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  • Best (functional?) programming language to learn coming from Mathematica

    - by Will Robertson
    As a mechanical engineering PhD student, I haven't had a great pedigree in programming as part of my “day job”. I started out in Matlab (having written some Hypercard and Applescript back in the day, and being introduced to Ada, of all things, in my 1st undergrad year), learned to program—if you can call it that—in (La)TeX; and finally discovered and fell for Mathematica. Now I'm interested in learning a "real" programming language that I can enjoy in the same sort of style as Mathematica, which tries to stress functional programming since it seems to map more nicely to how certain kinds of mathematics can be written algorithmically. So which functional language should I learn? I guess the obvious answer is “as many as possible”, but let's start out humble and give a single, well-considered option a good crack. I've heard good things about, say, Haskell and Scala, but I wonder if (given my non–computer science background) I'd be better off starting in more “grounded” territory and going with Ruby or Python (the latter having the big advantage of being used for Sage, which I'd also like to investigate…after my PhD). Well, I guess this is pretty subjective, so perhaps I could rephrase: would it be better to start looking at Haskell (say) straight after an ad-hoc education to functional programming in Mathematica, or will I get more out of learning Python (say) first? In reference to the question "what do I want to do with it?", I guess my answer is "fun, and learning more". I've got this list of languages that I'd like to look at, and I don't know how to trim them down. And I'd rather start with something a little higher-level than C simply so that I can be somewhat productive without having to re-invent many wheels for any code I'd like to write.

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  • Dom Traversal to Automate Keyboard Focus - Spatial Navigation

    - by Steve
    I'm going to start with a little background that will hopefully help my question make more sense. I am developing an application for a television. The concept is simple and basically works by overlaying a browser over the video plane of the TV. Now being a TV, there is no mouse or additional pointing device. All interaction is done through a remote control. Therefore, the user needs to be able to visually tell which element they are currently focused upon. To indicate that an element is focused, I currently append a colored transparent image over the element to indicate focus. Now, when a user hits the arrow keys, I need to respond by focusing on the correct elements according to the key pressed. So, if the down arrow is pressed I need to focus on the next focusable element in the DOM tree (which may be a child or sibling), and if they hit the up arrow, I need to respond to the previous element. This would essentially simulate spatial navigation within a browser. I am currently setting an attribute (focusable=true) on any DOM elements that should be able to receive focus. What I would like to do is determine the previous or next focusable element (i.e. attribute focusable=true) and apply focus to the element. I was hoping to traverse the DOM tree to determine the next and previously focusable elements, but I am not sure how to perform this in JQuery, or in general. I was leaning towards trying to use the JQuery tree travesal methods like next(), prev(), etc. What approach would you take to solve this type of issue? Thanks

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  • Including Data From DropDownList Into Gridview

    - by Mike Keller
    I feel a little embarassed posting two questions relating to the same problem, but the first one ended up answering a question that I believe is unrelated to the solution so I'm leaving it up and outlining what I'm trying to accomplish with the hopes that someone can help out a .Net noob. What I need to be able to do is create a field in my gridview that contains a link that passes two variables. One is pulled from within the gridviews datasource and the other needs to be pulled from a textbox control outside the gridview. From what I've read so far you cannot use a hyperlinkfield for this as the datanavigateurlfields cannot be set to pull from anything but the gridview's data source. What I attempted to do was create a template field where in the itemtemplate I called: <a href="example.aspx?e=<%# Eval(ExampleList.SelectedItem.Value) %>">Test</a> That comes back with an error like this: DataBinding: 'System.Data.DataRowView' does not contain a property with the value 'TestData' Any clues to make this happen would be appreciated, like I said I'm pretty new to .Net so please be gentle. I tried to do my homework before posting this.

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  • How to accommodate for the next iPhones totally different screen resolution?

    - by mystify
    This is a programming question! Read on before you vote to close! According to Gizmodo, the next iPhone will have a new screen resolution: The 3.5-inch screen has a resolution of 960?×?640 pixels This little detail affects our apps in a heavy way. Most of the demo apps on the net have one thing in common: They position views in the believe that the screen has a fixed size of 320 x 480 pixels. So what most -if not all- developers do is: They designed everything in such a way, that a touchable area is -for example- 50 x 50 pixels big. Just enough to tap it. Things have been positioned relative to the upper left, to reach a specific position on screen - let's say the center, or somewhere at the bottom. So the big question is: How will the developers compensate their layout and graphics? Are there already solutions which can be used to calculate coordinates and sizes in a normalized manner, which then appear to be exactly the same when viewing them on a screen of any resolution, assuming at least that the aspect ration won't change? This is community wiki. Just add anything that you think is relevant to this huge problem (constant screen res was one of the main reasons why I didn't go for Android!!).

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  • Counting a cell up per Objects

    - by Auro
    hey i got a problem once again :D a little info first: im trying to copy data from one table to an other table(structure is the same). now one cell needs to be incremented, beginns per group at 1 (just like a histroy). i have this table: create table My_Test/My_Test2 ( my_Id Number(8,0), my_Num Number(6,0), my_Data Varchar2(100)); (my_Id, my_Num is a nested PK) if i want to insert a new row, i need to check if the value in my_id already exists. if this is true then i need to use the next my_Num for this Id. i have this in my Table: My_Id My_Num My_Data 1 1 'test1' 1 2 'test2' 2 1 'test3' if i add now a row for my_Id 1, the row would look like this: i have this in my Table: My_Id My_Num My_Data 1 3 'test4' this sounds pretty easy ,now i need to make it in a SQL and on SQL Server i had the same problem and i used this: Insert Into My_Test (My_Id,My_Num,My_Data) SELECT my_Id, ( SELECT CASE ( CASE MAX(a.my_Num) WHEN NULL THEN 0 Else Max(A.My_Num) END) + b.My_Num WHEN NULL THEN 1 ELSE ( CASE MAX(a.My_Num) WHEN NULL THEN 0 Else Max(A.My_Num) END) + b.My_Num END From My_Test A where my_id = 1 ) ,My_Data From My_Test2 B where my_id = 1; this Select gives null back if no Rows are found in the subselect is there a way so i could use max in the case? and if it give null back it should use 0 or 1? greets Auro

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  • Change workarea size of Linux desktop

    - by nonoitall
    I'm trying to write a taskbar/panel for Linux (like fbpanel or pypanel) using GTK# and am a little hung up. I've created a Gtk.Window to act as the panel and positioned/resized it appropriately. I've also set its WindowTypeHint to Dock so that it remains on top of other windows. So far it 'looks' like a panel. However, if the panel is running and I maximize another window, that window fills the whole desktop - meaning the bottom portion of the window is covered up by my panel. I've gathered that I probably need to change the desktop's workarea. How can I go about doing this in C#? (Preferably using GTK#, but I don't mind using interop if it's necessary.) As a bit of a side point, I'm curious if anyone knows how I would go about 'informing' the window manager about where applications' taskbar buttons are. (For example, if the window manager wants to animate the minimize action so that the window shrinks down to its button on the taskbar, how do I let the window manager know where that button is on the taskbar?)

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  • PHP hashing function not working properly

    - by Jordan Foreman
    So I read a quick PHP login system securing article, and was trying to sort of duplicate their hashing method, and during testing, am not getting the proper output. Here is my code: function decryptPassword($pw, $salt){ $hash = hash('sha256', $salt . hash('sha256', $pw)); return $hash; } function encryptPassword($pw){ $hash = hash('sha256', $pw); $salt = substr(md5(uniqid(rand(), true)), 0, 3); $hash = hash('sha265', $salt . $hash); return array( 'salt' => $salt, 'hash' => $hash ); } And here is my testing code: $pw = $_GET['pw']; $enc = encryptPassword($pw); $hash = $enc['hash']; $salt = $enc['salt']; echo 'Pass: ' . $pw . '<br />'; echo 'Hash: ' . $hash . '<br />'; echo 'Salt: ' . $salt . '<br />'; echo 'Decrypt: ' . decryptPassword($hash, $salt); Now, the output of this should be pretty obvious, but unfortunately, the $hash variable always comes out empty! I'm trying to figure out what the problem could be, and my only guess would be the second $hash assignment line in the encryptPassword(..) function. After a little testing, I've determined that the first assignment works smoothly, but the second does not. Any suggestions? Thanks SO!

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  • How to avoid mouse move on Touch

    - by VirtualBlackFox
    I have a WPF application that is capable of being used both with a mouse and using Touch. I disable all windows "enhancements" to just have touch events : Stylus.IsPressAndHoldEnabled="False" Stylus.IsTapFeedbackEnabled="False" Stylus.IsTouchFeedbackEnabled="False" Stylus.IsFlicksEnabled="False" The result is that a click behave like I want except on two points : The small "touch" cursor (little white star) appears where clicked an when dragging. Completely useless as the user finger is already at this location no feedback is required (Except my element potentially changing color if actionable). Elements stay in the "Hover" state after the movement / Click ends. Both are the consequences of the fact that while windows transmit correctly touch events, he still move the mouse to the last main-touch-event. I don't want windows to move the mouse at all when I use touch inside my application. Is there a way to completely avoid that? Notes: Handling touch events change nothing to this. Using SetCursorPos to move the mouse away make the cursor blink and isn't really user-friendly. Disabling the touch panel to act as an input device completely disable all events (And I also prefer an application-local solution, not system wide). I don't care if the solution involve COM/PInvoke or is provided in C/C++ i'll translate. If it is necessary to patch/hook some windows dlls so be it, the software will run on a dedicated device anyway. I'm investigating the surface SDK but I doubt that it'll show any solution. As a surface is a pure-touch device there is no risk of bad interaction with the mouse.

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  • Update text on CCLabelTFF end in bad access?

    - by TheDeveloper
    I'm doing a little game in Coco2D and I have a countdown clock Note: As I am just trying to fix a bug, I am not working on cleanup so the timer can stop, etc. Here is my code I'm using to setup the label and start the timer: timer = [CCLabelTTF labelWithString:@"10.0000" fontName:@"Helvetica" fontSize:20]; timerDisplay = timer; timerDisplay.position = ccp(277,310); [self addChild:timerDisplay]; timeLeft = 10; timerObject = [NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(updateTimer) userInfo:nil repeats:YES]; Note: timeLeft is a double This is updateTimers's code: -(void)updateTimer { NSLog(@"Got Called!"); timeLeft = timeLeft -0.1; [timer setString:[NSString stringWithFormat:@"%f",timeLeft]]; timerDisplay = timer; timerDisplay.position = ccp(277,310); [self removeChild:timerDisplay cleanup:YES]; //[self addChild:timerDisplay]; if (timeLeft <= 0) { [timerObject invalidate]; } } When I run this I toggle between crashing on this this: [timer setString:[NSString stringWithFormat:@"%f",timeLeft]]; and in the green arrow thing it gives Thread 1: EXEC_BAD_ACCESS (code=2, address=0x8) and 0x197a7ff: movl 16(%edi), %esi and in the green arrow thing it gives Thread 1: EXEC_BAD_ACCESS (code=2, address=0x8)

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  • Execute SSH commands on Cisco router. Codeigniter SSH library

    - by jomajo
    I have a little problem. I'm using Codeigniter with SSH library written by Shuky (https://bitbucket.org/quicktips/codeigniter-ssh2-library/src/a444968345ba/SSH.php -- You can see the code by following this link). Everything related with SSH works fine with other devices, but when I try to use this library and execute commands on Cisco devices, nothing happens (commands are not executed). I know that the connection is successful, but I can't execute any commands. When I try to run and execute comands through SSH on Cisco devices I get this error: A PHP Error was encountered Severity: Warning Message: stream_set_blocking() expects parameter 1 to be resource, boolean given Filename: libraries/SSH.php Line Number: 128 A PHP Error was encountered Severity: Warning Message: fread() expects parameter 1 to be resource, boolean given Filename: libraries/SSH.php Line Number: 129 In the library these lines look like this: /** * Get stream data * * @access privte * @return bool */ function _get_stream_data($stream) { stream_set_blocking( $stream, true ); while( $buf = fread($stream,4096) ) { $this->data .= $buf.'~'; } return TRUE; } line 128 - stream_set_blocking( $stream, true ); line 129 - while( $buf = fread($stream,4096) ) { Maybe you guys know where the problem is? Thank you for your time and your answers!

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  • newbie hibernate first level cache confusion

    - by Bruce
    Hi all I'm just geting to grips with hibernate. Little bit confused. I just wanted to watch the operation of the first level cache, which I understood to batch up queries until the end of the session. But if I create an object, hibernate saves it immediately, so that when I later update it in the same transaction, it has to do an update too: Session session = factory.getCurrentSession(); session.beginTransaction(); Test1 test1 = new Test1(); test1.setName("Test 1"); test1.setValue(10); // Touch it session.save(test1); System.out.println("At checkpoint 1"); test1.setValue(20); session.getTransaction().commit(); I see the sql for the save, then 'At checkpoint 1', then the sql for the update. Do I have something set up wrong or am I misunderstanding hibernate's first level cache? Is there a good document on the first level cache - I didn't find anything in the hibernate docs, but I could easily have missed it.. Thanks!

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  • optimized search using ajax and keypress

    - by ooo
    i have the following code as i want to search a database as a user is typing into a textbox. This code below works fine but it seems a little inefficient as if a user is typing really fast, i am potentially doing many more searches than necessary. So if a user is typing in "sailing" i am searching on "sail", "saili", "sailin", and "sailing" i wanted to see if there was a way to detect any particular time between keypresses so only search if user stops typing for 500 milliseconds or something like this. is there a best practices for something like this? $('#searchString').keypress(function(e) { if (e.keyCode == 13) { var url = '/Tracker/Search/' + $("#searchString").val(); $.get(url, function(data) { $('div#results').html(data); $('#results').show(); }); } else { var existingString = $("#searchString").val(); if (existingString.length > 2) { var url = '/Tracker/Search/' + existingString; $.get(url, function(data) { $('div#results').html(data); $('#results').show(); }); } }

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  • Navigating the timeline

    - by Dean 'Deacon' Beard
    O.K, being a little new to this, I have hit a brick wall, I'm using AS3 in Flash CS5. All I want to do is have a tweened animation which stops at a frame and which has a clickable button to access another part of the maintime line. Also there will be a button on the animation to skip it. How does one set this up? Obviously you need a stop(); at the stop frame of the time line and an event listener and function for both buttons right? Any more help besides that. I have it set up like this; totalSlides:Number = 60; currentSlideNumber:Number = 1; skipbutton.addEventListener(MouseEvent.CLICK,skipbuttonPress); function skipbuttonPress(evt:MouseEvent):void{ currentframelabel = currentframelabel+1; if(currentSlideNumber>=0){ currentframelabel = introstop; } framelabel.gotoAndStop(introstop); } and the frame it stops on is set up as follows stop(); totalSlides:Number = 60; currentSlideNumber:Number = 5; click01.addEventListener(MouseEvent.CLICK,click01Press); function click01Press( evt : MouseEvent ) : void { currentSlideNumber = currentSlideNumber+1; if (currentSlideNumber >= 0) { currentSlideNumber = 25; } framelabel.gotoAndStop(mainpage); } As I need this for a project, any help would be greatly valued. Many Thanks

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  • Long primitive or AtomicLong for a counter?

    - by Rich
    Hi I have a need for a counter of type long with the following requirements/facts: Incrementing the counter should take as little time as possible. The counter will only be written to by one thread. Reading from the counter will be done in another thread. The counter will be incremented regularly (as much as a few thousand times per second), but will only be read once every five seconds. Precise accuracy isn't essential, only a rough idea of the size of the counter is good enough. The counter is never cleared, decremented. Based upon these requirements, how would you choose to implement your counter? As a simple long, as a volatile long or using an AtomicLong? Why? At the moment I have a volatile long but was wondering whether another approach would be better. I am also incrementing my long by doing ++counter as opposed to counter++. Is this really any more efficient (as I have been led to believe elsewhere) because there is no assignment being done? Thanks in advance Rich

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  • How to make DataGrid Row really fully selectable (clicking on non-cell area)

    - by Samuel
    The question might be a little misleading. Here is a screenshot of a DataGrid that has some dummy values (code provided below) Is there a way to make the white area not covered by a cell clickable? My intention: I want to have full row selection. This can be achieved by SelectionUnit="FullRow" which is fine but how can I make the white area implicitly select the entire row without expanding available cells in width and avoiding code behind Here is the repro code: Xaml: <Window x:Class="DGVRowSelectTest.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="MainWindow" Height="350" Width="525" DataContext="{Binding RelativeSource={RelativeSource Self}}"> <DataGrid ItemsSource="{Binding Names}" SelectionMode="Single" SelectionUnit="FullRow" > </DataGrid> </Window> Dummy Code behind of it (just sets the two entries up) using System.Collections.Generic; using System.Windows; namespace DGVRowSelectTest { public partial class MainWindow : Window { private IList<KeyValuePair<string, string>> _names = new List<KeyValuePair<string, string>>{new KeyValuePair<string, string>("A1", "A2"),new KeyValuePair<string, string>("B1","B2")}; public IList<KeyValuePair<string, string>> Names{get { return _names; }set { _names = value; }} public MainWindow() { InitializeComponent(); } } }

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  • SQL Binary Microsoft Access - Combining two tables if specific field values are equal

    - by Jordan
    I am new to Microsoft Access and SQL but have a decent programming background and I believe this problem should be relatively simple. I have two tables that I have imported into Access. I will give you a little context. One table is huge and contains generic, global data. The other table is still big but contains specific, regional data. There is only one common field (or column) between the two tables. Let’s call this common field CF. The other fields in both tables are different. I’ll take you through one iteration of what I need to do. I need to take each CF value in the regional, smaller table and find the common CF value in the larger, global table. After finding the match, I need to take the whole “record” or “row” from the global data and copy it over to the corresponding record in the smaller regional table (This should involve creating the new fields). I need to do this for all CF values in the regional, smaller table. I was recommended to use SQL and a binary search, but I am unfamiliar. Let me know if you have any questions. I appreciate the help!

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  • What are the javascript performance tradeoffs in adding id's to dom elements?

    - by Blinky
    For example, I have a website which has a dynamically-generated segment of its dom which looks roughly like this: <div id="master"> <div class="child"> ... </div> <div class="child"> ... </div> <div class="child"> ... </div> ... <div class="child"> ... </div> </div> There might be hundreds of child elements in this manner, and they, too, might have yet more children. At present, none of them have id's except for the master. Javascript manipulates them via dom-walking. It's a little scary. I'd like to add id's, e.g.: <div id="master"> <div id="child1" class="child"> ... </div> <div id="child2" class="child"> ... </div> <div id="child3" class="child"> ... </div> ... <div id="childN" class="child"> ... </div> </div> What are the tradeoffs in adding id's to these divs? Certainly, jQuery must maintain a hash of id's, so there's going to be some sort of performance hit. Any general guidelines in when adding additional id's is a bad idea? Is jQuery so awesome that, in practice, it doesn't matter?

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  • Confusion with a while statement evaluating if a number is triangular

    - by Darkkurama
    I've been having troubles trying to figure out how to solve a function. I've been assigned the development of a little programme which tells if a number is "triangular" (a number is triangular when the addition of certain consecutive numbers in the [1,n] interval is n. Following the definition, the number 10 is triangular, because in the [1,10] interval, 1+2+3+4=10). I've coded this so far: class TriangularNumber{ boolean numTriangular(int n) { boolean triangular = false; int i = n; while(n>=0 && triangular){ //UE06 is a class which contains the function "f0", which makes the addition of all the numbers in a determined interval UE06 p = new UE06(); if ((p.f0(1, i))==n) triangular = true; else i=i-1; } return triangular; } boolean testTriangular = numTriangular(10) == true && numTriangular(7) == false && numTriangular(6) == true; public static void main(String[] args){ TriangularNumber p = new TriangularNumber(); System.out.println("testTriangular = " + p.testTriangular); } } According to those boolean tests I made, the function is wrong. As I see the function, it goes like this: I state that the input number in the initial state isn't triangular (triangular=false) and i=n (determining the interval [1,i] where the function is going to be evaluated While n is greater or equals 0 and the number isn't triangular, the loop starts The loop goes like this: if the addition of all the numbers in the [1,i] interval is n, the number is triangular, causing the loop to end. If that statement is false, i goes from i to (i-1), starting the loop again with that particular interval, and so on till the addition is n. I can't spot the error in my "algorithm", any advice? Thanks!

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  • WP7 - listbox Binding

    - by Jeff V
    I have an ObservableCollection that I want to bind to my listbox... lbRosterList.ItemsSource = App.ViewModel.rosterItemsCollection; However, in that collection I have another collection within it: [DataMember] public ObservableCollection<PersonDetail> ContactInfo { get { return _ContactInfo; } set { if (value != _ContactInfo) { _ContactInfo = value; NotifyPropertyChanged("ContactInfo"); } } } PersonDetail contains 2 properties: name and e-mail I would like the listbox to have those values for each item in rosterItemsCollection RosterId = 0; RosterName = "test"; ContactInfo.name = "Art"; ContactInfo.email = "[email protected]"; RosterId = 0; RosterName = "test" ContactInfo.name = "bob"; ContactInfo.email = "[email protected]"; RosterId = 1; RosterName = "test1" ContactInfo.name = "chris"; ContactInfo.email = "[email protected]"; RosterId = 1; RosterName = "test1" ContactInfo.name = "Sam"; ContactInfo.email = "[email protected]"; I would like that listboxes to display the ContactInfo information. I hope this makes sense... My XAML that I've tried with little success: <listbox x:Name="lbRosterList" ItemsSource="rosterItemCollection"> <textblock x:name="itemText" text="{Binding Path=name}"/> What am I doing incorrectly?

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  • All connections in pool are in use

    - by veljkoz
    We currently have a little situation on our hands - it seems that someone, somewhere forgot to close the connection in code. Result is that the pool of connections is relatively quickly exhausted. As a temporary patch we added Max Pool Size = 500; to our connection string on web service, and recycle pool when all connections are spent, until we figure this out. So far we have done this: SELECT SPId FROM MASTER..SysProcesses WHERE DBId = DB_ID('MyDb') and last_batch < DATEADD(MINUTE, -15, GETDATE()) to get SPID's that aren't used for 15 minutes. We're now trying to get the query that was executed last using that SPID with: DBCC INPUTBUFFER(61) but the queries displayed are various, meaning either something on base level regarding connection manipulation was broken, or our deduction is erroneous... Is there an error in our thinking here? Does the DBCC / sysprocesses give results we're expecting or is there some side-effect catch? (for example, connections in pool influence?) (please, stick to what we could find out using SQL since the guys that did the code are many and not all present right now)

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  • Creating UTF-8 files in Java from a runnable Jar

    - by RuntimeError
    I have a little Java project where I've set the properties of the class files to UTF-8 (I use a lot of foreign characters not found on the default CP1252). The goal is to create a text file (in Windows) containing a list of items. When running the class files from Eclipse itself (hitting Ctrl+F11) it creates the file flawlessly and opening it in another editor (I'm using Notepad++) I can see the characters as I wanted. +--------------------------------------------------+ ¦ Universidade2010 (18/18)¦ ¦ hidden: 0¦ +--------------------------------------------------¦ But, when I export the project (using Eclipse) as a runnable Jar and run it using 'javaw -jar project.jar' the new file created is a mess of question marks ???????????????????????????????????????????????????? ? Universidade2010 (19/19)? ? hidden: 0? ???????????????????????????????????????????????????? I've followed some tips on how to use UTF-8 (which seems to be broken by default on Java) to try to correct this so now I'm using Writer w = new OutputStreamWriter(fos, "UTF-8"); and writing the BOM header to the file like in this question already answered but still without luck when exporting to Jar Am I missing some property or command-line command so Java knows I want to create UTF-8 files by default ?

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  • sending large data .getJSON or proxy ?

    - by numerical25
    Hey guys. I was told that the only trick to sending data to a external server (i.e x-domain) is to use getJSON. Well my problem is that the data I am sending exceeds the getJSON data limit. I am tracking mouse movements on a screen for analytics. Another option is I could also send a little data at a time. probably every time the mouse moves. but that seems as if it would slow things down. I could setup a proxy server. My question is which would be better? Setting up a proxy server ? or Just sending bits of information via javascript or JQUERY. What do the professionals use (Google and other company's that build mash-ups that send a lot of data to x-domain sites.) I need to know the best practices. Thanx!! Also the data is put into JSON.

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  • In this example where is the C++ assignment operator used rather than the copy constructor ?

    - by Bill Forster
    As part of an ongoing process of trying to upgrade my C++ skills, I am trying to break some old habits. My old school C programmer inclination is to write this; void func( Widget &ref ) { Widget w; // default constructor int i; for( i=0; i<10; i++ ) { w = ref; // assignment operator // do stuff that modifies w } } This works well. But I think the following is closer to best practice; void func( Widget &ref ) { for( int i=0; i<10; i++ ) { Widget w = ref; // ?? // do stuff that modifies w } } With my Widget class at least, this works fine. But I don't fully understand why. I have two theories; 1) The copy constructor runs 10 times. 2) The copy constructor runs once then the assignment operator runs 9 times. Both of these trouble me a little. 2) in particular seems artificial and wrong. Is there a third possibility that I am missing ?

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  • Dependencyproperty doesn't have value on load

    - by Jakob
    My problem is this, I have a UC called profile that contains another UC called FollowImageControl. In my Profile.xaml i declaretively bind a property of FollowImageControl called FollowerId to a CurrentUserId from Profile.xaml.cs. Problem is that I CurrentUserId is assigned in Profile.xaml.cs; the Profile.xaml code-behind. This means that I do not initially get the FollowerId. I have these methods in the FollowImageControl.xaml.cs: public static readonly DependencyProperty _followUserId = DependencyProperty.Register("FollowUserId", typeof(Guid), typeof(FollowImageControl), null); public Guid FollowUserId { get { return (Guid)GetValue(_followUserId); } set { SetValue(_followUserId, value); } } public FollowImageControl() { // Required to initialize variables InitializeComponent(); LoggedInUserId = WebContext.Current.User.UserId; var ctx = new NotesDomainContext(); if (ctx.IsFollowingUser(LoggedInUserId, FollowUserId).Value) SwitchToDelete.Begin(); } private void AddImg_MouseLeftButtonDown(object sender, MouseButtonEventArgs e) { if (LoggedInUserId != FollowUserId) { var ctx = new NotesDomainContext(); ctx.FollowUser(FollowUserId, LoggedInUserId); ctx.SubmitChanges(); } } THE WEIRD THING IS that when i insert breakpoints the FollowerUserId in FollowImageControl() is 0, but it has a value in AddImg_MouseLeftButtonDown, and there is no inbetween logic that sets the value of it. How is this??? Here's a little more code info: This is my binding from profile.xaml <internalCtrl:FollowImageControl FollowUserId="{Binding ElementName=ProfileCtrl, Path=CurrentUserId}" /> this is my constructor in profile.xaml.cs wherein the CurrentUserId is set public static readonly DependencyProperty _CurrentUserId = DependencyProperty.Register("CurrentUserId", typeof(Guid), typeof(Profile), null); public Guid CurrentUserId { get { return (Guid)GetValue(_CurrentUserId); } set { SetValue(_CurrentUserId, value); } } public Profile(Guid UserId) { CurrentUserId = UserId; InitializeComponent(); Loaded += new RoutedEventHandler(Profile_Loaded); } I'm seriously dumbfound that one minute the FollowerId has no value, and the next it holds the right, without me having changed the value in the code-behind.

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  • How to pass variables to slot methods in QT?

    - by Neko
    Hi. I'm making a little chat messenger program, which needs a list of chat channels the user has joined. To represent this list graphically, I have made a list of QPushButtons, which all represent a different channel. These buttons are made with the following method, and that's where my problem kicks in: void Messenger::addToActivePanels(std::string& channel) { activePanelsContents = this->findChild<QWidget *>(QString("activePanelsContents")); pushButton = new QPushButton(activePanelsContents); pushButton->setObjectName("pushButton"); pushButton->setGeometry(QRect(0, 0, 60, 60)); pushButton->setText(""); pushButton->setToolTip(QString(channel.c_str())); pushButton->setCheckable(true); pushButton->setChecked(false); connect(pushButton, SIGNAL(clicked()), this, SLOT(switchTab(channel))); } (activePanelContents is a QWidget that holds the list.) The point is that each button should call the switchTab(string& tabname) method when clicked, including the specific channel's name as variable. This implementation doesn't work though, and I haven't been able to find out how to properly do this, even after reading several pages on it on the internet. Can anybody please tell me how to do this? It'd be greatly appreciated, as always. :)

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