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• Java: fastest way to do random reads on huge disk file(s)

  - by cocotwo

  I've got a moderately big set of data, about 800 MB or so, that is basically some big precomputed table that I need to speed some computation by several orders of magnitude (creating that file took several mutlicores computers days to produce using an optimized and multi-threaded algo... I do really need that file). Now that it has been computed once, that 800MB of data is read only. I cannot hold it in memory. As of now it is one big huge 800MB file but splitting in into smaller files ain't a problem if it can help. I need to read about 32 bits of data here and there in that file a lot of time. I don't know before hand where I'll need to read these data: the reads are uniformly distributed. What would be the fastest way in Java to do my random reads in such a file or files? Ideally I should be doing these reads from several unrelated threads (but I could queue the reads in a single thread if needed). Is Java NIO the way to go? I'm not familiar with 'memory mapped file': I think I don't want to map the 800 MB in memory. All I want is the fastest random reads I can get to access these 800MB of disk-based data. btw in case people wonder this is not at all the same as the question I asked not long ago: http://stackoverflow.com/questions/2346722/java-fast-disk-based-hash-set

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• Symfony2 entity field type alternatives to "property" or "__toString()"?

  - by Polmonino

  Using Symfony2 entity field type one should specify property option: $builder->add('customers', 'entity', array( 'multiple' => true, 'class' => 'AcmeHelloBundle:Customer', 'property' => 'first', )); But sometimes this is not sufficient: think about two customers with the same name, so display the email (unique) would be mandatory. Another possibility is to implement __toString() into the model: class Customer { public $first, $last, $email; public function __toString() { return sprintf('%s %s (%s)', $this->first, $this->last, $this->email); } } The disadvances of the latter is that you are forced to display the entity the same way in all your forms. Is there any other way to make this more flexible? I mean something like a callback function: $builder->add('customers', 'entity', array( 'multiple' => true, 'class' => 'AcmeHelloBundle:Customer', 'property' => function($data) { return sprintf('%s %s (%s)', $data->first, $data->last, $data->email); }, ));

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• Nesting arbitrary objects in Java

  - by user1502381

  I am having trouble solving a particular problem in Java (which I did not find by search). I do not know how to create a nested lists of objects - with a different type of object/primitive type at the end. For example: *Note: only an example. I am actually doing this below with something other than Employee, but it serves as simple example. I have an array of an object Employee. It contains information on the Employee. public class Employee { int age int salary int yearsWorking public Employee () { // constructor... } // Accessors } What I need to do is organize the Employees by quantiles/percentiles. I have done so by the following: import org.apache.commons.math.stat.descriptive.rank.Percentile; public class EmployeeSort { public void main(String args[]) { Percentile p = new Percentile(); Employee[] employeeArray = new Employee(100); // filled employeeArray double[] ageArray new double[100]; // filled ageArray with ages from employeeArray int q = 25; // Percentile cutoff for (int i = 1; i*q < 100; i++) { // assign percentile cutoff to some array to contain the values } } } Now, the problem I have is that I need to organize the Employees first by the percentiles of age, then percentiles of yearsWorking, and finally by percentiles of salary. My Java knowledge is inadequate right now to solve this problem, but the project I was handed was in Java. I am primarily a python guy, so this problem would have been a lot easier in that language. No such luck.

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• Javascript cloned object looses its prototype functions

  - by Jake M

  I am attempting to clone an object in Javascript. I have made my own 'class' that has prototype functions. My Problem: When I clone an object, the clone cant access/call any prototype functions. I get an error when I go to access a prototype function of the clone: clone.render is not a function Can you tell me how I can clone an object and keep its prototype functions This simple JSFiddle demonstrates the error I get: http://jsfiddle.net/VHEFb/1/ function cloneObject(obj) { // Handle the 3 simple types, and null or undefined if (null == obj || "object" != typeof obj) return obj; // Handle Date if (obj instanceof Date) { var copy = new Date(); copy.setTime(obj.getTime()); return copy; } // Handle Array if (obj instanceof Array) { var copy = []; for (var i = 0, len = obj.length; i < len; ++i) { copy[i] = cloneObject(obj[i]); } return copy; } // Handle Object if (obj instanceof Object) { var copy = {}; for (var attr in obj) { if (obj.hasOwnProperty(attr)) copy[attr] = cloneObject(obj[attr]); } return copy; } throw new Error("Unable to copy obj! Its type isn't supported."); } function MyObject(name) { this.name = name; // I have arrays stored in this object also so a simple cloneNode(true) call wont copy those // thus the need for the function cloneObject(); } MyObject.prototype.render = function() { alert("Render executing: "+this.name); } var base = new MyObject("base"); var clone = cloneObject(base); clone.name = "clone"; base.render(); clone.render(); // Error here: "clone.render is not a function"

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• Retrieving ids from MySQL query

  - by Matt Maclennan

  I am having trouble accessing the "model_id" and "brand_id" from the foreach loop that I am using. They are the right field names, because I have echoed them successfully, and I have also "var_dumped" the array, and the IDs are there. It is just a case of implementing the relevant links on each list section. Below is the code I have. <? $output = mysqli_query("SELECT * FROM bikes, bikeTypes WHERE bikes.model_id = bikeTypes.model_id"); $result = array(); while($row = mysqli_fetch_array($output)) { $result[$row['model']][] = $row; } foreach ($result as $category => $values) { echo "<li><a href='test.php?id=" . $row['model_id'] . "'>".$category.'</a><ul>'; foreach ($values as $value) { echo "<li><a href='details.php?id=" . $row['brand_id'] . "'>" . $value['bikeName'] . "</a></li>"; } echo '</ul>'; echo '</li>'; } ?>

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• Simple average calculation

  - by sasquatch90

  I'm trying to write program calculating average of given numbers stored in an array. Amount of numbers should be not more than 100, and user should input them until a !int variable is given : #include <iostream> #include <conio.h> using namespace std; double average(int tab[], int i){ int sum=0; for(int j=0; j<i; ++j){ sum+=tab[j]; } return (double)sum/i; } int main() { int tab[100]; int n=0; int number=0; do { if(n < 100){ cout << "Give " << n+1 << " number : "; cin >> number; tab[n]=number; number=0; ++n; } else{ break; } } while( !isdigit(number) ); cout << average(tab, n) << endl; getch(); return 0; } Why after giving char, it prints me 'Give n number:' for all empty cells of my array ? It should end and use only given numbers.

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• Update Options on Existing jQuery Object

  - by Vince Kronlein

  I'm using Bootstrap and DataTables in my app and I have a default initializer for tables based on class. I can just add the class data-table to the table and it gets instantiated with the default values I want. I'd like to know how to change or update specific options based on a specific table. if ($.fn.dataTable) { $('.data-table').dataTable( { sDom: "R<'row'<'span6'l><'span6'f>r>t<'row'<'span6'i><'span6'p>>", sPaginationType: "bootstrap", oLanguage: { "sLengthMenu": "_MENU_ &nbsp; records per page" }, aoColumnDefs: [ { "bSortable": false, "aTargets": [ 0 ] } ] }); } All my data tables have a checkbox in the first column so the above removal of sorting works for all of them. But I'd like to be able to update the aoColumnDefs on a table by table basis so I can add other columns that I don't want sorted. So let's say I have a table: $('#member-list'), how do I access this object and update it's datatables options in jQuery? I can't find any reference or help anywhere. Thanks a lot! -V

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• Getting directory's permissions via FTP

  - by Gotys

  I am trying to get permissions of a directory via FTP command "STAT" like this: $directory_list = ftp_raw($conn_id,'STAT '.$path); The above command lists entire directory contents , including files and subdirs. I then search the returned data array for the directory i need to check, and retrieve something like: drwxr-xr-x 3 user group 77824 May 13 10:15 Targetdir This will let me parse the drwxr-xr-x string to find out that the chmod of the Targetdir is 0755. Problem is, when the containing directory has 5000 files. A) It takes a very long time, and B) the ftp_raw function just returns empty array 1 in 10 runs. I don't know if it's timing out or what exactely is the problem. Is there are a better way to find directory's permissions ? Is there a way to limit number of retrieved fiels in "STAT" command ? I really need just the top 5 , no need for the other 4995 files. Does anyone know, why would my command NOT run 100% of the time? Why would it break ? I cannot even reproduce my error, it happens randomly.

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• Optimize a views drawing code

  - by xon1c

  Hi, in a simple drawing application I have a model which has a NSMutableArray curvedPaths holding all the lines the user has drawn. A line itself is also a NSMutableArray, containing the point objects. As I draw curved NSBezier paths, my point array has the following structure: linePoint, controlPoint, controlPoint, linePoint, controlPoint, controlPoint, etc... I thought having one array holding all the points plus control points would be more efficient than dealing with 2 or 3 different arrays. Obviously my view draws the paths it gets from the model, which leads to the actual question: Is there a way to optimize the following code (inside the view's drawRect method) in terms of speed? int lineCount = [[model curvedPaths] count]; // Go through paths for (int i=0; i < lineCount; i++) { // Get the Color NSColor *theColor = [model getColorOfPath:[[model curvedPaths] objectAtIndex:i]]; // Get the points NSArray *thePoints = [model getPointsOfPath:[[model curvedPaths] objectAtIndex:i]]; // Create a new path for performance reasons NSBezierPath *path = [[NSBezierPath alloc] init]; // Set the color [theColor set]; // Move to first point without drawing [path moveToPoint:[[thePoints objectAtIndex:0] myNSPoint]]; int pointCount = [thePoints count] - 3; // Go through points for (int j=0; j < pointCount; j+=3) { [path curveToPoint:[[thePoints objectAtIndex:j+3] myNSPoint] controlPoint1:[[thePoints objectAtIndex:j+1] myNSPoint] controlPoint2:[[thePoints objectAtIndex:j+2] myNSPoint]]; } // Draw the path [path stroke]; // Bye stuff [path release]; [theColor release]; } Thanks, xonic

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• How do I pass an NSString through 3 ViewControllers?

  - by dBloc

  hey, I'm currently using the iPhone SDK and I'm having trouble passing an NSString through 3 views I am able to pass an NSString between 2 view controllers but I am unable to pass it through another one. My code is as follows... `- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)index`Path { NSString *string1 = nil; NSDictionary *dictionary = [listOfItems objectAtIndex:indexPath.section]; NSArray *array = [dictionary objectForKey:@"items"]; string1 = [array objectAtIndex:indexPath.row]; //Initialize the detail view controller and display it. ViewController2 *vc2 = [[ViewController2 alloc] initWithNibName:@"ViewController2" bundle:[NSBundle mainBundle]]; vc2.string1 = string1; [self.navigationController pushViewController:vc2 animated:YES]; [vc2 release]; vc2 = nil; } in the "ViewController 2" implementations I am able use "string1" in the title bar by doing the following.... - (void)viewDidLoad { [super viewDidLoad]; self.navigationItem.title = string1; UIBarButtonItem *addButton = [[[UIBarButtonItem alloc] initWithImage:[UIImage imageNamed:@"icon_time.png"] style:UIBarButtonItemStylePlain //style:UIBarButtonItemStyleBordered target:self action:@selector(goToThirdView)] autorelease]; self.navigationItem.rightBarButtonItem = addButton; } but I also have a NavBar Button on the right side that I would like to push a new view - (void)goToThirdView { ViewController3 *vc3 = [[ViewController3 alloc] initWithNibName:@"ViewController3" bundle:[NSBundle mainBundle]]; [self.navigationController pushViewController:NESW animated:YES]; vc3.string1 = string1 ; [vc3 release]; vc3 = nil; } How do I pass on that same string to the third view? (or fourth)

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• Java ArrayList remove dupes without sets

  - by Kieran

  I'm having problems removing duplicates from an ArrayList. It's for an assignment for college. Here's the code I have already: public int numberOfDiffWords() { ArrayList<String> list = new ArrayList<>(); for(int i=0; i<words.size()-1; i++) { for(int j=i+1; j<words.size(); j++) { if(words.get(i).equals(words.get(j))) { // do nothing } else { list.add(words.get(i)); } } } return list.size(); } The problem is in the numberOfDiffWords() method. The populate list method is working correctly, as my instructor has given me a sample string (containing 4465 words) to analyse - printing words.size() gives the correct result. I want to return the size of the new ArrayList with all duplicates removed. words is an ArrayList class attribute. UPDATE: I should have mentioned I'm only allowed to use dynamic indexed-based storage for this part of the assignment, which means no hash-based storage.

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• C# Type conversion between two similar Datatable objects

  - by Ali

  I have .NET project with sync framework and two separate Datasets for MS SQL and Compact SQL. in my base class I have a generic DataTable object. in my derived classed I assign Typed DataTable to the generic object based on whether the application is operating online or offline: example: if (online) _dataTable = new MSSQLDataSet.Customer; else _dataTable = new CompactSQLDataSet.Customer; Now every where in my code i have to check and do a cast based on the current network mode like this: public void changeCustomerID(int ID) { if (online) (MSSQLDataSet.CustomerDataTable)_dataTable)[i].CustomerID = value; else (CompactMSSQLDataSet.CustomerDataTable)_dataTable)[i].CustomerID = value; } but I don't think this is very efficient and I believe it can be done in a smarter way to only use one line of code by dynamically getting the Type of _dataTable on the run time. my problem is at the design time, in order to acess datatable porperties such as "CustomerID" it has to be casted to either MSSQLDataSet.CustomerDataTable or CompactMSSQLDataSet.CustomerDataTable. Is there a way to have a function or a operator to convert the _datatable to its runtime type but still be able to use it's design time properties which are the same between the two types? something like: ((aType)_dataTable)[i].CustomerID = value; //or GetRuntimeType(_dataTable)[i].CustomerID = value;

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• Is this linear search implementation actually useful?

  - by Helper Method

  In Matters Computational I found this interesting linear search implementation (it's actually my Java implementation ;-)): public static int linearSearch(int[] a, int key) { int high = a.length - 1; int tmp = a[high]; // put a sentinel at the end of the array a[high] = key; int i = 0; while (a[i] != key) { i++; } // restore original value a[high] = tmp; if (i == high && key != tmp) { return NOT_CONTAINED; } return i; } It basically uses a sentinel, which is the searched for value, so that you always find the value and don't have to check for array boundaries. The last element is stored in a temp variable, and then the sentinel is placed at the last position. When the value is found (remember, it is always found due to the sentinel), the original element is restored and the index is checked if it represents the last index and is unequal to the searched for value. If that's the case, -1 (NOT_CONTAINED) is returned, otherwise the index. While I found this implementation really clever, I wonder if it is actually useful. For small arrays, it seems to be always slower, and for large arrays it only seems to be faster when the value is not found. Any ideas?

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• passing string to a AJAX/JSON function

  - by Mikey1980

  I’m having trouble getting a AJAX/JSON function to work correctly. I had this function grabbing value from a drop down box but now I want to use an anchor tag to set it's value. I thought it would be easy to just use the onClick event to pass string to the function I was using for the drop down box but it doesn’t do anything. I’m stumped! Here how I set it up: 1st I add an onClick event… <a href="<?php echo Settings::get('app.webroot'); ?>?view=schedule&action=questions" onmouseout="MM_swapImgRestore();" onmouseover="MM_swapImage('bre','','template/images/schedule/bre_f2.gif',1) onclick="assignCallType('testing')";> 2nd I check main.js.php function assignCallType(type) { alert(type); //just for debugging new Request.JSON({ url: "ajax.php", onSuccess: function(rtndata,txt){ if (rtndata['STATUS'] != 'OK') alert('Error assigning call type to call'); }, onFailure: function (xhr) { alert('Error assigning call type to call'); } }).get({ 'action': 'assignCallType', 'call_type': type }); } 3rd Ajax.php: the variable is back in PHP and values don’t get added to the db, but I also didn’t get the alert from main.js.php if ($_GET['action'] == "assignCallType") { if ($USER->isInsideSales()) { $call_type = $_GET['call_type']; $_SESSION['callinfo']->setCallType($call_type); $_SESSION['callinfo']->save($callid); echo json_encode(array('STATUS'=>'OK')); } else { echo json_encode(array('STATUS'=>'DENIED')); } } Any idea where I am going wrong. The only difference between this and the working drop down is how the function was called, I used onchange="assignCallType(this.value)".

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• codeigniter active record and mysql

  - by sea_1987

  I am running a query with Active Record in a modal of my codeigniter application, the query looks like this, public function selectAllJobs() { $this->db->select('*') ->from('job_listing') ->join('job_listing_has_employer_details', 'job_listing_has_employer_details.employer_details_id = job_listing.id', 'left'); //->join('employer_details', 'employer_details.users_id = job_listing_has_employer_details.employer_details_id'); $query = $this->db->get(); return $query->result_array(); } This returns an array that looks like this, [0]=> array(13) { ["id"]=> string(1) "1" ["job_titles_id"]=> string(1) "1" ["location"]=> string(12) "Huddersfield" ["location_postcode"]=> string(7) "HD3 4AG" ["basic_salary"]=> string(19) "£20,000 - £25,000" ["bonus"]=> string(12) "php, html, j" ["benefits"]=> string(11) "Compnay Car" ["key_skills"]=> string(1) "1" ["retrain_position"]=> string(3) "YES" ["summary"]=> string(73) "Lorem Ipsum is simply dummy text of the printing and typesetting industry" ["description"]=> string(73) "Lorem Ipsum is simply dummy text of the printing and typesetting industry" ["job_listing_id"]=> NULL ["employer_details_id"]=> NULL } } The job_listing_id and employer_details_id return as NULL however if I run the SQL in phpmyadmin I get full set of results, the query i running in phpmyadmin is, SELECT * FROM ( `job_listing` ) LEFT JOIN `job_listing_has_employer_details` ON `job_listing_has_employer_details`.`employer_details_id` LIMIT 0 , 30 Is there a reason why I am getting differing results?

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• Nested functions not allowed in drawrect problem

  - by Martin

  I have a custom view onto which I draw some graphics from the drawrect function, which works fine. However I like to draw based on the contens of an array I pass on the the view just before I do a setNeedsDisplay. In the drawRect function I try to access the array but then I get a nested functions error which I do not understand. Here's my code: // // MyView.h // window // #import <UIKit/UIKit.h> @interface MyView : UIView { NSArray * nary; } @property (nonatomic, copy) NSArray *nary; @end // // MyView.m // window // #import "MyView.h" @implementation MyView @synthesize nary; CGContextRef c; CGFloat black[4] = {0.0f, 0.0f, 0.0f, 1.0f}; - (id)initWithFrame:(CGRect)frame { if (self = [super initWithFrame:frame]) { // Initialization code } return self; } - (void)drawRect:(CGRect)rect { c = UIGraphicsGetCurrentContext(); CGContextSetStrokeColor(c, black); NSLog(@"mview"); NSArray *ns = [nary objectAtIndex:0]; } - (void)dealloc { [super dealloc]; } @end

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• How do i make multi call with SudzC

  - by laxonline

  I am developing magento eCommerce stores in iPhone. For that, i have using Sudzc service class for SOAP WS call. Now, I'm trying to create a cart session its working fine. im getting the cardid. And i need to add one product to cart with some arguments. below is the php request example i need to call same this PHP Request Example $proxy = new SoapClient('http://beta.saletab.com/api/soap/?wsdl'); $sessionId = $proxy->login('xxxx', 'zzzzzzzzzzzzzzzzzzzzzzzzz'); //print_r($sessionId); $shoppingCartId = $proxy->call( $sessionId, 'cart.create'); $result = $proxy->call($sessionId,'cart_product.add',array($shoppingCartId,array('product_id'=>"3109",'qty' => 2)),0); echo "REQUEST HEADERS:\n" . $result->__getLastRequestHeaders() . "\n"; IOS Request im trying to send some product details like productid, sku & cardid SDZMagentoService *service = [SDZMagentoService service]; NSString *sessionId = [IMAPP_DELEGATE getUserDefault:IMAPI_SESSIONID]; NSString *cartId = [IMAPP_DELEGATE getUserDefault:IMAPI_CARTSESSIONID]; NSDictionary *argu = [[NSDictionary alloc] initWithObjectsAndKeys:@"3109",@"product_id",@"2",@"qty",cartId,@"card_id", nil]; [service call:self action:@selector(cartTest:) sessionId:sessionId resourcePath:@"cart_product.add" args:argu];

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• how to send image to remote server using web services in android

  - by Aswan

  get image from sdcard and store that image to remote server. i am getting the image from sdcard and i converterd that image to bytearray by using bitmap .but what's the problem if i oberver byte array it is showing some different values it is not matching with .net image byte array conversion. can u pl help if you have any solution it is very urgent to me following is the code i am using can u pl suggest me FileInputStream fin = new FileInputStream(new File("/sdcard/pictures/1.jpg")); BufferedInputStream bis = new BufferedInputStream(fin,3000); byte[] data = new byte[bis.available()]; bis.read(data, 0, data.length); byte[] data1=new byte[data.length]; for (int i = 0; i < data.length; i++) { System.out.print(data[i]); data1[i]=data[i]; } System.out.println("5..................."+data1); Bitmap bitmap = BitmapFactory.decodeByteArray(data1,0,data1.length); System.out.println("6..................."+data1.length); Log.v("hgfjohfjghjdfhgj",""+bitmap); if(bitmap!=null) image.setImageBitmap(bitmap); else Log.e("Bitmap "," Not Created");

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• Out-of-memory algorithms for addressing large arrays

  - by reve_etrange

  I am trying to deal with a very large dataset. I have k = ~4200 matrices (varying sizes) which must be compared combinatorially, skipping non-unique and self comparisons. Each of k(k-1)/2 comparisons produces a matrix, which must be indexed against its parents (i.e. can find out where it came from). The convenient way to do this is to (triangularly) fill a k-by-k cell array with the result of each comparison. These are ~100 X ~100 matrices, on average. Using single precision floats, it works out to 400 GB overall. I need to 1) generate the cell array or pieces of it without trying to place the whole thing in memory and 2) access its elements (and their elements) in like fashion. My attempts have been inefficient due to reliance on MATLAB's eval() as well as save and clear occurring in loops. for i=1:k [~,m] = size(data{i}); cur_var = ['H' int2str(i)]; %# if i == 1; save('FileName'); end; %# If using a single MAT file and need to create it. eval([cur_var ' = cell(1,k-i);']); for j=i+1:k [~,n] = size(data{j}); eval([cur_var '{i,j} = zeros(m,n,''single'');']); eval([cur_var '{i,j} = compare(data{i},data{j});']); end save(cur_var,cur_var); %# Add '-append' when using a single MAT file. clear(cur_var); end The other thing I have done is to perform the split when mod((i+j-1)/2,max(factor(k(k-1)/2))) == 0. This divides the result into the largest number of same-size pieces, which seems logical. The indexing is a little more complicated, but not too bad because a linear index could be used. Does anyone know/see a better way?

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• How do I get Facebook Application Login to work

  - by Javaaaa

  I just started making an application for Facebook, however I ran into problem early on. The first step I want people to do is to give permission to access their profile. All over the web are examples of how to do this with: $user_id = $facebook->require_login(); However, this is the way it works using the Old PHP API. I have downloaded and installed the new one in my application folder and it is not working anymore. My question is (and i really have been searching for an answer for a long time) what is the code to do this with the new API? (and related question: is it better to use the old API, or learn to work with the new one when I am just starting making apps right now) I have this code now; <?php // Awesome Facebook Application // // Name: - // require_once 'facebook-php-sdk/src/facebook.php'; // Create our Application instance. $facebook = new Facebook(array( 'appId' => $app_id, 'secret' => $app_secret, 'cookie' => true )); $loginUrl = $facebook->getLoginUrl(array( 'req_perms' => 'email,user_birthday,publish_stream,sms,status_update,user_location' )); echo "<p>hello, <fb:name uid=\"$user_id\" useyou=\"false\" />!</p>"; ?>

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• What is the difference between these two linq implementations?

  - by Mahesh Velaga

  I was going through Jon Skeet's Reimplemnting Linq to Objects series. In the implementation of where article, I found the following snippets, but I don't get what is the advantage that we are gettting by splitting the original method into two. Original Method: // Naive validation - broken! public static IEnumerable<TSource> Where<TSource>( this IEnumerable<TSource> source, Func<TSource, bool> predicate) { if (source == null) { throw new ArgumentNullException("source"); } if (predicate == null) { throw new ArgumentNullException("predicate"); } foreach (TSource item in source) { if (predicate(item)) { yield return item; } } } Refactored Method: public static IEnumerable<TSource> Where<TSource>( this IEnumerable<TSource> source, Func<TSource, bool> predicate) { if (source == null) { throw new ArgumentNullException("source"); } if (predicate == null) { throw new ArgumentNullException("predicate"); } return WhereImpl(source, predicate); } private static IEnumerable<TSource> WhereImpl<TSource>( this IEnumerable<TSource> source, Func<TSource, bool> predicate) { foreach (TSource item in source) { if (predicate(item)) { yield return item; } } } Jon says - Its for eager validation and then defferring for the rest of the part. But, I don't get it. Could some one please explain it in a little more detail, whats the difference between these 2 functions and why will the validations be performed in one and not in the other eagerly? Conclusion/Solution: I got confused due to my lack of understanding on which functions are determined to be iterator-generators. I assumed that, it is based on signature of a method like IEnumerable<T>. But, based on the answers, now I get it, a method is an iterator-generator if it uses yield statements.

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• 2D Histogram in R: Converting from Count to Frequency within a Column

  - by Jac

  Would appreciate help with generating a 2D histogram of frequencies, where frequencies are calculated within a column. My main issue: converting from counts to column based frequency. Here's my starting code: # expected packages library(ggplot2) library(plyr) # generate example data corresponding to expected data input x_data = sample(101:200,10000, replace = TRUE) y_data = sample(1:100,10000, replace = TRUE) my_set = data.frame(x_data,y_data) # define x and y interval cut points x_seq = seq(100,200,10) y_seq = seq(0,100,10) # label samples as belonging within x and y intervals my_set$x_interval = cut(my_set$x_data,x_seq) my_set$y_interval = cut(my_set$y_data,y_seq) # determine count for each x,y block xy_df = ddply(my_set, c("x_interval","y_interval"),"nrow") # still need to convert for use with dplyr # convert from count to frequency based on formula: freq = count/sum(count in given x interval) ################ TRYING TO FIGURE OUT ################# # plot results fig_count <- ggplot(xy_df, aes(x = x_interval, y = y_interval)) + geom_tile(aes(fill = nrow)) # count fig_freq <- ggplot(xy_df, aes(x = x_interval, y = y_interval)) + geom_tile(aes(fill = freq)) # frequency I would appreciate any help in how to calculate the frequency within a column. Thanks! jac EDIT: I think the solution will require the following steps 1) Calculate and store overall counts for each x-interval factor 2) Divide the individual bin count by its corresponding x-interval factor count to obtain frequency. Not sure how to carry this out though. .

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• Switch front-end's of a website after X amount of hits

  - by Derek Adair

  Sorry about the title - not sure what to call this one. A client of mine would like to redirect users to different front-ends of his eCommerce site based on a hit-counter (possibly a timer?). important: -The content is moderately different in the two sites, enough to consider them two different websites. Knowing this client he will likely add more drastic content changes and other front-ends. So for this question consider the content to be -This site has a rather large back-end. With affiliate networking, multiple payment gateways, order-tracking, and several other features in the works. It is essential that these two front-ends have identical back-end functionality I know that if it was just a simple CSS swap this would be as simple as an if statement that ran off some kind of counter stored in a DB... but the different HTML markup is throwing me for a loop. Q: How can I serve two different front-ends (HTML/CSS) based on a hit counter? Also, I don't have any clue what to tag this one as...

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• Length-1 arrays can be converted to python scalars error? python

  - by Randy

  from numpy import * from pylab import * from math import * def LogisticMap(a,x): return 4.*a*x*(1.-x) def CosineMap(a,x): return a*cos(x/(2.*pi)) def TentMap(a,x): if x>= 0 or x<0.5: return 2.*a*x if x>=0.5 or x<=1.: return 2.*a*(1.-x) a = 0.98 N = 40 xaxis = arange(0.0,N,1.0) Func = CosineMap subplot(211) title(str(Func.func_name) + ' at a=%g and its second iterate' %a) ylabel('X(n+1)') # set y-axis label plot(xaxis,Func(a,xaxis), 'g', antialiased=True) subplot(212) ylabel('X(n+1)') # set y-axis label xlabel('X(n)') # set x-axis label plot(xaxis,Func(a,Func(a,xaxis)), 'bo', antialiased=True) My program is supposed to take any of the three defined functions and plot it. They all take in a value x from the array xaxis from 0 to N and then return the value. I want it to plot a graph of xaxis vs f(xaxis) with f being any of the three above functions. The logisticmap function works fine, but for CosineMap i get the error "only length-1 arrays can be converted to python scalars" and for TentMap i get error "The truth value of an array with more than one element is ambiguous, use a.any() or a.all()". My tent map function is suppose to return 2*a*x if 0<=x<0.5 and it's suppose to return 2*a*(1-x) if 0.5<=0<=1.

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• Doctrine: Unable to execute either CROSS JOIN or SELECT FROM Table1, Table2?

  - by ropstah

  Using Doctrine I'm trying to execute either a 1. CROSS JOIN statement or 2. a SELECT FROM Table1, Table2 statement. Both seem to fail. The CROSS JOIN does execute, however the results are just wrong compared to executing in Navicat. The multiple table SELECT doesn't event execute because Doctrine automatically tries to LEFT JOIN the second table. The cross join statement (this runs, however it doesn't include the joined records where the refClass User_Setting doesn't have a value): $q = new Doctrine_RawSql(); $q->select('{s.*}, {us.*}') ->from('User u CROSS JOIN Setting s LEFT JOIN User_Setting us ON us.usr_auto_key = u.usr_auto_key AND us.set_auto_key = s.set_auto_key') ->addComponent('u', 'User u') ->addComponent('s', 'Setting s') ->addComponent('us', 'u.User_Setting us') ->where('s.sct_auto_key = ? AND u.usr_auto_key = ?',array(1, $this->usr_auto_key)); And the select from multiple tables (this doesn't event run. It does not spot the many-many relationship between User and Setting in the first ->from() part and throws an exception: "User_Setting" with an alias of "us" in your query does not reference the parent component it is related to.): $q = new Doctrine_RawSql(); $q->select('{s.*}, {us.*}') ->from('User u, Setting s LEFT JOIN User_Setting us ON us.usr_auto_key = u.usr_auto_key AND us.set_auto_key = s.set_auto_key') ->addComponent('u', 'User u') ->addComponent('s', 'Setting s') ->addComponent('us', 'u.User_Setting us') ->where('s.sct_auto_key = ? AND u.usr_auto_key = ?',array(1, $this->usr_auto_key));

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