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  • Java hashcode based on identity

    - by hjfreyer
    The default behavior of Object.hashCode() is to return essentially the "address" of the object so that a.hashCode() == b.hashCode() if and only if a == b. How can I get this behavior in a user-defined class if a superclass already defines hashCode()? For instance: class A { public int hashCode() { return 0; } } class B extends A { public int hashCode() { // Now I want to return a unique hashcode for each object. // In pythonic terms, it'd look something like: return Object.hashCode(this); } } Ideas?

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  • "Ambiguous template specialization" problem

    - by Setien
    I'm currently porting a heap of code that has previously only been compiled with Visual Studio 2008. In this code, there's an arrangement like this: template <typename T> T convert( const char * s ) { // slow catch-all std::istringstream is( s ); T ret; is >> ret; return ret; } template <> inline int convert<int>( const char * s ) { return (int)atoi( s ); } Generally, there are a lot of specializations of the templated function with different return types that are invoked like this: int i = convert<int>( szInt ); The problem is, that these template specializations result in "Ambiguous template specialization". If it was something besides the return type that differentiated these function specializations, I could obviously just use overloads, but that's not an option. How do I solve this without having to change all the places the convert functions are called?

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  • Fibonacci Function Question

    - by DMan
    I was calculating the Fibonacci sequence, and stumbled across this code, which I saw a lot: int Fibonacci (int x) { if (x<=1) { return 1; } return Fibonacci (x-1)+Fibonacci (x-2); } What I don't understand is how it works, especially the return part at the end: Does it call the Fibonacci function again? Could someone step me through this function?

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  • c# reading integer fields from database

    - by arnoldino
    what is wrong with this code? try { if (cmd == null) getConnection(); cmd.CommandText = "Select id from HMonthInventary where machine_id=37"; SQLiteDataReader reader = cmd.ExecuteReader(); if (reader.HasRows==true) { reader.Read(); string s = reader[0].ToString(); // return first element reader.Close(); return s; } reader.Close(); return null; } catch (Exception e) { MessageBox.Show("Caught exception: " + e.Message+"|"+cmd.CommandText); return null; } I checked the sql statement, it turns the right value. why can't I read it? the returnvalue is "".

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  • java: retrieving the "canonical value" from a Set<T> where T has a custom equals()

    - by Jason S
    I have a class Foo which overrides equals() and hashCode() properly. I would like to also would like to use a HashSet<Foo> to keep track of "canonical values" e.g. I have a class that I would like to write like this, so that if I have two separate objects that are equivalent I can coalesce them into references to the same object: class Canonicalizer<T> { final private Set<T> values = new HashSet<T>(); public T findCanonicalValue(T value) { T canonical = this.values.get(value); if (canonical == null) { // not in the set, so put it there for the future this.values.add(value); return value; } else { return canonical; } } } except that Set doesn't have a "get" method that would return the actual value stored in the set, just the "contains" method that returns true or false. (I guess that it assumes that if you have an object that is equal to a separate object in the set, you don't need to retrieve the one in the set) Is there a convenient way to do this? The only other thing I can think of is to use a map and a list: class Canonicalizer<T> { // warning: neglects concurrency issues final private Map<T, Integer> valueIndex = new HashMap<T, Integer>(); final private List<T> values = new ArrayList<T>(); public T findCanonicalValue(T value) { Integer i = this.valueIndex.get(value); if (i == null) { // not in the set, so put it there for the future i = this.values.size(); this.values.add(value); this.valueIndex.put(value, i); return value; } else { // in the set return this.values.get(i); } } }

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  • Correct way to use Drupal 7 Entities and Field API

    - by Martin Petts
    I'm trying to use Drupal 7's entities and field API to correctly build a new module. What I have been unable to understand from the documentation is the correct way to use the new API to create a 'content type' (not a node type) with a number of set fields, such as Body. I'm trying to set up the entity using hook_entity_info, then I believe I need to add the body field using field_create_instance, but I can't seem to get it to work. In mycontenttype.module: /** * Implements hook_entity_info(). */ function mycontenttype_entity_info() { $return = array( 'mycontenttype' => array( 'label' => t('My Content Type'), 'controller class' => 'MyContentTypeEntityController', 'base table' => 'content_type', 'uri callback' => 'content_type_uri', 'entity keys' => array( 'id' => 'cid', 'label' => 'title' ), 'bundles' => array( 'mycontenttype' => array( 'label' => 'My Content Type', 'admin' => array( 'path' => 'admin/contenttype', 'access arguments' => array('administer contenttype') ) ) ), 'fieldable' => true ) ); return $return; } /** * Implements hook_field_extra_fields(). */ function mycontenttype_field_extra_fields() { $return['mycontenttype']['mycontenttype'] = array( 'form' = array( 'body' = array( 'label' = 'Body', 'description' = t('Body content'), 'weight' = 0, ), ), ); return $return; } Then does this go in the .install file? function mycontenttype_install() { $field = array( 'field_name' => 'body', 'type' => 'text_with_summary', 'entity_types' => array('survey'), 'translatable' => TRUE, ); field_create_field($field); $instance = array( 'entity_type' => 'mycontenttype', 'field_name' => 'body', 'bundle' => 'mycontenttype', 'label' => 'Body', 'widget_type' => 'text_textarea_with_summary', 'settings' => array('display_summary' => TRUE), 'display' => array( 'default' => array( 'label' => 'hidden', 'type' => 'text_default', ), 'teaser' => array( 'label' => 'hidden', 'type' => 'text_summary_or_trimmed', ) ) ); field_create_instance($instance); }

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  • how to query an embedded entity by using a query builder

    - by user577719
    I've searched quite a time for an answer to this question. Following Codesmell: @Entity public class Person { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) protected Integer id; @Column(nullable = true, length = 50) @Size(max = 50) private String name; @Embedded @Valid protected Adress adress; public void setId(Integer id) { this.id = id; } public Integer getId() { return this.id; } public void setName(String name) { this.name = name; } public void getName() { return this.name; } public void setAdress(Adress adress) { this.adress = adress; } public void getAdress() { return this.adress; } } @Embeddable public class Adress { @Column(nullable = false, length = 50) @Size(max = 50) @NotNull private String place; public void setPlace(String place) { this.place = place; } public void getPlace() { return this.place; } } public class PersonDaoJpa { public List<Ort> findByPerson(final Person person) { CriteriaBuilder builder = this.entityManager.getCriteriaBuilder(); CriteriaQuery<Person> query = builder.createQuery(Person.class); Root<Person> rootPerson = query.from(Person.class); List<Predicate> wherePredicates = new ArrayList<Predicate>(); if (person.getName() != null) { wherePredicates.add( builder.like(builder.lower(rootPerson.<String>get("name")), ort.getName().toLowerCase()) ); } Adresse adresse = ort.getAdresse(); if (adresse != null) { if(adresse.getPlace() != null) { // this won't work wherePredicates.add( builder.like(builder.lower(rootPerson.<String>get("person.adress.place")), adresse.getPlace().toLowerCase()) ); } } Predicate whereClause = builder.and(wherePredicates.toArray(new Predicate[0])); query.where(whereClause); return this.entityManager.createQuery(query).getResultList(); } } How can I access the Adress.place through rootPerson? rootPerson.get("place"), or rootPerson.get("adress.place") won't work...

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  • jQuery form zip code to state function

    - by Dakota R.
    I'm trying to convert a preexisting javascript function into a jQuery function. The function comes from http://javascript.internet.com/forms/zip-to-state.html and aims to convert a user-entered zip code into a state. I'm using jQuery 1.3.2, with all the necessary plugins, but I'm not very familiar with jQuery syntax and how to convert this from plain ol' Javascript syntax. The setState function takes two parameters, the zip code element and the state element, so I'm trying to do something like this: $('$zip_code').change( function () { setState($(this), $('#state')); }); Any thoughts on this syntax? Thanks, Dakota function getState(zip) { if ((parseInt(zipString.substr(zip / 4, 1), 16) & Math.pow(2, zip % 4)) && (zip.length == 5)) for (var i = 0; i < stateRange.length; i += 7) if (zip <= 1 * stateRange.substr(i, 5)) return stateRange.substr(i + 5, 2); return null; } function setState(txtZip, optionBox) { if (txtZip.value.length != 5 || isNaN(txtZip.value / 4)) { optionBox.options[0].selected = true; alert("Please enter a 5 digit, numeric zip code."); return; } var state = getState(txtZip.value); for (var i = 0; i < optionBox.options.length; i++) if (optionBox.options[i].value == state) return optionBox.options[i].selected = true; for (var i = 0; i < optionBox.options.length; i++) if (optionBox.options[i].value == "XX") return optionBox.options[i].selected = true; }

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  • How to write a jUnit test for this class?

    - by flash
    Hi, I would like to know what's the best approach to test the method "pushEvent()" in the following class with a jUnit test. My problem is, that the private method "callWebsite()" always requires a connection to the network. How can I avoid this requirement or refactor my class that I can test it without a connection to the network? class MyClass { public String pushEvent (Event event) { //do something here String url = constructURL (event); //construct the website url String response = callWebsite (url); return response; } private String callWebsite (String url) { try { URL requestURL = new URL (url); HttpURLConnection connection = null; connection = (HttpURLConnection) requestURL.openConnection (); String responseMessage = responseParser.getResponseMessage (connection); return responseMessage; } catch (MalformedURLException e) { e.printStackTrace (); return e.getMessage (); } catch (IOException e) { e.printStackTrace (); return e.getMessage (); } } }

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  • Basic C programming question

    - by Amit
    Hi all, I've just started to learn C and it's going pretty slow...I wanted to write a program that takes in an integer argument and returns it's doubled value (aka take in integer, multiply by 2, and printf that value). I purposely did not want to use the scanf function. Here's what I have so far and what is not compiling... #include <stdio.h> int main(int index) { if (!(index)) { printf("No index given"); return 1; } a = index*2; printf("Mult by 2 %d",a); return 0; } So basically when the program is executed I want to supply the index integer. So, in cygwin, I would write something like ./a 10 and 10 would be stored into the index variable. Also, I want to program to return "No index given" and exit if no index value was supplied... Anyone care to help what I'm doing wrong? EDIT: This code returns 1 error upon compilation and is based on the help by @James: #include <stdio.h> int main(int 1, char index) { int index, a; if (!(index)) { printf("No index given"); return 1; } a = index*2; printf("Mult by 2 %d",a); return 0; } Thanks! Amit

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  • Ladder word-like game GUI problems

    - by sasquatch90
    Ok so I've written my own version of game which should look like this : http://img199.imageshack.us/img199/6859/lab9a.jpg but mine looks like that : http://img444.imageshack.us/img444/7671/98921674.jpg How can I fix this ? Is there a way to do the layout completely differently ? Here's the code : Main.java : import java.util.Scanner; import javax.swing.*; import java.awt.*; public class Main { public static void main(String[] args){ final JFrame f = new JFrame("Ladder Game"); Scanner sc = new Scanner(System.in); System.out.println("Creating game data..."); System.out.println("Height: "); while (!sc.hasNextInt()) { System.out.println("int, please!"); sc.next(); } final int height = sc.nextInt(); Grid[]game = new Grid[height]; for(int L = 0; L < height; L++){ Grid row = null; int i = L+1; String s; do { System.out.println("Length "+i+", please!"); s = sc.next(); } while (s.length() != i); Element[] line = new Element[s.length()]; Element single = null; String[] temp = null; String[] temp2 = new String[s.length()]; temp = s.split(""); for( int j = temp2.length; j>0; j--){ temp2[j-1] = temp[j]; } for (int k = 0 ; k < temp2.length ; k++) { if( k == 0 ){ single = new Element(temp2[k], 2); } else{ single = new Element(temp2[k], 1); } line[k] = single; } row = new Grid(line); game[L] = row; } //############################################ //THE GAME STARTS HERE //############################################ JPanel panel = new JPanel(); panel.setLayout(new BoxLayout(panel, BoxLayout.X_AXIS)); panel.setBackground(Color.ORANGE); panel.setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10)); for(int i = 0; i < game.length; i++){ panel.add(game[i].create()); } f.setContentPane(panel); f.pack(); f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); f.setVisible(true); boolean end = false; boolean word = false; String tekst; while( !end ){ while( !word ){ tekst = JOptionPane.showInputDialog("Input word: "); for(int i = 0; i< game.length; i++){ if(game[i].equalLength(tekst)){ if(game[i].equalValue(tekst)){ word = true; for(int j = 0; j< game.length; j++){ game[i].repaint(); } } } } } word = false; for(int i = 0; i < game.length; i++){ if(game[i].solved()){ end = true; } else { end = false; } } } } } Grid.java import javax.swing.*; import java.awt.*; public class Grid extends JPanel{ private Element[]e; private Grid[]g; public Grid(){} public Grid( Element[]elements ){ e = new Element[elements.length]; for(int i=0; i< e.length; i++){ e[i] = elements[i]; } } public Grid(Grid[]grid){ g = new Grid[grid.length]; for(int i=0; i<g.length; i++){ g[i] = grid[i]; } Dimension d = new Dimension(600, 600); setMinimumSize(d); setPreferredSize(new Dimension(d)); setMaximumSize(d); } public JPanel create(){ JPanel panel = new JPanel(); panel.setLayout(new BoxLayout(panel, BoxLayout.PAGE_AXIS)); panel.setBorder(BorderFactory.createEmptyBorder(2, 2, 2, 2)); for(int j = 0; j < e.length; j++){ panel.add(e[j].paint()); } return panel; } @Override public void repaint(){ } public boolean equalLength(String s){ int len = s.length(); boolean equal = false; for(int j = 0; j < e.length; j++){ if(e.length == len){ equal = true; } } return equal; } public boolean equalValue(String s){ int len = s.length(); boolean equal = false; String[] temp = null; String[] temp2 = new String[len]; temp = s.split(""); for( int j = len; j>0; j--){ temp2[j-1] = temp[j]; } for(int j = 0; j < e.length; j++){ if( e[j].letter().equals(temp2[j]) ){ equal = true; } else { equal = false; } } if(equal){ for(int i = 0; i < e.length; i++){ e[i].changeState(3); } } return equal; } public boolean solved(){ boolean solved = false; for(int j = 0; j < e.length; j++){ if(e[j].getState() == 3){ solved = true; } else { solved = false; } } return solved; } @Override public String toString(){ return ""; } } Element.java import javax.swing.*; import java.awt.*; public class Element { final int INVISIBLE = 0; final int EMPTY = 1; final int FIRST_LETTER = 2; final int OTHER_LETTER = 3; private int state; private String letter; public Element(){ } //empty block public Element(int state){ this("", 0); } //filled block public Element(String s, int state){ this.state = state; this.letter = s; } public JButton paint(){ JButton button = null; if( state == EMPTY ){ button = new JButton(""); button.setBackground(Color.WHITE); } else if ( state == FIRST_LETTER ){ button = new JButton(letter); button.setBackground(Color.red); } else { button = new JButton(letter); button.setBackground(Color.yellow); } button.setSize(20,20); return button; } public void changeState(int s){ state = s; } public String letter(){ return letter; } public int getState(){ return state; } @Override public String toString(){ return "["+letter+"]"; } }

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  • Inserting a string array as a row into an Excel document using the Open XML SDK 2.0

    - by Sam
    The code runs, but corrupts my excel document. Any help would be mucho appreciated! I used this as a reference. public void AddRow(string fileName, string[] values) { using (SpreadsheetDocument doc = SpreadsheetDocument.Open(fileName, true)) { SharedStringTablePart sharedStringPart = GetSharedStringPart(doc); WorksheetPart worksheetPart = doc.WorkbookPart.WorksheetParts.First(); uint rowIdx = AppendRow(worksheetPart); for (int i = 0; i < values.Length; ++i) { int stringIdx = InsertSharedString(values[i], sharedStringPart); Cell cell = InsertCell(i, rowIdx, worksheetPart); cell.CellValue = new CellValue(stringIdx.ToString()); cell.DataType = new EnumValue<CellValues>( CellValues.SharedString); worksheetPart.Worksheet.Save(); } } } private SharedStringTablePart GetSharedStringPart( SpreadsheetDocument doc) { if (doc.WorkbookPart. GetPartsCountOfType<SharedStringTablePart>() > 0) return doc.WorkbookPart. GetPartsOfType<SharedStringTablePart>().First(); else return doc.WorkbookPart. AddNewPart<SharedStringTablePart>(); } private uint AppendRow(WorksheetPart worksheetPart) { SheetData sheetData = worksheetPart.Worksheet. GetFirstChild<SheetData>(); uint rowIndex = (uint)sheetData.Elements<Row>().Count(); Row row = new Row() { RowIndex = rowIndex }; sheetData.Append(row); return rowIndex; } private int InsertSharedString(string s, SharedStringTablePart sharedStringPart) { if (sharedStringPart.SharedStringTable == null) sharedStringPart.SharedStringTable = new SharedStringTable(); int i = 0; foreach (SharedStringItem item in sharedStringPart.SharedStringTable. Elements<SharedStringItem>()) { if (item.InnerText == s) return i; ++i; } sharedStringPart.SharedStringTable.AppendChild( new Text(s)); sharedStringPart.SharedStringTable.Save(); return i; } private Cell InsertCell(int i, uint rowIdx, WorksheetPart worksheetPart) { SheetData sheetData = worksheetPart.Worksheet. GetFirstChild<SheetData>(); string cellReference = AlphabetMap.Instance[i] + rowIdx; Cell cell = new Cell() { CellReference = cellReference }; Row row = sheetData.Elements<Row>().ElementAt((int)rowIdx); row.InsertAt(cell, i); worksheetPart.Worksheet.Save(); return cell; }

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  • "No keyboard for id 0"?

    - by Mellon
    I am new in Android app. development, now I have encountered a strange problem with the Menu button. Here is the thing: I have two activities, "ActivityOne" and "ActivityTwo", where "ActivityTwo" is the child Activity of "ActivityOne". In both activity, I have defined the menu button options like following: @Override public boolean onCreateOptionsMenu(Menu menu) { super.onCreateOptionsMenu(menu); MenuItem insertMenuItem = menu.add(0, INSERT_ID, 0, R.string.menu_insert); insertMenuItem.setIcon(R.drawable.ic_menu_add); MenuItem settingMenuItem = menu.add(0, SETTING_ID, 0, R.string.menu_setting); settingMenuItem.setIcon(R.drawable.ic_menu_settings); MenuItem aboutMenuItem = menu.add(0, ABOUT_ID, 0, R.string.menu_about); aboutMenuItem.setIcon(R.drawable.ic_menu_about); logPrinter.println("creating menu options..."); return true; } @Override public boolean onMenuItemSelected(int featureId, MenuItem item) { switch(item.getItemId()) { case INSERT_ID: doInsert(); return true; case SETTING_ID: return true; case ABOUT_ID: showAbout(); return true; } return super.onMenuItemSelected(featureId, item); } In "ActivityOne", when I click the physical Menu button, there is no menu options pop up from screen bottom, when I checked the LogCat console, there are two warning messages, which are "No keyboard for id 0" and "Using default keyMap:/system/usr/keychars/qwerty.kcm.bin" . BUT, in "ActivityTwo", the menu button works fine, it shows me those menu options I defined. Why the menu button does not work in "ActivityOne" ?? What does the warning msg mean???

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  • Java Regular Expression. Check if String contains ONLY Letters

    - by user69514
    How do I check if a String contains only letters in java? I want to write an if statement that will return false if there is a white space, a number, a symbol or anything else other than a-z A-Z. My string must contain ONLY letters. I thought I could do it this way, but I'm doing it wrong: if( ereg("[a-zA-Z]+", $myString)) return true; else return false;

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  • XAML get new width and height for Canvas

    - by Jack Navarro
    I have searched through many times but have not seen this before. Probably really simple question but can't wrap my head around it. Wrote a VSTO add-in for Excel that draws a Grid dynamically. Then launches a new window and replaces the contents of the Canvas with the generated Grid. The problem is with printing. When I call the print procedure the canvas.height and canvas.width returned is the old value prior to replacing it with the grid. Sample: string="<Grid Name=\"CanvasGrid\" xmlns=\"http://schemas.microsoft.com/winfx/2006/xaml/presentation\">..Lots of stuff..</Grid>"; // Launch new window and replace the Canvas element WpfUserControl newWindow = new WpfUserControl(); newWindow.Show(); //To test MessageBox.Show(myCanvas.ActualWidth.ToString()); //return 894 Grid testGrid = myCanvas.FindName("CanvasGrid") as Grid; MessageBox.Show("Grid " + testGrid.ActualWidth.ToString()); //return 234 StringReader stringReader = new StringReader(LssAllcChrt); XmlReader xmlReader = XmlReader.Create(stringReader); Canvas myCanvas = newWindow.FindName("GrphCnvs") as Canvas; myCanvas.Children.Clear(); myCanvas.Children.Add((UIElement)XamlReader.Load(xmlReader)); //To test MessageBox.Show(myCanvas.ActualWidth.ToString()); //return 894 but should be much larger the Grid spans all three of my screens Grid testGrid = myCanvas.FindName("CanvasGrid") as Grid; MessageBox.Show("Grid " + testGrid.ActualWidth.ToString()); //return 234 but should be much larger the Grid spans all three of my screens //Run code from WpfUserControl.cs after it loads from button click Grid testGrid = canvas.FindName("CanvasGrid") as Grid; MessageBox.Show("Grid " + testGrid.ActualWidth.ToString()); //return 234 but should be much larger the Grid spans all three of my screens So basically I have no way of telling what my new width and height are.

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  • How to eval javascript code with iPhone SDK?

    - by overboming
    I need to fetch some result on a webpage, which use some javascript code to generate the part I am interesting in like following eval(function(p,a,c,k,e,d){e=function(c){return c};if(!''.replace(/^/,String)){while(c--)d[c]=k[c]||c;k=[function(e){return d[e]}];e=function(){return'\\w+'};c=1;};while(c--)if(k[c])p=p.replace(new RegExp('\\b'+e(c)+'\\b','g'),k[c]);return p;}('5 11=17;5 12=["/3/2/1/0/13.4","/3/2/1/0/15.4","/3/2/1/0/14.4","/3/2/1/0/7.4","/3/2/1/0/6.4","/3/2/1/0/8.4","/3/2/1/0/10.4","/3/2/1/0/9.4","/3/2/1/0/23.4","/3/2/1/0/22.4","/3/2/1/0/24.4","/3/2/1/0/26.4","/3/2/1/0/25.4","/3/2/1/0/18.4","/3/2/1/0/16.4","/3/2/1/0/19.4","/3/2/1/0/21.4"];5 20=0;',10,27,'40769|54|Images|Files|png|var|imanhua_005_140430179|imanhua_004_140430179|imanhua_006_140430226|imanhua_008_140430242|imanhua_007_140430226|len|pic|imanhua_001_140429664|imanhua_003_140430117|imanhua_002_140430070|imanhua_015_140430414||imanhua_014_140430382|imanhua_016_140430414|sid|imanhua_017_140430429|imanhua_010_140430289|imanhua_009_140430242|imanhua_011_140430367|imanhua_013_140430382|imanhua_012_140430367'.split('|'),0,{})) How do I get the evaluation output?

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  • Does my TPL partitioner cause a deadlock?

    - by Scott Chamberlain
    I am starting to write my first parallel applications. This partitioner will enumerate over a IDataReader pulling chunkSize records at a time from the data-source. protected class DataSourcePartitioner<object[]> : System.Collections.Concurrent.Partitioner<object[]> { private readonly System.Data.IDataReader _Input; private readonly int _ChunkSize; public DataSourcePartitioner(System.Data.IDataReader input, int chunkSize = 10000) : base() { if (chunkSize < 1) throw new ArgumentOutOfRangeException("chunkSize"); _Input = input; _ChunkSize = chunkSize; } public override bool SupportsDynamicPartitions { get { return true; } } public override IList<IEnumerator<object[]>> GetPartitions(int partitionCount) { var dynamicPartitions = GetDynamicPartitions(); var partitions = new IEnumerator<object[]>[partitionCount]; for (int i = 0; i < partitionCount; i++) { partitions[i] = dynamicPartitions.GetEnumerator(); } return partitions; } public override IEnumerable<object[]> GetDynamicPartitions() { return new ListDynamicPartitions(_Input, _ChunkSize); } private class ListDynamicPartitions : IEnumerable<object[]> { private System.Data.IDataReader _Input; int _ChunkSize; private object _ChunkLock = new object(); public ListDynamicPartitions(System.Data.IDataReader input, int chunkSize) { _Input = input; _ChunkSize = chunkSize; } public IEnumerator<object[]> GetEnumerator() { while (true) { List<object[]> chunk = new List<object[]>(_ChunkSize); lock(_Input) { for (int i = 0; i < _ChunkSize; ++i) { if (!_Input.Read()) break; var values = new object[_Input.FieldCount]; _Input.GetValues(values); chunk.Add(values); } if (chunk.Count == 0) yield break; } var chunkEnumerator = chunk.GetEnumerator(); lock(_ChunkLock) //Will this cause a deadlock? { while (chunkEnumerator.MoveNext()) { yield return chunkEnumerator.Current; } } } } IEnumerator IEnumerable.GetEnumerator() { return ((IEnumerable<object[]>)this).GetEnumerator(); } } } I wanted IEnumerable object it passed back to be thread safe (the .Net example was so I am assuming PLINQ and TPL could need it) will the lock on _ChunkLock near the bottom help provide thread safety or will it cause a deadlock? From the documentation I could not tell if the lock would be released on the yeld return. Also if there is built in functionality to .net that will do what I am trying to do I would much rather use that. And if you find any other problems with the code I would appreciate it.

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  • How to specify number of headers in section UITableView.

    - by Mr. McPepperNuts
    if ([tempArray containsObject: [sectionInfo indexTitle]]) { return nil; }else { [tempArray addObject: [sectionInfo indexTitle]]; return [sectionInfo indexTitle]; } return [sectionInfo indexTitle]; The code above groups the cells in alphabetical order but displays a blank header instead of the appropriate title. Could this possibly be because I did not specify the number of headers? This would naturally be a single header for every letter in the alphabet.

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  • C - What is the proper format to allow a function to show an error was encountered?

    - by BrainSteel
    I have a question about what a function should do if the arguments to said function don't line up quite right, through no fault of the function call. Since that sentence doesn't make much sense, I'll offer my current issue. To keep it simple, here is the most relevant and basic function I have. float getYValueAt(float x, PHYS_Line line, unsigned short* error) *error = 0; if(x < line.start.x || x > line.end.x){ *error = 1; return -1; } if(line.slope.value != 0){ //line's equation: y - line.start.y = line.slope.value(x - line.start.x) return line.slope.value * (x - line.start.x) + line.start.y; } else if(line.slope.denom == 0){ if(line.start.x == x) return line.start.y; else{ *error = 1; return -1; } } else if(line.slope.num == 0){ return line.start.y; } } The function attempts to find the point on a line, given a certain x value. However, under some circumstances, this may not be possible. For example, on the line x = 3, if 5 is passed as a value, we would have a problem. Another problem arises if the chosen x value is not within the interval the line is on. For this, I included the error pointer. Given this format, a function call could work as follows: void foo(PHYS_Line some_line){ unsigned short error = 0; float y = getYValueAt(5, some_line, &error); if(error) fooey(); else do_something_with_y(y); } My question pertains to the error. Note that the value returned is allowed to be negative. Returning -1 does not ensure that an error has occurred. I know that it is sometimes preferred to use the following method to track an error: float* getYValueAt(float x, PHYS_Line line); and then return NULL if an error occurs, but I believe this requires dynamic memory allocation, which seems even less sightly than the solution I was using. So, what is standard practice for an error occurring?

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  • Replace conditional with polymorphism refactoring or similar?

    - by Anders Svensson
    Hi, I have tried to ask a variant of this question before. I got some helpful answers, but still nothing that felt quite right to me. It seems to me this shouldn't really be that hard a nut to crack, but I'm not able to find an elegant simple solution. (Here's my previous post, but please try to look at the problem stated here as procedural code first so as not to be influenced by the earlier explanation which seemed to lead to very complicated solutions: http://stackoverflow.com/questions/2772858/design-pattern-for-cost-calculator-app ) Basically, the problem is to create a calculator for hours needed for projects that can contain a number of services. In this case "writing" and "analysis". The hours are calculated differently for the different services: writing is calculated by multiplying a "per product" hour rate with the number of products, and the more products are included in the project, the lower the hour rate is, but the total number of hours is accumulated progressively (i.e. for a medium-sized project you take both the small range pricing and then add the medium range pricing up to the number of actual products). Whereas for analysis it's much simpler, it is just a bulk rate for each size range. How would you be able to refactor this into an elegant and preferably simple object-oriented version (please note that I would never write it like this in a purely procedural manner, this is just to show the problem in another way succinctly). I have been thinking in terms of factory, strategy and decorator patterns, but can't get any to work well. (I read Head First Design Patterns a while back, and both the decorator and factory patterns described have some similarities to this problem, but I have trouble seeing them as good solutions as stated there. The decorator example seems very complicated for just adding condiments, but maybe it could work better here, I don't know. And the factory pattern example with the pizza factory...well it just seems to create such a ridiculous explosion of classes, at least in their example. I have found good use for factory patterns before, but I can't see how I could use it here without getting a really complicated set of classes) The main goal would be to only have to change in one place (loose coupling etc) if I were to add a new parameter (say another size, like XSMALL, and/or another service, like "Administration"). Here's the procedural code example: public class Conditional { private int _numberOfManuals; private string _serviceType; private const int SMALL = 2; private const int MEDIUM = 8; public int GetHours() { if (_numberOfManuals <= SMALL) { if (_serviceType == "writing") return 30 * _numberOfManuals; if (_serviceType == "analysis") return 10; } else if (_numberOfManuals <= MEDIUM) { if (_serviceType == "writing") return (SMALL * 30) + (20 * _numberOfManuals - SMALL); if (_serviceType == "analysis") return 20; } else //i.e. LARGE { if (_serviceType == "writing") return (SMALL * 30) + (20 * (MEDIUM - SMALL)) + (10 * _numberOfManuals - MEDIUM); if (_serviceType == "analysis") return 30; } return 0; //Just a default fallback for this contrived example } } All replies are appreciated! I hope someone has a really elegant solution to this problem that I actually thought from the beginning would be really simple... Regards, Anders

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  • How to check if a number is a power of 2

    - by configurator
    Today I needed a simple algorithm for checking if a number is a power of 2. The algorithm needs to be: Simple Correct for any ulong value. I came up with this simple algorithm: private bool IsPowerOfTwo(ulong number) { if (number == 0) return false; for (ulong power = 1; power > 0; power = power << 1) { // this for loop used shifting for powers of 2, meaning // that the value will become 0 after the last shift // (from binary 1000...0000 to 0000...0000) then, the for // loop will break out if (power == number) return true; if (power > number) return false; } return false; } But then I thought, how about checking if log2x is an exactly round number? But when I checked for 2^63+1, Math.Log returned exactly 63 because of rounding. So I checked if 2 to the power 63 is equal to the original number - and it is, because the calculation is done in doubles and not in exact numbers: private bool IsPowerOfTwo_2(ulong number) { double log = Math.Log(number, 2); double pow = Math.Pow(2, Math.Round(log)); return pow == number; } This returned true for the given wrong value: 9223372036854775809. Does anyone have any suggestion for a better algorithm?

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  • I need to modify a program to use arrays and a method call. Should I modify the running file, the data collection file, or both?

    - by g3n3rallyl0st
    I have to have multiple classes for this program. The problem is, I don't fully understand arrays and how they work, so I'm a little lost. I will post my program I have written thus far so you can see what I'm working with, but I don't expect anyone to DO my assignment for me. I just need to know where to start and I'll try to go from there. I think I need to use a double array since I will be working with decimals since it deals with money, and my method call needs to calculate total price for all items entered by the user. Please help: RUNNING FILE package inventory2; import java.util.Scanner; public class RunApp { public static void main(String[] args) { Scanner input = new Scanner( System.in ); DataCollection theProduct = new DataCollection(); String Name = ""; double pNumber = 0.0; double Units = 0.0; double Price = 0.0; while(true) { System.out.print("Enter Product Name: "); Name = input.next(); theProduct.setName(Name); if (Name.equalsIgnoreCase("stop")) { return; } System.out.print("Enter Product Number: "); pNumber = input.nextDouble(); theProduct.setpNumber(pNumber); System.out.print("Enter How Many Units in Stock: "); Units = input.nextDouble(); theProduct.setUnits(Units); System.out.print("Enter Price Per Unit: "); Price = input.nextDouble(); theProduct.setPrice(Price); System.out.print("\n Product Name: " + theProduct.getName()); System.out.print("\n Product Number: " + theProduct.getpNumber()); System.out.print("\n Amount of Units in Stock: " + theProduct.getUnits()); System.out.print("\n Price per Unit: " + theProduct.getPrice() + "\n\n"); System.out.printf("\n Total cost for %s in stock: $%.2f\n\n\n", theProduct.getName(), theProduct.calculatePrice()); } } } DATA COLLECTION FILE package inventory2; public class DataCollection { String productName; double productNumber, unitsInStock, unitPrice, totalPrice; public DataCollection() { productName = ""; productNumber = 0.0; unitsInStock = 0.0; unitPrice = 0.0; } //setter methods public void setName(String name) { productName = name; } public void setpNumber(double pNumber) { productNumber = pNumber; } public void setUnits(double units) { unitsInStock = units; } public void setPrice(double price) { unitPrice = price; } //getter methods public String getName() { return productName; } public double getpNumber() { return productNumber; } public double getUnits() { return unitsInStock; } public double getPrice() { return unitPrice; } public double calculatePrice() { return (unitsInStock * unitPrice); } }

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  • ajax checkbox filter

    - by user1018298
    I need some help with a checkbox filter I am working in. I have four groups of checkboxes (type, vehicle, availability, price) and I would like to filter the content on the page based on the user's input. I can get the filter working OK but I am having issues with the groups. I can only seem to match one checkbox from each group rather than all checkboxes from each group. For example, a visitor can select 1 option in group 1, all options in group 2, 1 option in group three and 1 option in group 4. I am using ajax to build an SLQ query to return the correct filtered results from my database. here is my code: $('div.filters').delegate('input:checkbox', 'change', function() { var type = $('input.exp_type:checked').map(function () { return $(this).attr('value'); }).get().join(','); var vehicle = $('input.vehicle_type:checked').map(function () { return $(this).attr('value'); }).get().join(','); var avail = $('input.availability:checked').map(function () { return $(this).attr('value'); }).get().join(','); var price = $('input.price:checked').map(function () { return $(this).attr('value'); }).get().join(','); //alert($options); $.ajax({ type:"POST", url:"filtervouchers.php", data:"type="+type+"&vehicle="+vehicle+"&avail="+avail+"&price="+price, success:function(data){ $('.results').html(data); } });//end ajax }) and the php code: $type = mysql_real_escape_string($_POST['type']); $vehicles = mysql_real_escape_string($_POST['vehicle']); $avail = mysql_real_escape_string($_POST['avail']); $price = mysql_real_escape_string($_POST['price']); if ($type != '') { $sql2 = " AND exp_type IN ($type)"; } if ($vehicles != '') { $sql3 = " AND vehicle_type LIKE '%$vehicles%'"; } if ($avail != '') { $sql4 = " AND availability LIKE '%,' $avail% ','"; } if ($price != '') { $sql5 = " AND price_band IN ($price)"; } Can this be done using jquery?

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  • Blackberry (Java) - Can't get KeyListener to work

    - by paullb
    I am trying to get the KeyListener working for Blackberry, but none of the Dialogs pop up indicating that a key has been pressed (see code below, each action has a dialog popup in them). Any ideas on what i might be doing wrong? public class CityInfo extends UiApplication implements KeyListener { static CityInfo application; public static void main(String[] args) { //create a new instance of the application //and start the application on the event thread application.enterEventDispatcher(); } public CityInfo() { //display a new screen application = new CityInfo(); pushScreen(new WorkflowDisplayScreen()); this.addKeyListener(this); } public boolean keyChar(char arg0, int arg1, int arg2) { // TODO Auto-generated method stub Dialog.alert("key pressed : " + arg0); return true; } public boolean keyDown(int keycode, int time) { // TODO Auto-generated method stub Dialog.alert("keyDown : " + keycode); return false; } public boolean keyRepeat(int keycode, int time) { // TODO Auto-generated method stub Dialog.alert("keyRepeat : " + keycode); return false; } public boolean keyStatus(int keycode, int time) { // TODO Auto-generated method stub Dialog.alert("keyStatus : " + keycode); return false; } public boolean keyUp(int keycode, int time) { Dialog.alert("keyUp : " + keycode); // TODO Auto-generated method stub return false; } } I also tried implementing keyChar on the MainScreen class but that did not yield any results either.

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