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  • Pros and cons of ways of storing an unsigned int without an unsigned int data type

    - by fields
    I have values that are 64-bit unsigned ints, and I need to store them in mongodb, which has no unsigned int type. I see three main possibilities for storing them in other field types, and converting on going in and out: Using a signed int is probably easiest and most space efficient, but has the disadvantage that they're not human readable and if someone forgets to do the conversion, some of them will work, which may obscure errors. Raw binary is probably most difficult for inexperienced programmers to deal with, and also suffers from non-human-readability. A string representation is the least space efficient (~40 bytes in unicode vs 8 bytes per field), but then at least all of the possible values will map properly, and for querying only a conversion to string is required instead of a more complicated conversion. I need these values to be available from different platforms, so a single driver-specific solution isn't an option. Any major pros and cons I've missed? Which one would you use?

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  • HT create a new vector in data frame that takes correlation of existing vectors

    - by Milktrader
    I have a time series of two indexes, with each row representing the closing price on the same day. I'd like to go to row 30 and lookback over the last 30 'days' and calculate the pearson correlation. And then store that value in a new vector. Then, repeat the calculation for the entire time series. It is a trivial task in Excel, so I'm convinced it can be done in R. I don't know the method to use though.

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  • Powerbuilder : How to compare the old value and new value of a column in data window

    - by Archangel
    Suppose I have a datawindow object which is attached to a datawindow control named 'dw_detail". This object uses grid presentation style and has a database column named 'found'. Now when a user modifies that column's value, I want to compare it with the original value that was fetched from the database. I know I can access the value of that column as 'dw_detail.object.found[row_no]'. Now I am trying to access the original value of the column as 'dw_detail.object.found.original[row_no]', but it is not working. It is not giving any compiling error, but when I debugged, 'dw_detail.object.found.original[row_no]' contains no values. How can I access the original value of that column?

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  • How to pull data from a MySQL column and put it into a single array

    - by Rob
    Basically, this is what I currently use in an included file: $sites[0]['url'] = "http://example0.com"; $sites[1]['url'] = "http://example1.com"; $sites[2]['url'] = "http://example2.com"; $sites[3]['url'] = "http://example3.com"; $sites[4]['url'] = "http://example4.com"; $sites[5]['url'] = "http://example5.com"; And so I output it like so: foreach($sites as $s) But I want to make it easier to manage via a MySQL database. So my question is, how can I make it automatically add additional "$sites[x]['url'] = "http://examplex.com";" and output it appropriately from my MySQL table?

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  • UICollectionView with one static cell and N dynamic ones from a fetchresultscontroller exception

    - by nflacco
    I'm trying to make a UITableView that shows a blog post and comments for that post. My setup is a tableview in storyboard with two dynamic prototype cells. The first cell is for the post and should never change. The second cell represents the 0 to N comments. My cellForRowAtIndexPath method shows the post cell properly, but fails to get the comment at the given index path (though if I comment out the fetch I get the appropriate number of comment cells with a green background that I set as a visual debug thing). let comment = fetchedResultController.objectAtIndexPath(indexPath) as Comment I get the following exception on this line: 2014-08-24 15:06:40.712 MessagePosting[21767:3266409] *** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM objectAtIndex:]: index 1 beyond bounds [0 .. 0]' *** First throw call stack: ( 0 CoreFoundation 0x0000000101aa43e5 __exceptionPreprocess + 165 1 libobjc.A.dylib 0x00000001037f9967 objc_exception_throw + 45 2 CoreFoundation 0x000000010198f4c3 -[__NSArrayM objectAtIndex:] + 227 3 CoreData 0x00000001016e4792 -[NSFetchedResultsController objectAtIndexPath:] + 162 Section and cell setup: override func tableView(tableView: UITableView!, numberOfRowsInSection section: Int) -> Int { // #warning Incomplete method implementation. // Return the number of rows in the section. switch section { case 0: return 1 default: if let realPost:Post = post { return fetchedResultController.sections[0].numberOfObjects } else { return 0 } } } override func tableView(tableView: UITableView!, cellForRowAtIndexPath indexPath: NSIndexPath!) -> UITableViewCell! { switch indexPath.section { case 0: let cell = tableView.dequeueReusableCellWithIdentifier(postViewCellIdentifier, forIndexPath: indexPath) as UITableViewCell cell.backgroundColor = lightGrey if let realPost:Post = self.post { cell.textLabel.text = realPost.text } return cell default: let cell = tableView.dequeueReusableCellWithIdentifier(commentCellIdentifier, forIndexPath: indexPath) as UITableViewCell cell.backgroundColor = UIColor.greenColor() let comment = fetchedResultController.objectAtIndexPath(indexPath) as Comment // <---------------------------- :( cell.textLabel.text = comment.text return cell } } FRC: func controllerDidChangeContent(controller: NSFetchedResultsController!) { tableView.reloadData() } func getFetchedResultController() -> NSFetchedResultsController { fetchedResultController = NSFetchedResultsController(fetchRequest: taskFetchRequest(), managedObjectContext: managedObjectContext, sectionNameKeyPath: nil, cacheName: nil) return fetchedResultController } func taskFetchRequest() -> NSFetchRequest { if let realPost:Post = self.post { let fetchRequest = NSFetchRequest(entityName: "Comment") let sortDescriptor = NSSortDescriptor(key: "date", ascending: false) fetchRequest.predicate = NSPredicate(format: "post = %@", realPost) fetchRequest.sortDescriptors = [sortDescriptor] return fetchRequest } else { return NSFetchRequest(entityName: "") } }

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  • Neural Network: Handling unavailable inputs (missing or incomplete data)

    - by Mike
    Hopefully the last NN question you'll get from me this weekend, but here goes :) Is there a way to handle an input that you "don't always know"... so it doesn't affect the weightings somehow? Soo... if I ask someone if they are male or female and they would not like to answer, is there a way to disregard this input? Perhaps by placing it squarely in the centre? (assuming 1,0 inputs at 0.5?) Thanks

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  • How to send large objects using boost::asio

    - by Max
    Good day. I'm receiving a large objects via the net using boost::asio. And I have a code: for (int i = 1; i <= num_packets; i++) boost::asio::async_read(socket_, boost::asio::buffer(Obj + packet_size * (i - 1), packet_size), boost::bind(...)); Where My_Class * Obj. I'm in doubt if that approach possible (because i have a pointer to an object here)? Or how it would be better to receive this object using packets of fixed size in bytes? Thanks in advance.

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  • Free country/city suggestion list/database

    - by Ilian Iliev
    I'm looking for something similar to facebook suggestion list with cities and countries. You can see what I'm exactly talking about when you try to create new event in facebook, click to add address, and then start typing in the City field. I prefer finding working suggestion tool in jQuery(with the date), but database with city/country will do the trick too. Thanks in advance, Ilian Iliew

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  • pass form builder in remote_function in rails ?

    - by richard moss
    hi all i have select box where on change i need to grab the value and via remote function get some field names from db and then generate those field further down the form depwning on whatoption from the select box is chosen. The problem is is that the fields are in a f.form_for so are using the formbuilder f that has the select box in. So when i render the partial via ajax in the controller i get an error as i dont have a reference to the local form builder f. does anyone know how or if i can get reference to the form builder orif can pass it in a remote function call and then pass into my locals in the partial ? thanks alot, any help will be great as been stuck on this a long time! cheers rick

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  • What's the best general programming book to review basic development concepts?

    - by Charles S.
    I'm looking for for a programming book that reviews basic concepts like implementing linked lists, stacks, queues, hash tables, tree traversals, search algorithms, etc. etc. Basically, I'm looking for a review of everything I learned in college but have forgotten. I prefer something written in the last few years that includes at least a decent amount of code in object-oriented languages. This is to study for job interview questions but I already have the "solving interview questions" books. I'm looking for something with a little more depth and explanation. Any good recommendations?

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  • GWT: library for encoding/decoding arbitrary data in URL fragments

    - by Caffeine Coma
    Ajax applications, and GWT in particular, use the URL fragment (e.g. http://example.com/myapp#fragment) to maintain application state on the client without reloading the page. Is there a GWT library that facilitates the encoding and decoding of arbitrary parameters into the URL fragment? I'm looking for something analogous to the Servlet API's getParameter() method, but for client-side URL parameters.

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  • Mapping class properties to generic columns in table .NET

    - by Tony_Henrich
    I have have a SQL Server table which has generic names like Text1, Text2.. etc. The table was designed like this because the same structure is used for different projects. I have a class in .NET which has properties. Say a Customer class has a property called FirstName. How can I do the mapping from FirstName to Text1 just once (central place) in the application so that I don't have to remember and hard code the mappings all over the app when I create the different DAL methods? For example, I want the app to know when I want to update, insert a FirstName, the DAL automatically uses Text1. Basically I don't have to remember which property goes to which column. The idea is so the developers do not map the properlies/columns in a wrong way. It's always consistent. Note: Database inserts, updates and deletes are allowed through stored procedures only.

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  • Visual Studio ReportViewer repeating data block on every page

    - by muhan
    I am using Reportviewer to generate a sales invoice to be printed by the user. How can I get databound fields to be printed on every page of a multi page invoice? The invoice is printed on a pre-printed form. I want the printed form to look roughly like: page 1 customer john smith 123 main st. city, CA 90000 some item1 $100 some item2 $150 some item3 $150 page 2 customer john smith 123 main st. city, CA 90000 some item4 $500 some item5 $250 some item6 $950 Total $2100 Using 1 list which contains databound textbox fields for the customer info, and a table for the items. The problem is if there are many items such that the items flow over to page 2, the next page only contains items, and not the customer info which needs to be printed on second page as well. I tried using page header, but I can't use databound items in page header. Please Help!

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  • How to properly use CoreData validation & error framework ?

    - by Xav
    I've created a model in Xcode, and for various attributes I have minimum & maximum values defined and that are enforced by coreData at runtime. I'm using NSManagedObject validateValue:forKey:error to check for user input values. I was a bit disappointed to see that the localized error message is not specific, and I get a "The operation couldn't be completed. (Cocoa error 1620)" for too small values and a "The operation couldn't be completed. (Cocoa error 1610)" for too large values. It's written in the coreData documentation that "you can localize most aspects of a managed object model, including entity and property names and error messages". Unfortunately it's not very detailed on how you implement it for error messages. So How do you customize error message ? How do you localize them ? Is it possible to customize it in a way where it will mentioned the reference value ex: "Value should be lower than %@" or "Value should be higher than %@" ?

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  • If attacker has original data and encrypted data, can they determine the passphrase?

    - by Brad Cupit
    If an attacker has several distinct items (for example: e-mail addresses) and knows the encrypted value of each item, can the attacker more easily determine the secret passphrase used to encrypt those items? Meaning, can they determine the passphrase without resorting to brute force? This question may sound strange, so let me provide a use-case: User signs up to a site with their e-mail address Server sends that e-mail address a confirmation URL (for example: https://my.app.com/confirmEmailAddress/bill%40yahoo.com) Attacker can guess the confirmation URL and therefore can sign up with someone else's e-mail address, and 'confirm' it without ever having to sign in to that person's e-mail account and see the confirmation URL. This is a problem. Instead of sending the e-mail address plain text in the URL, we'll send it encrypted by a secret passphrase. (I know the attacker could still intercept the e-mail sent by the server, since e-mail are plain text, but bear with me here.) If an attacker then signs up with multiple free e-mail accounts and sees multiple URLs, each with the corresponding encrypted e-mail address, could the attacker more easily determine the passphrase used for encryption? Alternative Solution I could instead send a random number or one-way hash of their e-mail address (plus random salt). This eliminates storing the secret passphrase, but it means I need to store that random number/hash in the database. The original approach above does not require storage in the database. I'm leaning towards the the one-way-hash-stored-in-the-db, but I still would like to know the answer: does having multiple unencrypted e-mail addresses and their encrypted counterparts make it easier to determine the passphrase used?

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  • wxpython GUI and multiprocessing - how to send data back from the long running process

    - by wxpydon
    Hello everyone, Trying to run a time consuming task from a wxpython GUI. The basic idea is to start the long time task from the GUI (pressing a button) and then, a static text on the dialog should be updated from it. First I tried some threading (http://wiki.wxpython.org/LongRunningTasks and many other resourses seen), and I want to show back the messages using Publisher.class. It didn't went so well, after a message or two, the GUI seems to frozen. Now I want to achieve that with multiprocessing. I have this method inside my 'GUI' class: def do_update(self, e): self.txt_updatemsg.SetLabel("Don't stop this \n") ... pub = Publisher() # i tried also calling directly from dbob object # Publisher() is a singleton so this must be useless? pub.subscribe(self.__update_txt_message, ('updatedlg', 'message')) dbob = dbutils.DBUtils() # DBUtils is the class with 'long time' tasks dbob.publisher = pub p = Process(target=self.do_update_process, args=(dbob,)) p.start() while p.is_alive: wx.Yield def do_update_process(self, dbob): dbob.do_update() __update_txt_message is a simple function what sets the static text on dialog. Question is: how can I send back some text messages from this Process (just simple text, that's all I need) Thanks guys!

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  • Change an access Primary key with relationships

    - by DiegoMaK
    I have a database in access 2007 accdb extension , there are more or less 30-40 tables with related primary key "local_number". it is a text primary key with 10 lenght. How can I change the length of this primary key to 30 WITHOUT delete previosly all the 30 relationship. 2,A similar question. I need add a compose primary key to my PK "local_number". I need Add a "Date" as composed PK. Then access just allow this if I first delete all relationships. How can Avoid this warning and change my PK ignoring this message.

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  • Using Linq2Sql to insert data into multiple tables using an auto incremented primary key

    - by Thomas
    I have a Customer table with a Primary key (int auto increment) and an Address table with a foreign key to the Customer table. I am trying to insert both rows into the database in one nice transaction. using (DatabaseDataContext db = new DatabaseDataContext()) { Customer newCustomer = new Customer() { Email = customer.Email }; Address b = new Address() { CustomerID = newCustomer.CustomerID, Address1 = billingAddress.Address1 }; db.Customers.InsertOnSubmit(newCustomer); db.Addresses.InsertOnSubmit(b); db.SubmitChanges(); } When I run this I was hoping that the Customer and Address table automatically had the correct keys in the database since the context knows this is an auto incremented key and will do two inserts with the right key in both tables. The only way I can get this to work would be to do SubmitChanges() on the Customer object first then create the address and do SubmitChanges() on that as well. This would create two roundtrips to the database and I would like to see if I can do this in one transaction. Is it possible? Thanks

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  • How to perform undirected graph processing from SQL data

    - by recipriversexclusion
    I ran into the following problem in dynamically creating topics for our ActiveMQ system: I have a number of processes (M_1, ..., M_n), where n is not large, typically 5-10. Some of the processes will listen to the output of others, through a message queue; these edges are specified in an XML file, e.g. <link from="M1" to="M3"</link> <link from="M2" to="M4"</link> <link from="M3" to="M4"</link> etc. The edges are sparse, so there won't be many of them. I will parse this XML and store this information in an SQL DB, one table for nodes and another for edges. Now, I need to dynamically create strings of the form M1.exe --output_topic=T1 M2.exe --output_topic=T2 M3.exe --input_topic=T1 --output_topic=T3 M4.exe --input_topic=T2 --input_topic=T3 where the tags are sequentially generated. What is the best way to go about querying SQL to obtain these relationships? Are there any tools or other tutorials you can point me to? I've never done graps with SQL. Using SQL is imperative, because we use it for other stuff, too. Thanks!

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  • How to Delete all data from a table which contain self referencing foreign key

    - by Shantanu Gupta
    I have a table which has employee relationship defined within itself. i.e. EmpID Name SeniorId ----------------------- 1 A NULL 2 B 1 3 C 1 4 D 3 and so on... Where Senior ID is a foreign key whose primary key table is same with refrence column EmpId I want to clear all rows from this table without removing any constraint. How can i do this? Deletion need to be performed like this 4, 3 , 2 , 1 How can I do this

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  • Extracting attribute data from a raster

    - by user308827
    Hi, I have a raster file (basically 2D array) with close to a million points. I am trying to extract a circle from the raster (and all the points that lie within the circle. Using ArcGIS is exceedingly slow for this. Can anyone suggest any image processing library that is both easy to learn and powerful and quick enough for something like this? Thanks!

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  • Storing expression references to data base

    - by Marcus
    I have standard arithmetic expressions sotred as strings eg. "WIDTH * 2 + HEIGHT * 2" In this example WIDTH and HEIGHT references other objects in my system and the literals WIDTH and HEIGHT refers to a property (Name) on those objects. The problem I'm having is when the Name property on an expression object changes the expression won't match anymore. One solution I came up with is to instead of storing "WIDTH * 2 + HEIGHT * 2" i store "{ID_OF_WIDTH} * 2 + {ID_OF_HEIGHT} * 2" And let my parser be able to parse this new syntax and implement an interface or such on referenced objects IExpressionReference { string IdentifierName { get; } } Anyone have a better/alternative solution to my problem?

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