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  • Changing type of object in a conditional

    - by David Doria
    I'm having a bit of trouble with dynamic_casting. I need to determine at runtime the type of an object. Here is a demo: include include class PersonClass { public: std::string Name; virtual void test(){}; //it is annoying that this has to be here... }; class LawyerClass : public PersonClass { public: void GoToCourt(){}; }; class DoctorClass : public PersonClass { public: void GoToSurgery(){}; }; int main(int argc, char *argv[]) { PersonClass* person = new PersonClass; if(true) { person = dynamic_cast(person); } else { person = dynamic_cast(person); } person-GoToCourt(); return 0; } I would like to do the above. The only legal way I found to do it is to define all of the objects before hand: PersonClass* person = new PersonClass; LawyerClass* lawyer; DoctorClass* doctor; if(true) { lawyer = dynamic_cast(person); } else { doctor = dynamic_cast(person); } if(true) { lawyer-GoToCourt(); } The main problem with this (besides having to define a bunch of objects that won't be use) is that I have to change the name of the 'person' variable. Is there a better way? (I am not allowed to change any of the classes (Person, Lawyer, or Doctor) because they are part of a library that people who will use my code have and won't want to change). Thanks, Dave

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  • Basic SWIG C++ use for Java

    - by duckworthd
    I've programmed a couple years in both C++ and Java, but I've finally come to a point where I need to bring a little unification between the two -- ideally, using SWIG. I've written a tiny and fairly pointless little class called Example: #include <stdio.h> class Example { public: Example(); ~Example(); int test(); }; #include "example.h" Example::Example() { printf("Example constructor called\n"); } Example::~Example() { printf("Example destructor called\n"); } int Example::test() { printf("Holy sh*t, I work!\n"); return 42; } And a corresponding interface file: /* File: example.i */ %module test %{ #include "example.h" %} %include "example.h" Now I have questions. Firstly, when I want to actually run SWIG initially, am I supposed to use the example_wrap.c (from swig -java example.i) or example_wrap.cxx (from swig -c++ example.i) file when recompiling with my original example.cpp? Or perhaps both? I tried both and the latter seemed most likely, but when I recompile as so: g++ example.cpp example_wrap.cxx -I/usr/lib/jvm/java-6-sun-.../include/ I get a host of errors regarding TcL of all things, asking me for the tcl.h header. I can't even wrap my mind around why it wants that much less needs it, and as such have found myself where I don't even know how to begin using SWIG.

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  • Checking if a file is a directory or just a file.

    - by Jookia
    I'm writing a program to check if something is a file or is a directory. Is there a better way to do it than this? #include <stdio.h> #include <sys/types.h> #include <dirent.h> #include <errno.h> int isFile(const char* name) { DIR* directory = opendir(name); if(directory != NULL) { closedir(directory); return 0; } if(errno == ENOTDIR) { return 1; } return -1; } int main(void) { const char* file = "./testFile"; const char* directory = "./"; printf("Is %s a file? %s.\n", file, ((isFile(file) == 1) ? "Yes" : "No")); printf("Is %s a directory? %s.\n", directory, ((isFile(directory) == 0) ? "Yes" : "No")); return 0; }

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  • Procesing 16bit sample audio

    - by user2431088
    Right now i have an audio file (2 Channels, 44.1kHz Sample Rate, 16bit Sample size, WAV) I would like to pass it into this method but i am not sure of any way to convert the WAV file to a byte array. /// <summary> /// Process 16 bit sample /// </summary> /// <param name="wave"></param> public void Process(ref byte[] wave) { _waveLeft = new double[wave.Length / 4]; _waveRight = new double[wave.Length / 4]; if (_isTest == false) { // Split out channels from sample int h = 0; for (int i = 0; i < wave.Length; i += 4) { _waveLeft[h] = (double)BitConverter.ToInt16(wave, i); _waveRight[h] = (double)BitConverter.ToInt16(wave, i + 2); h++; } } else { // Generate artificial sample for testing _signalGenerator = new SignalGenerator(); _signalGenerator.SetWaveform("Sine"); _signalGenerator.SetSamplingRate(44100); _signalGenerator.SetSamples(16384); _signalGenerator.SetFrequency(5000); _signalGenerator.SetAmplitude(32768); _waveLeft = _signalGenerator.GenerateSignal(); _waveRight = _signalGenerator.GenerateSignal(); } // Generate frequency domain data in decibels _fftLeft = FourierTransform.FFTDb(ref _waveLeft); _fftRight = FourierTransform.FFTDb(ref _waveRight); }

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  • Bruteforcing Blackberry PersistentStore?

    - by Haoest
    Hello, I am experimenting with Blackberry's Persistent Store, but I have gotten nowhere so far, which is good, I guess. So I have written a a short program that attempts iterator through 0 to a specific upper bound to search for persisted objects. Blackberry seems to intentionally slow the loop. Check this out: String result = "result: \n"; int ub = 3000; Date start = Calendar.getInstance().getTime(); for(int i=0; i<ub; i++){ PersistentObject o = PersistentStore.getPersistentObject(i); if (o.getContents() != null){ result += (String) o.getContents() + "\n"; } } result += "end result\n"; result += "from 0 to " + ub + " took " + (Calendar.getInstance().getTime().getTime() - start.getTime()) / 1000 + " seconds"; From 0 to 3000 took 20 seconds. Is this enough to conclude that brute-forcing is not a practical method to breach the Blackberry? In general, how secure is BB Persistent Store?

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  • Images won't load if they are of high size

    - by Fahim Parkar
    I have created web-application using JSF 2.0 and mysql. I am storing images in DB using MEDIUMBLOB. When I try to load image, I am able to see those images. However if the image size is big (1 MB or more), I can see half or 3/4th image on the browser. Any idea how to overcome this issue? Do I need to set any variable in JSF or MySQL? I know I should have saved the images over disk instead of DB, however this was client requirement. Client wanted to backup data and provide it to someone else and client don't want to backup DB and images also. Edit 1 Do I need to set any variables on mysql like query_cache. Edit 2 When I download same image and put below code it works perfectly. <h:graphicImage value="images/myImage4.png" width="50%" /> Edit 3 code is as below. <h:graphicImage value="DisplayImage?mainID=drawing" /> DisplayImage.java String imgLen = rs1.getString(1); int len = imgLen.length(); byte[] rb = new byte[len]; InputStream readImg = rs1.getBinaryStream(1); InputStream inputStream = readImg; int index = readImg.read(rb, 0, len); response.reset(); response.setHeader("Content-Length", String.valueOf(len)); response.setHeader("Content-disposition", "inline;filename=/file.png"); response.setContentType("image/png"); response.getOutputStream().write(rb, 0, len); response.getOutputStream().flush(); When I print len I get value as len=1548432

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  • Generating a python file

    - by fema
    Hi! I'm havin issues with python (imo python itself is an issue). I have a txt file, it contains a custom language and I have to translate it to a working python code. The input: import sys n = int(sys.argv[1]) ;;print "Beginning of the program!" LOOP i in range(1,n) {print "The number:";;print i} BRANCH n < 5 {print n ;;print "less than 5"} The wanted output looks exactly like this: import sys n = int(sys.argv[1]) print "Beginning of the program!" for i in range(1,n) : print "The number:" print i if n < 5 : print n print "less than 5" The name of the input file is read from parameter. The out file is out.py. In case of a wrong parameter, it gives an error message. The ;; means a new line. When I tried to do it, I made an array, I read all the lines into it, split by " ". Then I wanted to strip it from the marks I don't need. I made 2 loops, one for the lines, one for the words. So then I started to replace the things. Everything went fine until it came to the } mark. It finds it, but it can not replace or strip it. I have no more idea what to do. Could someone help me, please? Thanks in advance!

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  • Small openmp programm freezes sometimes (gcc, c, linux)

    - by osgx
    Hello Just write a small omp test, and it does not work correctly all the times: #include <omp.h> int main() { int i,j=0; #pragma omp parallel for(i=0;i<1000;i++) { #pragma omp barrier j+= j^i; } return j; } The usage of j for writing from all threads is incorrect in this example, BUT there must be only nondeterministic value of j I have a freeze. Compiled with gcc-4.3.1 -fopenmp a.c -o gcc -static Run on 4-core x86_Core2 Linux server: $ ./gcc and got freeze (sometimes; like 1 freeze for 4-5 fast runs). Strace: [pid 13118] <... futex resumed> ) = 0 [pid 13118] futex(0x80d3014, FUTEX_WAIT, 2, NULL <unfinished ...> [pid 13120] <... futex resumed> ) = 0 [pid 13119] futex(0x80d3014, FUTEX_WAIT, 2, NULL <unfinished ...> [pid 13120] futex(0x80d3014, FUTEX_WAKE, 1) = 1 [pid 13120] futex(0x80cd798, FUTEX_WAIT, 1, NULL <unfinished ...> [pid 13109] <... futex resumed> ) = 0 [pid 13109] futex(0x80d3014, FUTEX_WAKE, 1) = 1 [pid 13109] futex(0x80d3020, FUTEX_WAIT, 251, NULL <unfinished ...> [pid 13118] <... futex resumed> ) = 0 [pid 13118] futex(0x80d3014, FUTEX_WAKE, 1) = 1 [pid 13119] <... futex resumed> ) = 0 [pid 13118] futex(0x80d3020, FUTEX_WAIT, 251, NULL <unfinished ...> [pid 13119] futex(0x80d3014, FUTEX_WAKE, 1) = 0 [pid 13119] futex(0x80d3020, FUTEX_WAIT, 251, NULL <freeze> Why do I have a freeze (deadlock)?

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  • Does breaking chained Select()s in LINQ to objects hurt performance?

    - by Justin
    Take the following pseudo C# code: using System; using System.Data; using System.Linq; using System.Collections.Generic; public IEnumerable<IDataRecord> GetRecords(string sql) { // DB logic goes here } public IEnumerable<IEmployer> Employers() { string sql = "select EmployerID from employer"; var ids = GetRecords(sql).Select(record => (record["EmployerID"] as int?) ?? 0); return ids.Select(employerID => new Employer(employerID) as IEmployer); } Would it be faster if the two Select() calls were combined? Is there an extra iteration in the code above? Is the following code faster? public IEnumerable<IEmployer> Employers() { string sql = "select EmployerID from employer"; return Query.Records(sql).Select(record => new Employer((record["EmployerID"] as int?) ?? 0) as IEmployer); } I think the first example is more readable if there is no difference in performance.

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  • [nHibernate] casting string to bool using nHibernate Criteria

    - by code-zoop
    I have an nHibernate query using Criteria, and I am trying to cast a string to bool in the query itself. I have done the same with casting a string to int, and that works well (the "DataField" property is "1" as a string): var result = Session .CreateCriteria<Car>() .Add(Restrictions.Eq((Projections.Cast(NHibernateUtil.Int32, Projections.Property("DataField"), 1)) .List<Car>(); tx.Commit(); But I am trying to do the same with bool, but I do not get the expected result: var result = Session .CreateCriteria<Car>() .Add(Restrictions.Eq((Projections.Cast(NHibernateUtil.bool, Projections.Property("DataField"), true)) .List<Car>(); tx.Commit(); "DataField" is the string "True", but the result in an empty list, where it should contain 100 elements with the "DataField" property string set to "True". I have tried with the string "true", and "1", but the result is still an empty List. [EDIT] As Commented below, I could check for the string "True" or "False", but I would say this is a more general question than just for the Boolean. Note that the idea is to have some sort of key value representation of the data, where the value can be different data types. I need the value table to contain all data, so storing the data as string seems like the cleanest solution! I have been able to use the method above to store both int and double as string, and to the cast in the query, but I have not succeeded using the same method for DateDime and Boolean. And for DateTime it is crucial to have the actual DateTime object. How can I make the cast from string to bool, and string to DateTime work in the queries? Thanks

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  • c# How to find if two objects are equal

    - by Simon G
    Hi, I'm needing to know the best way to compare two objects and to find out if there equal. I'm overriding both GethashCode and Equals. So a basic class looks like: public class Test { public int Value { get; set; } public string String1 { get; set; } public string String2 { get; set; } public override int GetHashCode() { return Value ^ String1.GetHashCode() ^ String2.GetHashCode(); } public override bool Equals( object obj ) { return GetHashCode() == obj.GetHashCode(); } } So for testing purposes I created two objects: Test t = new Test() { Value = 1, String1 ="One", String2 = "One" }; Test t2 = new Test() { Value = 1, String1 = "Two", String2 = "Two" }; bool areEqual = t.Equals( t2 ); In testing this areEqual returns true event though both objects are different. I realise this is because String1 and String2 are the same value in each object and thus cancels each other out when hashing. Is there a better way off hashing object that the method I have that will resolve my issue?

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  • How to sort data in a table data structure in Java?

    - by rgksugan
    I need to sort data based on the third column of the table data structure. I tried based on the answers for the following question. But my sorting does not work. Please help me in this. Here goes my code. Object[] data = new Object[y]; rst.beforeFirst(); while (rst.next()) { int p_id = Integer.parseInt(rst.getString(1)); String sw2 = "select sum(quantity) from tbl_order_detail where product_id=" + p_id; rst1 = stmt1.executeQuery(sw2); rst1.next(); String sw3 = "select max(order_date) from tbl_order where tbl_order.`Order_ID` in (select tbl_order_detail.`Order_ID` from tbl_order_detail where product_id=" + p_id + ")"; rst2 = stmt2.executeQuery(sw3); rst2.next(); data[i] = new Object[]{new String(rst.getString(2)), new String(rst.getString(3)), new Integer(rst1.getString(1)), new String(rst2.getString(1))}; i++; } ColumnComparator cc = new ColumnComparator(2); Arrays.sort(data, cc); if (i == 0) { table.addCell(""); table.addCell(""); table.addCell(""); table.addCell(""); } else { for (int j = 0; j < y; j++) { Object[] theRow = (Object[]) data[j]; table.addCell((String) theRow[0]); table.addCell((String) theRow[1]); table.addCell((String) theRow[2]); table.addCell((String) theRow[3]); }

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  • Moving a high quality line on a panel c#

    - by user1787601
    I want to draw a line on a panel and then move it as the mouse moves. To do so, I draw the line and when the mouse moves I redraw the line to the new location and remove the previous line by drawing a line with the background color on it. It works fine if I do not use the high quality smoothing mode. But if use high quality smoothing mode, it leave traces on the panel. Does anybody know how to fix this? Thank you. Here is the code int x_previous = 0; int y_previous = 0; private void panel1_MouseMove(object sender, MouseEventArgs e) { Pen pen1 = new System.Drawing.Pen(Color.Black, 3); Pen pen2 = new System.Drawing.Pen(panel1.BackColor, 3); Graphics g = panel1.CreateGraphics(); g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; g.DrawLine(pen2, new Point(0, 0), new Point(x_previous, y_previous)); g.DrawLine(pen1, new Point(0, 0), new Point(e.Location.X, e.Location.Y)); x_previous = e.Location.X; y_previous = e.Location.Y; } Here is the snapshot with SmoothingMode Here is the snapshot without SmoothingMode

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  • Two Objects created with the same Address in Flex

    - by James
    Hi, I have an issue in flex which is causing a bit of a headache! I am adding objects to an ArrayCollection but in doing so, another ArrayCollection is also picking up these changes even though there is no binding occurring. I can see from the debug that the two ACs have the same address but for the life of me can't figure out why. I have two Array Collections: model.index.rows //The main array collection model.index.holdRows //The array collection that imitates the above This phantom data binding occurs only for the first iteration in the loop and for all others it will just write it the once. The reason this is proving troublesome is that it creates duplicate entries in my datagrid. public override function handleMessage(message:IMessage):void { super.handleMessage(message); if (message is IndexResponse) { var response:IndexResponse = message as IndexResponse; model.index.rows.removeAll(); model.index.indexIsEmpty = response.nullIndex; if (model.index.indexIsEmpty !== true) { //Update the index model from the response. Note: each property of the row object will be shown in the UI as a column in the grid response.index.forEach(function(entry:EntryData, i:int, a:Array):void { var row:Object = { fileID: entry.fileID, dadName: entry.dadName }; entry.tags.forEach(function(tag:Tag, i:int, a:Array):void { row[tag.name] = tag.value; }); model.index.rows.addItem(row); }); if(model.index.indexForNetworkView == true){ model.index.holdRows.source = model.index.holdRows.source.concat(model.index.rows.source); model.index.indexCounter++; model.index.indexForNetworkView = false; controller.indexController.showNetwork(model.index.indexCounter); } model.index.rows.refresh(); controller.networkController.show(); } } Has anyone else who has encountered something simillar propose a solution?

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  • Stuck in a loop

    - by Luke
    while (true) { //read in the file StreamReader convert = new StreamReader("../../convert.txt"); //define variables string line = convert.ReadLine(); double conversion; int numberIn; double conversionFactor; //ask for the conversion information Console.WriteLine("Enter the conversion in the form (Amount, Convert from, Convert to)"); String inputMeasurement = Console.ReadLine(); string[] inputMeasurementArray = inputMeasurement.Split(','); //loop through the lines looking for a match while (line != null) { string[] fileMeasurementArray = line.Split(','); if (fileMeasurementArray[0] == inputMeasurementArray[1]) { if (fileMeasurementArray[1] == inputMeasurementArray[2]) { Console.WriteLine("The conversion factor for {0} to {1} is {2}", inputMeasurementArray[1], inputMeasurementArray[2], fileMeasurementArray[2]); //convert to int numberIn = Convert.ToInt32(inputMeasurementArray[0]); conversionFactor = Convert.ToDouble(fileMeasurementArray[2]); conversion = (numberIn * conversionFactor); Console.WriteLine("{0} {1} is {2} {3} \n", inputMeasurementArray[0], inputMeasurementArray[1], conversion, inputMeasurementArray[2]); break; } } else { Console.WriteLine("Please enter two valid conversion types \n"); break; } line = convert.ReadLine(); } } The file consists of the following: ounce,gram,28.0 pound,ounce,16.0 pound,kilogram,0.454 pint,litre,0.568 inch,centimetre,2.5 mile,inch,63360.0 The user will input something like 6,ounce,gram The idea is that it finds the correct line by checking if the first and second words in the file are the same as the second and third the user enters. The problem is that if it checks the first line and it fails the if statement, if goes through to the else statement and stops. I am trying to find a way where it will stop after the it finds the correct line but not until. If someone types in a value that isn't in the file, then it should show an error.

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  • Java Matrix Transpose strangeness going on

    - by user1459976
    ok so im making my own Matrix class. and i have a transpose method that transposes a matrix. this is the block in the main method Matrix m1 = new Matrix(4,2); m1.fillMatrix(1,2,3,4,5,6,7,8); System.out.println("before " + m1.toString()); m1.transpose(); System.out.println("after " + m1.toString()); this is where it gets messed up, at m1.transpose(); in the transpose() method public Matrix transpose() { if(isMatrix2) { Matrix tempMatrix = new Matrix(row, col); // matrix2 contents are emptied once this line is executed for(int i=0; i < row; i++) { for(int j=0; j < col; j++) tempMatrix.matrix2[i][j] = matrix2[i][j]; } so for some reason, the tempMatrix.matrix2 has the same id as this.matrix2. so when the codes executes Matrix tempMatrix = new Matrix(row,col); then the contents of this.matrix2 is emptied. anyone know what might be going on here?

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  • Array loading with doubles in C

    - by user2892120
    I am trying to load a 3x8 array of doubles but my code keeps outputting 0.00 for all of the values. The code should be outputting the array (same as the input) under the Read#1 Read#2 Read#3 lines, with the average under average. Here is my code: #include <stdio.h> double getAvg(double num1, double num2, double num3); int main() { int numJ,month,day,year,i,j; double arr[3][8]; scanf("%d %d %d %d",&numJ,&month,&day,&year); for (i = 0; i < 8; i++) { scanf("%f %f %f",&arr[i][0], &arr[i][1], &arr[i][2]); } printf("\nJob %d Date: %d/%d/%d",numJ,month,day,year); printf("\n\nLocation Read#1 Read#2 Read#3 Average"); for (j = 0; j < 8; j++) { printf("\n %d %.2f %.2f %.2f %.2f",j+1,arr[j][0],arr[j] [1],arr[j][2],getAvg(arr[j][0],arr[j][1],arr[j][2])); } return 0; } double getAvg(double num1, double num2, double num3) { double avg = (num1 + num2 + num3) / 3; return avg; } Input example: 157932 09 01 2013 0.00 0.00 0.00 0.36 0.27 0.23 0.18 0.16 0.26 0.27 0.00 0.34 0.24 0.00 0.31 0.16 0.33 0.36 0.29 0.36 0.00 0.21 0.36 0.00

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  • How to receive sms from a special phone number?

    - by Pariya
    I wrote a send and receive sms in android successfully. I want my program to be able to receive sms from a special number("+9856874236"). But, if the SMS is from any other number, it should go to the phone's message inbox and not to my application. import android.content.BroadcastReceiver; import android.content.Context; import android.content.Intent; import android.os.Bundle; import android.telephony.SmsMessage; import android.util.Log; public class SmsReceiver extends BroadcastReceiver { public String str = ""; @Override public void onReceive(Context context, Intent intent) { Bundle bundle = intent.getExtras(); Object messages[] = (Object[]) bundle.get("pdus"); SmsMessage[] msgs = null; if (bundle != null) { Object[] pdus = (Object[]) bundle.get("pdus"); SmsMessage smsMessage[] = new SmsMessage[messages.length]; String msg_from=""; for (int n = 0; n < messages.length; n++) { smsMessage[n] = SmsMessage.createFromPdu((byte[]) messages[n]); msg_from += msgs[n].getOriginatingAddress(); } String receivedMessage = smsMessage[0].getMessageBody().toString().toUpperCase(); if(msg_from .equals("+989124236870")) { for (int n = 0; n < messages.length; n++) { smsMessage[n] = SmsMessage.createFromPdu((byte[]) pdus[n]); str += "SMS from " + msgs[n].getOriginatingAddress(); str += " :"; //str += "sms az shomare makhsus"; str += msgs[n].getMessageBody().toString(); str += "\n"; abortBroadcast(); } Intent act = new Intent(context, MainActivity.class); act.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK); act.putExtra("message", str); context.startActivity(act); } } } }

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  • Fluent NHibernate Mappings ClassMap<Entities>....

    - by Pandiya Chendur
    I was going through fluent hibernate getting started tutorial.... In my asp.net mvc web application i have created Entities and Mapping folder as they stated... I created an entity class and i tried to map it my mapping class using this, using System; using System.Collections.Generic; using System.Linq; using System.Web; using FluentNhibernateMVC.Entities; namespace FluentNhibernateMVC.Mappings { public class ClientMap : ClassMap<Client> { } } I cant able to find a ClassMap keyword in my autosuggest list why? This is my entity class using System; using System.Collections.Generic; using System.Linq; using System.Web; namespace FluentNhibernateMVC.Entities { public class Client { public int ClientId { get; set; } public string ClientName { get; set; } public string ClientMobNo { get; set; } public string ClientAddress { get; set; } public DateTime CreatedDate { get; set; } public byte IsDeleted { get; set; } public int CreatedBy { get; set; } } } I have added all references to my project...Am i missing some thing...

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  • Why do I need to close fds when reading and writing to the pipe?

    - by valentimsousa
    However, what if one of my processes needs to continuously write to the pipe while the other pipe needs to read? This example seems to work only for one write and one read. I need multi read and write void executarComandoURJTAG(int newSock) { int input[2], output[2], estado, d; pid_t pid; char buffer[256]; char linha[1024]; pipe(input); pipe(output); pid = fork(); if (pid == 0) {// child close(0); close(1); close(2); dup2(input[0], 0); dup2(output[1], 1); dup2(output[1], 2); close(input[1]); close(output[0]); execlp("jtag", "jtag", NULL); } else { // parent close(input[0]); close(output[1]); do { read(newSock, linha, 1024); /* Escreve o buffer no pipe */ write(input[1], linha, strlen(linha)); close(input[1]); while ((d = read(output[0], buffer, 255))) { //buffer[d] = '\0'; write(newSock, buffer, strlen(buffer)); puts(buffer); } write(newSock, "END", 4); } while (strcmp(linha, "quit") != 0); } }

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  • How to convert a lambda to an std::function using templates

    - by retep998
    Basically, what I want to be able to do is take a lambda with any number of any type of parameters and convert it to an std::function. I've tried the following and neither method works. std::function([](){});//Complains that std::function is missing template parameters template <typename T> void foo(function<T> f){} foo([](){});//Complains that it cannot find a matching candidate The following code does work however, but it is not what I want because it requires explicitly stating the template parameters which does not work for generic code. std::function<void()>([](){}); I've been mucking around with functions and templates all evening and I just can't figure this out, so any help would be much appreciated. As mentioned in a comment, the reason I'm trying to do this is because I'm trying to implement currying in C++ using variadic templates. Unfortunately, this fails horribly when using lambdas. For example, I can pass a standard function using a function pointer. template <typename R, typename...A> void foo(R (*f)(A...)) {} void bar() {} int main() { foo(bar); } However, I can't figure out how to pass a lambda to such a variadic function. Why I'm interested in converting a generic lambda into an std::function is because I can do the following, but it ends up requiring that I explicitly state the template parameters to std::function which is what I am trying to avoid. template <typename R, typename...A> void foo(std::function<R(A...)>) {} int main() { foo(std::function<void()>([](){})); }

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  • insert data using sqlite issue on iphone ( not reflecting on table)

    - by prajakta
    i can insert my data but i cant show them on my table view ..i did [tableview reload data] but of no success here is my code -(void)gButtonTapped:(id)sender { NSLog(@"right nav bar button is hit%@ ",storePaths); //[self readAnimalsFromDatabase2]; appDelegate = (DatabaseTestAppDelegate *)[[UIApplication sharedApplication] delegate]; sqlite3 *database; sqlite3_stmt *compiled_statement1; if(sqlite3_open([storePaths UTF8String], &database) == SQLITE_OK) { //const char *sqlStatement = NSString *newQuery = [NSString stringWithFormat:@"insert into cat_tbl (cat_id,names,imgs) values ('12','test1','r.png')"]; // NSString *newQuery = [NSString stringWithFormat:@"select * from list_tbl"]; const char *sql = [newQuery cStringUsingEncoding:NSASCIIStringEncoding]; NSLog(@"update query is %@",newQuery); if(sqlite3_prepare_v2(database, sql, -1, &compiled_statement1, NULL) == SQLITE_OK) { int result = sqlite3_step(compiled_statement1); sqlite3_reset(compiled_statement1); NSLog(@"result %d", result); if(result != SQLITE_ERROR) { int lastInsertId = sqlite3_last_insert_rowid(database); NSLog(@"x %d", lastInsertId); } } } sqlite3_finalize(compiled_statement1); sqlite3_close(database); [tabelView reloadData];// this is also not working }

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  • C++, generic programming and virtual functions. How do I get what I want?

    - by carleeto
    This is what I would like to do using templates: struct op1 { virtual void Method1() = 0; } ... struct opN { virtual void MethodN() = 0; } struct test : op1, op2, op3, op4 { virtual void Method1(){/*do work1*/}; virtual void Method2(){/*do work2*/}; virtual void Method3(){/*do work3*/}; virtual void Method4(){/*do work4*/}; } I would like to have a class that simply derives from a template class that provides these method declarations while at the same time making them virtual. This is what I've managed to come up with: #include <iostream> template< size_t N > struct ops : ops< N - 1 > { protected: virtual void DoStuff(){ std::cout<<N<<std::endl; }; public: template< size_t i > void Method() { if( i < N ) ops<i>::DoStuff(); } //leaving out compile time asserts for brevity } struct test : ops<6> { }; int main( int argc, char ** argv ) { test obj; obj.Method<3>(); //prints 3 return 0; } However, as you've probably guessed, I am unable to override any of the 6 methods I have inherited. I'm obviously missing something here. What is my error? No, this isn't homework. This is curiosity.

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  • stdio data from write not making it into a file

    - by user1551209
    I'm having a problem with using stdio commands for manipulating data in a file. I short, when I write data into a file, write returns an int indicating that it was successful, but when I read it back out I only get the old data. Here's a stripped down version of the code: fd = open(filename,O_RDWR|O_APPEND); struct dE *cDE = malloc(sizeof(struct dE)); //Read present data printf("\nreading values at %d\n",off); printf("SeekStatus <%d>\n",lseek(fd,off,SEEK_SET)); printf("ReadStatus <%d>\n",read(fd,cDE,deSize)); printf("current Key/Data <%d/%s>\n",cDE->key,cDE->data); printf("\nwriting new values\n"); //Change the values locally cDE->key = //something new cDE->data = //something new //Write them back printf("SeekStatus <%d>\n",lseek(fd,off,SEEK_SET)); printf("WriteStatus <%d>\n",write(fd,cDE,deSize)); //Re-read to make sure that it got written back printf("\nre-reading values at %d\n",off); printf("SeekStatus <%d>\n",lseek(fd,off,SEEK_SET)); printf("ReadStatus <%d>\n",read(fd,cDE,deSize)); printf("current Key/Data <%d/%s>\n",cDE->key,cDE->data); Furthermore, here's the dE struct in case you're wondering: struct dE { int key; char data[DataSize]; }; This prints: reading values at 1072 SeekStatus <1072> ReadStatus <32> current Key/Data <27/old> writing new values SeekStatus <1072> WriteStatus <32> re-reading values at 1072 SeekStatus <1072> ReadStatus <32> current Key/Data <27/old>

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  • VC9 C1083 Cannot open include file: 'boost...' after trying to abstract an include dependency

    - by ronivek
    Hey, So I've been working on a project for the past number of weeks and it uses a number of Boost libraries. In particular I'm using the boost::dynamic_bitset library quite extensively. I've had zero issues up until now; but tonight I discovered a dependency between some includes which I had to resolve; and I tried to do so by providing an abstract callback class. Effectively I now have the following: First include... class OtherClassCallback { public: virtual int someOtherMethod() const = 0; }; class SomeClass { public: void someMethod(OtherClassCallback *oc) { ... oc->someOtherMethod(); ... } }; Second include... #include "SomeClass.h" class SomeOtherClass : public OtherClassCallback { public: int someOtherMethod() const { return this->someInt; } }; Here is the issue; ever since I implemented this class I'm now getting the following error: fatal error C1083: Cannot open include file: 'boost/dynamic_bitset/dynamic_bitset.hpp': No such file or directory Now I'm getting no other compiler errors; and it's a pretty substantial project. My include paths and so on are perfect; my files are fully accessible and removing the changes fixes the issue. Does anyone have any idea what might be going on? I'm compiling to native Windows executables in VS9. I should confess that I'm very inexperienced with C++ in general so go easy on me if it's something horribly straightforward; I can't figure it out.

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