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Scheme Homework Assignment

- by user1704677

In a course I am taking we recently had to learn the programming language Scheme. I get all of the basics, which is pretty much all that we have gone though. I'm just having trouble learning to think in the different way that Scheme consists of. I was given an assignment and really do not even know how to start. I have sat here for a few hours trying to figure out how to even get started, but I'm kind of stumped. For the record, I'm not asking for the code to solve this problem, but more of some thoughts to get me on the right track. Anyway, here is the gist of the assignment... We are given a list of ten numbers that represent a voter's votes. The numbers are -1, 0 or 1. Then we are given a list of lists of Candidates, with a name and then ten numbers corresponding to that candidate's votes. These numbers are also -1 0 and 1. So for example. '(0 0 0 -1 -1 1 0 1 0 -1) '(Adams 0 1 -1 0 1 1 0 -1 -1 0 0) We are asked to implement a function called best_candidates that will take in a list of numbers (Voter) and a list of lists of Candidates. Then we have to compare the votes of the voter against the list of each candidate and return a list of names with the most common votes. So far, I've come up with a few things. I'm just confused on how I will check the values and retain the name of the voter? I guess I'm still stuck in thinking C/Java and it's making this very tough. Any suggestions to help get me started?

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Not allow more than 5 digits after decimal. in on javascript "OnKeyUp"?

- by James123

I have a javascript code for textbox that will put commas on in digits like (11,23,233) mTextbox.Attributes.Add("OnKeyUp", "javascript:this.value=Comma(this.value);") function Comma(Num) { Num += ''; Num = Num.replace(',', ''); Num = Num.replace(',', ''); Num = Num.replace(',', ''); Num = Num.replace(',', ''); Num = Num.replace(',', ''); Num = Num.replace(',', ''); x = Num.split('.'); x1 = x[0]; x2 = x.length > 1 ? '.' + x[1] : ''; var rgx = /(\d+)(\d{3})/; while (rgx.test(x1)) x1 = x1.replace(rgx, '$1' + ',' + '$2'); return x1 + x2; } Now same here I need to restrict user to enter not morethan 5 digits after decimal (ex: Allow: 12,23,221.34323 Not Allow: 12,23,232.232423 I can change above javascript to work that?

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Sanitizing usser input before adding it to the DOM in Javascript

- by I GIVE TERRIBLE ADVICE

I'm writing the JS for a chat appication I'm working on in my free time, and I need to have HTML identifiers that change according to user submitted data. This is usually something conceptually shaky enough that I would not even attempt it, but I don't see myself having much of a choice this time. What I need to do then is to escape the HTML id to make sure it won't allow for XSS or breaking HTML. Here's the code: var user_id = escape(id) var txt = '<div class="chut">'+ '<div class="log" id="chut_'+user_id+'"></div>'+ '<textarea id="chut_'+user_id+'_msg"></textarea>'+ '<label for="chut_'+user_id+'_to">To:</label>'+ '<input type="text" id="chut_'+user_id+'_to" value='+user_id+' readonly="readonly" />'+ '<input type="submit" id="chut_'+user_id+'_send" value="Message"/>'+ '</div>'; What would be the best way to escape id to avoid any kind of problem mentioned above? As you can see, right now I'm using the built-in escape() function, but I'm not sure of how good this is supposed to be compared to other alternatives. I'm mostly used to sanitizing input before it goes in a text node, not an id itself.

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Modifying Django's pre_save/post_save Data

- by Rodrogo

Hi, I'm having a hard time to grasp this post_save/pre_save signals from django. What happens is that my model has a field called status and when a entry to this model is added/saved, it's status must be changed accordingly with some condition. My model looks like this: class Ticket(models.Model): (...) status = models.CharField(max_length=1,choices=OFFERT_STATUS, default='O') And my signal handler, configured for pre_save: def ticket_handler(sender, **kwargs): ticket = kwargs['instance'] (...) if someOtherCondition: ticket.status = 'C' Now, what happens if I put aticket.save() just bellow this last line if statement is a huge iteration black hole, since this action calls the signal itself. And this problem happens in both pre_save and post_save. Well... I guess that the capability of altering a entry before (or even after) saving it is pretty common in django's universe. So, what I'm doing wrong here? Is the Signals the wrong approach or I'm missing something else here? Also, would it be possible to, once this pre_save/post_save function is triggered, to access another model's instance and change a specific row entry on that? Thanks

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C++ const-reference semantics?

- by Kristoffer

Consider the sample application below. It demonstrates what I would call a flawed class design. #include <iostream> using namespace std; struct B { B() : m_value(1) {} long m_value; }; struct A { const B& GetB() const { return m_B; } void Foo(const B &b) { // assert(this != &b); m_B.m_value += b.m_value; m_B.m_value += b.m_value; } protected: B m_B; }; int main(int argc, char* argv[]) { A a; cout << "Original value: " << a.GetB().m_value << endl; cout << "Expected value: 3" << endl; a.Foo(a.GetB()); cout << "Actual value: " << a.GetB().m_value << endl; return 0; } Output: Original value: 1 Expected value: 3 Actual value: 4 Obviously, the programmer is fooled by the constness of b. By mistake b points to this, which yields the undesired behavior. My question: What const-rules should you follow when designing getters/setters? My suggestion: Never return a reference to a member variable if it can be set by reference through a member function. Hence, either return by value or pass parameters by value. (Modern compilers will optimize away the extra copy anyway.)

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MySQL table doesn't update, can't find the error message

- by mobius1ski

My knowledge level here is like zilch, but please bear with me. I have a site built in PHP/MySQL that uses the Smarty template engine. There's a registration form that, for some reason, isn't posting the data to the DB. Here's the function: $u = new H_User; $u->setFrom($p); $smarty->assign('user', $u); $val = $u->validate(); if ($val === true) { $temp = new H_User; $temp->orderBy('user_id desc'); $temp->find(true); $next_id = $temp->user_id + 1; $u->user_id = $next_id; $u->user_password = md5($p['user_password']); $u->user_regdate = mktime(); $u->user_active = 0; $u->insert(); $hash = md5($u->user_email . $u->user_regdate); $smarty->assign('hash', $hash); $smarty->assign('user', $u); $smarty->assign('registration_complete', true); $d = new H_Demographic; $d->setFrom($p); $d->insert(); How can I figure out what's wrong here? I don't get any PHP errors and I don't know how to get MySQL to display the errors that might indicate what's wrong with that syntax.

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session_set_cookie_params on multi-domain sites

- by nillls

Hi! I'm currently developing for an application (www.domain.se, .eu) where we're experiencing problems with sessions not propagating across domains. Internet Explorer is the root cause of this, as it will differentiate sessions depending on whether we're typing in "domain.se" or "www.domain.se". Due to some unfortunate redirecting, we're not able to keep the user on the same address the user typed in, instead we're always redirecting to www.domain.se on login. Needless to say, IE users can not login when typing "domain.se". To make this error go away, we implemented a function to try and set the session to be valid across all possible domains by doing the following: if($_SERVER['HTTP_HOST'] == "domain.se") { session_set_cookie_params(3600, '/', '.domain.se', true); } There are basically a few if:s that we go through depending on what address the user typed in, but the third argument stays the same. This, however, results in no-one being able to log in, regardless of domain. I've tried reading up on how session_set_cookie_params() works but to no avail. Any help is greatly appreciated!

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Rotating bits of any integer in C

- by Tim

Pass a integer 2 to this function and then return a integer which is 4 x = 2; x = rotateInt('L', x, 1); (left shift the bits by 1) Example: 00000010 - rotate left by 1 - 00000100 but if I pass this: x = rotateInt('R', x, 3); it will return 64, 01000000 Here is the code, can someone correct the error... thanks int rotateInt(char direction, unsigned int x, int y) { unsigned int mask = 0; int num = 0, result = 0; int i; for(i = 0; i < y; i++) { if(direction == 'R') { if((x & 1) == 1) x = (x ^ 129); else x = x >> 1; } else if(direction == 'L') { if((x & 128) == 1) x = (x ^ 129); else x = x << 1; } } result = (result ^ x); return result; }

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Qt - 2 QMainWindow glued - Size of Layout

- by user1773603

I have a main window that I center this way in main.cpp : int main(int argc, char *argv[]) { QApplication app(argc, argv); QMainWindow *qmain = new QMainWindow; Ui_MainWindow ui; ui.setupUi(qmain); QRect r = qmain->geometry(); r.moveCenter(QApplication::desktop()->availableGeometry().center()); qmain->setGeometry(r); qmain->show(); return app.exec(); } In this "qmain" main window, I can create another QMainWindow and I try to make stick (or glue I don't know how to say) the two windows. Actually, I would like the right-top corner of the first one to be located at the left-top of the second one. For this, I use the following Ui_MainWindow's member function : void Ui_MainWindow::generate_IC() { qmenu = new QMainWindow; DiskMenu = new Ui_DiskGalMenu; DiskMenu->setupUi(qmenu); setInitialDiskMenuPosition(qmenu, this); qmenu->show(); } and the setInitialDiskMenuPosition : void Ui_MainWindow::setInitialDiskMenuPosition(QMainWindow *MainWindow, Ui_MainWindow *parent) { QSize size = parent->widget->size(); QDesktopWidget* desktop = QApplication::desktop(); int width = desktop->width(); int height = desktop->height(); int mw = size.width(); int mh = size.height(); int right = (width/2) + (mw/2); int top = (height/2) - (mh/2); MainWindow->move(right, top); } But the problem is that I don't get exactly what I want since the centralwidget size "parent- widget-size()" only returns the size of the widget and not the whole "qmain" parent window. So I have a light shift because the borders of the "qmain" window are not taken in account like it is shown below : If I could have access to the size of the whole parent window... If anyone could help me

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optimization math computation (multiplication and summing)

- by wiso

Suppose you want to compute the sum of the square of the differences of items: $\sum_{i=1}^{N-1} (x_i - x_{i+1})^2$, the simplest code (the input is std::vector<double> xs, the ouput sum2) is: double sum2 = 0.; double prev = xs[0]; for (vector::const_iterator i = xs.begin() + 1; i != xs.end(); ++i) { sum2 += (prev - (*i)) * (prev - (*i)); // only 1 - with compiler optimization prev = (*i); } I hope that the compiler do the optimization in the comment above. If N is the length of xs you have N-1 multiplications and 2N-3 sums (sums means + or -). Now suppose you know this variable: sum = $x_1^2 + x_N^2 + 2 sum_{i=2}^{N-1} x_i^2$ Expanding the binomial square: $sum_i^{N-1} (x_i-x_{i+1})^2 = sum - 2\sum_{i=1}^{N-1} x_i x_{i+1}$ so the code becomes: double sum2 = 0.; double prev = xs[0]; for (vector::const_iterator i = xs.begin() + 1; i != xs.end(); ++i) { sum2 += (*i) * prev; prev = (*i); } sum2 = -sum2 * 2. + sum; Here I have N multiplications and N-1 additions. In my case N is about 100. Well, compiling with g++ -O2 I got no speed up (I try calling the inlined function 2M times), why?

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Can't call an object method. PHP reports variable undefined

- by user1285697

This is the weirdest bug! It is probably something silly, but I have no idea how to fix it. If anyone could help, I would be most grateful! I have three files, one is called items.php, another is called tableFunctions.php, and the third is called mysql.php. I use two global objects called 'mysql' and 'tableFunctions'. They are stored in the files 'mysql.php', and 'tableFunctions.php', respectively. In each file, I create an instance of its object, assigning it to the global variable $_mysql, or $_table. like this: In the file mysql.php: global $_mysql; $_mysql = new mysql(); In the file tableFunctions.php: global $_table; $_table = new tableFunctions(); Here's how it is supposed to work: The items.php file includes the tableFunctions.php file... Which in turn, needs the mysql.php file, so it includes it too. In the items.php file, I call the method getTable(), which is contained in the object tableFunctions.(and in the variable $_table.) Like this: $t = $_table->getTable('items'); The getTable function calls the method, arrayFromResult(), which is contained within in the object mysql.(and in the variable $_mysql.) Like this: $result = $_mysql->arrayFromResult($r); That's where I get the error. PHP says that the variable '$_mysql' is undefined, but I defined it in the 'mysql.php' file.(see above) I also included mysql.php with the following code: include_once 'mysql.php'; I have no idea what is wrong! If anyone can help that would be much appreciated. The source files can be downloaded with the following link: https://www.dropbox.com/sh/bjj2gyjsybym89r/YLxqyNvQdn

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jquery to create array from form data

- by AndrewStevens

I've been wrestling with this problem for a couple hours now. Essentially, what I need to do is take the following or similar HTML: <div id="excpdivs"> <div class="excpdiv" id="excpdiv0"> Date: <input name="excp[0][date]"> Open: <input name="excp[0][open]"> Close: <input name="excp[0][close]"> </div> <div class="excpdiv" id="expdiv1"> Date: <input name="excp[1][date]"> Open: <input name="excp[1][open]"> Close: <input name="excp[1][close]"> </div> and get an array similar to the following to a php script: Array ( [0] => Array ( [date] => 2012-09-15 [open] => 3:00 [close] => 5:00 ) [1] => Array ( [date] => 2012-09-16 [open] => 2:00 [close] => 5:00 ) ) My main problem is getting the values from the input elements. My latest attempt is the following: var results = []; $(".excpdiv").each(function(){ var item = {}; var inpts = $(this).find("input"); item.date = $(inpts.get(0)).val(); item.open = $(inpts.get(1)).val(); item.close = $(inpts.get(2)).val(); results.push(item); }); Am I on the right track or am I hopelessly lost?

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Simpler / more efficient method of nested if ... else flow?

- by Scott

I'm currently working on an emulation server for a flash-client based game, which has a "pets system", and I was wondering if there was a simpler way of going about checking the level of specified pets. Current code: public int Level { get { if (Expirience > 100) // Level 2 { if (Expirience > 200) // Level 3 { if (Expirience > 400) // Level 4 - Unsure of Goal { if (Expirience > 600) // Level 5 - Unsure of Goal { if (Expirience > 1000) // Level 6 { if (Expirience > 1300) // Level 7 { if (Expirience > 1800) // Level 8 { if (Expirience > 2400) // Level 9 { if (Expirience > 3200) // Level 10 { if (Expirience > 4300) // Level 11 { if (Expirience > 7200) // Level 12 - Unsure of Goal { if (Expirience > 8500) // Level 13 - Unsure of Goal { if (Expirience > 10100) // Level 14 { if (Expirience > 13300) // Level 15 { if (Expirience > 17500) // Level 16 { if (Expirience > 23000) // Level 17 { return 17; // Bored } return 16; } return 15; } return 14; } return 13; } return 12; } return 11; } return 10; } return 9; } return 8; } return 7; } return 6; } return 5; } return 4; } return 3; } return 2; } return 1; } } Yes, I'm aware I've misspelt Experience, I had made the mistake in a previous function and hadn't gotten around to updating everything.

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Pass Element value to $ajax->link in cakephp

- by TwoThumbs

I need to pass the value of an element to an $ajax-link without using a form/submit structure. (because I have a dynamically set number of clickable links through which I am triggering the action) I used to do this in Ruby using the Prototype javascript function $F like this: <%= link_to_remote "#{item.to_s}", :url => { :action => :add_mpc }, :with => "'category=' + $F('mpc_category')" -%> But this does not seem to work in Cakephp: <?php echo $ajax->link(substr($vehicle['vehicles']['year'], -2), array('action' => 'add_mpc', 'category' => '$F("mpc_category")'), array('update' => 'results', 'position' => 'top')); ?> PHP sees $F as a variable instead of a call to javascript. I'm not too familiar with Javascript, but is there another way to pass the value of the 'mpc_category' input element to the controller through this link? I have been looking for a couple days and can't find anyone dealing with this specific issue. Thanks for any assistance. Edit: fixed syntax in php statement.

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Canvas draw calls are rendering out of sequence

- by Tom Murray

I have the following code for writing draw calls to a "back buffer" canvas, then placing those in a main canvas using drawImage. This is for optimization purposes and to ensure all images get placed in sequence. Before placing the buffer canvas on top of the main one, I'm using fillRect to create a dark-blue background on the main canvas. However, the blue background is rendering after the sprites. This is unexpected, as I am making its fillRect call first. Here is my code: render: function() { this.buffer.clearRect(0,0,this.w,this.h); this.context.fillStyle = "#000044"; this.context.fillRect(0,0,this.w,this.h); for (var i in this.renderQueue) { for (var ii = 0; ii < this.renderQueue[i].length; ii++) { sprite = this.renderQueue[i][ii]; // Draw it! this.buffer.fillStyle = "green"; this.buffer.fillRect(sprite.x, sprite.y, sprite.w, sprite.h); } } this.context.drawImage(this.bufferCanvas,0,0); } This also happens when I use fillRect on the buffer canvas, instead of the main one. Changing the globalCompositeOperation between 'source-over' and 'destination-over' (for both contexts) does nothing to change this. Paradoxically, if I instead place the blue fillRect inside the nested for loops with the other draw calls, it works as expected... Thanks in advance!

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Parse error after upgrading to PHP 5.3

- by poer

I have a php code that works well in PHP 5.2 but throwing "Parse error: syntax error, unexpected '}'" after upgrading to PHP 5.3. When I use echo/print or heredocs to print all the HTML part of the code, the error is gone. My question is, why this error occurred? Is this mean that in PHP 5.3 we are no longer allowed to put HTML code inside PHP code? This is my php code: function pk_stt2_admin_print_delete_form(){ global $wpdb; if ( isset($_POST['delete_terms']) && !empty($_POST['delete_terms']) ){ $msg = 'Search terms'; $success = pk_stt2_db_delete_searchterms( $_POST['delete_terms'] ); } elseif ( isset($_POST['delete_all']) ){ $msg = 'All search terms'; $success = pk_stt2_db_delete_searchterms( 'delete_all_terms' ); } else { ?> <div id="message" class="updated fade"> <p> Please enter the search terms to be deleted, separate them with a comma. </p> </div> <?php } if ( $success ){ ?> <div id="message" class="updated fade"> <p> <?php echo $msg; ?> have been deleted, <?php echo $success; ?> rows effected. </p> </div> <?php } else { ?> <div id="message" class="updated fade"> <p> Failed to delete search terms. </p> </div> <?php } } Thanks.

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Using data.table to aggregate

- by dayne

After multiple suggestions from SO users, I am finally trying to convert my code over to using data.tables. library(data.table) DT <- data.table(plate = paste0("plate",rep(1:2,each=5)), id = rep(c("CTRL","CTRL","ID1","ID2","ID3"),2), val = 1:10) > DT plate id val 1: plate1 CTRL 1 2: plate1 CTRL 2 3: plate1 ID1 3 4: plate1 ID2 4 5: plate1 ID3 5 6: plate2 CTRL 6 7: plate2 CTRL 7 8: plate2 ID1 8 9: plate2 ID2 9 10: plate2 ID3 10 What I would like to do is take the average of DT[,val] by plate when the id is "CTRL". I would normally aggregate the data frame, then use match to map the values back to a new column, 'ctrl'. Using the data.table package I can get: DT[id=="CTRL",ctrl:=mean(val),by=plate] > DT plate id val ctrl 1: plate1 CTRL 1 1.5 2: plate1 CTRL 2 1.5 3: plate1 ID1 3 NA 4: plate1 ID2 4 NA 5: plate1 ID3 5 NA 6: plate2 CTRL 6 6.5 7: plate2 CTRL 7 6.5 8: plate2 ID1 8 NA 9: plate2 ID2 9 NA 10: plate2 ID3 10 NA What I need is really: DT <- data.table(plate = paste0("plate",rep(1:2,each=5)), id = rep(c("CTRL","CTRL","ID1","ID2","ID3"),2), val = 1:10, ctrl = rep(c(1.5,6.5),each=5)) > DT plate id val ctrl 1: plate1 CTRL 1 1.5 2: plate1 CTRL 2 1.5 3: plate1 ID1 3 1.5 4: plate1 ID2 4 1.5 5: plate1 ID3 5 1.5 6: plate2 CTRL 6 6.5 7: plate2 CTRL 7 6.5 8: plate2 ID1 8 6.5 9: plate2 ID2 9 6.5 10: plate2 ID3 10 6.5 Eventually I would like to use much more complicated selections of the values, but I do not know how to select specific values, run some function, then map those values back to the appropriate row using data frames.

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Jquery image slider window resize scaling issue

- by eb_Dev

Hi, I have created image gallery slider, the images of which scale with the window size. My problem is I can't seem to create the right formula to ensure that the slider is at the right position when the window is scaled. If I am at the first image and the slider 'left' offset is 0 then the scaling works fine and my offset is correct, however when I am on image two and my slider is offset by say -1500 and then the window is resized, the slider is then at the wrong offset. Taking this into account I figured I could just add / subtract the new window size difference from the slider offset and therefore have everything in the right position. I was wrong. It works for the first two images but then If I am at the end of my slider on the last image I get a nice big gap between the end of the last image and the border of the page. Can someone please show my where I am going wrong please? I've spent days on this :( The relevant code is as follows: $(window).bind('resize', function(event, delta) { /* Resize work images - resizes all to document width */ resizeWorkImages('div.page.work div#work ul'); /* Position slider controls */ positionSliderControls(); /* Get the difference between the old window width and the new */ var windowDiff = (gLastWindowWidth - $(window).width()) * -1; /* Apply difference to slider left position */ var newSliderLeftPos = stripPx($('div.page.work div#work ul').css('left')) - windowDiff; /* Apply to slider */ $('div.page.work div#work ul').css('left',newSliderLeftPos+'px') /* Update gSlider settings */ gSlider.update(); /* Record new window width */ gLastWindowWidth = $(window).width(); }); Thanks, eb_dev

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submit in html on sql query

- by user1644661

i need to run this sql query , which give me a list of Id and Dates i want to click each result and take with me the Id value to the next form i wrote this query above but i see in the debager that the hidden ID get his value but not pass to the next form i think i have a problem with the submit() . where should i put him ? thanks anat function ShowAllCarts($user_email) { $connB = new ProductDAO(); $connB->Connect(); $pro_query = "SELECT * FROM Cart WHERE `Email`='$user_email';"; $db_result = $connB->ExecSQL($pro_query); $html_result = '<div data-role="content"> <ul data-role="listview" data-theme="b"> '; $html_result .= '<form action="PreviouscartProduct.php" method="POST"/>'; while($row_array = $db_result->fetch_array(MYSQLI_ASSOC)) { $Id= $row_array['Id']; $Date= $row_array['Date']; //$html_result // $html_result .="<li><a href='PreviouscartProduct.php'>Cart number: $Id from Date: $Date><input type='hidden' name='Id' value'<?=$Id?>'</input></a></li>'"; $html_result .= '<a onclick="this.form.submit();" </a>; } $html_result .= ' </ul> </div>'; $html_result .= '</form>'; $connB->Disconnect(); return $html_result; } //display all carts $func_result = ShowAllCarts($Email);

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How to multi-thread this?

- by WilliamKF

I wish to have two threads. The first thread1 occasionally calls the following pseudo function: void waitForThread2() { if (thread2 is not idle) { return; } notifyThread2IamReady(); while (thread2IsExclusive) { } } The second thread2 is forever in the following pseudo loop: for (;;) { Notify thread1 I am idle. while (!thread1IsReady()) { } Notify thread1 I am exclusive. Do some work while thread1 is blocked. Notify thread1 I am busy. Do some work in parallel with thread1. } What is the best way to write this such that both thread1 and thread2 are kept as busy as possible on a machine with multiple cores. I would like to avoid long delays between notification in one thread and detection by the other. I tried using pthread condition variables but found the delay between thread2 doing 'notify thread1 I am busy' and the loop in waitForThread2() on thear2IsExclusive() can be up to almost one second delay. I then tried using a volatile sig_atomic_t shared variable to control the same, but something is going wrong, so I must not be doing it correctly.

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what happens when you stop VS debugger?

- by mare

If I have a line like this ContentRepository.Update(existing); that goes into datastore repository to update some object and I have a try..catch block in this Update function like this: string file = XmlProvider.DataStorePhysicalPath + o.GetType().Name + Path.DirectorySeparatorChar + o.Slug + ".xml"; DataContractSerializer dcs = new DataContractSerializer(typeof (BaseContentObject)); using ( XmlDictionaryWriter myWriter = XmlDictionaryWriter.CreateTextWriter(new FileStream(file, FileMode.Truncate, FileAccess.Write), Encoding.UTF8)) { try { dcs.WriteObject(myWriter, o); myWriter.Close(); } catch (Exception) { // if anything goes wrong, delete the created file if (File.Exists(file)) File.Delete(file); if(myWriter.WriteState!=WriteState.Closed) myWriter.Close(); } } then why would Visual Studio go on with calling Update() if I click "Stop" in debugging session on the above line? For instance, I came to that line by going line by line pressing F10 and now I'm on that line which is colored yellow and I press Stop. Apparently what happens is, VS goes to execute the Update() method and somehow figures out something gone wrong and goes into "catch" and deletes the file, which is wrong, because I want my catch to work when there is a true exception not when I debug a program and force to stop it.

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java class that simulates a simple database table

- by ericso

I have a collection of heterogenous data that I pull from a database table mtable. Then, for every unique value uv in column A, I compute a function of (SELECT * FROM mtable WHERE A=uv). Then I do the same for column B, and column C. There are rather a lot of unique values, so I don't want to hit the db repeatedly - I would rather have a class that replicates some of the functionality (most importantly some version of SELECT WHERE). Additionally, I would like to abstract the column names away from the class definition, if that makes any sense - the constructor should take a list of names as a parameter, and also, I suppose, a list of types (right now this is just a String[], which seems hacky). I'm getting the initial data from a RowSet. I've more or less done this by using a hashmap that maps Strings to lists/arrays of Objects, but I keep getting bogged down in comparisons and types, and am thinking that my current implementation really isn't as clean and clear as it could be. I'm pretty new to java, also, and am not sure if I'm not going down a completely incorrect path. Does anyone have any suggestions?

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[Django] One single page to create a Parent object and its associated child objects

- by ahmoo

Hi all, This is my very first post on this awesome site, from which I have been finding answers to a handful of challenging questions. Kudos to the community! I am new to the Django world, so am hoping to find help from some Django experts here. Thanks in advance. Item model: class Item(models.Model): name = models.CharField(max_length=50) ItemImage model: class ItemImage(models.Model): image = models.ImageField(upload_to=get_unique_filename) item = models.ForeignKey(Item, related_name='images') As you can tell from the model definitions above, every Item object can have many ItemImage objects. My requirements are as followings: A single web page that allows users to create a new Item while uploading the images associated with the Item. The Item and the ItemImages objects should be created in the database all together, when the "Save" button on the page is clicked. I have created a variable in a custom config file, called NUMBER_OF_IMAGES_PER_ITEM. It is based on this variable that the system generates the number of image fields per item. Questions: What should the forms and the template be like? Can ModelForm be used to achieve the requirements? For the view function, what do I need to watch out other than making sure to save Item before ItemImage objects?

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Initializing an object to all zeroes

- by dash-tom-bang

Oftentimes data structures' valid initialization is to set all members to zero. Even when programming in C++, one may need to interface with an external API for which this is the case. Is there any practical difference between: some_struct s; memset(s, 0, sizeof(s)); and simply some_struct s = { 0 }; Do folks find themselves using both, with a method for choosing which is more appropriate for a given application? For myself, as mostly a C++ programmer who doesn't use memset much, I'm never certain of the function signature so I find the second example is just easier to use in addition to being less typing, more compact, and maybe even more obvious since it says "this object is initialized to zero" right in the declaration rather than waiting for the next line of code and seeing, "oh, this object is zero initialized." When creating classes and structs in C++ I tend to use initialization lists; I'm curious about folks thoughts on the two "C style" initializations above rather than a comparison against what is available in C++ since I suspect many of us interface with C libraries even if we code mostly in C++ ourselves.

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Javascript for disabling dropdown in ASP.NET

- by Lijo

Hi Team, I am using JScript in ASP.NET 2005. I have a page with a checkbox and a dropdown list. When the checkbox is checked the dropdown is to be disabled. During Postback of the page this should be retained. I am using a javascript function as follows if((chkOwner[1].checked==true)) { document.getElementById(ddlClientID).disabled=true; document.getElementById(ddlClientID).className = "form-disabled"; document.getElementById(ddlClientID).selectedIndex = 0; } else { document.getElementById(ddlClientID).disabled=false; document.getElementById(ddlClientID).className = "form-input"; document.getElementById(ddlClientID).selectedIndex = 0; } This works, almost. However, the dropdown selection is not retained after postback (when checkbox is not selected). Apprently the solution is to remove the last line, i.e, in the else part, remove the selectedIndex =0 setting. But, when I do that the disabling of dropdown (when check box is selected) is not working after post back. Could you please help on this? Thanks Lijo

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