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• Why use third-party vector libraries at all?

  - by Patrick Powns

  So I'm thinking of using the Eigen matrix library for a project I'm doing (2D space simulator). I just went ahead and profiled some code with Eigen::Vector2d, and with bare arrays. I noticed a 10x improvement in assigning values to elements in the array, and a 40x improvement in calculating the dot products. Here is my profiling if you want to check it out, basically it's ~4.065s against ~0.110s. Obviously bare arrays are much more efficient at dot products and assigning stuff. So why use the Eigen library (or any other library, Eigen just seemed the fastest)? Is it stability? Complicated maths that would be hard to code by yourself efficiently?

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• (C++) While reading a file (ifstream), is there any way to direct it to make a new line?

  - by Enzo

  While reading a file (ifstream), is there any way to direct it to make a new line? For instance, I would like for THIS to happen: myfilearray[1]array[2]endl; Obviously, the "endl" just isn't allowed. Is there another way to do this? Edit---thanks for the quick responses guys! From a text file, I'm trying to store two strings from that file into arrays and then do the same with the next line (or until I desire, using a for loop) Using strings is important to me as it will make my future program a lot more flexible.

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• php adding value to session

  - by antikbd

  I am trying to implement a 'shopping cart' where, if the 'Add to Cart' has been clicked, the respective item is either added to the cart or incremented by one if already present. However, the following code isn't working and giving me a "Cannot use a scalar value as an array" error. Any help would be highly appreciated. if (isset($_POST['fan']) && ($_POST['fan']=="Add to Cart")) { if (($_SESSION['cart']['fan']==0) || (!isset($_SESSION['cart']['fan']))) { $_SESSION['cart']['fan']=1; } else { $_SESSION['cart']['fan']++; } }

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• php,codigniter, upload the zip file problem

  - by user345804

  function upload( &$data = array() ) { $config['upload_path'] = 'system/application/orginalimage/'; $config['allowed_types'] = 'gif|jpg|png|zip'; $config['allowed_type'] = 'application/zip'; $config['allowed_type'] = 'application/x-zip-compressed'; $config['allowed_type'] = 'application/x-compress'; $config['allowed_type'] = 'application/x-compressed'; $config['allowed_type'] = 'application/octet-stream'; $config['allowed_type'] = 'multipart/x-zip'; $config['max_size'] = '100'; $config['max_width'] = '1024'; $config['max_height'] = '768'; $this->load->library('upload', $config); if ( $this->upload->do_upload( 'uploadimage')) { $data = $this->upload->data() ; return true ; } return false ; } uploading a zip file is not working help me

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• Is there a way to get a reference to all the paragraphs or headings in a web page in JavaScript?

  - by mattbd

  I'm writing a simple Greasemonkey script to strip out all the images, headings and paragraphs from a web page (it's because someone wants to use images of several popular websites with the images and text removed in a presentation about branding of websites). I've figured out how to do so with images by using a for loop and the document.images array like this: var i = 0; var imglngth = document.images.length; for(i=0;i<imglngth;i++) { document.images[i].style.display="none"; } However, I don't believe there's an object representing paragraphs or headers. Any suggestions as to how I could implement this?

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• ListView Item Detail Screen: New or Same Activity?

  - by stormin986

  I have a listview where each item correlates to an instance of an item in an array. When the user selects an item, it will bring up a 'Details' page that reads and displays other data members of the list item. Would this be better implemented with the Details page as its own activity, or a new view within the same activity? Pros and cons of each? A new activity makes my job a little easier in terms of handling the 'back' button, but then I have the challenge of how do I pass the rest of the data structure to the new activity since I can't bundle it up (unless I serialize it).

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• Waiting for DialogActivity to return before continuing executing of the main thread

  - by jax

  How would I force the current thread to wait until another has finished before continuing. In my program the user selects a MODE from an AlertDialog, I want to halt executing of the program before continuing as the mode holds important configuration for the gameplay. new AlertDialog.Builder(this) .setItems(R.array.game_modes, new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int which) { switch (which) { case 0: setMode(TRAINING_MODE); case 1: setMode(QUIZ_MODE); default: setMode(TRAINING_MODE); break; } //continue loading the rest of onCreate(); contineOnCreate(); } }) .create().show(); If this is impossible can anyone give a possible solution?

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• Switching from php to python

  - by ts

  Hello I am trying to make a list of things which can be difficult/surprising to someone who is changing language from PHP to Python. so far i have rather short list: forget require / include, learn import (this was most difficult to me - to understand package - module - class - object hierarchy and its mapping to filesystem) you can't just upload file on server to have webpage (-mod_python, wsgi etc) learn the python way for use variable class names (new $class() vs import + getattr) / operator in python 2.x and all float-related horrors those were difficult to me, it takes few days before mind adapts a new paradigm after i found that there is few other areas which could be challenging for someone with (too) many years of php: everything is an object you have to live with exceptions array vs list, set, dictionary, tuple ... learn (effective) list comprehensions learn generators any other ideas / personal experiences ?

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• is the + in += on a Map a prefix operator of =?

  - by Steve

  In the book "Programming in Scala" from Martin Odersky there is a simple example in the first chapter: var capital = Map("US" -> "Washington", "France" -> "Paris") capital += ("Japan" -> "Tokyo") The second line can also be written as capital = capital + ("Japan" -> "Tokyo") I am curious about the += notation. In the class Map, I didn't found a += method. I was able to the same behaviour in an own example like class Foo() { def +(value:String) = { println(value) this } } object Main { def main(args: Array[String]) = { var foo = new Foo() foo = foo + "bar" foo += "bar" } } I am questioning myself, why the += notation is possible. It doesn't work if the method in the class Foo is called test for example. This lead me to the prefix notation. Is the + a prefix notation for the assignment sign (=)? Can somebody explain this behaviour?

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• Convert Date MMDDYY to Date for database Insert

  - by lesponce

  I got an array with a date set as 071712 . no / slash characters for the date, no dash. nothing, just plain 071712 (coming from a text file). I need to convert the date so I can include it in a SqlServer insert statement. I'm calling a stored procedure for the insert. So far I have this: // This is not working so far. DateTime date = Convert.ToDateTime(fileLines[4]); (date will be used as a parm for the stored procedure)

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• PHP: reusing database class

  - by citricsquid

  Hi, I built a class that allows me to do: $db->query($query); and it works perfectly, although if I want to do: $db->query($query); while($row = $db->fetch_assoc()){ $db->query($anotherquery); echo $db->result(); } it "breaks" the class. I don't want to constantly have to redeclare my class (eg: $seconddb = new database()), is there a way to get around this? I want to be able to reuse $db within $db, without overwriting the "outside" db. currently I'm create an array of data (from db-fetch_assoc() then doing a foreach and then doing the db call inside that: $db->query('SELECT * FROM table'); while($row = $db->fetch_assoc()){ $arr[] = $row; } foreach($arr as $a){ $db->query(); // query and processing here } Is this the best method or am I missing the obvious? Should I consider passing a connection link ID with the database connection?

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• Is it a good idea to include a large text variable in compiled code?

  - by gladman

  I am writing a program that produces a formatted file for the user, but it's not only producing the formatted file, it does more. I want to distribute a single binary to the end user and when the user runs the program, it will generate the xml file for the user with appropriate data. In order to achieve this, I want to give the file contents to a char array variable that is compiled in code. When the user runs the program, I will write out the char file to generate an xml file for the user. char* buffers = "a xml format file contents, \ this represent many block text \ from a file,..."; I have two questions. Q1. Do you have any other ideas for how to compile my file contents into binary, i.e, distribute as one binary file. Q2. Is this even a good idea as I described above?

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• fields_for to stop pluralizing.

  - by Dmitriy Likhten

  I have a fields_for tag, where I specify the prefix (lets say for some good reasons), and this is supposed to represent a one-to-one relationship. I am trying to represent a relationship widget has_many thingamagigs thingamagig has_one whatchamacallit The field_for code is: fields_for "widgt[thingamagigs_attributes][][whatchamacallit_attributes]", thingamagig.whatchamacallit do |x| which generates names (wrongly): widget[thingamagigs_attributes][][whatchamacallit_attributes][][value] The better solution would be t.fields_for :whatchamacallit do |x| where t = fields_for the thingamagig... However if I do that, the following names are generated widgt[thingamagigs_attributes][whatchamacallit_attributes][] which is completely wrong as all other fields for a thingamagig is... widgt[thingamagigs_attributes][][name] So in all cases I am screwed. The original field_for using a string cannot be used with accepts_nested_attributes_for :whatchamacallit since whatchamacallit is a singular relationship and an object is expected not an array. The second fields_for will simply not work because rails cannot parse the params object correctly. Is there a way to tell the first forms_for to not add the [] after [whatchamacallit_attributes] in all field names?

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• How to load image from NSMutableArray

  - by pbcoder

  I want to load the image URL from my NSMutableArray. Here is my Code: id path = (NSString *)[[stories objectAtIndex: storyIndex] objectForKey: @"icon"]; NSURL *url = [NSURL URLWithString:path]; NSData *data = [NSData dataWithContentsOfURL:url]; UIImage *img = [[UIImage alloc] initWithData:data cache:NO]; If I use: id path = @"http://www.xzy.de/icon.png"; it´s all right, but not if I want to extract the imageURL from my Array Anyone who can help me? Thanks!

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• C++ Function Calling Itself

  - by Ben

  Suppose I wish to have a function that fills an array either in pattern x,y,x,y,x,ywhere x and y are variables defined by some algorithm and x,y,z,x,y,z where x, y and z are variables defined by the same algorithm. This should continue for all number of variables. Is this a viable way to implement it. int recurse_n(int n) { while(n > 0) { --n; recurse_n(n); n = 0; // Use algorithm here } }

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• iphone - Images (slide show) and audio snychronization

  - by Qaiser

  I have 20 images and some audio. I would like to show a single image at a time and change the images at (unequal) intervals. For example, I want to show image 1 for 1.44 seconds and image 2 for 1.67 seconds and so on. Can someone suggest how to go about doing this please? What I have seen are examples that show how to setup an array of images with one field that denotes total time. This causes the images to show for an equal amount of time (each). ... and that not what I am looking for ...

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• Java exception translations

  - by user3079275

  Apologies if this has been discussed on other threads but I find it helps clarify my thinking when I am forced to write down my questions. I am trying to properly understand the concept of checked vs unchecked exceptions and exception translation in Java but I am getting confused. So far I understood that checked exceptions are exceptions that need to be always caught in a try/catch block otherwise I get a compile time error. This is to force programmers to think about abnormal situations that might happen at run time (like disk full etc). Is this right? What I did not get was why we have unchecked exceptions, when are they useful? Is it only during development time to debug code that might access an illegal array index etc? This confusion is because I see that Error exceptions are also unchecked as is RunTimeException but its not clear to me why they are both lumped together into an unchecked category?

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• Solution to compiler warning for generic varargs

  - by TJR

  A puzzle from this blog. Similar to SO1445233. Given the following source listing, explain why the compiler is producing a warning at invocation to the list method and give a solution for removing the warning without resorting to @SuppressWarnings annotation. public class JavaLanguagePuzzle3 { public static void main(String[] args) { list("1", 2, new BigDecimal("3.5")); } private static <T> List<T> list(T... items) { return Arrays.asList(items); } } Warning: Type safety: A generic array of Object&Serializable&Comparable<?> is created for a varargs parameter

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• Putting sql result set into JList

  - by 0vertone

  hi there. im working on my second year project and im nearly finished but ive got a problem. i have a table set up in oracle that holds user names, recipients, and messages. i wanted to make a contacts list for sendin messages that would take the user names and put them into a swing jlist but i cant figure out how. i thought maybe if i put the usernames into an array from the sql itd be easier but that didnt work. any ideas?

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• Getting MATLAB variable (string) from C

  - by Hamming

  Hi! I'm writing a small C application that launchs a Matlab script (.m file). I need to exchange some variables and I don't know how to get an array of chars that exists in Matlab. I'm doing something like this: enter code here result = engGetVariable(ep,"X"); if (!result) { printf ("Error..."); exit -1; } int n = mxGetN(result); char *varx = NULL; memcpy(varx, mxGetData(result),n*sizeof(char)); It doesn't work. Does someone know how to get a Matlab string in C? I've read Matlab documentation about engGetVariable() and the provided example but any of this things clarify me.

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• Creating methods with infinite overloads ? (.NET)

  - by MarceloRamires

  In C# you can do this: foo = string.Format("{0} {1} {2} {3} ...", "aa", "bb", "cc" ...); This method Format() accepts infinite parameters, being the first one how the string should be formatted and the rest are values to be put in the string. Today I've come to a situation where I had to get a set of strings and test them, then I remembered this language functionality, but I had no clue. After a few unsuccessful web searches, I've realised it would be more prudent to just get an array, which didn't make me quite satisfied. Q: How do I make a function that accepts infinite parameters? And how do I use it ?

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• How to parse out html links from a huge string with html links and other text (Java).

  - by Robert

  Hello, my question is how would i be able to go through a string and take out only the links and erase all the rest? I thought about using some type of delemiter, but wouldnt know how to go about using it in java. an example of what i am trying to do: this is my String: String myString = "The file is http: // www. .com/hello.txt and the second file is " + "http: // www. .com/hello2.dat"; I would want the output to be: "http: // www. .com/hello.txt http: // www. .com/hello2.dat" or each could be added to an array, separately. I just want some ideas, id like to write the code myself but am having trouble on how to do it. Any help would be awesome.

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• referencing struct fields in c with square brackets and an index instead of . and ->?

  - by lsiebert

  Assuming I have a structure such as: typedef struct { char * string1; char * string2; } TWO_WORDS; such that all the fields are of the same type, and my main has TWO_WORDS tw; can I reference string1 with tw[0] and string2 with two[1]? If so: is this part of the c standard? do i have to cast the struct to an array first? what about fields which are different sizes in memory what about fields which are different types but the same size? can you do pointer arithmetic within a structure? -

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• Is there a good way to remove a character from a string without copying all the characters following

  - by piemesons

  I was given an interview question: // 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)=????? The obvious answer is to copy the rest of the array "back" one position. But this seems... unpleasant. Surely there is some better way?

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• How can I improve the performance of this algorithm

  - by Justin

  // Checks whether the array contains two elements whose sum is s. // Input: A list of numbers and an integer s // Output: return True if the answer is yes, else return False public static boolean calvalue (int[] numbers, int s){ for (int i=0; i< numbers.length; i++){ for (int j=i+1; j<numbers.length;j++){ if (numbers[i] < s){ if (numbers[i]+numbers[j] == s){ return true; } } } } return false; }

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