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• C pointer to array/array of pointers disambiguation

  - by Richard J. Terrell

  What is the difference between the following declarations: int* arr1[8]; int (*arr2)[8]; int *(arr3[8]); What is the general rule for understanding more complex declarations?

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• MS Access to sql server searching

  - by malou17

  How to use this code if we are going to use sql server database becaUSE in this code we used MS Access as the database private void btnSearch_Click(object sender, System.EventArgs e) { String pcode = txtPcode.Text; int ctr = productsDS1.Tables[0].Rows.Count; int x; bool found = false; for (x = 0; x<ctr; x++) { if (productsDS1.Tables[0].Rows[x][0].ToString() == pcode) { found = true; break; } } if (found == true) { txtPcode.Text = productsDS1.Tables[0].Rows[x][0].ToString(); txtDesc.Text = productsDS1.Tables[0].Rows[x][1].ToString(); txtPrice.Text = productsDS1.Tables[0].Rows[x][2].ToString(); } else { MessageBox.Show("Record Not Found"); } private void btnNew_Click(object sender, System.EventArgs e) { int cnt = productsDS1.Tables[0].Rows.Count; string lastrec = productsDS1.Tables[0].Rows[cnt][0].ToString(); int newpcode = int.Parse(lastrec) + 1; txtPcode.Text = newpcode.ToString(); txtDesc.Clear(); txtPrice.Clear(); txtDesc.Focus(); here's the connectionstring Jet OLEDB:Global Partial Bulk Ops=2;Jet OLEDB:Registry Path=;Jet OLEDB:Database Locking Mode=0;Data Source="J:\2009-2010\1st sem\VC#\Sample\WindowsApplication_Products\PointOfSales.mdb"

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• How to explain method calls?

  - by forki23

  Hi, let's consider a small method: int MyFunction(string foo, int bar) { ... } and some calls: MyFunction("",0) int x = MyFunction(foo1,bar1) How would you explain this to a non-technical persons? Has anybody a nice metaphor? I tried to explain method calling (or function application) several times, but I failed. Seems I can't find the right words here. Regards, forki

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• Public class DiscoLight help

  - by luvthug

  Hi All, If some one can point me in the right direction for this code for my assigment I would really appreciate it. I have pasted the whole code that I need to complete but I need help with the following method public void changeColour(Circle aCircle) which is meant to allow to change the colour of the circle randomly, if 0 comes the light of the circle sgould change to red, 1 for green and 2 for purple. public class DiscoLight { /* instance variables */ private Circle light; // simulates a circular disco light in the Shapes window private Random randomNumberGenerator; /** * Default constructor for objects of class DiscoLight */ public DiscoLight() { super(); this.randomNumberGenerator = new Random(); } /** * Returns a randomly generated int between 0 (inclusive) * and number (exclusive). For example if number is 6, * the method will return one of 0, 1, 2, 3, 4, or 5. */ public int getRandomInt(int number) { return this.randomNumberGenerator.nextInt(number); } /** * student to write code and comment here for setLight(Circle) for Q4(i) */ public void setLight(Circle aCircle) { this.light = aCircle; } /** * student to write code and comment here for getLight() for Q4(i) */ public Circle getLight() { return this.light; } /** * Sets the argument to have a diameter of 50, an xPos * of 122, a yPos of 162 and the colour GREEN. * The method then sets the receiver's instance variable * light, to the argument aCircle. */ public void addLight(Circle aCircle) { //Student to write code here, Q4(ii) this.light = aCircle; this.light.setDiameter(50); this.light.setXPos(122); this.light.setYPos(162); this.light.setColour(OUColour.GREEN); } /** * Randomly sets the colour of the instance variable * light to red, green, or purple. */ public void changeColour(Circle aCircle) { //student to write code here, Q4(iii) if (getRandomInt() == 0) { this.light.setColour(OUColour.RED); } if (this.getRandomInt().equals(1)) { this.light.setColour(OUColour.GREEN); } else if (this.getRandomInt().equals(2)) { this.light.setColour(OUColour.PURPLE); } } /** * Grows the diameter of the circle referenced by the * receiver's instance variable light, to the argument size. * The diameter is incremented in steps of 2, * the xPos and yPos are decremented in steps of 1 until the * diameter reaches the value given by size. * Between each step there is a random colour change. The message * delay(anInt) is used to slow down the graphical interface, as required. */ public void grow(int size) { //student to write code here, Q4(iv) } /** * Shrinks the diameter of the circle referenced by the * receiver's instance variable light, to the argument size. * The diameter is decremented in steps of 2, * the xPos and yPos are incremented in steps of 1 until the * diameter reaches the value given by size. * Between each step there is a random colour change. The message * delay(anInt) is used to slow down the graphical interface, as required. */ public void shrink(int size) { //student to write code here, Q4(v) } /** * Expands the diameter of the light by the amount given by * sizeIncrease (changing colour as it grows). * * The method then contracts the light until it reaches its * original size (changing colour as it shrinks). */ public void lightCycle(int sizeIncrease) { //student to write code here, Q4(vi) } /** * Prompts the user for number of growing and shrinking * cycles. Then prompts the user for the number of units * by which to increase the diameter of light. * Method then performs the requested growing and * shrinking cycles. */ public void runLight() { //student to write code here, Q4(vii) } /** * Causes execution to pause by time number of milliseconds */ private void delay(int time) { try { Thread.sleep(time); } catch (Exception e) { System.out.println(e); } } }

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• basic c# question

  - by CoffeeCode

  why doesn't the element get swapped public static void SwapArray(ref int[,] arr) { for (int i = 0; i < arr.GetLength(0); i++) { for (int j = 0; j < arr.GetLength(0); j++) { int temp = arr[i, j]; arr[i, j] = arr[j, i]; arr[j, i] = temp; Console.Write(arr[i, j] + " "); } Console.WriteLine(); } } even if the parameter is without a ref modifier the array doesn't change. a copy of the reference is passed as a parameter right?

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• Displaying Array in Select - FORM API Drupal

  - by Krishma

  Hi: I want to add key(type_id) and value(type_description) to select in drupal form API $result_x-product_types-RPMProductType is array result from Database :- array(4) { [0]= object(stdClass)#18 (2) { ["type_description"]= string(10) "Calendered" ["type_id"]= int(1) } [1]= object(stdClass)#19 (2) { ["type_description"]= string(8) "Extruded" ["type_id"]= int(2) } [2]= object(stdClass)#20 (2) { ["type_description"]= string(6) "Molded" ["type_id"]= int(3) } [3]= object(stdClass)#21 (2) { ["type_description"]= string(5) "Other" ["type_id"]= int(4) } } foreach ($result_x-product_types-RPMProductType as $data) { $form['manufacturer_add_new_sales']['product_type'] = array( '#type' = 'select', '#title' = t('Product Type'), '#options'=array($data-type_id=$data-type_description), ); } When do so I am getting only last value i.e Other. How to correctly loop to bind Select to display all the array Key - Values. Thank you in advance.

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• Problems compiliing c++ code using cygwin

  - by user343403

  I am trying to compile some source code in cygwin (in windows 7) and get the following error when I run the make file g++ -DHAVE_CONFIG_H -I. -I.. -I.. -Wall -Wextra -Werror -g -O2 -MT libcommon_a Fcntl.o -MD -MP -MF .deps/libcommon_a-Fcntl.Tpo -c -o libcommon_a-Fcntl.o `test -f 'Fcntl.cpp' || echo './'`Fcntl.cpp Fcntl.cpp: In function int setCloexec(int): Fcntl.cpp:8: error: 'F_GETFD' was not declared in this scope Fcntl.cpp:8: error: 'fcntl' was not declared in this scope Fcntl.cpp:11: error: 'FD_CLOEXEC' was not declared in this scope Fcntl.cpp:12: error: 'F_SETFD' was not declared in this scope make[4]: *** [libcommon_a-Fcntl.o] Error 1 make[4]: Leaving directory `/abyss-1.1.2/Common' make[3]: *** [all-recursive] Error 1 make[3]: Leaving directory `/abyss-1.1.2' make[2]: *** [all] Error 2 make[2]: Leaving directory `/abyss-1.1.2' make[1]: *** [.build-conf] Error 2 make[1]: Leaving directory `/cygdrive/c/Users/Martin/Documents/NetBeansProjects/abyss-1.1.2_1' make: *** [.build-impl] Error 2 The problem file is:- #include "Fcntl.h" #include <fcntl.h> /* Set the FD_CLOEXEC flag of the specified file descriptor. */ int setCloexec(int fd) { int flags = fcntl(fd, F_GETFD, 0); if (flags == -1) return -1; flags |= FD_CLOEXEC; return fcntl(fd, F_SETFD, flags); } I don't understand what is going on, the file fcntl.h is available and the varaiables that it says were not declared in this scope do not give an error when I compile the file on its own Any help would be much appreciated Many Thanks

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• Sockets receiving null (Android)

  - by Henrik

  I have a android app that is communicating with a server (written in java). Between these two parts I have established a Socket connection and want to send data. The problem I am having is that sometimes, for some users, the information that reaches the server is null. This works (for all phones, all users): Server: int a = Integer.parseInt(in.readLine()); int b = Integer.parseInt(in.readLine()); int c = Integer.parseInt(in.readLine()); int d = Integer.parseInt(in.readLine()); String checksum = in.readLine(); String model = in.readLine(); String device = in.readLine(); String name = in.readLine(); Client: out.println(a); out.println(b); out.println(c); out.println(d); out.println(hash); out.println(Build.MODEL); out.println(Build.DEVICE); String name = fixName(); out.print(name); out.flush(); This does not work (for some users): Server: int a = Integer.parseInt(in.readLine()); String checksum = in.readLine(); String model = in.readLine(); String device = in.readLine(); String name = in.readLine(); String msg = in.readLine(); int version = -1; String test = "hej"; try{ test = in.readLine(); version = Integer.parseInt(test); }catch(Exception e){ e.printStackTrace(); } Client: out.println(a); out.println(hash); out.println(Build.MODEL); out.println(Build.DEVICE); String name = fixName(); if(name == null) name = "John Doe"; out.println(name); String msg = fixMsg(); if(msg == null) name = "nada"; out.println(msg); out.println(curversion); out.flush(); Sometimes, in the second case, the name, msg, and version (the string test) are null at the server side. The catch is triggered because test is null. curversion,a are ints, the rest are strings. Any ideas?

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• How do you write interrupts in assembly?

  - by Daywalker

  I need to how the int 13h and int 16h are written.where to find Assembly source codes of them thanks

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• NSTimer calculate hours

  - by Nic Hubbard

  I am using an NSTimer which I have working to show minutes and seconds. But I am confused about the math needed to calculate hours. I am using: - (void)updateCounter:(NSTimer *)theTimer { static int count = 0; count += 1; int seconds = count % 60; int minutes = (count - seconds) / 60; // Not sure how to calculate hours int hours = (count - minutes) / 60; self.timer.text = [NSString stringWithFormat:@"%.2d:%.2d:%.2d", hours, minutes, seconds]; } What calculation should I use for hours?

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• try catch finally

  - by gligom

  Maby this is simple for you, but for me is not. I have this code: Private int InsertData() { int rezultat = 0; try { if (sqlconn.State != ConnectionState.Open) { sqlconn.Open(); } rezultat = (int)cmd.ExecuteScalar(); } catch (Exception ex) { lblMesaje.Text = "Eroare: " + ex.Message.ToString(); } finally { if (sqlconn.State != ConnectionState.Closed) { sqlconn.Close(); } } return rezultat; } Is just for inserting a new record in a table. Even if this throw an error "Specified cast is not valid." "rezultat=(int)cmd.ExecuteScalar();" - the code is executed and the row is inserted in the database, and the execution continues. Why it continues? Maby i don't understand the try catch finally yet Smile | :) Thank you!

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• c# Resize Function

  - by Tyler

  So my logic is flawed and I need a better and correct way to resize an image in my c# app I need a function similar to this setup public void ResizeImageForWeb(string OriginalFile, string NewFile, int MaxWidth, int MaxHeight, int Quality) { // Resize Code } Basically, I'm a web designer lost trying to programming a desktop app.

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• CakePHP. How can i make a model test in a table with another primary key?

  - by Marcelo

  I have this table CREATE TABLE myexamples.problems ( id INT, name VARCHAR(45) NULL , pk_id INT AUTO_INCREMENT PRIMARY KEY ); But when I try test a model in cakephp, it fails because the table has two autoincrement attributes. The following query CREATE TABLE `test_suite_problems` ( `id` int(11) NOT NULL AUTO_INCREMENT, `name` varchar(45) DEFAULT NULL, `pk_id` int(11) NOT NULL AUTO_INCREMENT, PRIMARY KEY (`pk_id`) ) DEFAULT CHARSET=latin1, COLLATE=latin1_swedish_ci, ENGINE=InnoDB; raise this error: "1075: Incorrect table definition; there can be only one auto column and it must be defined as a key" I have in the model class <?php class Problem extends AppModel { var $name = 'Problem'; var $displayField = 'name'; var $primaryKey='problems'; } ?> But I don't know how to make the field ID not having an autoincrement attribute, and I can't change the table structure.

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• Returning the element number of the longest string in an array

  - by JohnRoberts

  I'm trying to get the longestS method to take the user-inputted array of strings, then return the element number of the longest string in that array. I got it to the point where I was able to return the number of chars in the longest string, but I don't believe that will work for what I need. My problem is that I keep getting incompatible type errors when trying to figure this out. I don't understand the whole data type thing with strings yet. It's confusing me how I go about return a number of the array yet the array is of strings. The main method is fine, I got stuck on the ???? part. { public static void main(String [] args) { Scanner inp = new Scanner( System.in ); String [] responseArr= new String[4]; for (int i=0; i<4; i++) { System.out.println("Enter string "+(i+1)); responseArr[i] = inp.nextLine(); } int highest=longestS(responseArr); } public static int longestS(String[] values) { int largest=0 for( int i = 1; i < values.length; i++ ) { if ( ????? ) } return largest; } }

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• Optimising movement on hex grid

  - by Mloren

  I am making a turn based hex-grid game. The player selects units and moves them across the hex grid. Each tile in the grid is of a particular terrain type (eg desert, hills, mountains, etc) and each unit type has different abilities when it comes to moving over the terrain (e.g. some can move over mountains easily, some with difficulty and some not at all). Each unit has a movement value and each tile takes a certain amount of movement based on its terrain type and the unit type. E.g it costs a tank 1 to move over desert, 4 over swamp and cant move at all over mountains. Where as a flying unit moves over everything at a cost of 1. The issue I have is that when a unit is selected, I want to highlight an area around it showing where it can move, this means working out all the possible paths through the surrounding hexes, how much movement each path will take and lighting up the tiles based on that information. I got this working with a recursive function and found it took too long to calculate, I moved the function into a thread so that it didn't block the game but still it takes around 2 seconds for the thread to calculate the moveable area for a unit with a move of 8. Its over a million recursions which obviously is problematic. I'm wondering if anyone has an clever ideas on how I can optimize this problem. Here's the recursive function I'm currently using (its C# btw): private void CalcMoveGridRecursive(int nCenterIndex, int nMoveRemaining) { //List of the 6 tiles adjacent to the center tile int[] anAdjacentTiles = m_ThreadData.m_aHexData[nCenterIndex].m_anAdjacentTiles; foreach(int tileIndex in anAdjacentTiles) { //make sure this adjacent tile exists if(tileIndex == -1) continue; //How much would it cost the unit to move onto this adjacent tile int nMoveCost = m_ThreadData.m_anTerrainMoveCost[(int)m_ThreadData.m_aHexData[tileIndex].m_eTileType]; if(nMoveCost != -1 && nMoveCost <= nMoveRemaining) { //Make sure the adjacent tile isnt already in our list. if(!m_ThreadData.m_lPassableTiles.Contains(tileIndex)) m_ThreadData.m_lPassableTiles.Add(tileIndex); //Now check the 6 tiles surrounding the adjacent tile we just checked (it becomes the new center). CalcMoveGridRecursive(tileIndex, nMoveRemaining - nMoveCost); } } } At the end of the recursion, m_lPassableTiles contains a list of the indexes of all the tiles that the unit can possibly reach and they are made to glow. This all works, it just takes too long. Does anyone know a better approach to this?

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• Time Stamp and byte array

  - by JB_SO

  Hi, I'm trying to insert a timestamp (hour:min:sec) into a two-byte array and i'm a little confused on how to accomplish this...any help is greatly appreciated! int Hour = CTime::GetCurrentTime().GetHour(); int Minute = CTime::GetCurrentTime().GetMinute(); int Second = CTime::GetCurrentTime().GetSecond(); BYTE arry[2]; //Need to insert 'Hour', 'Minute', & 'Second' into 'arry' Thanks!

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• Problem while inserting data from GUI layer to database

  - by Rahul

  Hi all, I am facing problem while i am inserting new record from GUI part to database table. I have created database table Patient with id, name, age etc....id is identity primary key. My problem is while i am inserting duplicate name in table the control should go to else part, and display the message like...This name is already exits, pls try with another name... but in my coding not getting..... Here is all the code...pls somebody point me out whats wrong or how do this??? GUILayer: protected void BtnSubmit_Click(object sender, EventArgs e) { if (!Page.IsValid) return; int intResult = 0; string name = TxtName.Text.Trim(); int age = Convert.ToInt32(TxtAge.Text); string gender; if (RadioButtonMale.Checked) { gender = RadioButtonMale.Text; } else { gender = RadioButtonFemale.Text; } string city = DropDownListCity.SelectedItem.Value; string typeofdisease = ""; foreach (ListItem li in CheckBoxListDisease.Items) { if (li.Selected) { typeofdisease += li.Value; } } typeofdisease = typeofdisease.TrimEnd(); PatientBAL PB = new PatientBAL(); PatientProperty obj = new PatientProperty(); obj.Name = name; obj.Age = age; obj.Gender = gender; obj.City = city; obj.TypeOFDisease = typeofdisease; try { intResult = PB.ADDPatient(obj); if (intResult > 0) { lblMessage.Text = "New record inserted successfully."; TxtName.Text = string.Empty; TxtAge.Text = string.Empty; RadioButtonMale.Enabled = false; RadioButtonFemale.Enabled = false; DropDownListCity.SelectedIndex = 0; CheckBoxListDisease.SelectedIndex = 0; } else { lblMessage.Text = "Name [<b>" + TxtName.Text + "</b>] alredy exists, try another name"; } } catch (Exception ex) { lblMessage.Text = ex.Message.ToString(); } finally { obj = null; PB = null; } } BAL layer: public class PatientBAL { public int ADDPatient(PatientProperty obj) { PatientDAL pdl = new PatientDAL(); try { return pdl.InsertData(obj); } catch { throw; } finally { pdl=null; } } } DAL layer: public class PatientDAL { public string ConString = ConfigurationManager.ConnectionStrings["ConString"].ConnectionString; public int InsertData(PatientProperty obj) { SqlConnection con = new SqlConnection(ConString); con.Open(); SqlCommand com = new SqlCommand("LoadData",con); com.CommandType = CommandType.StoredProcedure; try { com.Parameters.AddWithValue("@Name", obj.Name); com.Parameters.AddWithValue("@Age",obj.Age); com.Parameters.AddWithValue("@Gender",obj.Gender); com.Parameters.AddWithValue("@City", obj.City); com.Parameters.AddWithValue("@TypeOfDisease", obj.TypeOFDisease); return com.ExecuteNonQuery(); } catch { throw; } finally { com.Dispose(); con.Close(); } } } Property Class: public class PatientProperty { private string name; private int age; private string gender; private string city; private string typedisease; public string Name { get { return name; } set { name = value; } } public int Age { get { return age; } set { age = value; } } public string Gender { get { return gender; } set { gender = value; } } public string City { get { return city; } set { city = value; } } public string TypeOFDisease { get { return typedisease; } set { typedisease = value; } } } This is my stored Procedure: CREATE PROCEDURE LoadData ( @Name varchar(50), @Age int, @Gender char(10), @City char(10), @TypeofDisease varchar(50) ) as insert into Patient(Name, Age, Gender, City, TypeOfDisease)values(@Name,@Age, @Gender, @City, @TypeofDisease) GO

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• Django Comments and Users integration

  - by Patrick

  Hi folks, I am new to django. I am trying to use django.contrib.comments, I saw the table in the database like this, but how can I integrate it with user_id, user_photos, user_name, user_email....and those things with the django commenting system? I also tried to use thread-comments, but I can't configure it properly, is the django threadedcomments table similar to following ? Please let me know if any of you have done this before....all I need is a user login, and post comments, and then show list of comments with users' profile photos and username, as well as there comments. I think shouldn't be that hard. Thank you very much again. +-----------------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-----------------+--------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | content_type_id | int(11) | NO | MUL | NULL | | | object_pk | longtext | NO | | NULL | | | site_id | int(11) | NO | MUL | NULL | | | user_id | int(11) | YES | MUL | NULL | | | user_name | varchar(50) | NO | | NULL | | | user_email | varchar(75) | NO | | NULL | | | user_url | varchar(200) | NO | | NULL | | | comment | longtext | NO | | NULL | | | submit_date | datetime | NO | | NULL | | | ip_address | char(15) | YES | | NULL | | | is_public | tinyint(1) | NO | | NULL | | | is_removed | tinyint(1) | NO | | NULL | | +-----------------+--------------+------+-----+---------+----------------+

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• Image resizing - sometimes very poor quality?!

  - by eWolf

  I'm resizing some images to the screen resolution of the user; if the aspect ratio is wrong, the image should be cut. My code looks like this: protected void ConvertToBitmap(string filename) { var origImg = System.Drawing.Image.FromFile(filename); var widthDivisor = (double)origImg.Width / (double)System.Windows.Forms.Screen.PrimaryScreen.Bounds.Width; var heightDivisor = (double)origImg.Height / (double)System.Windows.Forms.Screen.PrimaryScreen.Bounds.Height; int newWidth, newHeight; if (widthDivisor < heightDivisor) { newWidth = (int)((double)origImg.Width / widthDivisor); newHeight = (int)((double)origImg.Height / widthDivisor); } else { newWidth = (int)((double)origImg.Width / heightDivisor); newHeight = (int)((double)origImg.Height / heightDivisor); } var newImg = origImg.GetThumbnailImage(newWidth, newHeight, null, IntPtr.Zero); newImg.Save(this.GetBitmapPath(filename), System.Drawing.Imaging.ImageFormat.Bmp); } In most cases, this works fine. But for some images, the result has an extremely poor quality. It looks like the would have been resized to something very small (thumbnail size) and enlarged again.. But the resolution of the image is correct. What can I do? Example orig image: Example resized image: Note: I have a WPF application but I use the WinForms function for resizing because it's easier and because I already need a reference to System.Windows.Forms for a tray icon.

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• How to handle an "infinite" IEnumerable?

  - by Danvil

  A trivial example of an "infinite" IEnumerable would be IEnumerable<int> Numbers() { int i=0; while(true) { yield return i++; } } I know, that foreach(int i in Numbers().Take(10)) { Console.WriteLine(i); } and var q = Numbers(); foreach(int i in q.Take(10)) { Console.WriteLine(i); } both work fine (and print out the number 0-9). But are there any pitfalls when copying or handling expressions like q? Can I rely on the fact, that they are always evaluated "lazy"? Is there any danger to produce an infinite loop?

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• Intellij IDEA: How can I format the code and how can I see the changes made?

  - by aaron

  Cand I make the format code option to do something like this: Before int a = 1; int b = 2; return a+b; After int a = 1; int b = 2; return a+b; Second Question: I have a web app. I start the web app and after that, I made a change in a java file. How can I see the change, without stoping and restarting the server - a shorter method?

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• Arduino crashes when sending bytes from Java [on hold]

  - by francisaugusto

  I used the sample program from the arduino website in order to send and receive data via serial to my Arduino one. However, for some reason, even when I try to send only one byte, the Arduino crashes after a while. It doesn't happen if I send the chars manually via the IDE's own serial monitor. I wrote the following method to output the character to Arduino: public synchronized void serialWrite(char sendIt){ try { output.write((byte)'0'); output.flush(); for (int j=0;j<1000000000;j++){ } }catch (Exception e){System.out.println("Not connected...");} notify(); } What I try above is to send just one character when the method is called. I send just a '0' char for testing. After manually calling the method two or three times, Arduino crashes. Is there anything I should be looking into? The Arduino code: #include <SoftwareSerial.h> int buttonState=0; int lastButtonState=0; int buttonPushCounter=0; long previousMillis=0; long interval=250; int ledState=LOW; int ledState2=LOW; int ledState3=LOW; long timeElapsed=0; SoftwareSerial portOne(10,11); void setup(){ pinMode(3,OUTPUT); pinMode(4,OUTPUT); pinMode(5,OUTPUT); pinMode(2,INPUT); Serial.begin(9600); portOne.begin(9600); } boolean turnoff; void loop(){ if(portOne.overflow()){ Serial.println("There's an overflow here!"); } buttonState= digitalRead(2); if(buttonState!=lastButtonState){ if (buttonState==HIGH){ buttonPushCounter++; } } lastButtonState=buttonState; if (turnoff){ unsigned long currentMillis=millis(); if (currentMillis-previousMillis>0 && currentMillis-previousMillis<interval){ ledState=HIGH; ledState2=LOW; ledState3=LOW; }else if (currentMillis-previousMillis>interval && currentMillis-previousMillis<interval*2){ ledState=LOW; ledState2=LOW; ledState3=HIGH; }else if (currentMillis-previousMillis>interval*2 && currentMillis-previousMillis<interval*3){ ledState=LOW; ledState2=HIGH; ledState3=LOW; }else if (currentMillis-previousMillis>interval*3){ previousMillis=currentMillis; } digitalWrite(3,ledState); digitalWrite(4,ledState2); digitalWrite(5,ledState3); }else{ digitalWrite(3,LOW); digitalWrite(4,LOW); digitalWrite(5,LOW); } if (buttonPushCounter==1){ Serial.print("Button pressed!\n"); turnoff=!turnoff; buttonPushCounter=0; } noInterrupts(); char ch=Serial.read(); delay(1); if(ch=='0'){ Serial.println("Changed by serial"+turnoff); Serial.println(ch); turnoff=!turnoff; } interrupts(); }

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• In C++, what is the scope resolution ("order of precedence") for shadowed variable names?

  - by Emile Cormier

  In C++, what is the scope resolution ("order of precedence") for shadowed variable names? I can't seem to find a concise answer online. For example: #include <iostream> int shadowed = 1; struct Foo { Foo() : shadowed(2) {} void bar(int shadowed = 3) { std::cout << shadowed << std::endl; // What does this output? { int shadowed = 4; std::cout << shadowed << std::endl; // What does this output? } } int shadowed; }; int main() { Foo().bar(); } I can't think of any other scopes where a variable might conflict. Please let me know if I missed one. What is the order of priority for all four shadow variables when inside the bar member function?

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• Why can't I reclaim my dynamically allocated memory using the "delete" keyword?

  - by synaptik

  I have the following class: class Patient { public: Patient(int x); ~Patient(); private: int* RP; }; Patient::Patient(int x) { RP = new int [x]; } Patient::~Patient() { delete [] RP; } I create an instance of this class on the stack as follows: void f() { Patient p(10); } Now, when f() returns, I get a "double free or corruption" error, which signals to me that something is attempted to be deleted more than once. But I don't understand why that would be so. The space for the array is created on the heap, and just because the function from inside which the space was allocated returns, I wouldn't expect the space to be reclaimed. I thought that if I allocate space on the heap (using the new keyword), then the only way to reclaim that space is to use the delete keyword. Help! :)

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• SetWindowHookEx and execution blocking

  - by Kalaz

  Hello, I just wonder... I mainly use .NET but now I started to investigate WINAPI calls. For example I am using this piece of code to hook to the API functions. It starts freezing, when I try to debug the application... using System; using System.Diagnostics; using System.Runtime.InteropServices; using System.Threading; using System.Windows.Forms; public class Keyboard { private const int WH_KEYBOARD_LL = 13; private const int WM_KEYDOWN = 0x0100; private static LowLevelKeyboardProc _proc = HookCallback; private static IntPtr _hookID = IntPtr.Zero; public static event Action<Keys,bool, bool> KeyDown; public static void Hook() { new Thread(new ThreadStart(()=> { _hookID = SetHook(_proc); Application.Run(); })).Start(); } public static void Unhook() { UnhookWindowsHookEx(_hookID); } private static IntPtr SetHook(LowLevelKeyboardProc proc) { using (Process curProcess = Process.GetCurrentProcess()) using (ProcessModule curModule = curProcess.MainModule) { return SetWindowsHookEx(WH_KEYBOARD_LL, proc, GetModuleHandle(curModule.ModuleName), 0); } } private delegate IntPtr LowLevelKeyboardProc( int nCode, IntPtr wParam, IntPtr lParam); private static IntPtr HookCallback( int nCode, IntPtr wParam, IntPtr lParam) { if (nCode >= 0 && wParam == (IntPtr)WM_KEYDOWN) { int vkCode = Marshal.ReadInt32(lParam); Keys k = (Keys) vkCode; if (KeyDown != null) { KeyDown.BeginInvoke(k, IsKeyPressed(VirtualKeyStates.VK_CONTROL), IsKeyPressed(VirtualKeyStates.VK_SHIFT),null,null); } } return CallNextHookEx(_hookID, nCode, wParam, lParam); } private static bool IsKeyPressed(VirtualKeyStates virtualKeyStates) { return (GetKeyState(virtualKeyStates) & (1 << 7))==128; } [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)] private static extern IntPtr SetWindowsHookEx(int idHook, LowLevelKeyboardProc lpfn, IntPtr hMod, uint dwThreadId); [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)] [return: MarshalAs(UnmanagedType.Bool)] private static extern bool UnhookWindowsHookEx(IntPtr hhk); [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)] private static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode, IntPtr wParam, IntPtr lParam); [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)] private static extern IntPtr GetModuleHandle(string lpModuleName); [DllImport("user32.dll")] static extern short GetKeyState(VirtualKeyStates nVirtKey); } enum VirtualKeyStates : int { VK_LBUTTON = 0x01, VK_RBUTTON = 0x02, VK_CANCEL = 0x03, VK_MBUTTON = 0x04, // VK_XBUTTON1 = 0x05, VK_XBUTTON2 = 0x06, // VK_BACK = 0x08, VK_TAB = 0x09, // VK_CLEAR = 0x0C, VK_RETURN = 0x0D, // VK_SHIFT = 0x10, VK_CONTROL = 0x11, VK_MENU = 0x12, VK_PAUSE = 0x13, VK_CAPITAL = 0x14, // VK_KANA = 0x15, VK_HANGEUL = 0x15, /* old name - should be here for compatibility */ VK_HANGUL = 0x15, VK_JUNJA = 0x17, VK_FINAL = 0x18, VK_HANJA = 0x19, VK_KANJI = 0x19, // VK_ESCAPE = 0x1B, // VK_CONVERT = 0x1C, VK_NONCONVERT = 0x1D, VK_ACCEPT = 0x1E, VK_MODECHANGE = 0x1F, // VK_SPACE = 0x20, VK_PRIOR = 0x21, VK_NEXT = 0x22, VK_END = 0x23, VK_HOME = 0x24, VK_LEFT = 0x25, VK_UP = 0x26, VK_RIGHT = 0x27, VK_DOWN = 0x28, VK_SELECT = 0x29, VK_PRINT = 0x2A, VK_EXECUTE = 0x2B, VK_SNAPSHOT = 0x2C, VK_INSERT = 0x2D, VK_DELETE = 0x2E, VK_HELP = 0x2F, // VK_LWIN = 0x5B, VK_RWIN = 0x5C, VK_APPS = 0x5D, // VK_SLEEP = 0x5F, // VK_NUMPAD0 = 0x60, VK_NUMPAD1 = 0x61, VK_NUMPAD2 = 0x62, VK_NUMPAD3 = 0x63, VK_NUMPAD4 = 0x64, VK_NUMPAD5 = 0x65, VK_NUMPAD6 = 0x66, VK_NUMPAD7 = 0x67, VK_NUMPAD8 = 0x68, VK_NUMPAD9 = 0x69, VK_MULTIPLY = 0x6A, VK_ADD = 0x6B, VK_SEPARATOR = 0x6C, VK_SUBTRACT = 0x6D, VK_DECIMAL = 0x6E, VK_DIVIDE = 0x6F, VK_F1 = 0x70, VK_F2 = 0x71, VK_F3 = 0x72, VK_F4 = 0x73, VK_F5 = 0x74, VK_F6 = 0x75, VK_F7 = 0x76, VK_F8 = 0x77, VK_F9 = 0x78, VK_F10 = 0x79, VK_F11 = 0x7A, VK_F12 = 0x7B, VK_F13 = 0x7C, VK_F14 = 0x7D, VK_F15 = 0x7E, VK_F16 = 0x7F, VK_F17 = 0x80, VK_F18 = 0x81, VK_F19 = 0x82, VK_F20 = 0x83, VK_F21 = 0x84, VK_F22 = 0x85, VK_F23 = 0x86, VK_F24 = 0x87, // VK_NUMLOCK = 0x90, VK_SCROLL = 0x91, // VK_OEM_NEC_EQUAL = 0x92, // '=' key on numpad // VK_OEM_FJ_JISHO = 0x92, // 'Dictionary' key VK_OEM_FJ_MASSHOU = 0x93, // 'Unregister word' key VK_OEM_FJ_TOUROKU = 0x94, // 'Register word' key VK_OEM_FJ_LOYA = 0x95, // 'Left OYAYUBI' key VK_OEM_FJ_ROYA = 0x96, // 'Right OYAYUBI' key // VK_LSHIFT = 0xA0, VK_RSHIFT = 0xA1, VK_LCONTROL = 0xA2, VK_RCONTROL = 0xA3, VK_LMENU = 0xA4, VK_RMENU = 0xA5, // VK_BROWSER_BACK = 0xA6, VK_BROWSER_FORWARD = 0xA7, VK_BROWSER_REFRESH = 0xA8, VK_BROWSER_STOP = 0xA9, VK_BROWSER_SEARCH = 0xAA, VK_BROWSER_FAVORITES = 0xAB, VK_BROWSER_HOME = 0xAC, // VK_VOLUME_MUTE = 0xAD, VK_VOLUME_DOWN = 0xAE, VK_VOLUME_UP = 0xAF, VK_MEDIA_NEXT_TRACK = 0xB0, VK_MEDIA_PREV_TRACK = 0xB1, VK_MEDIA_STOP = 0xB2, VK_MEDIA_PLAY_PAUSE = 0xB3, VK_LAUNCH_MAIL = 0xB4, VK_LAUNCH_MEDIA_SELECT = 0xB5, VK_LAUNCH_APP1 = 0xB6, VK_LAUNCH_APP2 = 0xB7, // VK_OEM_1 = 0xBA, // ';:' for US VK_OEM_PLUS = 0xBB, // '+' any country VK_OEM_COMMA = 0xBC, // ',' any country VK_OEM_MINUS = 0xBD, // '-' any country VK_OEM_PERIOD = 0xBE, // '.' any country VK_OEM_2 = 0xBF, // '/?' for US VK_OEM_3 = 0xC0, // '`~' for US // VK_OEM_4 = 0xDB, // '[{' for US VK_OEM_5 = 0xDC, // '\|' for US VK_OEM_6 = 0xDD, // ']}' for US VK_OEM_7 = 0xDE, // ''"' for US VK_OEM_8 = 0xDF, // VK_OEM_AX = 0xE1, // 'AX' key on Japanese AX kbd VK_OEM_102 = 0xE2, // "<>" or "\|" on RT 102-key kbd. VK_ICO_HELP = 0xE3, // Help key on ICO VK_ICO_00 = 0xE4, // 00 key on ICO // VK_PROCESSKEY = 0xE5, // VK_ICO_CLEAR = 0xE6, // VK_PACKET = 0xE7, // VK_OEM_RESET = 0xE9, VK_OEM_JUMP = 0xEA, VK_OEM_PA1 = 0xEB, VK_OEM_PA2 = 0xEC, VK_OEM_PA3 = 0xED, VK_OEM_WSCTRL = 0xEE, VK_OEM_CUSEL = 0xEF, VK_OEM_ATTN = 0xF0, VK_OEM_FINISH = 0xF1, VK_OEM_COPY = 0xF2, VK_OEM_AUTO = 0xF3, VK_OEM_ENLW = 0xF4, VK_OEM_BACKTAB = 0xF5, // VK_ATTN = 0xF6, VK_CRSEL = 0xF7, VK_EXSEL = 0xF8, VK_EREOF = 0xF9, VK_PLAY = 0xFA, VK_ZOOM = 0xFB, VK_NONAME = 0xFC, VK_PA1 = 0xFD, VK_OEM_CLEAR = 0xFE } It works well even if you put messagebox into the event or something that blocks execution. But it gets bad if you try to put breakpoint into the event. Why? I mean event is not run in the same thread that the windows hook is. That means that It shouldn't block HookCallback. It does however... I would really like to know why is this happening. My theory is that Visual Studio when breaking execution temporarily stops all threads and that means that HookCallback is blocked... Is there any book or valuable resource that would explain concepts behind all of this threading?

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