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  • How does Python store lists internally?

    - by Mike Cooper
    How are lists in python stored internally? Is it an array? A linked list? Something else? Or does the interpreter guess at the right structure for each instance based on length, etc. If the question is implementation dependent, what about the classic CPython?

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  • This code appears to achieve the return of a null reference in C++

    - by Chuck
    Hi folks, My C++ knowledge is somewhat piecemeal. I was reworking some code at work. I changed a function to return a reference to a type. Inside, I look up an object based on an identifier passed in, then return a reference to the object if found. Of course I ran into the issue of what to return if I don't find the object, and in looking around the web, many people claim that returning a "null reference" in C++ is impossible. Based on this advice, I tried the trick of returning a success/fail boolean, and making the object reference an out parameter. However, I ran into the roadblock of needing to initialize the references I would pass as actual parameters, and of course there is no way to do this. I retreated to the usual approach of just returning a pointer. I asked a colleague about it. He uses the following trick quite often, which is accepted by both a recent version of the Sun compiler and by gcc: MyType& someFunc(int id) { // successful case here: // ... // fail case: return *static_cast<MyType*>(0); } // Use: ... MyType& mt = somefunc(myIdNum); if (&mt) // test for "null reference" { // whatever } ... I have been maintaining this code base for a while, but I find that I don't have as much time to look up the small details about the language as I would like. I've been digging through my reference book but the answer to this one eludes me. Now, I had a C++ course a few years ago, and therein we emphasized that in C++ everything is types, so I try to keep that in mind when thinking things through. Deconstructing the expression: "*static_cast(0);", it indeed seems to me that we take a literal zero, cast it to a pointer to MyType (which makes it a null pointer), and then apply the dereferencing operator in the context of assigning to a reference type (the return type), which should give me a reference to the same object pointed to by the pointer. This sure looks like returning a null reference to me. Any advice in explaining why this works (or why it shouldn't) would be greatly appreciated. Thanks, Chuck

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  • Haskell Add Function Return to List Until Certain Length

    - by kienjakenobi
    I want to write a function which takes a list and constructs a subset of that list of a certain length based on the output of a function. If I were simply interested in the first 50 elements of the sorted list xs, then I would use fst (splitAt 50 (sort xs)). However, the problem is that elements in my list rely on other elements in the same list. If I choose element p, then I MUST also choose elements q and r, even if they are not in the first 50 elements of my list. I am using a function finderFunc which takes an element a from the list xs and returns a list with the element a and all of its required elements. finderFunc works fine. Now, the challenge is to write a function which builds a list whose total length is 50 based on multiple outputs of finderFunc. Here is my attempt at this: finish :: [a] -> [a] -> [a] --This is the base case, which adds nothing to the final list finish [] fs = [] --The function is recursive, so the fs variable is necessary so that finish -- can forward the incomplete list to itself. finish ps fs -- If the final list fs is too small, add elements to it | length fs < 50 && length (fs ++ newrs) <= 50 = fs ++ finish newps newrs -- If the length is met, then add nothing to the list and quit | length fs >= 50 = finish [] fs -- These guard statements are currently lacking, not the main problem | otherwise = finish [] fs where --Sort the candidate list sortedps = sort ps --(finderFunc a) returns a list of type [a] containing a and all the -- elements which are required to go with it. This is the interesting -- bit. rs is also a subset of the candidate list ps. rs = finderFunc (head sortedps) --Remove those elements which are already in the final list, because -- there can be overlap newrs = filter (`notElem` fs) rs --Remove the elements we will add to the list from the new list -- of candidates newps = filter (`notElem` rs) ps I realize that the above if statements will, in some cases, not give me a list of exactly 50 elements. This is not the main problem, right now. The problem is that my function finish does not work at all as I would expect it to. Not only does it produce duplicate elements in the output list, but it sometimes goes far above the total number of elements I want to have in the list. The way this is written, I usually call it with an empty list, such as: finish xs [], so that the list it builds on starts as an empty list.

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  • Defining relationship in value objects using Hibernate

    - by kate
    Hi, We have three tables .We need to get data from these tables based upon particular conditions. Like if TableA.columv=TableB.columc=tableC.column then get data. We are using value objects to map Objects to relations. Question is how to maintain these relation ships in value objects. And how to retrieve data from it. We have one value object per table.

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  • Internet Explorer dont show a piece of my site

    - by Ramza
    Hi guys, i am creating a new site, based in a pre-existing web page The original site is http://oasisrio.intermediasp.com/ Its works great in Firefox, Chrome, and IE But the new one "oasisba.intermediasp.com" Dont show the right bar in IE, i check all that i can think about and i dont found the problem. Someone have any ideas why this is happening? PD: Sorry for my crapy english

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  • Add data to a list box from a dropdown

    - by bachchan
    I have a listbox (listBox) and a dropdown list(dropDown). I want to be able to select an item from the dropDown and add them to the listBox. I have looked everywhere for this but all I ever see is adding data from a datasource instead of a dropdown. I want this to be dynamic so the listBox is populated based on the a user selected in the dropDown

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  • How to specify java script files required by an angular app

    - by Vishal Kaushik
    I'm looking for a way to specify required js files by an angular app. So that, we don't need to include an array of tag for all the files which may be required by some ng-app. The main idea behind this requirement is - we might not need to load all the resources on the browser at once. Which ever ng-app gets loaded onto the screen, will fetch its dependencies on its own from the server. Is there any existing way within angularJS to achieve this goal..?

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  • descending heap sort

    - by user1
    use heap sort to sort this in descending order and show the steps or explanation please below is the tree 79 33 57 8 25 48 below is the array 79 - 33 - 57 - 8 - 25 - 48 ok ascending is easy because the largest element is at the top we can exchange the last element and the first element and then use heapify as the sample code in wikipedia describes it.

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  • Passing table data to PRPT from xaction

    - by Manoj
    I am getting data from a query and processing it using Javascript in the xaction file. Now I want to pass the processed data (a 2D array) down to a prpt where it will be used to generate graph and table. What is the format in which Javascript would generate the data and how is it passed to and received by the prpt file from the xaction. Thanks...

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  • How do i generate hubernate models for java dotCMS plugins

    - by shuxer
    Hi I am trying to create a plugin for dotCMS. My plugin stores data in database. i defined hibernate mapping file and put in my plugin folder's conf dir and i have no idea how to hibernate generate models based my mapping definition. I am using hello world plugin's mapping file for mysql Any help or comment would be highly appreciated Thanks in advance

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  • jQuery trigger extra paramter

    - by fire
    According to the jQuery manual you can send extra parameters (as an array) when calling a trigger. I am using this at the moment: $('#page0').trigger('click', [true]); How would I pick up whether the paramter has come through or not when using this? $('ul.pages li a').click(function() { // Do stuff if true has been passed as an extra parameter });

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  • Using json_encode on objects in PHP

    - by Alan
    Hi, I'm trying to output lists of objects as json and would like to know if there's a way to make objects usable to json_encode? The code I've got looks something like $related = $user->getRelatedUsers(); echo json_encode($related); Right now, I'm just iterating through the array of users and individually exporting them into arrays for json_encode to turn into usable json for me. I've already tried making the objects iterable, but json_encode just seems to skip them anyway.

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  • Code to generate random numbers in C++

    - by user1678927
    Basically I have to write a program to generate random numbers to simulate the rolling of a pair of dice. This program should be constructed in multiple files. The main function should be in one file, the other functions should be in a second source file, and their prototypes should be in a header file. First I write a short function that returns a random value between 1 and 6 to simulate the rolling of a single 6-sided die.Second, i write a function that pretends to roll a pair of dice by calling this function twice. My program starts by asking the user how many rolls should be made. Then I write a function to simulate rolling the dice this many times, keeping a count of exactly how many times the values 2,3,4,5,6,7,8,9,10,11,12(each number is the sum of a pair of dice) occur in an array. Later I write a function to display a small bar chart using these counts that ideally would look something like below for a sample of 144 rolls, where the number of asterisks printed corresponds to the count: 2 3 4 5 6 7 8 9 10 11 12 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Next, to see how well the random number generator is doing, I write a function to compute the average value rolled. Compare this to the ideal average of 7. Also, print out a small table showing the counts of each roll made by the program, the ideal count based on the frequencies above given the total number of rolls, and the difference between these values in separate columns. This is my incomplete code so far: "Compiler visual studio 2010" int rolling(){ //Function that returns a random value between 1 and 6 rand(unsigned(time(NULL))); int dice = 1 + (rand() %6); return dice; } int roll_dice(int num1,int num2){ //it calls 'rolling function' twice int result1,result2; num1 = rolling(); num2 = rolling(); result1 = num1; result2 = num2; return result1,result2; } int main(void){ int times,i,sum,n1,n2; int c1,c2,c3,c4,c5,c6,c7,c8,c9,c10,c11;//counters for each sum printf("Please enter how many times you want to roll the dice.\n") scanf_s("%i",&times); I pretend to use counters to count each sum and store the number(the count) in an array. I know i need a loop (for) and some conditional statements (if) but m main problem is to get the values from roll_dice and store them in n1 and n2 so then i can sum them up and store the sum in 'sum'.

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  • MySQL Query to find consecutive available times of variable lenth

    - by Armaconn
    I have an events table that has user_id, date ('2013-10-01'), time ('04:15:00'), and status_id; What I am looking to find is a solution similar to http://stackoverflow.com/questions/2665574/find-consecutive-rows-calculate-duration but I need I need two additional components: 1) Take date into consideration, so 10/1/2013 at 11:00 PM - 10/2/2013 at 3:00AM. Feel free to just put in a fake date range (like '2013-10-01' to '2013-10-31') 2) Limit output to only include when there are 4+ consecutive times (each event is 15 minutes and I want it to display minimum blocks of an hour, but would also like to be able to switch this restriction to 1.5 hours or some other duration if possible). SUMMARY - Looking for a query that provides the start and end times for a set of events that have the same user_id, status_id, and are in a continuous series based on date and time. For which I can restrict results based on date range and minimum series duration. So the output should have: user_id, date_start, time_start, date_end, time_end, status_id, duration CREATE TABLE `events` ( `event_id` int(11) NOT NULL auto_increment COMMENT 'ID', `user_id` int(11) NOT NULL, `date` date NOT NULL, `time` time NOT NULL, `status_id` int(11) default NULL, PRIMARY KEY (`event_id`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 AUTO_INCREMENT=1568 ; INSERT INTO `events` VALUES(1, 101, '2013-08-14', '23:00:00', 2); INSERT INTO `events` VALUES(2, 101, '2013-08-14', '23:15:00', 2); INSERT INTO `events` VALUES(3, 101, '2013-08-14', '23:30:00', 2); INSERT INTO `events` VALUES(4, 101, '2013-08-14', '23:45:00', 2); INSERT INTO `events` VALUES(5, 101, '2013-08-15', '00:00:00', 2); INSERT INTO `events` VALUES(6, 101, '2013-08-15', '00:15:00', 1); INSERT INTO `events` VALUES(7, 500, '2013-08-14', '23:45:00', 1); INSERT INTO `events` VALUES(8, 500, '2013-08-15', '00:00:00', 1); INSERT INTO `events` VALUES(9, 500, '2013-08-15', '00:15:00', 2); INSERT INTO `events` VALUES(10, 500, '2013-08-15', '00:30:00', 2); INSERT INTO `events` VALUES(11, 500, '2013-08-15', '00:45:00', 1); Desired output row |user_id | date_start | time_start | date_end | time_end | status_id | duration 1 |101 |'2013-08-14'| '23:00:00' |'2013-08-15'|'00:15:00'| 2 | 5 2 |101 |'2013-08-15'| '00:00:15' |'2013-08-15'|'00:30:00'| 1 | 1 3 |500 |'2013-08-14'| '00:23:45' |'2013-08-15'|'00:15:00'| 1 | 2 4 |500 |'2013-08-15'| '00:00:15' |'2013-08-15'|'00:45:00'| 2 | 2 5 |500 |'2013-08-15'| '00:00:45' |'2013-08-15'|'01:00:00'| 2 | 1 *except that rows 2 and 5 wouldn't appear if duration had to be greater than 30 minutes Thanks for any help that you can provide! And please let me know if there is anything I can further clarify!!

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  • Using a user-defined type as a primary key

    - by Chris Kaminski
    Suppose I have a system where I have metadata such as: table: ====== key name address ... Then suppose I have a user-defined type described as so: datasource datasource-key A) are there systems where it's possible to have keys based on user-defined types? B) if so, how do you decompose the keys into a form suitable for querying? C) is this a case where I'm just better off with a composite primary key?

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  • PHP resized image functions and S3 upload functions - but how to merge the two?

    - by chocolatecoco
    I am using S3 to store images and I am resizing and compressing images before it gets uploaded using PHP. I'm using this class for storing the images to an S3 bucket - http://undesigned.org.za/2007/10/22/amazon-s3-php-class This all works fine if I'm not doing any file processing before the file is uploaded because it reads the file upload from the $_FILES array. The problem is I am resizing and compressing the image before storing to the S3 bucket. So I'm no longer able to read from the $_FILES array. The functions for resizing: public function resizeImage($newWidth, $newHeight, $option="auto") { // *** Get optimal width and height - based on $option $optionArray = $this->getDimensions($newWidth, $newHeight, $option); $optimalWidth = $optionArray['optimalWidth']; $optimalHeight = $optionArray['optimalHeight']; // *** Resample - create image canvas of x, y size $this->imageResized = imagecreatetruecolor($optimalWidth, $optimalHeight); imagecopyresampled($this->imageResized, $this->image, 0, 0, 0, 0, $optimalWidth, $optimalHeight, $this->width, $this->height); // *** if option is 'crop', then crop too if ($option == 'crop') { $this->crop($optimalWidth, $optimalHeight, $newWidth, $newHeight); } } The script I am using to store the file after resizing and compressing to a local directory: public function saveImage($savePath, $imageQuality="100") { // *** Get extension $extension = strrchr($savePath, '.'); $extension = strtolower($extension); switch($extension) { case '.jpg': case '.jpeg': if (imagetypes() & IMG_JPG) { imagejpeg($this->imageResized, $savePath, $imageQuality); } break; case '.gif': if (imagetypes() & IMG_GIF) { imagegif($this->imageResized, $savePath); } break; case '.png': // *** Scale quality from 0-100 to 0-9 $scaleQuality = round(($imageQuality/100) * 9); // *** Invert quality setting as 0 is best, not 9 $invertScaleQuality = 9 - $scaleQuality; if (imagetypes() & IMG_PNG) { imagepng($this->imageResized, $savePath, $invertScaleQuality); } break; // ... etc default: // *** No extension - No save. break; } imagedestroy($this->imageResized); } with this PHP code to invoke it: $resizeObj = new resize("$images_dir/$filename"); $resizeObj -> resizeImage($thumbnail_width, $thumbnail_height, 'crop'); $resizeObj -> saveImage($images_dir."/tb_".$filename, 90); How do I modify the code above so I can pass it through this function: $s3->putObjectFile($thefile, "s3bucket", $s3directory, S3::ACL_PUBLIC_READ)

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  • PODS + WordPress + User Registration

    - by Sharath
    So I have PODS installed on my wordpress site that I am developing. I need to put up a user registration system such that once the user registers, he/she can be directed to POD pages that I have created. Can I just use the default registration system that comes with wordpress and redirect users based on a default role I assign to them? I basically don't want my potential users to view any part of the admin site. Any help is appreciated.

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  • Simple doubt related to strings in C

    - by piemesons
    // The first example: char text[] = "henri"; char *p; p = text; *(p + 1) = 'E'; // Output = hEnri // Now If we want to remove the "e" ie hnri, we would go for????? *(p + 1)=????? Please dont say start copying the array. I am looking for the best solution

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  • How to find an audio file's length (in seconds)

    - by mIL3S
    Hi all! (Objective C) Just using simple AudioServicesPlaySystemSoundID and its counterparts, but I can't find in the documentation if there is already a way to find the length of an audio file. I know there is AudioServicesGetPropertyInfo, but that seems to return a byte-buffer - do audio files embed their length in themselves and I can just extract it with this? Or is there perhaps a formula based on bit-rate * fileSize to convert to length-of-time? mIL3S www.milkdrinkingcow.com

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  • Open an external program in Qt with an attached file extension

    - by Phil
    I am making a qt application which allows the user to select a file and then upon clicking ok, start the associated program with the file already loaded. The program I want to start is java based, and I know how to use QProcess to get it to open, I don't know however how to add the file extension which the user is selecting. Any suggestions?

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