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• F# Inline Function Specialization

  - by Ben

  Hi, My current project involves lexing and parsing script code, and as such I'm using fslex and fsyacc. Fslex LexBuffers can come in either LexBuffer<char> and LexBuffer<byte> varieties, and I'd like to have the option to use both. In order to user both, I need a lexeme function of type ^buf - string. Thus far, my attempts at specialization have looked like: let inline lexeme (lexbuf: ^buf) : ^buf -> string where ^buf : (member Lexeme: char array) = new System.String(lexbuf.Lexeme) let inline lexeme (lexbuf: ^buf) : ^buf -> string where ^buf : (member Lexeme: byte array) = System.Text.Encoding.UTF8.GetString(lexbuf.Lexeme) I'm getting a type error stating that the function body should be of type ^buf -> string, but the inferred type is just string. Clearly, I'm doing something (majorly?) wrong. Is what I'm attempting even possible in F#? If so, can someone point me to the proper path? Thanks!

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• I am looking for an actual functional web browser control for .NET, maybe a C++ library

  - by Joshua

  I am trying to emulate a web browser in order to execute JavaScript code and then parse the DOM. The System.Windows.Forms.WebBrowser object does not give me the functionality I need. It let's me set the headers, but you cannot set the proxy or clear cookies. Well you can, but it is not ideal and messes with IE's settings. I've been extending the WebBrowser control pinvoking native windows functions so far, but it is really one hack on top of another. I can mess with the proxy and also clear cookies and such, but this control has its issues as I mentioned. I found something called WebKit .NET (http://webkitdotnet.sourceforge.net/), but I don't see support for setting proxies or cookie manipulation. Can someone recommend a c++/.NET/whatever library to do this: Basically tell me what I need to do to get an interface to similar this in .NET: // this should probably pause the current thread for the max timeout, // throw an exception on failure or return null w/e, VAGUELY similar to this string WebBrowserEmu::FetchBrowserParsedHtml(Uri url, WebProxy p, int timeoutSeconds, byte[] headers, byte[] postdata); void WebBrowserEmu::ClearCookies(); I am not responsible for my actions.

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• How to sort HashSet() function data in sequence?

  - by vincent low

  I am new to Java, the function I would like to perform is to load a series of data from a file, into my hashSet() function. the problem is, I able to enter all the data in sequence, but I can't retrieve it out in sequence base on the account name in the file. Can anyone help? below is my code: public Set retrieveHistory(){ Set dataGroup = new HashSet(); try{ File file = new File("C:\\Documents and Settings\\vincent\\My Documents\\NetBeansProjects\\vincenttesting\\src\\vincenttesting\\vincenthistory.txt"); BufferedReader br = new BufferedReader(new FileReader(file)); String data = br.readLine(); while(data != null){ System.out.println("This is all the record:"+data); Customer cust = new Customer(); //break the data based on the , String array[] = data.split(","); cust.setCustomerName(array[0]); cust.setpassword(array[1]); cust.setlocation(array[2]); cust.setday(array[3]); cust.setmonth(array[4]); cust.setyear(array[5]); cust.setAmount(Double.parseDouble(array[6])); cust.settransaction(Double.parseDouble(array[7])); dataGroup.add(cust); //then proced to read next customer. data = br.readLine(); } br.close(); }catch(Exception e){ System.out.println("error" +e); } return dataGroup; } public static void main(String[] args) { FileReadDataModel fr = new FileReadDataModel(); Set customerGroup = fr.retrieveHistory(); System.out.println(e); for(Object obj : customerGroup){ Customer cust = (Customer)obj; System.out.println("Cust name :" +cust.getCustomerName()); System.out.println("Cust amount :" +cust.getAmount()); }

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• comparing salt and hashed passwords during login doesn't seem work right....

  - by Pandiya Chendur

  I stored salt and hash values of password during user registration... But during their login i then salt and hash the password given by the user, what happens is a new salt and a new hash is generated.... string password = collection["Password"]; reg.PasswordSalt = CreateSalt(6); reg.PasswordHash = CreatePasswordHash(password, reg.PasswordSalt); These statements are in both registration and login.... salt and hash during registration was eVSJE84W and 18DE22FED8C378DB7716B0E4B6C0BA54167315A2 During login it was 4YDIeARH and 12E3C1F4F4CFE04EA973D7C65A09A78E2D80AAC7..... Any suggestion.... public static string CreateSalt(int size) { //Generate a cryptographic random number. RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider(); byte[] buff = new byte[size]; rng.GetBytes(buff); // Return a Base64 string representation of the random number. return Convert.ToBase64String(buff); } public static string CreatePasswordHash(string pwd, string salt) { string saltAndPwd = String.Concat(pwd, salt); string hashedPwd = FormsAuthentication.HashPasswordForStoringInConfigFile( saltAndPwd, "sha1"); return hashedPwd; }

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• Apache HttpClient 4.0. Weird behavior.

  - by Mikhail T

  Hello. I'm using Apache HttpClient 4.0 for my web crawler. The behavior i found strange is: i'm trying to get page via HTTP GET method and getting response about 404 HTTP error. But if i try to get that page using browser it's done successfully. Details: 1. I upload multipart form to server this way: HttpPost httpPost = new HttpPost("http://[host here]/in.php"); MultipartEntity entity = new MultipartEntity(HttpMultipartMode.BROWSER_COMPATIBLE); entity.addPart("method", new StringBody("post")); entity.addPart("key", new StringBody("223fwe0923fjf23")); FileBody fileBody = new FileBody(new File("photo.jpg"), "image/jpeg"); entity.addPart("file", fileBody); httpPost.setEntity(entity); HttpResponse response = httpClient.execute(httpPost); HttpEntity result = response.getEntity(); String responseString = ""; if (result != null) { InputStream inputStream = result.getContent(); byte[] buffer = new byte[1024]; while(inputStream.read(buffer) > 0) responseString += new String(buffer); result.consumeContent(); } Uppload succefully ends. I'm getting some results from web server: HttpGet httpGet = new HttpGet("http://[host here]/res.php?key="+myKey+"&action=get&id="+id); HttpResponse response = httpClient.execute(httpGet); HttpEntity entity = response.getEntity(); I'm getting ClientProtocolException while execute method run. I was debugging this situation with log4j. Server answers "404 Not Found". But my browser loads me that page with no problem. Can anybody help me? Thank you.

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• Ruby -- looking for some sort of "Regexp unescape" method

  - by RubyNoobie

  I have a bunch of strings that appear to have been double-escaped -- eg, I have "\\014\"\\000\"\\016smoothing\"\\011mean\"\\022color\"\\011zero@\\016" but I want "\014"\000"\016smoothing"\011mean"\022color"\011zero@\016" Is there a method I can use to unescape them? I imagine that I could make a regex to remove 1 backslash from every consecutive n backslashes, but I don't have a lot of regex experience and it seems there ought to be a "more elegant" way to do it. For example, when I puts MyString it displays the output I'd like, but I don't know how I might capture that into a variable. Thanks! Edited to add context: I have this class that is being used to marshal / restore some stuff, but when I restore some old strings it spits out a type error which I've determined is because they weren't -- for some inexplicable reason -- stored as base64. They instead appear to be 'double-escaped', when I need them to be 'single-escaped' to get restored. require 'base64' class MarshaledStuff < ActiveRecord::Base validates_presence_of :marshaled_obj def contents obj = self.marshaled_obj return Marshal.restore(Base64.decode64(obj)) end def contents=(newcontents) self.marshaled_obj = Base64.encode64(Marshal.dump(newcontents)) end end

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• CLLocationManager class method not calling in iPodTouch

  - by Siddharth

  HI all, I was using a sample code which uses CLLocationManager class to determine the current location of user. when i run this app on iPad i am getting the correct location but when i run the same app on iPod Touch i am getting a blank label i.e nothing is displayed on the label .although wi-fi signal strength is good in both iPod and iPad.The code looks like... - (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation{ int degrees = newLocation.coordinate.latitude; double decimal = fabs(newLocation.coordinate.latitude - degrees); int minutes = decimal * 60; double seconds = decimal * 3600 - minutes * 60; NSString *lat = [NSString stringWithFormat:@"%d° %d' %1.4f\"", degrees, minutes, seconds]; latLabel.text = lat; [latLocationArray addObject:lat]; degrees = newLocation.coordinate.longitude; decimal = fabs(newLocation.coordinate.longitude - degrees); minutes = decimal * 60; seconds = decimal * 3600 - minutes * 60; NSString *longt = [NSString stringWithFormat:@"%d° %d' %1.4f\"", degrees, minutes, seconds]; longLabel.text = longt; [longLocationArray addObject:longt]; }

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• NSUserDefaults: Saved Number Always 0, iPhone

  - by Stumf

  Hello all, I have looked at other answers and the docs. Maybe I am missing something, or maybe I have another issue. I am trying to save a number on exiting the app, and then when the app is loaded I want to check if this value exists and take action accordingly. This is what I have tried: To save on exiting: - (void)applicationWillTerminate: (UIApplication *) application { double save = [label.text doubleValue]; [[NSUserDefaults standardUserDefaults] setDouble: save forKey: @"savedNumber"]; [[NSUserDefaults standardUserDefaults] synchronize]; } To check: - (IBAction)buttonclickSkip{ double save = [[NSUserDefaults standardUserDefaults] doubleForKey: @"savedNumber"]; if (save == 0) { [self performSelector:@selector(displayAlert) withObject:nil]; test.enabled = YES; test.alpha = 1.0; skip.enabled = NO; skip.alpha = 0.0; } else { label.text = [NSString stringWithFormat:@"%.1f %%", save]; } } The problem is I always get my alert message displayed, the saved value is not put into the label so somehow == 0 is always true. If it makes any difference I am testing this on the iPhone simulator. Many thanks, Stu

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• Need an explanation on this code - c#

  - by ltech

  I am getting familiar with C# day by day and I came across this piece of code public static void CopyStreamToStream( Stream source, Stream destination, Action<Stream,Stream,Exception> completed) { byte[] buffer = new byte[0x1000]; AsyncOperation asyncOp = AsyncOperationManager.CreateOperation(null); Action<Exception> done = e => { if (completed != null) asyncOp.Post(delegate { completed(source, destination, e); }, null); }; AsyncCallback rc = null; rc = readResult => { try { int read = source.EndRead(readResult); if (read > 0) { destination.BeginWrite(buffer, 0, read, writeResult => { try { destination.EndWrite(writeResult); source.BeginRead( buffer, 0, buffer.Length, rc, null); } catch (Exception exc) { done(exc); } }, null); } else done(null); } catch (Exception exc) { done(exc); } }; source.BeginRead(buffer, 0, buffer.Length, rc, null); } From this article Article What I fail to follow is that how does the delegate get notified that the copy is done? Say after the copy is done I want to perform an operation on the copied file.

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• Displaying windows-1252 text in a literal control

  - by GordonB

  I currently have an aspx page that has a placeholder on it. In the code-behind page i'm adding a literal control to the placeholder controls collection. The literal control just contains text/html read from a sql server database field. The only text character encoding i've used so far is UTF-8. I have the requirement for a specific page to use windows-1252 encoding. I've strapped this to the page, and browsers now recognise the proper encoding. <% Response.Charset= "windows-1252" %> My issue is that i have various german characters ( ö / ü / etc ) that aren't displaying correctly. As presumably they are still be written to the page in UTF-8 not in windows-1252. I'm looking at; Dim textEncoder = System.Text.Encoding.GetEncoding(1252) Which seems to be more geared up to dealing with byte arrays than text. Do i have to change my text to a byte array then encode as windows-1252 then get the text back out again, or is there a simpler way of achieving what i'm after?

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• C# delegate or Func for 'all methods'?

  - by Michel

  Hi, i've read something about Func's and delegates and that they can help you to pass a method as a parameter. Now i have a cachingservice, and it has this declaration: public static void AddToCache<T>(T model, double millisecs, string cacheId) where T : class public static T GetFromCache<T>(string cacheId) where T : class So in a place where i want to cache some data, i check if it exists in the cache (with GetFromCache) and if not, get the data from somewhere, and the add it to the cache (with AddToCache) Now i want to extend the AddToCache method with a parameter, which is the class+method to call to get the data Then the declaration would be like this public static void AddToCache<T>(T model, double millisecs, string cacheId, Func/Delegate methode) where T : class Then this method could check wether the cache has data or not, and if not, get the data itself via the method it got provided. Then in the calling code i could say: AddToCache<Person>(p, 10000, "Person", new PersonService().GetPersonById(1)); AddToCache<Advert>(a, 100000, "Advert", new AdvertService().GetAdverts(3)); What i want to achieve is that the 'if cache is empty get data and add to cache' logic is placed on only one place. I hope this makes sense :) Oh, by the way, the question is: is this possible?

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• When downloading a file using FileStream, why does page error message refers to aspx page name, not

  - by StuperUser

  After building a filepath (path, below) in a string (I am aware of Path in System.IO, but am using someone else's code and do not have the opportunity to refactor it to use Path). I am using a FileStream to deliver the file to the user (see below): FileStream myStream = new FileStream(path, FileMode.Open, FileAccess.Read); long fileSize = myStream.Length; byte[] Buffer = new byte[(int)fileSize + 1]; myStream.Read(Buffer, 0, (int)myStream.Length); myStream.Close(); Response.ContentType = "application/csv"; Response.AddHeader("content-disposition", "attachment; filename=" + filename); Response.BinaryWrite(Buffer); Response.Flush(); Response.End(); I have seen from: http://stackoverflow.com/questions/736301/asp-net-how-to-stream-file-to-user reasons to avoid use of Response.End() and Response.Close(). I have also seen several articles about different ways to transmit files and have diagnosed and found a solution to the problem (https and http headers) with a colleague. However, the error message that was being displayed was not about access to the file at path, but the aspx file. Edit: Error message is: Internet Explorer cannot download MyPage.aspx from server.domain.tld Internet Explorer was not able to open this Internet site. The requested site is either unavailable or cannot be found. Please try again later. (page name and address anonymised) Why is this? Is it due to the contents of the file coming from the HTTP response .Flush() method rather than a file being accessed at its address?

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• reading non-english html pages with c#

  - by Gal Miller

  I am trying to find a string in Hebrew in a website. The reading code is attached. Afterward I try to read the file using streamReader but I can't match strings in other languages. what am I suppose to do? // used on each read operation byte[] buf = new byte[8192]; // prepare the web page we will be asking for HttpWebRequest request = (HttpWebRequest) WebRequest.Create("http://www.webPage.co.il"); // execute the request HttpWebResponse response = (HttpWebResponse) request.GetResponse(); // we will read data via the response stream Stream resStream = response.GetResponseStream(); string tempString = null; int count = 0; FileStream fileDump = new FileStream(@"c:\dump.txt", FileMode.Create); do { count = resStream.Read(buf, 0, buf.Length); fileDump.Write(buf, 0, buf.Length); } while (count > 0); // any more data to read? fileDump.Close();

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• Something confusing about FormsOf (Sql server Full-Text searching)

  - by AspOnMyNet

  hi I'm using Sql Server 2008 1) A given <simple_term> within a <generation_term> will not match both nouns and verbs. If I understand the above text correctly, then query SELECT * FROM someTable WHERE CONTAINS ( *, ' FORMSOF ( INFLECTIONAL, park ) ' ) should search for either nouns or verbs derived from the root word “park”, but not for both? Thus out of the two rows, one containing noun parks and other verb parking, the above query should return just one of the two rows? But as it turns out, query returns both rows, so are perhaps my assumptions a bit off or is the above quote wrong?! 2) From Msdn: If freetext_string is enclosed in double quotation marks, a phrase match is instead performed; stemming and thesaurus are not performed. According to the above quote the following query shouldn’t return rows containing strings surfing ( due to query not performing stemming ), surf ( due to query performing phrase matching and not individual word matching ) and surfing with suzy’s sister ( due to query not performing stemming and due to query performing phrase matching and not word matching ), but it does. Thus, it appears that even when *freetext_string* is enclosed in double quotation marks, stemming is still preformed, while phrase matching is not: SELECT * FROM someTable WHERE FREETEXT( *, ' "surf sister" ' ) So is the above quote wrong or...? thanx

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• Python raw strings and trailing back slashes.

  - by dash-tom-bang

  I ran across something once upon a time and wondered if it was a Python "bug" or at least a misfeature. I'm curious if anyone knows of any justifications for this behavior. I thought of it just now reading "Code Like a Pythonista," which has been enjoyable so far. I'm only familiar with the 2.x line of Python. Raw strings are strings that are prefixed with an r. This is great because I can use backslashes in regular expressions and I don't need to double everything everywhere. It's also handy for writing throwaway scripts on Windows, so I can use backslashes there also. (I know I can also use forward slashes, but throwaway scripts often contain content cut&pasted from elsewhere in Windows.) So great! Unless, of course, you really want your string to end with a backslash. There's no way to do that in a 'raw' string. In [9]: r'\n' Out[9]: '\\n' In [10]: r'abc\n' Out[10]: 'abc\\n' In [11]: r'abc\' ------------------------------------------------ File "<ipython console>", line 1 r'abc\' ^ SyntaxError: EOL while scanning string literal In [12]: r'abc\\' Out[12]: 'abc\\\\' So one slash before the closing quote is an error, but two slashes gives you two slashes! Certainly I'm not the only one that is bothered by this? Thoughts on why 'raw' strings are 'raw, except for slash-quote'? I mean, if I wanted to embed a single quote in there I'd just use double quotes around the string, and vice versa. If I wanted both, I'd just triple quote. If I really wanted three quotes in a row in a raw string, well, I guess I'd have to deal, but is this considered "proper behavior"?

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• Weird camera Intent behavior

  - by David Erosa

  Hi all. I'm invoking the MediaStore.ACTION_IMAGE_CAPTURE intent with the MediaStore.EXTRA_OUTPUT extra so that it does save the image to that file. On the onActivityResult I can check that the image is being saved in the intended file, which is correct. The weird thing is that anyhow, the image is also saved in a file named something like "/sdcard/Pictures/Camera/1298041488657.jpg" (epoch time in which the image was taken). I've checked the Camera app source (froyo-release branch) and I'm almost sure that the code path is correct and wouldn't have to save the image, but I'm a noob and I'm not completly sure. AFAIK, the image saving process starts with this callback (comments are mine): private final class JpegPictureCallback implements PictureCallback { ... public void onPictureTaken(...){ ... // This is where the image is passed back to the invoking activity. mImageCapture.storeImage(jpegData, camera, mLocation); ... public void storeImage(final byte[] data, android.hardware.Camera camera, Location loc) { if (!mIsImageCaptureIntent) { // Am i an intent? int degree = storeImage(data, loc); // THIS SHOULD NOT BE CALLED WITHIN THE CAPTURE INTENT!! ....... // An finally: private int storeImage(byte[] data, Location loc) { try { long dateTaken = System.currentTimeMillis(); String title = createName(dateTaken); String filename = title + ".jpg"; // Eureka, timestamp filename! ... So, I'm receiving the correct data, but it's also being saved in the "storeImage(data, loc);" method call, which should not be called... It'd not be a problem if I could get the newly created filename from the intent result data, but I can't. When I found this out, I found about 20 image files from my tests that I didn't know were on my sdcard :) I'm getting this behavior both with my Nexus One with Froyo and my Huawei U8110 with Eclair. Could please anyone enlight me? Thanks a lot.

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• How do I best do balanced quoting with Perl's Regexp::Grammars?

  - by Evan Carroll

  Using Damian Conway's Regexp::Grammars, I'm trying to match different balanced quoting ('foo', "foo", but not 'foo") mechanisms -- such as parens, quotes, double quotes, and double dollars. This is the code I'm currently using. <token: pair> \'<literal>\'|\"<literal>\"|\$\$<literal>\$\$ <token: literal> [\S]+ This generally works fine and allows me to say something like: <rule: quote> QUOTE <.as>? <pair> My question is how do I reform the output, to exclude the needles notation for the pair token? { '' => 'QUOTE AS \',\'', 'quote' => { '' => 'QUOTE AS \',\'', 'pair' => { 'literal' => ',', '' => '\',\'' } } }, Here, there is obviously no desire to have pair in between, quote, and the literal value of it. Is there a better way to match 'foo', "foo", and $$foo$$, and maybe sometimes ( foo ) without each time creating a needless pair token? Can I preprocess-out that token or fold it into the above? Or, write a better construct entirely that eliminates the need for it?

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• Sms via a nokia phone over a serial port

  - by abigblackman

  Hi, I'm trying to send a sms via a Nokia phone over serial which is easy enough via putty. The commands from the nokia documentation works fine. However, trying to send the same commands from a c# application fails miserably. I've run Sysinternals PortMon and can see the commands come through OK, the only difference I can see is in the way it connects but I am having trouble finding the commands that would iron out those differences. The code I'm running looks a little bit like this using (SerialPort port = new SerialPort(comPort, 9600, Parity.None, 8, StopBits.One)) { port.DataReceived += new SerialDataReceivedEventHandler(port_DataReceived); port.ErrorReceived += new SerialErrorReceivedEventHandler(port_ErrorReceived); //port.ReceivedBytesThreshold = 1; port.DtrEnable = true; port.RtsEnable = true; port.ReadTimeout = 1; port.Handshake = Handshake.XOnXOff; try { port.Open(); port.WriteLine("AT"); port.WriteLine("AT+CMGF=1"); port.WriteLine("AT+CMGS=\"" + number + "\""); port.WriteLine(message); port.Write(new byte[] { (byte)26 }, 0, 1); } finally { if (port.IsOpen) { port.Close(); } } The differences I'm seeing in the trace from the serial port are At the start 0.00001844 aspnet_wp.exe IOCTL_SERIAL_SET_HANDFLOW USBSER001 SUCCESS Shake:1 Replace:43 XonLimit:4096 XoffLimit:4096 And at the very end 0.00061153 aspnet_wp.exe IOCTL_SERIAL_PURGE USBSER001 SUCCESS Purge: RXABORT RXCLEAR 0.00004442 aspnet_wp.exe IOCTL_SERIAL_PURGE USBSER001 SUCCESS Purge: TXABORT TXCLEAR Has anyone got any tips on how to iron out these issues? I also notice that the phone is not responding back to the application with any acknowledgement when I issue a command so I suspect the problem is with the connection, not those messages at the end.

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• How to give a textbox a fixed width of 17,5 cm?

  - by Natrium

  I have an application with a textbox, and the width of the textbox on the screen must always be 17,5 centimeters on the screen of the user. This is what I tried so far: const double centimeter = 17.5; // the width I need const double inches = centimeter * 0.393700787; // convert centimeter to inches float dpi = GetDpiX(); // get the dpi. 96 in my case. var pixels = dpi*inches; // this should give me the amount of pixels textbox1.Width = Convert.ToInt32(pixels); // set it. Done. private float GetDpiX() { floar returnValue; Graphics graphics = CreateGraphics(); returnValue = graphics.DpiX; graphics.Dispose(); // don’t forget to release the unnecessary resources return returnValue; } But this gives me different sizes with different resolutions. It gives me 13 cm with 1680 x 1050 and 19,5 cm with 1024 x 768. What am I doing wrong?

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• Bluetooth in Java Mobile: Handling connections that go out of range

  - by Albus Dumbledore

  I am trying to implement a server-client connection over the spp. After initializing the server, I start a thread that first listens for clients and then receives data from them. It looks like that: public final void run() { while (alive) { try { /* * Await client connection */ System.out.println("Awaiting client connection..."); client = server.acceptAndOpen(); /* * Start receiving data */ int read; byte[] buffer = new byte[128]; DataInputStream receive = client.openDataInputStream(); try { while ((read = receive.read(buffer)) > 0) { System.out.println("[Recieved]: " + new String(buffer, 0, read)); if (!alive) { return; } } } finally { System.out.println("Closing connection..."); receive.close(); } } catch (IOException e){ e.printStackTrace(); } } } It's working fine for I am able to receive messages. What's troubling me is how would the thread eventually die when a device goes out of range? Firstly, the call to receive.read(buffer) blocks so that the thread waits until it receives any data. If the device goes out of range, it would never proceed onward to check if meanwhile it has been interrupted. Secondly, it would never close the connection, i.e. the server would not accept the device once it goes back in range. Thanks! Any ideas would be highly appreciated! Merry Christmas!

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• How do calculators work with precision?

  - by zoul

  Hello! I wonder how calculators work with precision. For example the value of sin(M_PI) is not exactly zero when computed in double precision: #include <math.h> #include <stdio.h> int main() { double x = sin(M_PI); printf("%.20f\n", x); // 0.00000000000000012246 return 0; } Now I would certainly want to print zero when user enters sin(p). I can easily round somewhere on 1e–15 to make this particular case work, but that’s a hack, not a solution. When I start to round like this and the user enters something like 1e–20, they get a zero back (because of the rounding). The same thing happens when the user enters 1/10 and hits the = key repeatedly — when he reaches the rounding treshold, he gets zero. And yet some calculators return plain zero for sin(p) and at the same time they can work with expressions such as (1e–20)/10 comfortably. Where’s the trick?

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• while loop in c#

  - by Nave Tseva

  I have this code: using System; namespace _121119_zionAVGfilter { class Program { static void Main(string[] args) { int cnt = 0, zion, sum = 0; double avg; Console.Write("Enter first zion \n"); zion = int.Parse(Console.ReadLine()); while (zion != -1) { while (zion < -1 || zion > 100) { Console.Write("zion can be between 0 to 100 only! \nyou can rewrite the zion here, or Press -1 to see the avg\n"); zion = int.Parse(Console.ReadLine()); } cnt++; sum = sum + zion; Console.Write("Enter next zion, if you want to exit tap -1 \n"); zion = int.Parse(Console.ReadLine()); if (cnt != 0){} } if (cnt == 0) { Console.WriteLine("something doesn't make sence"); } else { avg = (double)sum / cnt; Console.Write("the AVG is {0}", avg); } Console.ReadLine(); } } } The problem here is that if in the beginning I enter a negative or bigger than hundred number, I will get this message: "zion can be between 0 to 100 only! \nyou can rewrite the zion here, or Press -1 to see the avg\n". If I then meenter -1, this what that shows up instead of the AVG: "Enter next zion, if you want to exit tap -1 \n." How can I solve this problem so when the number is negative or bigger than hundred and than tap -1 I will see the AVG an not another message?

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• C/C++: feedback in analyzing a code example

  - by KaiserJohaan

  Hello, I have a piece of code from an assignment I am uncertain about. I feel confident that I know the answer, but I just want to double-check with the community incase there's something I forgot. The title is basically secure coding and the question is just to explain the results. int main() { unsigned int i = 1; unsigned int c = 1; while (i > 0) { i = i*2; c++; } printf("%d\n", c); return 0; } My reasoning is this: At first glance you could imagine the code would run forever, considering it's initialized to a positive value and ever increasing. This of course is wrong because eventually the value will grow so large it will cause an integer overflow. This in turn is not entirely true either, because eventally it will force the variable 'i' to be signed by making the last bit to 1 and therefore regarded as a negative number, therefore terminating the loop. So it is not writing to unallocated memory and therefore cause integer overflow, but rather violating the data type and therefore causing the loop to terminate. I am quite sure this is the reason, but I just want to double check. Any opinions?

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• How do I rewrite a for loop with a shared dependency using actors

  - by Thomas Rynne

  We have some code which needs to run faster. Its already profiled so we would like to make use of multiple threads. Usually I would setup an in memory queue, and have a number of threads taking jobs of the queue and calculating the results. For the shared data I would use a ConcurrentHashMap or similar. I don't really want to go down that route again. From what I have read using actors will result in cleaner code and if I use akka migrating to more than 1 jvm should be easier. Is that true? However, I don't know how to think in actors so I am not sure where to start. To give a better idea of the problem here is some sample code: case class Trade(price:Double, volume:Int, stock:String) { def value(priceCalculator:PriceCalculator) = (priceCalculator.priceFor(stock)-> price)*volume } class PriceCalculator { def priceFor(stock:String) = { Thread.sleep(20)//a slow operation which can be cached 50.0 } } object ValueTrades { def valueAll(trades:List[Trade], priceCalculator:PriceCalculator):List[(Trade,Double)] = { trades.map { trade => (trade,trade.value(priceCalculator)) } } def main(args:Array[String]) { val trades = List( Trade(30.5, 10, "Foo"), Trade(30.5, 20, "Foo") //usually much longer ) val priceCalculator = new PriceCalculator val values = valueAll(trades, priceCalculator) } } I'd appreciate it if someone with experience using actors could suggest how this would map on to actors.

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• Equivalent to window.setTimeout() for C++

  - by bobobobo

  In javascript there's this sweet, sweet function window.setTimeout( func, 1000 ) ; which will asynchronously invoke func after 1000 ms. I want to do something similar in C++ (without multithreading), so I put together a sample loop like: #include <stdio.h> struct Callback { // The _time_ this function will be executed. double execTime ; // The function to execute after execTime has passed void* func ; } ; // Sample function to execute void go() { puts( "GO" ) ; } // Global program-wide sense of time double time ; int main() { // start the timer time = 0 ; // Make a sample callback Callback c1 ; c1.execTime = 10000 ; c1.func = go ; while( 1 ) { // its time to execute it if( time c1.execTime ) { c1.func ; // !! doesn't work! } time++; } } How can I make something like this work?

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