.fabs(x).min() < _ZERO_THRESHOLD if __name__ == '__main__': import sys def pca_svd(X): X = X - X.mean(0).repeat(X.shape[0], 0) [_, _, V] = np.linalg.svd(X) return V N = 1000 obs = np.matrix([np.random.normal(size=10) for _ in xrange(N)]) V = pca_svd(obs) print V[0:2] pca = IPCA(obs.shape[1], 2) for i in xrange(obs.shape[0]): x = obs[i,:].transpose() pca.update(x) U = pca.components print U

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  • Overriding Object.Equals() instance method in C#; now Code Analysis / FxCop warning CA2218: "should

    - by Chris W. Rea
    I've got a complex class in my C# project on which I want to be able to do equality tests. It is not a trivial class; it contains a variety of scalar properties as well as references to other objects and collections (e.g. IDictionary). For what it's worth, my class is sealed. To enable a performance optimization elsewhere in my system (an optimization that avoids a costly network round-trip), I need to be able to compare instances of these objects to each other for equality – other than the built-in reference equality – and so I'm overriding the Object.Equals() instance method. However, now that I've done that, Visual Studio 2008's Code Analysis a.k.a. FxCop, which I keep enabled by default, is raising the following warning: warning : CA2218 : Microsoft.Usage : Since 'MySuperDuperClass' redefines Equals, it should also redefine GetHashCode. I think I understand the rationale for this warning: If I am going to be using such objects as the key in a collection, the hash code is important. i.e. see this question. However, I am not going to be using these objects as the key in a collection. Ever. Feeling justified to suppress the warning, I looked up code CA2218 in the MSDN documentation to get the full name of the warning so I could apply a SuppressMessage attribute to my class as follows: [SuppressMessage("Microsoft.Naming", "CA2218:OverrideGetHashCodeOnOverridingEquals", Justification="This class is not to be used as key in a hashtable.")] However, while reading further, I noticed the following: How to Fix Violations To fix a violation of this rule, provide an implementation of GetHashCode. For a pair of objects of the same type, you must ensure that the implementation returns the same value if your implementation of Equals returns true for the pair. When to Suppress Warnings ----- Do not suppress a warning from this rule. [arrow & emphasis mine] So, I'd like to know: Why shouldn't I suppress this warning as I was planning to? Doesn't my case warrant suppression? I don't want to code up an implementation of GetHashCode() for this object that will never get called, since my object will never be the key in a collection. If I wanted to be pedantic, instead of suppressing, would it be more reasonable for me to override GetHashCode() with an implementation that throws a NotImplementedException? Update: I just looked this subject up again in Bill Wagner's good book Effective C#, and he states in "Item 10: Understand the Pitfalls of GetHashCode()": If you're defining a type that won't ever be used as the key in a container, this won't matter. Types that represent window controls, web page controls, or database connections are unlikely to be used as keys in a collection. In those cases, do nothing. All reference types will have a hash code that is correct, even if it is very inefficient. [...] In most types that you create, the best approach is to avoid the existence of GetHashCode() entirely. ... that's where I originally got this idea that I need not be concerned about GetHashCode() always.

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  • List<T> and IEnumerable difference

    - by Jonas Elfström
    While implementing this generic merge sort, as a kind of Code Kata, I stumbled on a difference between IEnumerable and List that I need help to figure out. Here's the MergeSort public class MergeSort<T> { public IEnumerable<T> Sort(IEnumerable<T> arr) { if (arr.Count() <= 1) return arr; int middle = arr.Count() / 2; var left = arr.Take(middle).ToList(); var right = arr.Skip(middle).ToList(); return Merge(Sort(left), Sort(right)); } private static IEnumerable<T> Merge(IEnumerable<T> left, IEnumerable<T> right) { var arrSorted = new List<T>(); while (left.Count() > 0 && right.Count() > 0) { if (Comparer<T>.Default.Compare(left.First(), right.First()) < 0) { arrSorted.Add(left.First()); left=left.Skip(1); } else { arrSorted.Add(right.First()); right=right.Skip(1); } } return arrSorted.Concat(left).Concat(right); } } If I remove the .ToList() on the left and right variables it fails to sort correctly. Do you see why? Example var ints = new List<int> { 5, 8, 2, 1, 7 }; var mergeSortInt = new MergeSort<int>(); var sortedInts = mergeSortInt.Sort(ints); With .ToList() [0]: 1 [1]: 2 [2]: 5 [3]: 7 [4]: 8 Without .ToList() [0]: 1 [1]: 2 [2]: 5 [3]: 7 [4]: 2 Edit It was my stupid test that got me. I tested it like this: var sortedInts = mergeSortInt.Sort(ints); ints.Sort(); if (Enumerable.SequenceEqual(ints, sortedInts)) Console.WriteLine("ints sorts ok"); just changing the first row to var sortedInts = mergeSortInt.Sort(ints).ToList(); removes the problem (and the lazy evaluation). EDIT 2010-12-29 I thought I would figure out just how the lazy evaluation messes things up here but I just don't get it. Remove the .ToList() in the Sort method above like this var left = arr.Take(middle); var right = arr.Skip(middle); then try this var ints = new List<int> { 5, 8, 2 }; var mergeSortInt = new MergeSort<int>(); var sortedInts = mergeSortInt.Sort(ints); ints.Sort(); if (Enumerable.SequenceEqual(ints, sortedInts)) Console.WriteLine("ints sorts ok"); When debugging You can see that before ints.Sort() a sortedInts.ToList() returns [0]: 2 [1]: 5 [2]: 8 but after ints.Sort() it returns [0]: 2 [1]: 5 [2]: 5 What is really happening here?

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  • C++ MySQL++ Delete query statement brain killer question

    - by shauny
    Hello all, I'm relatively new to the MySQL++ connector in C++, and have an really annoying issue with it already! I've managed to get stored procedures working, however i'm having issues with the delete statements. I've looked high and low and have found no documentation with examples. First I thought maybe the code needs to free the query/connection results after calling the stored procedure, but of course MySQL++ doesn't have a free_result method... or does it? Anyways, here's what I've got: #include <iostream> #include <stdio.h> #include <queue> #include <deque> #include <sys/stat.h> #include <mysql++/mysql++.h> #include <boost/thread/thread.hpp> #include "RepositoryQueue.h" using namespace boost; using namespace mysqlpp; class RepositoryChecker { private: bool _isRunning; Connection _con; public: RepositoryChecker() { try { this->_con = Connection(false); this->_con.set_option(new MultiStatementsOption(true)); this->_con.set_option(new ReconnectOption(true)); this->_con.connect("**", "***", "***", "***"); this->ChangeRunningState(true); } catch(const Exception& e) { this->ChangeRunningState(false); } } /** * Thread method which runs and creates the repositories */ void CheckRepositoryQueues() { //while(this->IsRunning()) //{ std::queue<RepositoryQueue> queues = this->GetQueue(); if(queues.size() > 0) { while(!queues.empty()) { RepositoryQueue &q = queues.front(); char cmd[256]; sprintf(cmd, "svnadmin create /home/svn/%s/%s/%s", q.GetPublicStatus().c_str(), q.GetUsername().c_str(), q.GetRepositoryName().c_str()); if(this->DeleteQueuedRepository(q.GetQueueId())) { printf("query deleted?\n"); } printf("Repository created!\n"); queues.pop(); } } boost::this_thread::sleep(boost::posix_time::milliseconds(500)); //} } protected: /** * Gets the latest queue of repositories from the database * and returns them inside a cool queue defined with the * RepositoryQueue class. */ std::queue<RepositoryQueue> GetQueue() { std::queue<RepositoryQueue> queues; Query query = this->_con.query("CALL sp_GetRepositoryQueue();"); StoreQueryResult result = query.store(); RepositoryQueue rQ; if(result.num_rows() > 0) { for(unsigned int i = 0;i < result.num_rows(); ++i) { rQ = RepositoryQueue((unsigned int)result[i][0], (unsigned int)result[i][1], (String)result[i][2], (String)result[i][3], (String)result[i][4], (bool)result[i][5]); queues.push(rQ); } } return queues; } /** * Allows the thread to be shut off. */ void ChangeRunningState(bool isRunning) { this->_isRunning = isRunning; } /** * Returns the running value of the active thread. */ bool IsRunning() { return this->_isRunning; } /** * Deletes the repository from the mysql queue table. This is * only called once it has been created. */ bool DeleteQueuedRepository(unsigned int id) { char cmd[256]; sprintf(cmd, "DELETE FROM RepositoryQueue WHERE Id = %d LIMIT 1;", id); Query query = this->_con.query(cmd); return (query.exec()); } }; I've removed all the other methods as they're not needed... Basically it's the DeleteQueuedRepository method which isn't working, the GetQueue works fine. PS: This is on a Linux OS (Ubuntu server) Many thanks, Shaun

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  • What's the most unsound program you've had to maintain?

    - by Robert Rossney
    I periodically am called upon to do maintenance work on a system that was built by a real rocket surgeon. There's so much wrong with it that it's hard to know where to start. No, wait, I'll start at the beginning: in the early days of the project, the designer was told that the system would need to scale, and he'd read that a source of scalability problems was traffic between the application and database servers, so he made sure to minimize this traffic. How? By putting all of the application logic in SQL Server stored procedures. Seriously. The great bulk of the application functions by the HTML front end formulating XML messages. When the middle tier receives an XML message, it uses the document element's tag name as the name of the stored procedure it should call, and calls the SP, passing it the entire XML message as a parameter. It takes the XML message that the SP returns and returns it directly back to the front end. There is no other logic in the application tier. (There was some code in the middle tier to validate the incoming XML messages against a library of schemas. But I removed it, after ascertaining that 1) only a small handful of messages had corresponding schemas, 2) the messages didn't actually conform to these schemas, and 3) after validating the messages, if any errors were encountered, the method discarded them. "This fuse box is a real time-saver - it comes from the factory with pennies pre-installed!") I've seen software that does the wrong thing before. Lots of it. I've written quite a bit. But I've never seen anything like the steely-eyed determination to do the wrong thing, at every possible turn, that's embodied in the design and programming of this system. Well, at least he went with what he knew, right? Um. Apparently, what he knew was Access. And he didn't really understand Access. Or databases. Here's a common pattern in this code: SELECT @TestCodeID FROM TestCode WHERE TestCode = @TestCode SELECT @CountryID FROM Country WHERE CountryAbbr = @CountryAbbr SELECT Invoice.*, TestCode.*, Country.* FROM Invoice JOIN TestCode ON Invoice.TestCodeID = TestCode.ID JOIN Country ON Invoice.CountryID = Country.ID WHERE Invoice.TestCodeID = @TestCodeID AND Invoice.CountryID = @CountryID Okay, fine. You don't trust the query optimizer either. But how about this? (Originally, I was going to post this in What's the best comment in source code you have ever encountered? but I realized that there was so much more to write about than just this one comment, and things just got out of hand.) At the end of many of the utility stored procedures, you'll see code that looks like the following: -- Fix NULLs SET @TargetValue = ISNULL(@TargetValue, -9999) Yes, that code is doing exactly what you can't allow yourself to believe it's doing lest you be driven mad. If the variable contains a NULL, he's alerting the caller by changing its value to -9999. Here's how this number is commonly used: -- Get target value EXEC ap_GetTargetValue @Param1, @Param2, OUTPUT @TargetValue -- Check target value for NULL value IF @TargetValue = -9999 ... Really. For another dimension of this system, see the article on thedailywtf.com entitled I Think I'll Call Them "Transactions". I'm not making any of this up. I swear. I'm often reminded, when I work on this system, of Wolfgang Pauli's famous response to a student: "That isn't right. It isn't even wrong." This can't really be the very worst program ever. It's definitely the worst one I've worked

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  • Using jQuery to call a web service

    - by Matt
    I have created a web service which takes a username and password as parameters and returns a list of children in JSON (the user is a Social Worker). The web service is hosted locally with IIS7. I am attempting to access the web service using javascript/jquery because it will eventually need to run as a mobile app. I'm not really experienced with web services, or javascript for that matter, but the following two links seemed to point me in the right direction: http://williamsportwebdeveloper.com/cgi/wp/?p=494 http://encosia.com/using-jquery-to-consume-aspnet-json-web-services/ This is my html page: <%@ Page Title="" Language="C#" MasterPageFile="~/MasterPage.Master" AutoEventWireup="true" CodeBehind="TestWebService.aspx.cs" Inherits="Sponsor_A_Child.TestWebService" %> <asp:Content ID="Content1" ContentPlaceHolderID="stylesPlaceHolder" runat="server"> <script type="text/javascript" src="Scripts/jquery-1.7.1.js"> $(document).ready(function () { }); function LoginClientClick() { $("#query_results").empty(); $("#query_results").append('<table id="ResultsTable" class="ChildrenTable"><tr><th>Child_ID</th><th>Child_Name</th><th>Child_Surname</th></tr>'); $.ajax({ type: "POST", contentType: "application/json; charset=utf-8", url: "http://localhost/PhoneWebServices/GetChildren.asmx/GetMyChildren", data: '{ "email" : "' + $("#EmailBox").val() + '", "password": "' + $("#PasswordBox").val() + '" }', dataType: "json", success: function (msg) { var c = eval(msg.d); alert("" + c); for (var i in c) { $("#ResultsTable tr:last").after("<tr><td>" + c[i][0] + "</td><td>" + c[i][1] + "</td><td>" + c[i][2] + "</td></tr>"); } } }); } </script> </asp:Content> <asp:Content ID="Content2" ContentPlaceHolderID="contentPlaceHolder" runat="server"> <div id="LoginDiv"> Email: <input id="EmailBox" type="text" /><br /> Password: <input id="PasswordBox" type="password" /><br /> <input id="LoginButton" type="button" value="Submit" onclick="LoginClientClick()" /> </div> <div id="query_results"> </div> </asp:Content> And this is my web service code: [WebMethod (Description="Returns the list of children for whom the social worker is responsible.")] public String GetMyChildren(String email,String password) { DataSet MyChildren=new DataSet(); int ID=SocialWorkerLogin(email, password); if (ID > 0) { MyChildren = FillChildrenTable(ID); } MyChildren.DataSetName = "My Children"; //To prevent 'DataTable name not set' error string[][] JaggedArray = new string[MyChildren.Tables[0].Rows.Count][]; int i = 0; foreach (DataRow rs in MyChildren.Tables[0].Rows) { JaggedArray[i] = new string[] { rs["Child_ID"].ToString(), rs["Child_Name"].ToString(), rs["Child_Surname"].ToString() }; i = i + 1; } // Return JSON data JavaScriptSerializer js = new JavaScriptSerializer(); string strJSON = js.Serialize(JaggedArray); return strJSON; } I followed the examples in the provided links, but when I press submit, only the table headers appear but not the list of children. When I test the web service on it's own though, it does return a JSON string so that part seems to be working. Any help is greatly appreciated :)

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  • C socket: problem with connect() and/or accept() between clients. 111: Connection refused

    - by Fantastic Fourier
    Hello ladies and gents, I'm having a bit of problem with accept(). I have a multiple clients and one server. The clients can connect and communicate just fine with server. But at one point, I need some clients to be directly connected to each other and I'm having a bit of difficulty there. The clients have bunch of threads going on, where one of them is handle_connection() and it has a while(1), looping forever to listen() and accept() whatever incoming connections. Whenever a client tries to connect() to other client, connect() returns an error, 111: Connection Refused. I know I have the right IP address and right port (I have specified a port just for between-client connections). The client that is waiting for connection doesn't notice anything, no new connection, nada. I copied some parts of the code, in hopes that someone can point out what I'm doing wrong. Thanks for any inputs! This is all client side code. void * handle_connections(void * arg) is a thread that loops forever to accept() any incoming connections. My server has a very similar thang going on and it works very well. (not sure why it doesn't work here..) This is the part of client that is waiting for a new incoming connection. int handle_request(void * arg, struct message * msg) is called at one point during program and tries to connect to a client that is specified in struct message * msg which includes struct sockaddr_in with IP address and port number and whatever. #define SERVER_PORT 10000 #define CLIENT_PORT 3456 #define MAX_CONNECTION 20 #define MAX_MSG 50 void * handle_connections(void * arg) { struct fd_info * info; struct sockaddr_in client_address; struct timeval timeout; fd_set readset, copyset; bzero((char * ) &client_address, sizeof(client_address)); // copy zeroes into string client_address.sin_family = AF_INET; client_address.sin_addr.s_addr = htonl(INADDR_ANY); client_address.sin_port = htons(CLIENT_PORT); sockfd = socket(AF_INET, SOCK_STREAM, 0); rv = listen(sockfd,MAX_CONNECTION); while(1) { new_sockfd = accept(sockfd, (struct sockaddr *) &client_address, &client_addr_len); //blocks if (new_sockfd < 0) { printf("C: ERROR accept() %i: %s \n", errno, strerror(errno)); sleep(2); } else { printf("C: accepted\n"); FD_SET(new_sockfd, &readset); // sets bit for new_sockfd to list of sockets to watch out for if (maxfd < new_sockfd) maxfd = new_sockfd; if (minfd > new_sockfd) minfd = new_sockfd; } //end if else (new_sockfd) } // end of the forever while loop } int handle_request(void * arg, struct message * msg) { char * cname, gname, payload; char * command[3]; int i, rv, sockfd, client_addr_len; struct sockaddr_in client_address; struct fd_info * info; info = (struct fd_info *) arg; sockfd = info->sock_fd; sockfd = socket(AF_INET, SOCK_STREAM, 0); if (sockfd == -1) { printf("HR: ERROR socket() %i: %s \n", errno, strerror(errno)); break; } else if (sockfd > 0) { printf("HR: new socks is %i \n", sockfd); printf("HR: sin_family is %i: %i\n", msg->peer.client_address.sin_family, msg->peer.client_address.sin_port); //************************************************************* //this is the part that returns error 111: Connection refused!!! //************************************************************* rv = connect(sockfd, (struct sockaddr *) &msg->peer.client_address, sizeof(struct sockaddr)); if (rv == -1) { printf("HR: ERROR: connect() %i: %s \n", errno, strerror(errno)); printf("HR: at %li \n", msg->peer.client_address.sin_addr.s_addr); break; } else if (rv > 0) { info->max_fd = sockfd; printf("HR: connected successfully!! \n"); } } }

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  • PostgreSQL triggers and passing parameters

    - by iandouglas
    This is a multi-part question. I have a table similar to this: CREATE TABLE sales_data ( Company character(50), Contract character(50), top_revenue_sum integer, top_revenue_sales integer, last_sale timestamp) ; I'd like to create a trigger for new inserts into this table, something like this: CREATE OR REPLACE FUNCTION add_contract() RETURNS VOID DECLARE myCompany character(50), myContract character(50), BEGIN myCompany = TG_ARGV[0]; myContract = TG_ARGV[1]; IF (TG_OP = 'INSERT') THEN EXECUTE 'CREATE TABLE salesdata_' || $myCompany || '_' || $myContract || ' ( sale_amount integer, updated TIMESTAMP not null, some_data varchar(32), country varchar(2) ) ;' EXECUTE 'CREATE TRIGGER update_sales_data BEFORE INSERT OR DELETE ON salesdata_' || $myCompany || '_' || $myContract || ' FOR EACH ROW EXECUTE update_sales_data( ' || $myCompany || ',' || $myContract || ', revenue);' ; END IF; END; $add_contract$ LANGUAGE plpgsql; CREATE TRIGGER add_contract AFTER INSERT ON sales_data FOR EACH ROW EXECUTE add_contract() ; Basically, every time I insert a new row into sales_data, I want to generate a new table where the name of the table will be defined as something like "salesdata_Company_Contract" So my first question is how can I pass the Company and Contract data to the trigger so it can be passed to the add_contract() stored procedure? From my stored procedure, you'll see that I also want to update the original sales_data table whenever new data is inserted into the salesdata_Company_Contract table. This trigger will do something like this: CREATE OR REPLACE FUNCTION update_sales_data() RETURNS trigger as $update_sales_data$ DECLARE myCompany character(50) NOT NULL, myContract character(50) NOT NULL, myRevenue integer NOT NULL BEGIN myCompany = TG_ARGV[0] ; myContract = TG_ARGV[1] ; myRevenue = TG_ARGV[2] ; IF (TG_OP = 'INSERT') THEN UPDATE sales_data SET top_revenue_sales = top_revenue_sales + 1, top_revenue_sum = top_revenue_sum + $myRevenue, updated = now() WHERE Company = $myCompany AND Contract = $myContract ; ELSIF (TG_OP = 'DELETE') THEN UPDATE sales_data SET top_revenue_sales = top_revenue_sales - 1, top_revenue_sum = top_revenue_sum - $myRevenue, updated = now() WHERE Company = $myCompany AND Contract = $myContract ; END IF; END; $update_sales_data$ LANGUAGE plpgsql; This will, of course, require that I pass several parameters around within these stored procedures and triggers, and I'm not sure (a) if this is even possible, or (b) practical, or (c) best practice and we should just put this logic into our other software instead of asking the database to do this work for us. To keep our table sizes down, as we'll have hundreds of thousands of transactions per day, we've decided to partition our data using the Company and Contract strings as part of the table names themselves so they're all very small in size; file IO for us is faster and we felt we'd get better performance. Thanks for any thoughts or direction. My thinking, now that I've written all of this out, is that maybe we need to write stored procedures where we pass our insert data as parameters, and call that from our other software, and have the stored procedure do the insert into "sales_data" then create the other table. Then, have a second stored procedure to insert new data into the salesdata_Company_Contract tables, where the table name is passed to the stored proc as a parameter, and again have that stored proc do the insert, then update the main sales_data table afterward. What approach would you take?

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  • Is asp.net caching my sql results?

    - by Christian W
    I have the following method in an App_Code/Globals.cs file: public static XmlDataSource getXmlSourceFromOrgid(int orgid) { XmlDataSource xds = new XmlDataSource(); var ctx = new SensusDataContext(); SqlConnection c = new SqlConnection(ctx.Connection.ConnectionString); c.Open(); SqlCommand cmd = new SqlCommand(String.Format("select orgid, tekst, dbo.GetOrgTreeXML({0}) as Subtree from tblOrg where OrgID = {0}", orgid), c); var rdr = cmd.ExecuteReader(); rdr.Read(); StringBuilder sb = new StringBuilder(); sb.AppendFormat("&lt;node orgid=\"{0}\" tekst=\"{1}\"&gt;",rdr.GetInt32(0),rdr.GetString(1)); sb.Append(rdr.GetString(2)); sb.Append("&lt;/node&gt;"); xds.Data = sb.ToString(); xds.ID = "treedata"; rdr.Close(); c.Close(); return xds; } This gives me an XML-structure to use with the asp.net treeview control (I also use the CssFriendly extender to get nicer code) My problem is that if I logon on my pc with a code that gives me access on a lower level in the tree hierarchy (it's an orgianization hierarchy), it somehow "remembers" what level i logon at. So when my coworker tests from her computer with another code, giving access to another place in the tree, she get's the same tree as me. (The tree is supposed to show your own level and down.) I have added a html-comment to show what orgid it passes to the function, and the orgid passed is correct. So either the treeview caches something serverside, or the sqlquery caches it's result somehow... Any ideas? Sql function: ALTER function [dbo].[GetOrgTreeXML](@orgid int) returns XML begin RETURN (select org.orgid as '@orgid', org.tekst as '@tekst', [dbo].GetOrgTreeXML(org.orgid) from tblOrg org where (@orgid is null and Eier is null) or Eier=@orgid for XML PATH('NODE'), TYPE) end Extra code as requested: int orgid = int.Parse(Session["org"].ToString()); string orgname = context.Orgs.Where(q => q.OrgID == orgid).First().Tekst; debuglit.Text = String.Format("<!-- Id: {0} \n name: {1} -->", orgid, orgname); var orgxml = Globals.getXmlSourceFromOrgid(orgid); tvNavtree.DataSource = orgxml; tvNavtree.DataBind(); Where "debuglit" is a asp:Literal in the aspx file. EDIT: I have narrowed it down. All functions returns correct values. It just doesn't bind to it. I suspect the CssFriendly adapter to have something to do with it. I disabled the CssFriendly adapter and the problem persists... Stepping through it in debug it's correct all the way, with the stepper standing on "tvNavtree.DataBind();" I can hover the pointer over the tvNavtree.Datasource and see that it actually has the correct data. So something must be faulting in the binding process...

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  • Unit testing authorization in a Pylons app fails; cookies aren't been correctly set or recorded

    - by Ian Stevens
    I'm having an issue running unit tests for authorization in a Pylons app. It appears as though certain cookies set in the test case may not be correctly written or parsed. Cookies work fine when hitting the app with a browser. Here is my test case inside a paste-generated TestController: def test_good_login(self): r = self.app.post('/dologin', params={'login': self.user['username'], 'password': self.password}) r = r.follow() # Should only be one redirect to root assert 'http://localhost/' == r.request.url assert 'Dashboard' in r This is supposed to test that a login of an existing account forwards the user to the dashboard page. Instead, what happens is that the user is redirected back to the login. The first POST works, sets the user in the session and returns cookies. Although those cookies are sent in the follow request, they don't seem to be correctly parsed. I start by setting a breakpoint at the beginning of the above method and see what the login response returns: > nosetests --pdb --pdb-failure -s foo.tests.functional.test_account:TestMainController.test_good_login Running setup_config() from foo.websetup > /Users/istevens/dev/foo/foo/tests/functional/test_account.py(33)test_good_login() -> r = self.app.post('/dologin', params={'login': self.user['username'], 'password': self.password}) (Pdb) n > /Users/istevens/dev/foo/foo/tests/functional/test_account.py(34)test_good_login() -> r = r.follow() # Should only be one redirect to root (Pdb) p r.cookies_set {'auth_tkt': '"4c898eb72f7ad38551eb11e1936303374bd871934bd871833d19ad8a79000000!"'} (Pdb) p r.request.environ['REMOTE_USER'] '4bd871833d19ad8a79000000' (Pdb) p r.headers['Location'] 'http://localhost/?__logins=0' A session appears to be created and a cookie sent back. The browser is redirected to the root, not the login, which also indicates a successful login. If I step past the follow(), I get: > /Users/istevens/dev/foo/foo/tests/functional/test_account.py(35)test_good_login() -> assert 'http://localhost/' == r.request.url (Pdb) p r.request.headers {'Host': 'localhost:80', 'Cookie': 'auth_tkt=""\\"4c898eb72f7ad38551eb11e1936303374bd871934bd871833d19ad8a79000000!\\"""; '} (Pdb) p r.request.environ['REMOTE_USER'] *** KeyError: KeyError('REMOTE_USER',) (Pdb) p r.request.environ['HTTP_COOKIE'] 'auth_tkt=""\\"4c898eb72f7ad38551eb11e1936303374bd871934bd871833d19ad8a79000000!\\"""; ' (Pdb) p r.request.cookies {'auth_tkt': ''} (Pdb) p r <302 Found text/html location: http://localhost/login?__logins=1&came_from=http%3A%2F%2Flocalhost%2F body='302 Found...y. '/149> This indicates to me that the cookie was passed in on the request, although with dubious escaping. The environ appears to be without the session created on the prior request. The cookie has been copied to the environ from the headers, but the cookies in the request seems incorrectly set. Lastly, the user is redirected to the login page, indicating that the user isn't logged in. Authorization in the app is done via repoze.who and repoze.who.plugins.ldap with repoze.who_friendlyform performing the challenge. I'm using the stock tests.TestController created by paste: class TestController(TestCase): def __init__(self, *args, **kwargs): if pylons.test.pylonsapp: wsgiapp = pylons.test.pylonsapp else: wsgiapp = loadapp('config:%s' % config['__file__']) self.app = TestApp(wsgiapp) url._push_object(URLGenerator(config['routes.map'], environ)) TestCase.__init__(self, *args, **kwargs) That's a webtest.TestApp, by the way. The encoding of the cookie is done in webtest.TestApp using Cookie: >>> from Cookie import _quote >>> _quote('"84533cf9f661f97239208fb844a09a6d4bd8552d4bd8550c3d19ad8339000000!"') '"\\"84533cf9f661f97239208fb844a09a6d4bd8552d4bd8550c3d19ad8339000000!\\""' I trust that that's correct. My guess is that something on the response side is incorrectly parsing the cookie data into cookies in the server-side request. But what? Any ideas?

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  • Algorithm to select groups of similar items in 2d array

    - by mafutrct
    There is a 2d array of items (in my case they are called Intersections). A certain item is given as a start. The task is to find all items directly or indirectly connected to this item that satisfy a certain function. So the basic algorithm is like this: Add the start to the result list. Repeat until no modification: Add each item in the array that satisfies the function and touches any item in the result list to the result list. My current implementation looks like this: private IList<Intersection> SelectGroup ( Intersection start, Func<Intersection, Intersection, bool> select) { List<Intersection> result = new List<Intersection> (); Queue<Intersection> source = new Queue<Intersection> (); source.Enqueue (start); while (source.Any ()) { var s = source.Dequeue (); result.Add (s); foreach (var neighbour in Neighbours (s)) { if (select (start, neighbour) && !result.Contains (neighbour) && !source.Contains (neighbour)) { source.Enqueue (neighbour); } } } Debug.Assert (result.Distinct ().Count () == result.Count ()); Debug.Assert (result.All (x => select (x, result.First ()))); return result; } private List<Intersection> Neighbours (IIntersection intersection) { int x = intersection.X; int y = intersection.Y; List<Intersection> list = new List<Intersection> (); if (x > 1) { list.Add (GetIntersection (x - 1, y)); } if (y > 1) { list.Add (GetIntersection (x, y - 1)); } if (x < Size) { list.Add (GetIntersection (x + 1, y)); } if (y < Size) { list.Add (GetIntersection (x, y + 1)); } return list; } (The select function takes a start item and returns true iff the second item satisfies.) This does its job and turned out to be reasonable fast for the usual array sizes (about 20*20). However, I'm interested in further improvements. Any ideas? Example (X satisfies in relation to other Xs, . does never satisfy): .... XX.. .XX. X... In this case, there are 2 groups: a central group of 4 items and a group of a single item in the lower left. Selecting the group (for instance by starting item [2, 2]) returns the former, while the latter can be selected using the starting item and sole return value [0, 3]. Example 2: .A.. ..BB A.AA This time there are 4 groups. The 3 A groups are not connected, so they are returned as separate groups. The bigger A and B groups are connected, but A does not related to B so they are returned as separate groups.

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  • Why is parsing a jSON response to a jQUERY ajax request not working

    - by Ankur
    I know there are several similar questions on SO, I have used some of them to get this far. I am trying to list a set of urls that match my input values. I have a servlet which takes some input e.g. "aus" in the example below and returns some output using out.print() e.g. the two urls I have shown below. EXAMPLE Input: "aus" Output: [{"url":"http://dbpedia.org/resource/Stifel_Nicolaus"},{"url":"http://sempedia.org/ontology/object/Australia"}] Which is exactly what I want. I have seen that firebug doesn't seem to have anything in the response section despite having called out.print(jsonString); and it seems that out.print(jsonString); is working as expected which suggests that the variable 'jsonString' contains the expected values. However I am not exactly sure what is wrong. -------- The jQuery --------- $(document).ready(function() { $("#input").keyup(function() { var input = $("#input").val(); //$("#output").html(input); ajaxCall(input); }); }); function ajaxCall(input) { // alert(input); $.ajax({ url: "InstantSearchServlet", data: "property="+input, beforeSend: function(x) { if(x && x.overrideMimeType) { x.overrideMimeType("application/j-son;charset=UTF-8"); } }, dataType: "json", success: function(data) { for (var i = 0, len = datalength; i < len; ++i) { var urlData = data[i]; $("#output").html(urlData.url); } } }); } ------ The Servlet that calls the DAO class - and returns the results ------- public class InstantSearchServlet extends HttpServlet{ private static final long serialVersionUID = 1L; public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { System.out.println("You called?"); response.setContentType("application/json"); PrintWriter out = response.getWriter(); InstantSearch is = new InstantSearch(); String input = (String)request.getParameter("property"); System.out.println(input); try { ArrayList<String> urllist; urllist = is.getUrls(input); String jsonString = convertToJSON(urllist); out.print(jsonString); System.out.println(jsonString); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } private String convertToJSON(ArrayList<String> urllist) { Iterator<String> itr = urllist.iterator(); JSONArray jArray = new JSONArray(); int i = 0; while (itr.hasNext()) { i++; JSONObject json = new JSONObject(); String url = itr.next(); try { json.put("url",url); } catch (JSONException e) { // TODO Auto-generated catch block e.printStackTrace(); } jArray.put(json); } String results = jArray.toString(); return results; } }

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  • BFS Shortest Path: Edge weight either 1 or 2

    - by Hackster
    I am trying to implement a shortest path algorithm using BFS. That is I am trying to find the shortest path from a specified vertex to every other vertex. However, its a special case where all edge weights are either 1 or 2. I know it could be done with Dijkstra's algorithm but I must use Breadth First Search. So far I have a working version of BFS that searches first for a vertex connected with an edge of weight 1. If it cannot find it, then returns a vertex connected with an edge of weight 2. After thinking about it, this is not the correct way to find the shortest path. The problem is I cannot think of any reasoning why BFS would work with weights 1 or 2, as opposed to any weight. Here is the code: public void addEdge(int start, int end, int weight) { adjMat[start][end] = 1; adjMat[end][start] = 1; edge_weight[start][end] = weight; edge_weight[end][start] = weight; } // ------------------------------------------------------------- public void bfs() // breadth-first search { // begin at vertex 0 vertexList[0].wasVisited = true; // mark it displayVertex(0); // display it theQueue.insert(0); // insert at tail int v2; while( !theQueue.isEmpty() ) // until queue empty, { int v1 = theQueue.remove(); // remove vertex at head // until it has no unvisited neighbors while( (v2=getAdjUnvisitedVertex(v1)) != -1 ){// get one, vertexList[v2].wasVisited = true; // mark it displayVertex(v2); // display it theQueue.insert(v2); // insert it } } // end while(queue not empty) // queue is empty, so we're done for(int j=0; j<nVerts; j++) // reset flags vertexList[j].wasVisited = false; } // end bfs() // ------------------------------------------------------------- // returns an unvisited vertex adj to v -- ****WITH WEIGHT 1**** public int getAdjUnvisitedVertex(int v) { for (int j = 0; j < nVerts; j++) if (adjMat[v][j] == 1 && vertexList[j].wasVisited == false && edge_weight[v][j] == 1){ //System.out.println("Vertex found with 1:"+ vertexList[j].label); return j; } for (int k = 0; k < nVerts; k++) if (adjMat[v][k] == 1 && vertexList[k].wasVisited == false && edge_weight[v][k] == 2){ //System.out.println("Vertex found with 2:"+vertexList[k].label); return k; } return -1; } // end getAdjUnvisitedVertex() // ------------------------------------------------------------- } //////////////////////////////////////////////////////////////// public class BFS{ public static void main(String[] args) { Graph theGraph = new Graph(); theGraph.addVertex('A'); // 0 (start for bfs) theGraph.addVertex('B'); // 1 theGraph.addVertex('C'); // 2 theGraph.addEdge(0, 1,2); // AB theGraph.addEdge(1, 2,1); // BC theGraph.addEdge(2, 0,1); // AD System.out.print("Visits: "); theGraph.bfs(); // breadth-first search System.out.println(); } // end main() } The problem then is, that I don't know why BFS can work for the shortest path problem with edges of weight 1 or 2 as opposed to any edges of any weight. Any help is appreciated. Thanks!

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  • Create and Share a File (Also a mysterious error)

    - by Kirk
    My goal is to create a XML file and then send it through the share Intent. I'm able to create a XML file using this code FileOutputStream outputStream = context.openFileOutput(fileName, Context.MODE_WORLD_READABLE); PrintStream printStream = new PrintStream(outputStream); String xml = this.writeXml(); // get XML here printStream.println(xml); printStream.close(); I'm stuck trying to retrieve a Uri to the output file in order to share it. I first tried to access the file by converting the file to a Uri File outFile = context.getFileStreamPath(fileName); return Uri.fromFile(outFile); This returns file:///data/data/com.my.package/files/myfile.xml but I cannot appear to attach this to an email, upload, etc. If I manually check the file length, it's proper and shows there is a reasonable file size. Next I created a content provider and tried to reference the file and it isn't a valid handle to the file. The ContentProvider doesn't ever seem to be called a any point. Uri uri = Uri.parse("content://" + CachedFileProvider.AUTHORITY + "/" + fileName); return uri; This returns content://com.my.package.provider/myfile.xml but I check the file and it's zero length. How do I access files properly? Do I need to create the file with the content provider? If so, how? Update Here is the code I'm using to share. If I select Gmail, it does show as an attachment but when I send it gives an error Couldn't show attachment and the email that arrives has no attachment. public void onClick(View view) { Log.d(TAG, "onClick " + view.getId()); switch (view.getId()) { case R.id.share_cancel: setResult(RESULT_CANCELED, getIntent()); finish(); break; case R.id.share_share: MyXml xml = new MyXml(); Uri uri; try { uri = xml.writeXmlToFile(getApplicationContext(), "myfile.xml"); //uri is "file:///data/data/com.my.package/files/myfile.xml" Log.d(TAG, "Share URI: " + uri.toString() + " path: " + uri.getPath()); File f = new File(uri.getPath()); Log.d(TAG, "File length: " + f.length()); // shows a valid file size Intent shareIntent = new Intent(); shareIntent.setAction(Intent.ACTION_SEND); shareIntent.putExtra(Intent.EXTRA_STREAM, uri); shareIntent.setType("text/plain"); startActivity(Intent.createChooser(shareIntent, "Share")); } catch (FileNotFoundException e) { e.printStackTrace(); } break; } } I noticed that there is an Exception thrown here from inside createChooser(...), but I can't figure out why it's thrown. E/ActivityThread(572): Activity com.android.internal.app.ChooserActivity has leaked IntentReceiver com.android.internal.app.ResolverActivity$1@4148d658 that was originally registered here. Are you missing a call to unregisterReceiver()? I've researched this error and can't find anything obvious. Both of these links suggest that I need to unregister a receiver. Chooser Activity Leak - Android Why does Intent.createChooser() need a BroadcastReceiver and how to implement? I have a receiver setup, but it's for an AlarmManager that is set elsewhere and doesn't require the app to register / unregister. Code for openFile(...) In case it's needed, here is the content provider I've created. public ParcelFileDescriptor openFile(Uri uri, String mode) throws FileNotFoundException { String fileLocation = getContext().getCacheDir() + "/" + uri.getLastPathSegment(); ParcelFileDescriptor pfd = ParcelFileDescriptor.open(new File(fileLocation), ParcelFileDescriptor.MODE_READ_ONLY); return pfd; }

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  • What Good way to keep some different data in Cookies in asp.net?

    - by Dmitriy
    Hello! I want to keep some different data in one cookie file and write this class, and want to know - is this good? For example - user JS enable.When user open his first page on my site, i write to session his GMT time and write with this manager JS state. (GMT time is ajax request with js). And i want to keep some data in this cookie (up to 10 values). Have any advices or tips? /// <summary> /// CookiesSettings /// </summary> internal enum CookieSetting { IsJsEnable = 1, } internal class CookieSettingValue { public CookieSetting Type { get; set; } public string Value { get; set; } } /// <summary> /// Cookies to long time of expire /// </summary> internal class CookieManager { //User Public Settings private const string CookieValueName = "UPSettings"; private string[] DelimeterValue = new string[1] { "#" }; //cookie daat private List<CookieSettingValue> _data; public CookieManager() { _data = LoadFromCookies(); } #region Save and load /// <summary> /// Load from cookie string value /// </summary> private List<CookieSettingValue> LoadFromCookies() { if (!CookieHelper.RequestCookies.Contains(CookieValueName)) return new List<CookieSettingValue>(); _data = new List<CookieSettingValue>(); string data = CookieHelper.RequestCookies[CookieValueName].ToString(); string[] dels = data.Split(DelimeterValue, StringSplitOptions.RemoveEmptyEntries); foreach (string delValue in dels) { int eqIndex = delValue.IndexOf("="); if (eqIndex == -1) continue; int cookieType = ValidationHelper.GetInteger(delValue.Substring(0, eqIndex), 0); if (!Enum.IsDefined(typeof(CookieSetting), cookieType)) continue; CookieSettingValue value = new CookieSettingValue(); value.Type = (CookieSetting)cookieType; value.Value = delValue.Substring(eqIndex + 1, delValue.Length - eqIndex-1); _data.Add(value); } return _data; } public void Save() { CookieHelper.SetValue(CookieValueName, ToCookie(), DateTime.UtcNow.AddMonths(6)); } #endregion #region Get value public bool Bool(CookieSetting type, bool defaultValue) { CookieSettingValue inList = _data.SingleOrDefault(x => x.Type == type); if (inList == null) return defaultValue; return ValidationHelper.GetBoolean(inList.Value, defaultValue); } #endregion #region Set value public void SetValue(CookieSetting type, int value) { CookieSettingValue inList = _data.SingleOrDefault(x => x.Type == type); if (inList == null) { inList = new CookieSettingValue(); inList.Type = type; inList.Value = value.ToString(); _data.Add(inList); } else { inList.Value = value.ToString(); } } public void SetValue(CookieSetting type, bool value) { CookieSettingValue inList = _data.SingleOrDefault(x => x.Type == type); if (inList == null) { inList = new CookieSettingValue(); inList.Type = type; inList.Value = value.ToString(); _data.Add(inList); } else { inList.Value = value.ToString(); } } #endregion #region Private methods private string ToCookie() { StringBuilder sb = new StringBuilder(); for (int i = 0; i < _data.Count; i++) { sb.Append((int)_data[i].Type); sb.Append("="); sb.Append(_data[i].Value); sb.Append(DelimeterValue[0]); } return sb.ToString(); } /// <summary> /// Cookie length in bytes. Max - 4 bytes /// </summary> /// <returns></returns> private int GetLength() { return System.Text.Encoding.UTF8.GetByteCount(ToCookie()); } #endregion } P.S. i want to keep many data in one cookies file to compress data and decrease cookies count.

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  • Converting switch statements to more elegant solution.

    - by masfenix
    I have a 9 x 9 matrix. (think of suduko). 4 2 1 6 8 1 8 5 8 3 1 5 8 1 1 7 5 8 1 1 4 0 5 6 7 0 4 6 2 5 5 4 4 8 1 2 6 8 8 2 8 1 6 3 5 8 4 2 6 4 7 4 1 1 1 3 5 3 8 8 5 2 2 2 6 6 0 8 8 8 0 6 8 7 2 3 3 1 1 7 4 now I wanna be able to get a "quadrant". for example (according to my code) the quadrant 2 , 2 returns the following: 5 4 4 2 8 1 6 4 7 If you've noticed, this is the matrix from the very center of the 9 x 9. I've split everything up in to pairs of "3" if you know what i mean. the first "ROW" is from 0 - 3, the second from 3 - 6, the third for 6 - 9.. I hope this makes sense ( I am open to alternate ways to go about this) anyways, heres my code. I dont really like this way, even though it works. I do want speed though beccause i am making a suduko solver. //a quadrant returns the mini 3 x 3 //row 1 has three quads,"1", "2", 3" //row 2 has three quads "1", "2", "3" etc public int[,] GetQuadrant(int rnum, int qnum) { int[,] returnMatrix = new int[3, 3]; int colBegin, colEnd, rowBegin, rowEnd, row, column; //this is so we can keep track of the new matrix row = 0; column = 0; switch (qnum) { case 1: colBegin = 0; colEnd = 3; break; case 2: colBegin = 3; colEnd = 6; break; case 3: colBegin = 6; colEnd = 9; break; default: colBegin = 0; colEnd = 0; break; } switch (rnum) { case 1: rowBegin = 0; rowEnd = 3; break; case 2: rowBegin = 3; rowEnd = 6; break; case 3: rowBegin = 6; rowEnd = 9; break; default: rowBegin = 0; rowEnd = 0; break; } for (int i = rowBegin ; i < rowEnd; i++) { for (int j = colBegin; j < colEnd; j++) { returnMatrix[row, column] = _matrix[i, j]; column++; } column = 0; row++; } return returnMatrix; }

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  • (SQL) Selecting from a database based on multiple pairs of pairs

    - by Owen Allen
    The problem i've encountered is attempting to select rows from a database where 2 columns in that row align to specific pairs of data. IE selecting rows from data where id = 1 AND type = 'news'. Obviously, if it was 1 simple pair it would be easy, but the issue is we are selecting rows based on 100s of pair of data. I feel as if there must be some way to do this query without looping through the pairs and querying each individually. I'm hoping some SQL stackers can provide guidance. Here's a full code break down: Lets imagine that I have the following dataset where history_id is the primary key. I simplified the structure a bit regarding the dates for ease of reading. table: history history_id id type user_id date 1 1 news 1 5/1 2 1 news 1 5/1 3 1 photo 1 5/2 4 3 news 1 5/3 5 4 news 1 5/3 6 1 news 1 5/4 7 2 photo 1 5/4 8 2 photo 1 5/5 If the user wants to select rows from the database based on a date range we would take a subset of that data. SELECT history_id, id, type, user_id, date FROM history WHERE date BETWEEN '5/3' AND '5/5' Which returns the following dataset history_id id type user_id date 4 3 news 1 5/3 5 4 news 1 5/3 6 1 news 1 5/4 7 2 photo 1 5/4 8 2 photo 1 5/5 Now, using that subset of data I need to determine how many of those entries represent the first entry in the database for each type,id pairing. IE is row 4 the first time in the database that id: 3, type: news appears. So I use a with() min() query. In real code the two lists are programmatically generated from the result sets of our previous query, here I spelled them out for ease of reading. WITH previous AS ( SELECT history_id, id, type FROM history WHERE id IN (1,2,3,4) AND type IN ('news','photo') ) SELECT min(history_id) as history_id, id, type FROM previous GROUP BY id, type Which returns the following data set. history_id id type user_id date 1 1 news 1 5/1 2 1 news 1 5/1 3 1 photo 1 5/2 4 3 news 1 5/3 5 4 news 1 5/3 6 1 news 1 5/4 7 2 photo 1 5/4 8 2 photo 1 5/5 You'll notice it's the entire original dataset, because we are matching id and type individually in lists, rather than as a collective pairs. The result I desire is, but I can't figure out the SQL to get this result. history_id id type user_id date 1 1 news 1 5/1 4 3 news 1 5/3 5 4 news 1 5/3 7 2 photo 1 5/4 Obviously, I could go the route of looping through each pair and querying the database to determine it's first result, but that seems an inefficient solution. I figured one of the SQL gurus on this site might be able to spread some wisdom. In case I'm approaching this situation incorrectly, the gist of the whole routine is that the database stores all creations and edits in the same table. I need to track each users behavior and determine how many entries in the history table are edits or creations over a specific date range. Therefore I select all type:id pairs from the date range based on a user_id, and then for each pairing I determine if the user is responsible for the first that occurs in the database. If first, then creation else edit. Any assistance would be awesome.

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  • Why doesn't the default model binder update my partial view model on postback?

    - by bdnewbe
    I have a class that contains another class as one of its properties. public class SiteProperties { public SiteProperties() { DropFontFamily = "Arial, Helvetica, Sans-serif"; } public string DropFontFamily { get; set; } private ResultPageProperties m_ResultPagePropertyList; public ResultPageProperties ResultPagePropertyList { get { if (m_ResultPagePropertyList == null) m_ResultPagePropertyList = new ResultPageProperties(); return m_ResultPagePropertyList; } set { m_ResultPagePropertyList = value; } } } The second class has just one property public class ResultPageProperties { public ResultPageProperties() { ResultFontFamily = "Arial, Helvetica, Sans-serif"; } public string ResultFontFamily { get; set; } } My controller just grabs the SiteProperties and returns the view. On submit, it accepts SiteProperties and returns the same view. public class CompanyController : Controller { public ActionResult SiteOptions(int id) { SiteProperties site = new SiteProperties(); PopulateProperyDropDownLists(); return View("SiteOptions", site); } [AcceptVerbs(HttpVerbs.Post)] public ActionResult SiteOptions(SiteProperties properties) { PopulateProperyDropDownLists(); return View("SiteOptions", properties); } private void PopulateProperyDropDownLists() { var fontFamilyList = new List<SelectListItem>(); fontFamilyList.Add(new SelectListItem() { Text = "Arial, Helvetica, Sans-serif", Value = "Arial, Helvetica, Sans-serif" }); fontFamilyList.Add(new SelectListItem() { Text = "Times New Roman, Times, serif", Value = "Times New Roman, Times, serif" }); fontFamilyList.Add(new SelectListItem() { Text = "Courier New, Courier, Monospace", Value = "Courier New, Courier, Monospace" }); ViewData["FontFamilyList"] = fontFamilyList; } } The view contains a partial view that renders the ResultPageProperties Model. <% using (Html.BeginForm("SiteOptions", "Company", FormMethod.Post)) {%> <p><input type="submit" value="Submit" /></p> <div>View level input</div> <div> <label>Font family</label><br /> <%= Html.DropDownListFor(m => m.DropFontFamily, ViewData["FontFamilyList"] as List<SelectListItem>, new { Class = "UpdatesDropDownExample" })%> </div> <% Html.RenderPartial("ResultPagePropertyInput", Model.ResultPagePropertyList); %> <% } %> The partial is just <div style='margin-top: 1em;'>View level input</div> <div> <label>Font family</label><br /> <%= Html.DropDownListFor(m => m.ResultFontFamily, ViewData["FontFamilyList"] as List<SelectListItem>, new { Class = "UpdatesResultPageExample" })%> </div> OK, so when the page renders, you get "Arial, ..." in both selects. If you choose another option for both and click submit, the binder populates the SiteProperties object and passes it to the controller. However, the ResultFontFamily always contains the original value. I was expecting it to have the value the user selected. What am I missing?

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