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  • Removing an array dimension where the elements sum to zero

    - by James
    Hi, I am assigning a 3D array, which contains some information for a number of different loadcases. Each row in the array defines a particular loadcase (of which there are 3) and I would like to remove the loadcase (i.e. the row) if ALL the elements of the row (in 3D) are equal to zero. The code I have at the moment is: Array = zeros(3,5) % Initialise array Numloadcases = 3; Array(:,:,1) = [10 10 10 10 10; 0 0 0 0 0; 0 0 0 0 0;]; % Expand to a 3D array Array(:,:,2) = [10 10 10 10 10; 0 0 0 0 0; 0 0 0 0 0;]; Array(:,:,3) = [10 10 10 10 10; 0 0 0 0 0; 0 0 20 0 0;]; Array(:,:,4) = [10 10 10 10 10; 0 0 0 0 0; 0 0 20 0 0;]; % I.e. the second row should be removed. for i = 1:Numloadcases if sum(Array(i,:,:)) == 0; Array(i,:,:) = [] end end At the moment, the for loop I have to remove the rows causes an indexing error, as the size of the array changes in the loop. Can anyone see a work around for this? Thanks

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  • Delphi TRttiType.GetMethods return zero TRttiMethod instances

    - by conciliator
    I've recently been able to fetch a TRttiType for an interface using TRttiContext.FindType using Robert Loves "GetType"-workaround ("registering" the interface by an explicit call to ctx.GetType, e.g. RType := ctx.GetType(TypeInfo(IMyPrettyLittleInterface));). One logical next step would be to iterate the methods of said interface. Consider program rtti_sb_1; {$APPTYPE CONSOLE} uses SysUtils, Rtti, mynamespace in 'mynamespace.pas'; var ctx: TRttiContext; RType: TRttiType; Method: TRttiMethod; begin ctx := TRttiContext.Create; RType := ctx.GetType(TypeInfo(IMyPrettyLittleInterface)); if RType <> nil then begin for Method in RType.GetMethods do WriteLn(Method.Name); end; ReadLn; end. This time, my mynamespace.pas looks like this: IMyPrettyLittleInterface = interface ['{6F89487E-5BB7-42FC-A760-38DA2329E0C5}'] procedure SomeProcedure; end; Unfortunately, RType.GetMethods returns a zero-length TArray-instance. Are there anyone able to reproduce my troubles? (Note that in my example I've explicitly fetched the TRttiType using TRttiContext.GetType, not the workaround; the introduction is included to warn readers that there might be some unresolved issues regarding rtti and interfaces.) Thanks!

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  • Why does my perl script return a zero return code when I explicitly call exit with a non-zero parame

    - by Tom Duckering
    I have a perl script which calls another script. The perl script should be propagating the script's return code but seems to be returning zero to its caller (a Java application) desipte the explicit call to exit $scriptReturnCode. It's probably something dumb since I'm by no means a perl expert. Code and output as follows (I realise that <=> could/should be != but that's what I have): print "INFO: Calling ${scriptDirectory}/${script} ${args}" $scriptReturnCode = system("${scriptDirectory}/${script} ${args}"); if ( $scriptReturnCode <=> 0 ) { print "ERROR: The script returned $scriptReturnCode\n"; exit $scriptReturnCode; } else { print "INFO: The script returned $scriptReturnCode.\n"; exit 0; } The output I have from my Java is: 20/04/2010 14:40:01 - INFO: Calling /path/to/script/script.ksh arg1 arg2 20/04/2010 14:40:01 - Could not find installer files <= this is from the script.ksh 20/04/2010 14:40:01 - ERROR: The script returned 256 20/04/2010 14:40:01 - Command Finished. Exit Code: 0 <= this is the Java app.

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  • Value is zero after filter SQL in C#

    - by Chuki2
    I`m new in C#.. I have write function to filter department. And this function will return idDepartment. New problem is, department keep value "System.Windows.Forms.Label, Text : ADMIN ", that`s why i got zero. So how can i take "ADMIN" only and keep to department? Update : public partial class frmEditStaff : Form { private string connString; private string userId, department; //Department parameter coming from here private string conString = "Datasource"; public frmEditStaff(string strUserID, string strPosition) { InitializeComponent(); //Pass value from frmListStaff to userID text box tbStaffId.Text = strUserID.ToString(); userId = strUserID.ToString(); department = strPosition.ToString(); } This code below is working, don`t have any problem. public int lookUpDepart() { int idDepart=0; using (SqlConnection openCon = new SqlConnection(conString)) { string lookUpDepartmenId = "SELECT idDepartment FROM tbl_department WHERE department = '" + department + "';"; openCon.Open(); using (SqlCommand querylookUpDepartmenId = new SqlCommand(lookUpDepartmenId, openCon)) { SqlDataReader read = querylookUpDepartmenId.ExecuteReader(); while (read.Read()) { idDepart = int.Parse(read[0].ToString()); break; } } openCon.Close(); return idDepart; } } Thanks for help. Happy nice day!

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  • [Java] RSA BadPaddingException : data must start with zero

    - by Robin Monjo
    Hello everyone. I try to implement an RSA algorithm in a Java program. I am facing the "BadPaddingException : data must start with zero". Here are the methods used to encrypt and decrypt my data : public byte[] encrypt(byte[] input) throws Exception { Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");// cipher.init(Cipher.ENCRYPT_MODE, this.publicKey); return cipher.doFinal(input); } public byte[] decrypt(byte[] input) throws Exception { Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");/// cipher.init(Cipher.DECRYPT_MODE, this.privateKey); return cipher.doFinal(input); } privateKey and publicKey attributes are read from files this way : public PrivateKey readPrivKeyFromFile(String keyFileName) throws IOException { PrivateKey key = null; try { FileInputStream fin = new FileInputStream(keyFileName); ObjectInputStream ois = new ObjectInputStream(fin); BigInteger m = (BigInteger) ois.readObject(); BigInteger e = (BigInteger) ois.readObject(); RSAPrivateKeySpec keySpec = new RSAPrivateKeySpec(m, e); KeyFactory fact = KeyFactory.getInstance("RSA"); key = fact.generatePrivate(keySpec); ois.close(); } catch (Exception e) { e.printStackTrace(); } return key; } Private key and Public key are created this way : public void Initialize() throws Exception { KeyPairGenerator keygen = KeyPairGenerator.getInstance("RSA"); keygen.initialize(2048); keyPair = keygen.generateKeyPair(); KeyFactory fact = KeyFactory.getInstance("RSA"); RSAPublicKeySpec pub = fact.getKeySpec(keyPair.getPublic(), RSAPublicKeySpec.class); RSAPrivateKeySpec priv = fact.getKeySpec(keyPair.getPrivate(), RSAPrivateKeySpec.class); saveToFile("public.key", pub.getModulus(), pub.getPublicExponent()); saveToFile("private.key", priv.getModulus(), priv.getPrivateExponent()); } and then saved in files : public void saveToFile(String fileName, BigInteger mod, BigInteger exp) throws IOException { FileOutputStream f = new FileOutputStream(fileName); ObjectOutputStream oos = new ObjectOutputStream(f); oos.writeObject(mod); oos.writeObject(exp); oos.close(); } I can't figured out how the problem come from. Any help would be appreciate ! Thanks in advance.

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  • Microsoft Charting Histogram Zero With Line

    - by Brownman98
    I am currently developing an application that uses chart control to create a histogram. The histogram displays data correctly however I would like to center the data. Right now the Min and Max are automatically set. I would like the graph to always force its to be displayed symmetrically. Here is an example of what I'm trying to accomplish. Basically I would like it to look like a normal distribution graph. Does anyone know how I can do the the following: Get the graph to be displayed symmetrically? Always show a zero line. Here is the aspx markup. <asp:Chart ID="ChartHistogram" runat="server" Height="200" Width="300"> <Series> <asp:Series Name="SeriesDataHistogram" ChartType="RangeColumn" Color="#4d5b6e" BorderColor="#ffffff" BorderDashStyle="NotSet"> </asp:Series> </Series> <ChartAreas> <asp:ChartArea Name="ChartAreaMain" BorderColor="#CCCCCC"> <AxisX TitleFont="Arial, 7pt" LabelAutoFitMaxFontSize="7"> <MajorGrid LineColor="#FFFFFF" Interval="5" /> <LabelStyle Format="P1" /> </AxisX> <AxisY Title="Frequency" TitleFont="Arial, 7pt" LabelAutoFitMaxFontSize="7"> <MajorGrid LineColor="#FFFFFF" /> </AxisY> </asp:ChartArea> </ChartAreas> </asp:Chart> Here is the code behind private void DrawHistogram(List<ReturnDataObject> list) { foreach (ReturnDataObject r in list) this.ChartHistogram.Series["SeriesDataHistogram"].Points.AddY(r.ReturnAmount); // HistogramChartHelper is a helper class found in the samples Utilities folder. HistogramChartHelper histogramHelper = new HistogramChartHelper(); // Show the percent frequency on the right Y axis. histogramHelper.ShowPercentOnSecondaryYAxis = false; // Create histogram series histogramHelper.CreateHistogram(ChartHistogram, "SeriesDataHistogram", "Histogram"); } Thanks for any help.

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  • How to remove the boundary effects arising due to zero padding in scipy/numpy fft?

    - by Omkar
    I have made a python code to smoothen a given signal using the Weierstrass transform, which is basically the convolution of a normalised gaussian with a signal. The code is as follows: #Importing relevant libraries from __future__ import division from scipy.signal import fftconvolve import numpy as np def smooth_func(sig, x, t= 0.002): N = len(x) x1 = x[-1] x0 = x[0] # defining a new array y which is symmetric around zero, to make the gaussian symmetric. y = np.linspace(-(x1-x0)/2, (x1-x0)/2, N) #gaussian centered around zero. gaus = np.exp(-y**(2)/t) #using fftconvolve to speed up the convolution; gaus.sum() is the normalization constant. return fftconvolve(sig, gaus/gaus.sum(), mode='same') If I run this code for say a step function, it smoothens the corner, but at the boundary it interprets another corner and smoothens that too, as a result giving unnecessary behaviour at the boundary. I explain this with a figure shown in the link below. Boundary effects This problem does not arise if we directly integrate to find convolution. Hence the problem is not in Weierstrass transform, and hence the problem is in the fftconvolve function of scipy. To understand why this problem arises we first need to understand the working of fftconvolve in scipy. The fftconvolve function basically uses the convolution theorem to speed up the computation. In short it says: convolution(int1,int2)=ifft(fft(int1)*fft(int2)) If we directly apply this theorem we dont get the desired result. To get the desired result we need to take the fft on a array double the size of max(int1,int2). But this leads to the undesired boundary effects. This is because in the fft code, if size(int) is greater than the size(over which to take fft) it zero pads the input and then takes the fft. This zero padding is exactly what is responsible for the undesired boundary effects. Can you suggest a way to remove this boundary effects? I have tried to remove it by a simple trick. After smoothening the function I am compairing the value of the smoothened signal with the original signal near the boundaries and if they dont match I replace the value of the smoothened func with the input signal at that point. It is as follows: i = 0 eps=1e-3 while abs(smooth[i]-sig[i])> eps: #compairing the signals on the left boundary smooth[i] = sig[i] i = i + 1 j = -1 while abs(smooth[j]-sig[j])> eps: # compairing on the right boundary. smooth[j] = sig[j] j = j - 1 There is a problem with this method, because of using an epsilon there are small jumps in the smoothened function, as shown below: jumps in the smooth func Can there be any changes made in the above method to solve this boundary problem?

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  • HP présente "Net-Zero Energy DataCenter", une architecture permettant une réduction de 30% de la consommation d'énergie et de 80% des coûts

    HP présente son architecture "Net-Zero Energy DataCenter", permettant une réduction de 30% de la consommation d'énergie et de 80% des coûts et dépendance des réseaux électriques HP vient de présenter son concept d'architecture « Net-Zero Energy » des centres de données économes en énergie, permettant de réduire la dépendance des réseaux électriques traditionnels. La vision de HP est de permettre aux entreprises de faire fonctionner les centres de données avec en utilisant leur propre énergie générée sur place, grâce à des sources renouvelables afin d'éliminer des dépendances comme l'emplacement, l'approvisionnement en énergie et les couts. L'architecture proposée ...

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  • Microsoft met en garde contre l'exploitation d'une faille zero-day dans Windows Vista, Office et Lync permettant d'exécuter du code distant

    Microsoft met en garde contre l'exploitation d'une faille zero-day dans Windows Vista, Office et Lync permettant d'exécuter du code distant Microsoft tire la sonnette d'alarme. Dans un récent avis de sécurité, la société met en garde les utilisateurs et les administrateurs contre des attaques ciblées touchant plusieurs de ses logiciels.L'éditeur affirme avoir pris connaissance de l'exploitation d'une faille zero-day dans ses plateformes par des pirates.La faille permettrait à un pirate d'exécuter...

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  • WCF zero application endpoint exception

    - by Lijo
    Hi Team, I am just trying with various WCF(in .Net 3.0) scenarios. I am using self hosting. I am getting an exception as "Service 'MyServiceLibrary.NameDecorator' has zero application (non-infrastructure) endpoints. This might be because no configuration file was found for your application, or because no service element matching the service name could be found in the configuration file, or because no endpoints were defined in the service element." I have a config file as follows (which has an endpoint) <?xml version="1.0" encoding="utf-8" ?> <configuration> <system.serviceModel> <services> <service name="Lijo.Samples.NameDecorator" behaviorConfiguration="WeatherServiceBehavior"> <host> <baseAddresses> <add baseAddress="http://localhost:8010/ServiceModelSamples/FreeServiceWorld"/> </baseAddresses> </host> <endpoint address="" binding="wsHttpBinding" contract="Lijo.Samples.IElementaryService" /> <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange" /> </service> </services> <behaviors> <serviceBehaviors> <behavior name="WeatherServiceBehavior"> <serviceMetadata httpGetEnabled="true"/> <serviceDebug includeExceptionDetailInFaults="False"/> </behavior> </serviceBehaviors> </behaviors> </system.serviceModel> </configuration> And a Host as using System.ServiceModel; using System.ServiceModel.Dispatcher; using System.ServiceModel.Channels; using System.ServiceModel.Description; using System.Runtime.Serialization; namespace MySelfHostConsoleApp { class Program { static void Main(string[] args) { System.ServiceModel.ServiceHost myHost = new ServiceHost(typeof(MyServiceLibrary.NameDecorator)); myHost.Open(); Console.ReadLine(); } } } My Service is as follows using System.ServiceModel; using System.Runtime.Serialization; namespace MyServiceLibrary { [ServiceContract(Namespace = "http://Lijo.Samples")] public interface IElementaryService { [OperationContract] CompanyLogo GetLogo(); } public class NameDecorator : IElementaryService { public CompanyLogo GetLogo() { CircleType cirlce = new CircleType(); CompanyLogo logo = new CompanyLogo(cirlce); return logo; } } [DataContract] public abstract class IShape { public abstract string SelfExplain(); } [DataContract(Name = "Circle")] public class CircleType : IShape { public override string SelfExplain() { return "I am a Circle"; } } [DataContract(Name = "Triangle")] public class TriangleType : IShape { public override string SelfExplain() { return "I am a Triangle"; } } [DataContract] [KnownType(typeof(CircleType))] [KnownType(typeof(TriangleType))] public class CompanyLogo { private IShape m_shapeOfLogo; [DataMember] public IShape ShapeOfLogo { get { return m_shapeOfLogo; } set { m_shapeOfLogo = value; } } public CompanyLogo(IShape shape) { m_shapeOfLogo = shape; } } } Could you please help me to understand what I am missing here? Thanks Lijo

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  • reloading page while an ajax request in progress gives empty response and status as zero

    - by Jayapal Chandran
    Hi, Browser is firefox 3.0.10 I am requesting a page using ajax. The response is in progress may be in readyState less than 4. In this mean time i am trying to reload the page. What happens is the request ends giving an empty response. I used alert to find what string has been given as response text. I assume that by this time the ready state 4 is reached. why it is empty string. when i alert the xmlhttpobject.status it displayed 0. when i alert the xmlhttpobject.statusText an exception occurs stating that NOT AVAILABLE. when i read in the document http://www.devx.com/webdev/Article/33024/0/page/2 it said for 3 and 4 status and statusText are available but when i tested only status is available but not satausText Here is a sample code. consider that i have requested a page and my callback function is as follows function cb(rt) { if(rt.readyState==4) { alert(rt.status); alert(rt.statusText); // which throws an exception } } and my server side script is as follows sleep(30); //flushing little drop down code besides these i noticed the following... assume again i am requesting the above script using ajax. now there will be an idle time till 30 seconds is over before that 30 seconds i press refresh. i got xmlhttpobject.status as 0 but still the browser did not reload the page untill that 30 seconds. WHY? so what is happening when i refresh a page before an ajax request is complete is the status value is set to zero and the ready state is set to 4 but the page still waits for the response from the server to end... what is happening... THE REASON FOR ME TO FACE SOME THING LIKE THIS IS AS FOLLOWS. when ever i do an ajax request ... if the process succeeded like inserting some thing or deleting something i popup a div stating that updated successfully and i will reload the page. but if there is any error then i do not reload the page instead i just alert that unable to process this request. what happens if the user reloads the page before any of this request is complete is i get an empty response which in my calculation is there is a server error. so i was debugging the ajax response to filter out that the connection has been interrupted because the user had pressed reload. so in this time i don't want to display unable to process this request when the user reloads the page before the request has been complete. oh... a long story. IT IS A LONG DESCRIPTION SO THAT I CAN MAKE EXPERTS UNDERSTAND MY DOUBT. so what i want form the above. any type of answer would clear my mind. or i would like to say all type of answers. EDIT: 19 dec. If i did not get any correct answer then i would delete this question and will rewrite with examples. else i will accept after experimenting.

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  • Table not Echoing out if another Table has a Zero value

    - by John
    Hello, The table below with mysql_query($sqlStr3) (the one with the word "Joined" in its row) does not echo if the result associated with mysql_query($sqlStr1) has a value of zero. This happens even if mysql_query($sqlStr3) returns a result. In other words, if a given loginid has an entry in the table "login", but not one in the table "submission", then the table associated with mysql_query($sqlStr3) does not echo. I don't understand why the "submission" table would have any effect on mysql_query($sqlStr3), since the $sqlStr3 only deals with another table, called "login", as seen below. Any ideas why this is happening? Thanks in advance, John W. <?php echo '<div class="profilename">User Profile for </div>'; echo '<div class="profilename2">'.$profile.'</div>'; $tzFrom = new DateTimeZone('America/New_York'); $tzTo = new DateTimeZone('America/Phoenix'); $profile = mysql_real_escape_string($_GET['profile']); $sqlStr = "SELECT l.username, l.loginid, s.loginid, s.submissionid, s.title, s.url, s.datesubmitted, s.displayurl FROM submission AS s INNER JOIN login AS l ON s.loginid = l.loginid WHERE l.username = '$profile' ORDER BY s.datesubmitted DESC"; $result = mysql_query($sqlStr); $arr = array(); echo "<table class=\"samplesrec1\">"; while ($row = mysql_fetch_array($result)) { $dt = new DateTime($row["datesubmitted"], $tzFrom); $dt->setTimezone($tzTo); echo '<tr>'; echo '<td class="sitename3">'.$dt->format('F j, Y &\nb\sp &\nb\sp g:i a').'</a></td>'; echo '<td class="sitename1"><a href="http://www.'.$row["url"].'">'.$row["title"].'</a></td>'; echo '</tr>'; } echo "</table>"; $sqlStr1 = "SELECT l.username, l.loginid, s.loginid, s.submissionid, s.title, s.url, s.datesubmitted, s.displayurl, l.created, count(s.submissionid) countSubmissions FROM submission AS s INNER JOIN login AS l ON s.loginid = l.loginid WHERE l.username = '$profile'"; $result1 = mysql_query($sqlStr1); $arr1 = array(); echo "<table class=\"samplesrec2\">"; while ($row1 = mysql_fetch_array($result1)) { echo '<tr>'; echo '<td class="sitename5">Submissions: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;'.$row1["countSubmissions"].'</td>'; echo '</tr>'; } echo "</table>"; $sqlStr2 = "SELECT l.username, l.loginid, c.loginid, c.commentid, c.submissionid, c.comment, c.datecommented, l.created, count(c.commentid) countComments FROM comment AS c INNER JOIN login AS l ON c.loginid = l.loginid WHERE l.username = '$profile'"; $result2 = mysql_query($sqlStr2); $arr2 = array(); echo "<table class=\"samplesrec3\">"; while ($row2 = mysql_fetch_array($result2)) { echo '<tr>'; echo '<td class="sitename5">Comments: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;'.$row2["countComments"].'</td>'; echo '</tr>'; } echo "</table>"; $tzFrom3 = new DateTimeZone('America/New_York'); $tzTo3 = new DateTimeZone('America/Phoenix'); $sqlStr3 = "SELECT created, username FROM login WHERE username = '$profile'"; $result3 = mysql_query($sqlStr3); $arr3 = array(); echo "<table class=\"samplesrec4\">"; while ($row3 = mysql_fetch_array($result3)) { $dt3 = new DateTime($row3["created"], $tzFrom3); $dt3->setTimezone($tzTo3); echo '<tr>'; echo '<td class="sitename5">Joined: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;'.$dt->format('F j, Y').'</td>'; echo '</tr>'; } echo "</table>"; ?> </body> </html>

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  • What’s New in Delphi XE6 Regular Expressions

    - by Jan Goyvaerts
    There’s not much new in the regular expression support in Delphi XE6. The big change that should be made, upgrading to PCRE 8.30 or later and switching to the pcre16 functions that use UTF-16, still hasn’t been made. XE6 still uses PCRE 7.9 and thus continues to require conversion from the UTF-16 strings that Delphi uses natively to the UTF-8 strings that older versions of PCRE require. Delphi XE6 does fix one important issue that has plagued TRegEx since it was introduced in Delphi XE. Previously, TRegEx could not find zero-length matches. So a regex like (?m)^ that should find a zero-length match at the start of each line would not find any matches at all with TRegEx. The reason for this is that TRegEx uses TPerlRegEx to do the heavy lifting. TPerlRegEx sets its State property to [preNotEmpty] in its constructor, which tells it to skip zero-length matches. This is not a problem with TPerlRegEx because users of this class can change the State property. But TRegEx does not provide a way to change this property. So in Delphi XE5 and prior, TRegEx cannot find zero-length matches. In Delphi XE6 TPerlRegEx’s constructor was changed to initialize State to the empty set. This means TRegEx is now able to find zero-length matches. TRegex.Replace() using the regex (?m)^ now inserts the replacement at the start of each line, as you would expect. If you use TPerlRegEx directly, you’ll need to set State to [preNotEmpty] in your own code if you relied on its behavior to skip zero-length matches. You will need to check existing applications that use TRegEx for regular expressions that incorrectly allow zero-length matches. In XE5 and prior, TRegEx using \d* would match all numbers in a string. In XE6, the same regex still matches all numbers, but also finds a zero-length match at each position in the string. RegexBuddy 4 warns about zero-length matches on the Create panel if you set it to Detailed mode. At the bottom of the regex tree there will be a node saying either “your regular expression may find zero-length matches” or “zero-length matches will be skipped” depending on whether your application allows zero-length matches (XE6 TRegEx) or not (XE–XE5 TRegEx).

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  • Is 1/0 a legal Java expression?

    - by polygenelubricants
    The following compiles fine in my Eclipse: final int j = 1/0; // compiles fine!!! // throws ArithmeticException: / by zero at run-time Java prevents many "dumb code" from even compiling in the first place (e.g. "Five" instanceof Number doesn't compile!), so the fact this didn't even generate as much as a warning was very surprising to me. The intrigue deepens when you consider the fact that constant expressions are allowed to be optimized at compile time: public class Div0 { public static void main(String[] args) { final int i = 2+3; final int j = 1/0; final int k = 9/2; } } Compiled in Eclipse, the above snippet generates the following bytecode (javap -c Div0) Compiled from "Div0.java" public class Div0 extends java.lang.Object{ public Div0(); Code: 0: aload_0 1: invokespecial #8; //Method java/lang/Object."<init>":()V 4: return public static void main(java.lang.String[]); Code: 0: iconst_5 1: istore_1 // "i = 5;" 2: iconst_1 3: iconst_0 4: idiv 5: istore_2 // "j = 1/0;" 6: iconst_4 7: istore_3 // "k = 4;" 8: return } As you can see, the i and k assignments are optimized as compile-time constants, but the division by 0 (which must've been detectable at compile-time) is simply compiled as is. javac 1.6.0_17 behaves even more strangely, compiling silently but excising the assignments to i and k completely out of the bytecode (probably because it determined that they're not used anywhere) but leaving the 1/0 intact (since removing it would cause an entirely different program semantics). So the questions are: Is 1/0 actually a legal Java expression that should compile anytime anywhere? What does JLS say about it? If this is legal, is there a good reason for it? What good could this possibly serve?

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  • How to efficiently compare the sign of two floating-point values while handling negative zeros

    - by François Beaune
    Given two floating-point numbers, I'm looking for an efficient way to check if they have the same sign, given that if any of the two values is zero (+0.0 or -0.0), they should be considered to have the same sign. For instance, SameSign(1.0, 2.0) should return true SameSign(-1.0, -2.0) should return true SameSign(-1.0, 2.0) should return false SameSign(0.0, 1.0) should return true SameSign(0.0, -1.0) should return true SameSign(-0.0, 1.0) should return true SameSign(-0.0, -1.0) should return true A naive but correct implementation of SameSign in C++ would be: bool SameSign(float a, float b) { if (fabs(a) == 0.0f || fabs(b) == 0.0f) return true; return (a >= 0.0f) == (b >= 0.0f); } Assuming the IEEE floating-point model, here's a variant of SameSign that compiles to branchless code (at least with with Visual C++ 2008): bool SameSign(float a, float b) { int ia = binary_cast<int>(a); int ib = binary_cast<int>(b); int az = (ia & 0x7FFFFFFF) == 0; int bz = (ib & 0x7FFFFFFF) == 0; int ab = (ia ^ ib) >= 0; return (az | bz | ab) != 0; } with binary_cast defined as follow: template <typename Target, typename Source> inline Target binary_cast(Source s) { union { Source m_source; Target m_target; } u; u.m_source = s; return u.m_target; } I'm looking for two things: A faster, more efficient implementation of SameSign, using bit tricks, FPU tricks or even SSE intrinsics. An efficient extension of SameSign to three values.

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  • Proper way to scan a range of IP addresses

    - by Josh G
    Given a range of IP addresses entered by a user (through various means), I want to identify which of these machines have software running that I can talk to. Here's the basic process: Ping these addresses to find available machines Connect to a known socket on the available machines Send a message to the successfully established sockets Compare the response to the expected response Steps 2-4 are straight forward for me. What is the best way to implement the first step in .NET? I'm looking at the System.Net.NetworkInformation.Ping class. Should I ping multiple addresses simultaneously to speed up the process? If I ping one address at a time with a long timeout it could take forever. But with a small timeout, I may miss some machines that are available. Sometimes pings appear to be failing even when I know that the address points to an active machine. Do I need to ping twice in the event of the request getting discarded? To top it all off, when I scan large collections of addresses with the network cable unplugged, Ping throws a NullReferenceException in FreeUnmanagedResources(). !? Any pointers on the best approach to scanning a range of IPs like this?

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  • How do I get the IPv4 subnetmask on interface with both v4 and v6 address?

    - by Per Fagrell
    I have an InterfaceAddress that returns an ipv4 address (4 octets). However the network prefix length seems to be for the ipv6 address associated with the interface (it's returning as 128). How do I find the correct network prefix length? Enumeration<NetworkInterface> NetworkInterface.getNetworkInterfaces() for (; interfaces.hasMoreElements();) { final List<InterfaceAddress>interfaceAddresses = interfaces.nextElement().getInterfaceAddresses(); for (final InterfaceAddress address : interfaceAddresses) { assert(address.getAddress().getAddress().length == 4); // [sic] assert(address.getNetworkPrefixLength() < 32); // <- Fails. Actually equals 128 } }

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  • [AS3/C#] Byte encryption ( DES-CBC zero pad )

    - by mark_dj
    Hi there, Currently writing my own AMF TcpSocketServer. Everything works good so far i can send and recieve objects and i use some serialization/deserialization code. Now i started working on the encryption code and i am not so familiar with this stuff. I work with bytes , is DES-CBC a good way to encrypt this stuff? Or are there other more performant/secure ways to send my data? Note that performance is a must :). When i call: ReadAmf3Object with the decrypter specified i get an: InvalidOperationException thrown by my ReadAmf3Object function when i read out the first byte the Amf3TypeCode isn't specified ( they range from 0 to 16 i believe (Bool, String, Int, DateTime, etc) ). I got Typecodes varying from 97 to 254? Anyone knows whats going wrong? I think it has something to do with the encryption part. Since the deserializer works fine w/o the encryption. I am using the right padding/mode/key? I used: http://code.google.com/p/as3crypto/ as as3 encryption/decryption library. And i wrote an Async tcp server with some abuse of the threadpool ;) Anyway here some code: C# crypter initalization code System.Security.Cryptography.DESCryptoServiceProvider crypter = new DESCryptoServiceProvider(); crypter.Padding = PaddingMode.Zeros; crypter.Mode = CipherMode.CBC; crypter.Key = Encoding.ASCII.GetBytes("TESTTEST"); AS3 private static var _KEY:ByteArray = Hex.toArray(Hex.fromString("TESTTEST")); private static var _TYPE:String = "des-cbc"; public static function encrypt(array:ByteArray):ByteArray { var pad:IPad = new NullPad; var mode:ICipher = Crypto.getCipher(_TYPE, _KEY, pad); pad.setBlockSize(mode.getBlockSize()); mode.encrypt(array); return array; } public static function decrypt(array:ByteArray):ByteArray { var pad:IPad = new NullPad; var mode:ICipher = Crypto.getCipher(_TYPE, _KEY, pad); pad.setBlockSize(mode.getBlockSize()); mode.decrypt(array); return array; } C# read/unserialize/decrypt code public override object Read(int length) { object d; using (MemoryStream stream = new MemoryStream()) { stream.Write(this._readBuffer, 0, length); stream.Position = 0; if (this.Decrypter != null) { using (CryptoStream c = new CryptoStream(stream, this.Decrypter, CryptoStreamMode.Read)) using (AmfReader reader = new AmfReader(c)) { d = reader.ReadAmf3Object(); } } else { using (AmfReader reader = new AmfReader(stream)) { d = reader.ReadAmf3Object(); } } } return d; }

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  • Find largest rectangle containing all zero's in an N X N binary matrix

    - by Rajendra
    Given an N X N binary matrix (containing only 0's or 1's). How can we go about finding largest rectangle containing all 0's? Example: I 0 0 0 0 1 0 0 0 1 0 0 1 II->0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 <--IV 0 0 1 0 0 0 IV is a 6 X 6 binary matrix, return value in this case will be Cell 1: (2, 1) and Cell 2: (4, 4). Resulting sub-matrix can be square or rectangle. Return value can be size of the largest sub-matrix of all 0's also, for example, here 3 X 4.

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  • Why is the HttpContext.Cache count always zero?

    - by jjr2527
    I set up a few pages with OutputCache profiles and confirmed that they are being cached by using multiple browsers and requests to retrieve the page with a timestamp which matched across all requests. When I try to enumerate the HttpContect.Cache it is always empty. Any ideas what is going on here or where I should be going for this information instead?

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  • Reading from a file, atoi() returns zero only on first element

    - by Nazgulled
    Hi, I don't understand why atoi() is working for every entry but the first one. I have the following code to parse a simple .csv file: void ioReadSampleDataUsers(SocialNetwork *social, char *file) { FILE *fp = fopen(file, "r"); if(!fp) { perror("fopen"); exit(EXIT_FAILURE); } char line[BUFSIZ], *word, *buffer, name[30], address[35]; int ssn = 0, arg; while(fgets(line, BUFSIZ, fp)) { line[strlen(line) - 2] = '\0'; buffer = line; arg = 1; do { word = strsep(&buffer, ";"); if(word) { switch(arg) { case 1: printf("[%s] - (%d)\n", word, atoi(word)); ssn = atoi(word); break; case 2: strcpy(name, word); break; case 3: strcpy(address, word); break; } arg++; } } while(word); userInsert(social, name, address, ssn); } fclose(fp); } And the .csv sample file is this: 900011000;Jon Yang;3761 N. 14th St 900011001;Eugene Huang;2243 W St. 900011002;Ruben Torres;5844 Linden Land 900011003;Christy Zhu;1825 Village Pl. 900011004;Elizabeth Johnson;7553 Harness Circle But this is the output: [900011000] - (0) [900011001] - (900011001) [900011002] - (900011002) [900011003] - (900011003) [900011004] - (900011004) What am I doing wrong?

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  • Decimal Value is Zero when it should be 0.0x

    - by Mike Wills
    If this was previously talked about, I'm sorry, I had a hard time searching on this. I am calculating a depreciation rate. One portion of our calculation is 1/life in months. My table stores this data in a decimal field. I tried test = 1 / estimatedLife; but the result of the calculation of test (which is defined as a decimal) is 0. Say the estimated life is 36 months. So 1/36 should equal 0.02777778. Any thoughts of what I am doing wrong? BTW, I changed the test to a double and had the same result.

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