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Search found 1939 results on 78 pages for 'electronic signature'.

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  • Make an ActiveX control work without a form?

    - by Earlz
    We are using Topaz Signature pads. They provide their APIs in the from of an ActiveX control which is to be put on a Winform control. Well, the way our project will work we do not want to have a form(at least not visible). We just want for the signature ActiveX control to get an image in the background. static AxSigPlus sig = new AxSIGPLUSLib.AxSigPlus(); public static void Begin() { ((System.ComponentModel.ISupportInitialize)(sig)).BeginInit(); sig.Name = "sig"; sig.Location = new System.Drawing.Point(0, 0); sig.Size = new System.Drawing.Size(0, 0); sig.Enabled = true; sig.TabletState = 1; //error here sig.SigCompressionMode = 0; } Ok so I get an error at the marked line. The exception is Exception of type 'System.Windows.Forms.AxHost+InvalidActiveXStateException' was thrown. What do I do to solve this problem? Would it just be easier to create a new hidden form and put the control on it so it's invisible?

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  • Problem with copying local data onto HDFS on a Hadoop cluster using Amazon EC2/ S3.

    - by Deepak Konidena
    Hi, I have setup a Hadoop cluster containing 5 nodes on Amazon EC2. Now, when i login into the Master node and submit the following command bin/hadoop jar <program>.jar <arg1> <arg2> <path/to/input/file/on/S3> It throws the following errors (not at the same time.) The first error is thrown when i don't replace the slashes with '%2F' and the second is thrown when i replace them with '%2F': 1) Java.lang.IllegalArgumentException: Invalid hostname in URI S3://<ID>:<SECRETKEY>@<BUCKET>/<path-to-inputfile> 2) org.apache.hadoop.fs.S3.S3Exception: org.jets3t.service.S3ServiceException: S3 PUT failed for '/' XML Error Message: The request signature we calculated does not match the signature you provided. check your key and signing method. Note: 1)when i submitted jps to see what tasks were running on the Master, it just showed 1116 NameNode 1699 Jps 1180 JobTracker leaving DataNode and TaskTracker. 2)My Secret key contains two '/' (forward slashes). And i replace them with '%2F' in the S3 URI. PS: The program runs fine on EC2 when run on a single node. Its only when i launch a cluster, i run into issues related to copying data to/from S3 from/to HDFS. And, what does distcp do? Do i need to distribute the data even after i copy the data from S3 to HDFS?(I thought, HDFS took care of that internally) IF you could direct me to a link that explains running Map/reduce programs on a hadoop cluster using Amazon EC2/S3. That would be great. Regards, Deepak.

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  • Issues with Rails, Amazon S3, and protected URLs

    - by Shpigford
    So I followed this little tutorial about protecting downloads of files that are uploaded to Amazon S3 with Paperclip. When I've developed locally, it's worked fine, but since pushing the exact same code to a production server...I now get this error from Amazon when I try to access the files: <Error> <Code>InvalidArgument</Code> <Message>Either the Signature query string parameter or the Authorization header should be specified, not both</Message> <ArgumentValue>Basic dGVjaHVrdWxlbGU6ZWxlbHVrdWhjZXQ=</ArgumentValue> <ArgumentName>Authorization</ArgumentName> <RequestId>F6E455857C54F95A</RequestId> <HostId>X4QA2pw9wpHtJtJ2T8qxCyINjq4PLHQVF4VrlYjpX7Ayh694BgQprh5p8H7NRCAt</HostId> </Error> Example URL: http://s3.amazonaws.com/media.example.com/assets/videos/1/original.mov?AWSAccessKeyId=MY_ACCESS_KEY&Expires=1271972624&Signature=7wWH2WYHPO0o9szwPJbimUMqAig%3D That URL is generated using AWS::S3::S3Object.url_for using the aws-s3 gem. So...not even sure where to start. The fact that it works fine when the app is running locally but not when in production really doesn't make sense. The production server is running Ubuntu 8.04.4 LTS (Hardy).

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  • MySql: Problem when using a temporary table

    - by Alex
    Hi, I'm trying to use a temporary tables to store some values I need for a query. The reason of using a temporary table is that I don't want to store the data permanently so different users can modify it at the same time. That data is just stored for a second, so I think a temporary table is the best approach for this. The thing is that it seems that the way I'm trying to use it is not right (the query works if I use a permanent one). This is an example of query: CREATE TEMPORARY TABLE SearchMatches (PatternID int not null primary key, Matches int not null) INSERT INTO SearchMatches (PatternID, Matches) VALUES ('12605','1'),('12503','1'),('12587','2'),('12456','1'), ('12457','2'),('12486','2'),('12704','1'),(' 12686','1'), ('12531','2'),('12549','1'),('12604','1'),('12504','1'), ('12586','1'),('12548','1'),('12 530','1'),('12687','2'), ('12485','1'),('12705','1') SELECT pat.id, signatures.signature, products.product, versions.version, builds.build, pat.log_file, sig_types.sig_type, pat.notes, pat.kb FROM patterns AS pat INNER JOIN signatures ON pat.signature = signatures.id INNER JOIN products ON pat.product = products.id INNER JOIN versions ON pat.version = versions.id INNER JOIN builds ON pat.build = builds.id INNER JOIN sig_types ON pat.sig_type = sig_types.id, SearchMatches AS sm INNER JOIN patterns ON patterns.id = sm.PatternID WHERE sm.Matches <> 0 ORDER BY sm.Matches DESC, products.product, versions.version, builds.build LIMIT 0 , 50 Any suggestion? Thanks.

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  • Get current timepoint from Totem application

    - by ??O?????
    I want to find the exact time where a media file is currently paused at (or playing) in a running Totem instance using D-Bus. To be precise, what I want is available from the Totem python console (if the plugin exists and is enabled) by the following command: >>> print totem_object.props.current_time 732616 which I understand is milliseconds. So far: I've never used D-Bus before, so I'm in the process of going through D-Bus and python-dbus documentation. I've also fired up D-Feet and found that the org.gnome.Totem bus name and the /Factory object I can use the org.freedesktop.DBus.Properties interface methods. I'm currently at this point: >>> import dbus >>> seb= dbus.SessionBus() >>> t= seb.get_object('org.gnome.Totem', '/Factory') >>> tif= dbus.Interface(t, 'org.freedesktop.DBus.Properties') >>> tif.GetAll('') dbus.Dictionary({}, signature=dbus.Signature('sv')) I can't find even a proper how-to, so any help will be greatly appreciated.

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  • What is the equivalent of .NET events in Ruby?

    - by Gishu
    The problem is very simple. An object needs to notify some events that might be of interest to observers. When I sat to validate a design that I cooked up now in Ruby just to validate it.. I find myself stumped as to how to implement the object events. In .Net this would be a one-liner.. .Net also does handler method signature verification,etc. e.g. // Object with events public delegate void HandlerSignature(int a); public event HandlerSignature MyEvent; public event HandlerSignature AnotherCriticalEvent; // Client MyObject.MyEvent += new HandlerSignature(MyHandlerMethod); // MyHandlerMethod has same signature as delegate Is there an EventDispatcher module or something that I am missing that I can strap on to a Ruby class ? Hoping for an answer that plays along with Ruby's principle of least surprise. An event would be the name of the event plus a queue of [observer, methodName] objects that need to be invoked when the event takes place.

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  • "Ambigous type variable" error when defining custom "read" function

    - by Tener
    While trying to compile the following code, which is enhanced version of read build on readMay from Safe package. readI :: (Typeable a, Read a) => String -> a readI str = case readMay str of Just x -> x Nothing -> error ("Prelude.read failed, expected type: " ++ (show (typeOf > (undefined :: a))) ++ "String was: " ++ str) I get an error from GHC: WavefrontSimple.hs:54:81: Ambiguous type variable `a' in the constraint: `Typeable a' arising from a use of `typeOf' at src/WavefrontSimple.hs:54:81-103 Probable fix: add a type signature that fixes these type variable(s)` I don't understand why. What should be fixed to get what I meant? EDIT: Ok, so the solution to use ScopedTypeVariables and forall a in type signature works. But why the following produces very similar error to the one above? The compiler should infer the right type since there is asTypeOf :: a -> a -> a used. readI :: (Typeable a, Read a) => String -> a readI str = let xx = undefined in case readMay str of Just x -> x `asTypeOf` xx Nothing -> error ("Prelude.read failed, expected type: " ++ (show (typeOf xx)) ++ "String was: " ++ str)

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  • My Website was hacked using Statcounter! Does Statcounter keep a record of cookies?

    - by Cyril Gupta
    I had a rather interesting case of hacking on my ASP.Net MVC website. For this website I had implemented a rather uncomplicated authentication system for my admin area -- an encrypted cookie which had an identifying signature for the member. Whenever the admin visits the website the cookie would be decrypted and signature verified. If matching he wouldn't have to sign in. Couple of days ago a visitor on my site told me that he was able to sign into my website simply by clicking no a referral link on his Statcounter console which pointed to my admin area (I had visited his site from a link inside my admin view). He just clicked on a link in statcounter and he was signed in as the admin! The only way this could have happened was if statcounter somehow recorded my cookies and used those when he clicked on the link pointing to my admin! Is that logical or fathomable? I don't understand what's going on. Do you have any suggestions as to how I can protect my website against things like this?

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  • How do I sign requests reliably for the Last.fm api in C#?

    - by Arda Xi
    I'm trying to implement authorization through Last.fm. I'm submitting my arguments as a Dictionary to make the signing easier. This is the code I'm using to sign my calls: public static string SignCall(Dictionary<string, string> args) { IOrderedEnumerable<KeyValuePair<string, string>> sortedArgs = args.OrderBy(arg => arg.Key); string signature = sortedArgs.Select(pair => pair.Key + pair.Value). Aggregate((first, second) => first + second); return MD5(signature + SecretKey); } I've checked the output in the debugger, it's exactly how it should be, however, I'm still getting WebExceptions every time I try. Here's my code I use to generate the URL in case it'll help: public static string GetSignedURI(Dictionary<string, string> args, bool get) { var stringBuilder = new StringBuilder(); if (get) stringBuilder.Append("http://ws.audioscrobbler.com/2.0/?"); foreach (var kvp in args) stringBuilder.AppendFormat("{0}={1}&", kvp.Key, kvp.Value); stringBuilder.Append("api_sig="+SignCall(args)); return stringBuilder.ToString(); } And sample usage to get a SessionKey: var args = new Dictionary<string, string> { {"method", "auth.getSession"}, {"api_key", ApiKey}, {"token", token} }; string url = GetSignedURI(args, true); EDIT: Oh, and the code references an MD5 function implemented like this: public static string MD5(string toHash) { byte[] textBytes = Encoding.UTF8.GetBytes(toHash); var cryptHandler = new System.Security.Cryptography.MD5CryptoServiceProvider(); byte[] hash = cryptHandler.ComputeHash(textBytes); return hash.Aggregate("", (current, a) => current + a.ToString("x2")); }

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  • Uploading to S3 using Curl

    - by Carl Crawley
    Hi All, I'm currently using cURL to upload a file from my server to S3 using AJAX to call the script. So I have the following: $fullfilepath = '/server/sitepath/files/' . $_POST['file']; $upload_url = 'https://'.$_POST['buckets'].'.s3.amazonaws.com/'; $params = array( 'key'=>$_POST['key'], 'AWSAccessKeyId'=>$_POST['AWSAccessKeyId'], 'acl'=>$_POST['acl'], 'success_action_status'=>$_POST['success_action_status'], 'policy'=>$_POST['policy'], 'signature'=>$_POST['signature'], 'Content-Type'=>$_POST['Content-Type'], 'file'=>"@$fullfilepath" ); $ch = curl_init(); curl_setopt($ch, CURLOPT_VERBOSE, 1); curl_setopt($ch, CURLOPT_URL, $upload_url); curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); curl_setopt($ch, CURLOPT_POSTFIELDS, $params); $response = curl_exec($ch); curl_close($ch); echo $response; However, I'm getting an S3 error as follows when it posts and I'm unsure why because I'm not passing JSON to it. <?xml version="1.0" encoding="UTF-8"?> <Error><Code>InvalidPolicyDocument</Code><Message>Invalid Policy: Invalid JSON.</Message><RequestId>B29469C6151BE0E8</RequestId><HostId>BFPk6W2kt1b6hTtx0mEq6dWdN/IhO0gNR5bct//7LAOwJxm1C3PrxS4RPv1blzJ8</HostId></Error> I've googled it for the last hour or so and can't seem to figure it out. If I change the order of the Array fields, it gives me a different error - I believe the order of the posted fields is important somehow. any help would be much appreciated! C

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  • Amazon access key showing in URL for Carrierwave and Fog

    - by kcurtin
    I just switched from storing my images uploaded via Carrierwave locally to using Amazon s3 via the fog gem in my Rails 3.1 app. While images are being added, when I click on an image in my application, the URL is providing my access key and a signature. Here is a sample URL (XXX replaced the string with the info): https://s3.amazonaws.com/bucketname/uploads/photo/image/2/IMG_4842.jpg?AWSAccessKeyId=XXX&Signature=XXX%3D&Expires=1332093418 This is happening in development (localhost:3000) and when I am using heroku for production. Here is my uploader: class ImageUploader < CarrierWave::Uploader::Base include CarrierWave::RMagick storage :fog def store_dir "uploads/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}" end process :convert => :jpg process :resize_to_limit => [640, 640] version :thumb do process :convert => :jpg process :resize_to_fill => [280, 205] end version :avatar do process :convert => :jpg process :resize_to_fill => [120, 120] end end And my config/initializers/fog.rb : CarrierWave.configure do |config| config.fog_credentials = { :provider => 'AWS', :aws_access_key_id => 'XXX', :aws_secret_access_key => 'XXX', } config.fog_directory = 'bucketname' config.fog_public = false end Anyone know how to make sure this information isn't available?

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  • Reflecting over classes in .NET produces methods only differing by a modifier

    - by mrjoltcola
    I'm a bit boggled by something, I hope the CLR gearheads can help. Apparently my gears aren't big enough. I have a reflector utility that generates assembly stubs for Cola for .NET, and I find classes have methods that only differ by a modifier, such as virtual. Example below, from Oracle.DataAccess.dll, method GetType(): class OracleTypeException : System.SystemException { virtual string ToString (); virtual System.Exception GetBaseException (); virtual void set_Source (string value); virtual void GetObjectData (System.Runtime.Serialization.SerializationInfo info, System.Runtime.Serialization.StreamingContext context); virtual System.Type GetType (); // here virtual bool Equals (object obj); virtual int32 GetHashCode (); System.Type GetType (); // and here } What is this? I have not been able to reproduce this with C# and it causes trouble for Cola as it thinks GetType() is a redefinition, since the signature is identical. My method reflector starts like this: static void DisplayMethod(MethodInfo m) { if ( // Filter out things Cola cannot yet import, like generics, pointers, etc. m.IsGenericMethodDefinition || m.ContainsGenericParameters || m.ReturnType.IsGenericType || !m.ReturnType.IsPublic || m.ReturnType.IsArray || m.ReturnType.IsPointer || m.ReturnType.IsByRef || m.ReturnType.IsPointer || m.ReturnType.IsMarshalByRef || m.ReturnType.IsImport ) return; // generate stub signature // [snipped] }

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  • Safe and polymorphic toEnum

    - by jetxee
    I'd like to write a safe version of toEnum: safeToEnum :: (Enum t, Bounded t) => Int -> Maybe t A naive implementation: safeToEnum :: (Enum t, Bounded t) => Int -> Maybe t safeToEnum i = if (i >= fromEnum (minBound :: t)) && (i <= fromEnum (maxBound :: t)) then Just . toEnum $ i else Nothing main = do print $ (safeToEnum 1 :: Maybe Bool) print $ (safeToEnum 2 :: Maybe Bool) And it doesn't work: safeToEnum.hs:3:21: Could not deduce (Bounded t1) from the context () arising from a use of `minBound' at safeToEnum.hs:3:21-28 Possible fix: add (Bounded t1) to the context of an expression type signature In the first argument of `fromEnum', namely `(minBound :: t)' In the second argument of `(>=)', namely `fromEnum (minBound :: t)' In the first argument of `(&&)', namely `(i >= fromEnum (minBound :: t))' safeToEnum.hs:3:56: Could not deduce (Bounded t1) from the context () arising from a use of `maxBound' at safeToEnum.hs:3:56-63 Possible fix: add (Bounded t1) to the context of an expression type signature In the first argument of `fromEnum', namely `(maxBound :: t)' In the second argument of `(<=)', namely `fromEnum (maxBound :: t)' In the second argument of `(&&)', namely `(i <= fromEnum (maxBound :: t))' As well as I understand the message, the compiler does not recognize that minBound and maxBound should produce exactly the same type as in the result type of safeToEnum inspite of the explicit type declaration (:: t). Any idea how to fix it?

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  • How do I get jQuery's Uploadify plugin to work with ASP.NET MVC?

    - by KingNestor
    I'm in the process of trying to get the jQuery plugin, Uploadify, to work with ASP.NET MVC. I've got the plugin showing up fine: With the following javascript snippet: <script type="text/javascript"> $(document).ready(function() { $('#fileUpload').fileUpload({ 'uploader': '/Content/Flash/uploader.swf', 'script': '/Placement/Upload', 'folder': '/uploads', 'multi': 'true', 'buttonText': 'Browse', 'displayData': 'speed', 'simUploadLimit': 2, 'cancelImg': '/Content/Images/cancel.png' }); }); </script> Which seems like all is well in good. If you notice, the "script" attribute is set to my /Placement/Upload, which is my Placement Controller and my Upload Action. The main problem is, I'm having difficulty getting this action to fire to receive the file. I've set a breakpoint on that action and when I select a file to upload, it isn't getting executed. I've tried changing the method signature based off this article: public string Upload(HttpPostedFileBase FileData) { /* * * Do something with the FileData * */ return "Upload OK!"; } But this still doesn't fire. Can anyone help me write and get the Upload controller action's signature correctly so it will actually fire? I can then handle dealing with the file data myself. I just need some help getting the method action to fire.

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  • iPhone: Using dispatch_after to mimick NSTimer

    - by Joseph Tura
    Don't know a whole lot about blocks. How would you go about mimicking a repeating NSTimer with dispatch_after? My problem is that I want to "pause" a timer when the app moves to the background, but subclassing NSTimer does not seem to work. I tried something which seems to work. I cannot judge its performance implications or whether it could be greatly optimized. Any input is welcome. #import "TimerWithPause.h" @implementation TimerWithPause @synthesize timeInterval; @synthesize userInfo; @synthesize invalid; @synthesize invocation; + (TimerWithPause *)scheduledTimerWithTimeInterval:(NSTimeInterval)aTimeInterval target:(id)aTarget selector:(SEL)aSelector userInfo:(id)aUserInfo repeats:(BOOL)aTimerRepeats { TimerWithPause *timer = [[[TimerWithPause alloc] init] autorelease]; timer.timeInterval = aTimeInterval; NSMethodSignature *signature = [[aTarget class] instanceMethodSignatureForSelector:aSelector]; NSInvocation *aInvocation = [NSInvocation invocationWithMethodSignature:signature]; [aInvocation setSelector:aSelector]; [aInvocation setTarget:aTarget]; [aInvocation setArgument:&timer atIndex:2]; timer.invocation = aInvocation; timer.userInfo = aUserInfo; if (!aTimerRepeats) { timer.invalid = YES; } [timer fireAfterDelay]; return timer; } - (void)fireAfterDelay { dispatch_time_t delay = dispatch_time(DISPATCH_TIME_NOW, self.timeInterval * NSEC_PER_SEC); dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0); dispatch_after(delay, queue, ^{ [invocation performSelectorOnMainThread:@selector(invoke) withObject:nil waitUntilDone:NO]; if (!invalid) { [self fireAfterDelay]; } }); } - (void)invalidate { invalid = YES; [invocation release]; invocation = nil; [userInfo release]; userInfo = nil; } - (void)dealloc { [self invalidate]; [super dealloc]; } @end

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  • How to use R's ellipsis feature when writing your own function?

    - by Ryan Thompson
    The R language has a nifty feature for defining functions that can take a variable number of arguments. For example, the function data.frame takes any number of arguments, and each argument becomes the data for a column in the resulting data table. Example usage: > data.frame(letters=c("a", "b", "c"), numbers=c(1,2,3), notes=c("do", "re", "mi")) letters numbers notes 1 a 1 do 2 b 2 re 3 c 3 mi The function's signature includes an ellipsis, like this: function (..., row.names = NULL, check.rows = FALSE, check.names = TRUE, stringsAsFactors = default.stringsAsFactors()) { [FUNCTION DEFINITION HERE] } I would like to write a function that does something similar, taking multiple values and consolidating them into a single return value (as well as doing some other processing). In order to do this, I need to figure out how to "unpack" the ... from the function's arguments within the function. I don't know how to do this. The relevant line in the function definition of data.frame is object <- as.list(substitute(list(...)))[-1L], which I can't make any sense of. So how can I convert the ellipsis from the function's signature into, for example, a list? To be more specific, how can I write get_list_from_ellipsis in the code below? my_ellipsis_function(...) { input_list <- get.list.from.ellipsis(...) output_list <- lapply(X=input_list, FUN=do_something_interesting) return(output_list) } my_ellipsis_function(a=1:10,b=11:20,c=21:30)

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  • How do I send an email with HTML with an address the user inputs?

    - by MeganSime
    I have an app i am designing and there is a page for emails. The user inputs their name, email address and message and then clicks 'submit'. this works, but i don't know how to make the user's input be on the email. this is the code so far; <form id="contacts-form" action="mailto:[email protected]"> <ul class = "rounded"> <li style = "color: #FFFFFF">Full Name:<input type="text" placeholder = "J. Doe" name = "signature" id = 'signature' /></li> <li style = "color: #FFFFFF">E-mail:<input type="text" placeholder = "[email protected]" name = "address" id = 'address' /></li> <li style = "color: #FFFFFF">Message:<input type = "text" placeholder = "Message" name = "message" id = 'message' /></li> <a href="mailto:address?subject=subject&body=message" class="button">Submit</a> </ul> </form> does anyone know how to change the code to allow the user input to go onto the email? Thanks a lot in advance x

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  • HMAC URLs instead of login?

    - by Tres
    In implementing my site (a Rails site if it makes any difference), one of my design priorities is to relieve the user of the need to create yet another username and password while still providing useful per-user functionality. The way I am planning to do this is: User enters information on the site. Information is associated with the user via server-side session. User completes entering information, server sends an access URL via e-mail to the user roughly in the form of: http://siteurl/<user identifier>/<signature: HMAC(secret + salt + user identifier)> User clicks URL, site looks up user ID and salt and computes the HMAC with the server-stored secret and authenticates if the computed HMAC and signature match. My question is: is this a reasonably secure way to accomplish what I'm looking to do? Are there common attacks that would render it useless? Is there a compelling reason to abandon my desire to avoid a username/password? Is there a must-read book or article on the subject? Note that I'm not dealing with credit card numbers or anything exceedingly private, but I would still like to keep the information reasonably secure.

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  • Why can't I create an abstract constructor on an abstract C# class?

    - by Anthony D
    I am creating an abstract class. I want each of my derived classes to be forced to implement a specific signature of constructor. As such, I did what I would have done has I wanted to force them to implement a method, I made an abstract one. public abstract class A { abstract A(int a, int b); } However I get a message saying the abstract modifier is invalid on this item. My goal was to force some code like this. public class B : A { public B(int a, int b) : base(a, b) { //Some other awesome code. } } This is all C# .NET code. Can anyone help me out? Update 1 I wanted to add some things. What I ended up with was this. private A() { } protected A(int a, int b) { //Code } That does what some folks are saying, default is private, and the class needs to implement a constructor. However that doesn't FORCE a constructor with the signature A(int a, int b). public abstract class A { protected abstract A(int a, int b) { } } Update 2 I should be clear, to work around this I made my default constructor private, and my other constructor protected. I am not really looking for a way to make my code work. I took care of that. I am looking to understand why C# does not let you do this.

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  • Is Safari on iOS 6 caching $.ajax results?

    - by user1684978
    Since the upgrade to iOS 6, we are seeing Safari's web view take the liberty of caching $.ajax calls. This is in the context of a PhoneGap application so it is using the Safari WebView. Our $.ajax calls are POST methods and we have cache set to false {cache:false}, but still this is happening. We tried manually adding a timestamp to the headers but it did not help. We did more research and found that Safari is only returning cached results for web services that have a function signature that is static and does not change from call to call. For instance, imagine a function called something like: getNewRecordID(intRecordType) This function receives the same input parameters over and over again, but the data it returns should be different every time. Must be in Apple's haste to make iOS 6 zip along impressively they got too happy with the cache settings. Has anyone else seen this behavior on iOS 6? If so, what exactly is causing it? The workaround that we found was to modify the function signature to be something like this: getNewRecordID(intRecordType, strTimestamp) and then always pass in a timestamp parameter as well, and just discard that value on the server side. This works around the issue. I hope this helps some other poor soul who spends 15 hours on this issue like I did!

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  • in haskell, why do I need to specify type constraints, why can't the compiler figure them out?

    - by Steve
    Consider the function, add a b = a + b This works: *Main> add 1 2 3 However, if I add a type signature specifying that I want to add things of the same type: add :: a -> a -> a add a b = a + b I get an error: test.hs:3:10: Could not deduce (Num a) from the context () arising from a use of `+' at test.hs:3:10-14 Possible fix: add (Num a) to the context of the type signature for `add' In the expression: a + b In the definition of `add': add a b = a + b So GHC clearly can deduce that I need the Num type constraint, since it just told me: add :: Num a => a -> a -> a add a b = a + b Works. Why does GHC require me to add the type constraint? If I'm doing generic programming, why can't it just work for anything that knows how to use the + operator? In C++ template programming, you can do this easily: #include <string> #include <cstdio> using namespace std; template<typename T> T add(T a, T b) { return a + b; } int main() { printf("%d, %f, %s\n", add(1, 2), add(1.0, 3.4), add(string("foo"), string("bar")).c_str()); return 0; } The compiler figures out the types of the arguments to add and generates a version of the function for that type. There seems to be a fundamental difference in Haskell's approach, can you describe it, and discuss the trade-offs? It seems to me like it would be resolved if GHC simply filled in the type constraint for me, since it obviously decided it was needed. Still, why the type constraint at all? Why not just compile successfully as long as the function is only used in a valid context where the arguments are in Num? Thank you.

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  • Strange type-related error

    - by vsb
    I wrote following program: isPrime x = and [x `mod` i /= 0 | i <- [2 .. truncate (sqrt x)]] primes = filter isPrime [1 .. ] it should construct list of prime numbers. But I got this error: [1 of 1] Compiling Main ( 7/main.hs, interpreted ) 7/main.hs:3:16: Ambiguous type variable `a' in the constraints: `Floating a' arising from a use of `isPrime' at 7/main.hs:3:16-22 `RealFrac a' arising from a use of `isPrime' at 7/main.hs:3:16-22 `Integral a' arising from a use of `isPrime' at 7/main.hs:3:16-22 Possible cause: the monomorphism restriction applied to the following: primes :: [a] (bound at 7/main.hs:3:0) Probable fix: give these definition(s) an explicit type signature or use -XNoMonomorphismRestriction Failed, modules loaded: none. If I specify signature for isPrime function explicitly: isPrime :: Integer -> Bool isPrime x = and [x `mod` i /= 0 | i <- [2 .. truncate (sqrt x)]] I can't even compile isPrime function: [1 of 1] Compiling Main ( 7/main.hs, interpreted ) 7/main.hs:2:45: No instance for (RealFrac Integer) arising from a use of `truncate' at 7/main.hs:2:45-61 Possible fix: add an instance declaration for (RealFrac Integer) In the expression: truncate (sqrt x) In the expression: [2 .. truncate (sqrt x)] In a stmt of a list comprehension: i <- [2 .. truncate (sqrt x)] 7/main.hs:2:55: No instance for (Floating Integer) arising from a use of `sqrt' at 7/main.hs:2:55-60 Possible fix: add an instance declaration for (Floating Integer) In the first argument of `truncate', namely `(sqrt x)' In the expression: truncate (sqrt x) In the expression: [2 .. truncate (sqrt x)] Failed, modules loaded: none. Can you help me understand, why am I getting these errors?

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  • Nested Lambdas in wxHaskell Library

    - by kunkelwe
    I've been trying to figure out how I can make staticText elements resize to fit their contents with wxHaskell. From what I can tell, this is the default behavior in wxWidgets, but the wxHaskell wrapper specifically disables this behavior. However, the library code that creates new elements has me very confused. Can anyone provide an explanation for what this code does? staticText :: Window a -> [Prop (StaticText ())] -> IO (StaticText ()) staticText parent props = feed2 props 0 $ initialWindow $ \id rect -> initialText $ \txt -> \props flags -> do t <- staticTextCreate parent id txt rect flags {- (wxALIGN_LEFT + wxST_NO_AUTORESIZE) -} set t props return t I know that feed2 x y f = f x y, and that the type signature of initialWindow is initialWindow :: (Id -> Rect -> [Prop (Window w)] -> Style -> a) -> [Prop (Window w)] -> Style -> a and the signature of initialText is initialText :: Textual w => (String -> [Prop w] -> a) -> [Prop w] -> a but I just can't wrap my head around all the lambdas.

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  • Template function overloading with identical signatures, why does this work?

    - by user1843978
    Minimal program: #include <stdio.h> #include <type_traits> template<typename S, typename T> int foo(typename T::type s) { return 1; } template<typename S, typename T> int foo(S s) { return 2; } int main(int argc, char* argv[]) { int x = 3; printf("%d\n", foo<int, std::enable_if<true, int>>(x)); return 0; } output: 1 Why doesn't this give a compile error? When the template code is generated, wouldn't the functions int foo(typename T::type search) and int foo(S& search) have the same signature? If you change the template function signatures a little bit, it still works (as I would expect given the example above): template<typename S, typename T> void foo(typename T::type s) { printf("a\n"); } template<typename S, typename T> void foo(S s) { printf("b\n"); } Yet this doesn't and yet the only difference is that one has an int signature and the other is defined by the first template parameter. template<typename T> void foo(typename T::type s) { printf("a\n"); } template<typename T> void foo(int s) { printf("b\n"); } I'm using code similar to this for a project I'm working on and I'm afraid that there's a subtly to the language that I'm not understanding that will cause some undefined behavior in certain cases. I should also mention that it does compile on both Clang and in VS11 so I don't think it's just a compiler bug.

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  • European Interoperability Framework - a new beginning?

    - by trond-arne.undheim
    The most controversial document in the history of the European Commission's IT policy is out. EIF is here, wrapped in the Communication "Towards interoperability for European public services", and including the new feature European Interoperability Strategy (EIS), arguably a higher strategic take on the same topic. Leaving EIS aside for a moment, the EIF controversy has been around IPR, defining open standards and about the proper terminology around standardization deliverables. Today, as the document finally emerges, what is the verdict? First of all, to be fair to those among you who do not spend your lives in the intricate labyrinths of Commission IT policy documents on interoperability, let's define what we are talking about. According to the Communication: "An interoperability framework is an agreed approach to interoperability for organisations that want to collaborate to provide joint delivery of public services. Within its scope of applicability, it specifies common elements such as vocabulary, concepts, principles, policies, guidelines, recommendations, standards, specifications and practices." The Good - EIF reconfirms that "The Digital Agenda can only take off if interoperability based on standards and open platforms is ensured" and also confirms that "The positive effect of open specifications is also demonstrated by the Internet ecosystem." - EIF takes a productive and pragmatic stance on openness: "In the context of the EIF, openness is the willingness of persons, organisations or other members of a community of interest to share knowledge and stimulate debate within that community, the ultimate goal being to advance knowledge and the use of this knowledge to solve problems" (p.11). "If the openness principle is applied in full: - All stakeholders have the same possibility of contributing to the development of the specification and public review is part of the decision-making process; - The specification is available for everybody to study; - Intellectual property rights related to the specification are licensed on FRAND terms or on a royalty-free basis in a way that allows implementation in both proprietary and open source software" (p. 26). - EIF is a formal Commission document. The former EIF 1.0 was a semi-formal deliverable from the PEGSCO, a working group of Member State representatives. - EIF tackles interoperability head-on and takes a clear stance: "Recommendation 22. When establishing European public services, public administrations should prefer open specifications, taking due account of the coverage of functional needs, maturity and market support." - The Commission will continue to support the National Interoperability Framework Observatory (NIFO), reconfirming the importance of coordinating such approaches across borders. - The Commission will align its internal interoperability strategy with the EIS through the eCommission initiative. - One cannot stress the importance of using open standards enough, whether in the context of open source or non-open source software. The EIF seems to have picked up on this fact: What does the EIF says about the relation between open specifications and open source software? The EIF introduces, as one of the characteristics of an open specification, the requirement that IPRs related to the specification have to be licensed on FRAND terms or on a royalty-free basis in a way that allows implementation in both proprietary and open source software. In this way, companies working under various business models can compete on an equal footing when providing solutions to public administrations while administrations that implement the standard in their own software (software that they own) can share such software with others under an open source licence if they so decide. - EIF is now among the center pieces of the Digital Agenda (even though this demands extensive inter-agency coordination in the Commission): "The EIS and the EIF will be maintained under the ISA Programme and kept in line with the results of other relevant Digital Agenda actions on interoperability and standards such as the ones on the reform of rules on implementation of ICT standards in Europe to allow use of certain ICT fora and consortia standards, on issuing guidelines on essential intellectual property rights and licensing conditions in standard-setting, including for ex-ante disclosure, and on providing guidance on the link between ICT standardisation and public procurement to help public authorities to use standards to promote efficiency and reduce lock-in.(Communication, p.7)" All in all, quite a few good things have happened to the document in the two years it has been on the shelf or was being re-written, depending on your perspective, in any case, awaiting the storms to calm. The Bad - While a certain pragmatism is required, and governments cannot migrate to full openness overnight, EIF gives a bit too much room for governments not to apply the openness principle in full. Plenty of reasons are given, which should maybe have been put as challenges to be overcome: "However, public administrations may decide to use less open specifications, if open specifications do not exist or do not meet functional interoperability needs. In all cases, specifications should be mature and sufficiently supported by the market, except if used in the context of creating innovative solutions". - EIF does not use the internationally established terminology: open standards. Rather, the EIF introduces the notion of "formalised specification". How do "formalised specifications" relate to "standards"? According to the FAQ provided: The word "standard" has a specific meaning in Europe as defined by Directive 98/34/EC. Only technical specifications approved by a recognised standardisation body can be called a standard. Many ICT systems rely on the use of specifications developed by other organisations such as a forum or consortium. The EIF introduces the notion of "formalised specification", which is either a standard pursuant to Directive 98/34/EC or a specification established by ICT fora and consortia. The term "open specification" used in the EIF, on the one hand, avoids terminological confusion with the Directive and, on the other, states the main features that comply with the basic principle of openness laid down in the EIF for European Public Services. Well, this may be somewhat true, but in reality, Europe is 30 year behind in terminology. Unless the European Standardization Reform gets completed in the next few months, most Member States will likely conclude that they will go on referencing and using standards beyond those created by the three European endorsed monopolists of standardization, CEN, CENELEC and ETSI. Who can afford to begin following the strict Brussels rules for what they can call open standards when, in reality, standards stemming from global standardization organizations, so-called fora/consortia, dominate in the IT industry. What exactly is EIF saying? Does it encourage Member States to go on using non-ESO standards as long as they call it something else? I guess I am all for it, although it is a bit cumbersome, no? Why was there so much interest around the EIF? The FAQ attempts to explain: Some Member States have begun to adopt policies to achieve interoperability for their public services. These actions have had a significant impact on the ecosystem built around the provision of such services, e.g. providers of ICT goods and services, standardisation bodies, industry fora and consortia, etc... The Commission identified a clear need for action at European level to ensure that actions by individual Member States would not create new electronic barriers that would hinder the development of interoperable European public services. As a result, all stakeholders involved in the delivery of electronic public services in Europe have expressed their opinions on how to increase interoperability for public services provided by the different public administrations in Europe. Well, it does not take two years to read 50 consultation documents, and the EU Standardization Reform is not yet completed, so, more pragmatically, you finally had to release the document. Ok, let's leave some of that aside because the document is out and some people are happy (and others definitely not). The Verdict Considering the controversy, the delays, the lobbying, and the interests at stake both in the EU, in Member States and among vendors large and small, this document is pretty impressive. As with a good wine that has not yet come to full maturity, let's say that it seems to be coming in in the 85-88/100 range, but only a more fine-grained analysis, enjoyment in good company, and ultimately, implementation, will tell. The European Commission has today adopted a significant interoperability initiative to encourage public administrations across the EU to maximise the social and economic potential of information and communication technologies. Today, we should rally around this achievement. Tomorrow, let's sit down and figure out what it means for the future.

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