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  • Right rotate of tree in Haskell: how is it work?

    - by Roman
    I don't know haskell syntax, but I know some FP concepts (like algebraic data types, pattern matching, higher-order functions ect). Can someone explain please, what does this code mean: data Tree ? = Leaf ? | Fork ? (Tree ?) (Tree ?) rotateR tree = case tree of Fork q (Fork p a b) c -> Fork p a (Fork q b c) As I understand, first line is something like Tree-type declaration (but I don't understand it exactly). Second line includes pattern matching (I don't understand as well why do we need to use pattern matching here). And third line does something absolutely unreadable for non-haskell developer. I've found definition of Fork as fork (f,g) x = (f x, g x) but I can't move further anymore.

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  • sp_help with wildcards

    - by serhio
    There is a command in SqlServer sp_help 'table_name' (table_name or other stuff) Is there a possibility to use it when you don't know the whole table name, with wildcards or something like this: sp_help admin_%

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  • When setting a form's opacity should I use a decimal or double?

    - by Eggs McLaren
    I'm new to C#, and I want to use a track-bar to change a form's opacity. This is my code: decimal trans = trackBar1.Value / 5000 this.Opacity = trans When I try to build it, I get this error: Cannot implicitly convert type 'decimal' to 'double' I tried making trans a double, but then the control doesn't work. This code worked fine for me in VB.NET. What do I need to do differently?

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  • Building and rendering a bitmap from a double array

    - by Ami
    I'm new to c# and I'm sure I'm missing something simple here. I'm trying to build a bitmap from integer values (0-255) in a double array and then render it in a PictureBox. I think my Bitmap is getting generated but it isn't displaying in my PictureBox. Bitmap bmp = new Bitmap(image_width, image_height); Color pxl_color = new Color(); for (int i = 0; i < image_width; i++) { for (int j = 0; j < image_height; j++) { pxl_color = Color.FromArgb(array_bitmap[i][j]); bmp.SetPixel(i, j, pxl_color); } } PictureBox1.Image = bmp; Thanks in advance.

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  • Java: what is the class for the isBinary-method?

    - by HH
    I am accustomed to java.io.* and java.util.* but not to the tree: com.starbase.util Class FileUtils java.lang.Object | +--com.starbase.util.FileUtils Source. So which class should I import to use the isBinary-method? Do I do "import java.lang.Object;" or "import java.lang.Object.com.starbase.util.FileUtils;"?

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  • Error in connection in ruby.

    - by piemesons
    require 'rubygems' require 'mysql' db = Mysql.connect('localhost', 'root', '', 'mohit') //db.rb:4: undefined method `connect' for Mysql:Class (NoMethodError) //undefined method `real_connect' for Mysql:Class (NoMethodError) db.query("CREATE TABLE people ( id integer primary key, name varchar(50), age integer)") db.query("INSERT INTO people (name, age) VALUES('Chris', 25)") begin query = db.query('SELECT * FROM people') puts "There were #{query.num_rows} rows returned" query.each_hash do |h| puts h.inspect end rescue puts db.errno puts db.error end error i am geting is: undefined method `connect' for Mysql:Class (NoMethodError) OR undefined method `real_connect' for Mysql:Class (NoMethodError) EDIT return value of Mysql.methods ["private_class_method", "inspect", "name", "tap", "clone", "public_methods", "object_id", "__send__", "method_defined?", "instance_variable_defined?", "equal?", "freeze", "extend", "send", "const_defined?", "methods", "ancestors", "module_eval", "instance_method", "hash", "autoload?", "dup", "to_enum", "instance_methods", "public_method_defined?", "instance_variables", "class_variable_defined?", "eql?", "constants", "id", "instance_eval", "singleton_methods", "module_exec", "const_missing", "taint", "instance_variable_get", "frozen?", "enum_for", "private_method_defined?", "public_instance_methods", "display", "instance_of?", "superclass", "method", "to_a", "included_modules", "const_get", "instance_exec", "type", "<", "protected_methods", "<=>", "class_eval", "==", "class_variables", ">", "===", "instance_variable_set", "protected_instance_methods", "protected_method_defined?", "respond_to?", "kind_of?", ">=", "public_class_method", "to_s", "<=", "const_set", "allocate", "class", "new", "private_methods", "=~", "tainted?", "__id__", "class_exec", "autoload", "untaint", "nil?", "private_instance_methods", "include?", "is_a?"] return value of Mysql.methods(false) is []... blank array

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  • resetting the image in an NSView

    - by Josan
    I think this is a very simple question, but I’m new to programming so I may be going about it in a wrong-headed way. I have a basic understanding of Objective-C writing terminal applications and am teaching myself how to use the Cocoa GUI. I understand how to use IBOutlet and IBAction to connect a simple button to a method that will repeatedly send random numbers to a textfield . I understand how to add a NSView file, connect it to a custom view in interface builder and draw a path through random points in the view when the application launches. (I’ve been putting this code inside the - (void)drawRect:(NSRect)dirtyRect method that is declared when the file is created). What I can’t seem to figure out is how to connect a button to an action that will then ‘refresh’ the view – in this case repopulate it with another set of random points connected with a path. Looking at the documentation, I think I should somehow be using – (void) setNeedsDisplay(BOOL)flag but nothing I have tried so far had worked. Please tell me, what am I missing here?

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  • Proper indentation for Python multiline strings

    - by ensnare
    What is the proper indentation for Python multiline strings within a function? def method: string = """line one line two line three""" or def method: string = """line one line two line three""" or something else? It looks kind of weird to have the string hanging outside the function in the first example. Thanks.

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  • Java: design problem with private-final-int-value and empty constructor

    - by HH
    $ javac InitInt.java InitInt.java:7: variable right might not have been initialized InitInt(){} ^ 1 error $ cat InitInt.java import java.util.*; import java.io.*; public class InitInt { private final int right; //DUE to new Klowledge: Design Problem //I think having an empty constructor like this // is an design problem, shall I remove it? What do you think? // When to use an empty constructor? InitInt(){} public static void main(String[] args) { InitInt test = new InitInt(); System.out.println(test.getRight()); } public int getRight(){return right;} } Initialization problem with Constructor InitInt{ // Still the error, "may not be initialized" // How to initialise it? if(snippetBuilder.length()>(charwisePos+25)){ right=charwisePos+25; }else{ right=snippetBuilder.length()-1; } }

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  • PHP Form checkbox question

    - by Sef
    Hello, I have a form that takes the following inputs: Name: IBM Surface(in m^2): 9 Floor: (Checkbox1) Phone: (Checkbox2) Network: (Checkbox3) Button to send to a next php page. All those values above are represented in a table when i press the submit button. The first two (name and surname) are properly displayed in the table. The problem is with the checkboxes. If i select the first checkbox the value in the table should be presented with 1. If its not selected the value in the table should be empty. echo "<td>$Name</td>"; // works properly echo "<td>$Surface</td>"; // works properly echo "<td>....no idea for the checkboxes</td>; Some part of my php code with the variables: <?php if (!empty($_POST)) { $standnaam = $_POST["name"]; $oppervlakte = $_POST["surface"]; $verdieping = $_POST["floor"]; $telefoon = $_POST["telefoon"]; $netwerk = $_POST["netwerk"]; if (is_numeric($surface)) { $_SESSION["name"]=$name; $_SESSION["surface"]=$surface; header("Location:ExpoOverzicht.php"); } else { echo "<h1>Wrong input, Pleasee fill in again</h1>"; } if(!empty($floor) && ($phone) && ($network)) { $_SESSION["floor"]=$floor; $_SESSION["phone"]=$phone; $_SESSION["network"]=$network; header("Location:ExpoOverzicht.php"); } } ?> Second page with table: <?php $name= $_SESSION["name"]; $surface= $_SESSION["surface"]; $floor= $_SESSION["floor"]; $phone= $_SESSION["phone"]; $network= $_SESSION["network"]; echo "<table class=\"tableExpo\">"; echo "<th>name</th>"; echo "<th>surface</th>"; echo "<th>floor</th>"; echo "<th>phone</th>"; echo "<th>network</th>"; echo "<th>total price</th>"; for($i=0; $i <= $_SESSION["name"]; $i++) { echo "<tr>"; echo "<td>$name</td>"; // gives right output echo "<td>$surface</td>"; // gives right output echo "<td>...</td>"; //wrong output (ment for checkbox 1) echo "<td>...</td>"; //wrong output (ment for checkbox 2) echo "<td>...</td>"; //wrong output (ment for checkbox 3) echo "<td>....</td>"; echo "</tr>;"; } echo "</table>"; <form action="<?php echo $_SERVER["PHP_SELF"]; ?>" method="post" id="form1"> <h1>Vul de gegevens in</h1> <table> <tr> <td>Name:</td> <td><input type="text" name="name" size="18"/></td> </tr> <tr> <td>Surface(in m^2):</td> <td><input type="text" name="surface" size="6"/></td> </tr> <tr> <td>Floor:</td> <td><input type="checkbox" name="floor" value="floor"/></td> </tr> <tr> <td>Phone:</td> <td><input type="checkbox" name="phone" value="phone"/></td> </tr> <tr> <td>Network:</td> <td><input type="checkbox" name="network" value="network"/></td> </tr> <tr> <td><input type="submit" name="verzenden" value="Verzenden"/></td> </tr> </table> There might be a few spelling mistakes since i had to translate it. Best regards.

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  • Writing a string which contains " "

    - by dotnetdev
    I have a string from an xml document: <title type="html"> Is there a way for me to write this string like "<title type="html">"? I've had similar problems writing javascript as a string but I did see some solutions in the past (which I can't remember)? Thanks

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  • How big can I make an Android application's canvas in terms of pixels?

    - by user279112
    I've determined an estimate of the size of my Android emulator's screen in pixels, although I think its resolution can be changed to other numbers. Quite frankly though that doesn't eliminate the general problem of not knowing how many pixels on each axis I have to work with on my Android applications in general. The main problem I'm trying to solve is this: How do I make sure I don't use a faulty resolution on Android applications if I want to keep things' sizes constant (so that if the application screen shrinks, for instances, objects will still show up just as big - there just won't be as many of them being shown) if I wish to do this with a single universal resolution for each program? Failing that, how do I make sure everything's alright if I try to do everything the same way with maybe a few different pre-set resolutions? Mainly it seems like a relevant question that must be answered before I can come across a complete answer for the general problem is how big can I always make my application in pixels, NOT regarding if and when a user resizes the application's screen to something smaller than the maximum size permitted by the phone and its operating system. I really want to try to keep this simple. If I were doing this for a modern desktop, for instance, I know that if I design the application with a 800x600 canvas, the user can still shrink the application to the point they're not doing themselves any favors, but at least I can basically count on it working right and not being too big for the monitor or something. Is there such a magic resolution for Android, assuming that I'm designing for API levels 3+ (Android 1.5+)? Thanks

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  • C++ initializing constants and inheritance

    - by pingvinus
    I want to initialize constant in child-class, instead of base class. And use it to get rid of dynamic memory allocation (I know array sizes already, and there will be a few child-classes with different constants). So I try: class A { public: const int x; A() : x(0) {} A(int x) : x(x) {} void f() { double y[this->x]; } }; class B : A { B() : A(2) {} }; Pretty simple, but compiler says: error C2057: expected constant expression How can I say to compiler, that it is really a constant?

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  • run multiple programs in linux

    - by Betamoo
    I am trying to write a .sh file that runs many programs simultaneously I tried this prog1 prog2 But that runs prog1 then waits until prog1 ends and then starts prog2... So how can I run them in parallel? Thanks

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  • Another dynamic memory allocation bug.

    - by m4design
    I'm trying to allocate memory for a multidimensional array (8 rows, 3 columns). Here's the code for the allocation (I'm sure the error is clear for you) char **ptr = (char **) malloc( sizeof(char) * 8); for (i = 0; i < 3; i++) ptr[i] = (char *) malloc( sizeof(char) * 3); The crash happens when I reference this: ptr[3][0]; Unhandled exception at 0x0135144d in xxxx.exe: 0xC0000005: Access violation writing location 0xabababab. Are there any recommended references/readings for this kind of subject? Thanks.

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  • In DOM is it OK to use .notation for getting/setting attributes?

    - by Ziggy
    Hi In DOM, is it OK to refer to an element's attributes like this: var universe = document.getElementById('universe'); universe.origin = 'big_bang'; universe.creator = null; universe.style.deterministic = true; ? My deep respect for objects and their privacy, and my sense that things might go terribly wrong if I am not careful, makes me want to do everything more like this: var universe = document.getElementById('universe'); if(universe.hasAttribute('origin')) then universe.origin = 'big_bang'; etc... Is it really necessary to use those accessor methods? Of course it may be more or less necessary depending on how certain I am that the elements I am manipulating will have the attributes I expect them to, but in general do the DOM guys consider it OK to use .notation rather than getters and setters? Thanks!

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  • Java: how to have global values inside a class?

    - by HH
    I want less methods. I want a common global TestClass from which I could use any of its value inside the class. import java.util.*; import java.io.*; public class TestClass { TestClass(String hello){ String hallo = hello; String halloSecond = "Saluto!"; } public static void main(String[] args) { TestClass test = new TestClass("Tjena!"); System.out.println("I want "Tjena!": " + test.hallo); TestClass testSecond = new TestClass("1"); System.out.println("I want Saluto!:" + test.halloSecond); System.out.println("I want Saluto!:" + testSecond.halloSecond); // How can I get glob.vars like the "Saluto!"? } }

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  • Which MS technologies would be suited for a data intensive application?

    - by steve.tse
    I'm a junior VB.net developer with little application design knowledge. I've been reading a lot of material online regarding different design patterns, frameworks, and methodologies. It's become a bit confusing for me. Right now I'm trying to decide on what language would be best suited to convert an existing VB6 application (with SQL server backend.) I need to update the UI and add more user functionality and reporting capabilities. Initially I was thinking of using WPF and attempting the MVVM model for this big project. Reports would be generated from SSRS. A peer suggested using ASP.net and I don't have enough experience to determine what would be better. The senior programmers here are stuck on using VB6 and don't have any input on what to use. They are encouraging me to use the latest technologies. This application would be for ~20 users in a central location. Ideally I would stick to a Microsoft .net language. Current interface is similar to a datagrid table where the user would click in to see the detail of each record. They would need to have multiple records open at any given time. I look forward to all the advice I can get. EDIT 2010/04/22 2:47 PM EST What is your audience? Internal clients within an intranet How complex are the interactions you expect to implement? not very... displaying data from SQL server to UI. Allow user updates to said data. Typically just one user modifying a record. Do you require near real-time data updates? no How often do you expect to update the application after the first release? twice/year Do you expect a well-defined set of client platforms? Yes, windows xp environment, potentially upgrading to Win7. Currently in IE.6 moving to IE7 or 8 within a couple of months. Do users need access from anywhere? No, just from their PC.

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