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• C++ smart pointer for non-object type?

  - by Brian

  Hi, I'm trying to use smart pointers such as auto_ptr, shared_ptr. However, I don't know how to use it in this situation. CvMemStorage *storage = cvCreateMemStorage(); ... use the pointer ... cvReleaseMemStorage(&storage); I'm not sure, but I think that the storage variable is just malloc'ed memory, not object. Is there a way to use the smart pointers for the storage variable? Thank you.

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• JavaFX - question regarding binding button's disabled state

  - by jamiebarrow

  I'm trying to create a dummy application that maintains a list of tasks. For now, all I'm trying to do is add to the list. I enter a task name in a text box, click on the add task button, and expect the list to be updated with the new item and the task name input to be cleared. I only want to be able to add tasks if the task name is not empty. The below code is my implementation, but I have a question regarding the binding. I'm binding the textbox's text variable to a string in my view model, and the button's disable variable to a boolean in my view model. I have a trigger to update the disabled state when the task name changes. When the binding of the task name happens the boolean is updated accordingly, but the button still appears disabled. But then when I mouse over the button, it becomes enabled. I believe this is due to JavaFX 1.3's binding being lazy - only updates the bound variable when it is read. Also, when I've added the task, I clear the task name in the model, but the textbox's text doesn't change - even though I'm using bind with inverse. Is there a way to make the textbox's text and the button's disabled state update automatically via the binding as I was expecting? Thanks, James AddTaskViewModel.fx: package jamiebarrow; import java.lang.System; public class AddTaskViewModel { function logChange(prop:String,oldValue,newValue):Void { println("{System.currentTimeMillis()} : {prop} [{oldValue}] to [{newValue}] "); } public var newTaskName: String on replace old { logChange("newTaskName",old,newTaskName); isAddTaskDisabled = (newTaskName == null or newTaskName.trim().length() == 0); }; public var isAddTaskDisabled: Boolean on replace old { logChange("isAddTaskDisabled",old,isAddTaskDisabled); }; public var taskItems = [] on replace old { logChange("taskItems",old,taskItems); }; public function addTask() { insert newTaskName into taskItems; newTaskName = ""; } } Main.fx: package jamiebarrow; import javafx.scene.control.Button; import javafx.scene.control.TextBox; import javafx.scene.control.ListView; import javafx.scene.Scene; import javafx.scene.layout.VBox; import javafx.stage.Stage; import javafx.scene.layout.HBox; def viewModel = AddTaskViewModel{}; var txtName: TextBox = TextBox { text: bind viewModel.newTaskName with inverse onKeyTyped: onKeyTyped }; function onKeyTyped(event): Void { txtName.commit(); // ensures model is updated cmdAddTask.disable = viewModel.isAddTaskDisabled;// the binding only occurs lazily, so this is needed } var cmdAddTask = Button { text: "Add" disable: bind viewModel.isAddTaskDisabled with inverse action: onAddTask }; function onAddTask(): Void { viewModel.addTask(); } var lstTasks = ListView { items: bind viewModel.taskItems with inverse }; Stage { scene: Scene { content: [ VBox { content: [ HBox { content: [ txtName, cmdAddTask ] }, lstTasks ] } ] } }

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• Problem with "scopes" of variables in try catch blocks in Java

  - by devoured elysium

  Could anyone explain me why in the last lines, br is not recognized as variable? I've even tried putting br in the try clause, setting it as final, etc. Does this have anything to do with Java not support closures? I am 99% confident similar code would work in C#. private void loadCommands(String fileName) { try { final BufferedReader br = new BufferedReader(new FileReader(fileName)); while (br.ready()) { actionList.add(CommandFactory.GetCommandFromText(this, br.readLine())); } } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { if (br != null) br.close(); //<-- This gives error. It doesn't // know the br variable. } } Thanks

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• Swift CMutablePointers in factories e.g. NewMusicSequence

  - by Gene De Lisa

  How do you use C level factory methods in Swift? Let's try using a factory such as NewMusicSequence(). OSStatus status var sequence:MusicSequence status=NewMusicSequence(&sequence) This errors out with "error: variable 'sequence' passed by reference before being initialized". Set sequence to nil, and you get EXC_BAD_INSTRUCTION. You can try being explicit like this: var sp:CMutablePointer<MusicSequence>=nil status=NewMusicSequence(sp) But then you get a bad access exception when you set sp to nil. If you don't set sp, you get an "error: variable 'sp' used before being initialized" Here's the reference.

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• Grails/Spring HttpServletRequest synchronization

  - by Jeff Storey

  I was writing a simple Grails app and I have a spot in a gsp where one of my java beans in modified. <g:each in="${myList}" status="i" var="myVar"> // if the user performs some view action, update one of the myVar elements </g:each> This works, but I don't think it's quite threadsafe. myList is an http request variable but in cases of pages that use ajax (or other client side manipulations), it is possible for two threads to be modifying the same request scope variable The Spring AbstractController class provides a setSynchronizeOnSession method. Does grails provide any equivalent functionality? If not, what's the best way to protect this non-threadsafe mutation? thanks, Jeff

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• Visual Studio Debugger Voodoo

  - by LoveMeSomeCode

  Ok, maybe this isn't so amazing considering I don't really understand how the debugger works in the first place, let alone Edit and Continue, which is totally amazing. But I was wondering if anyone knew what the debugger is doing with variable declarations in this scenario. I can be debugging through my code, move the line of execution ahead - past a variables initial declaration and assignment, and the code still runs ok. If it's a value type it will have it's default value, for a ref type, null. So if I create a function that uses a variable before it's declared it won't compile, but if I use the debugger to run it that way it will still run without error. Why is this? And is this related to the fact that you can't put a breakpoint on a declaration?

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• How to get physical memory in bash

  - by Neuquino

  I need to assign the RAM in bytes to a variable in bash, has anyone know how to do it? Thanks in advance

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• Where in memory are stored nullable types?

  - by Ondrej Slinták

  This is maybe a follow up to question about nullable types. Where exactly are nullable value types (int?...) stored in memory? First I thought it's clear enough, as Nullable<T> is struct and those are value types. Then I found Jon Skeet's article "Memory in .NET", which says: Note that a value type variable can never have a value of null - it wouldn't make any sense, as null is a reference type concept, meaning "the value of this reference type variable isn't a reference to any object at all". I am little bit confused after reading this statement. So let's say I have int? a = null;. As int is normally a value type, is it stored somehow inside struct Nullable<T> in stack (I used "normally" because I don't know what happens with value type when it becomes nullable)? Or anything else happens here - perhaps in heap?

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• @property, setter and getter question?

  - by fuzzygoat

  NSString *statusValue; NSString *currentValue; @property(retain, nonatomic) NSString *statusValue; @property(retain, nonatomic) NSString *currentValue; @synthesize statusValue; @sythnesize currentValue; Given the above, if I am setting one variable to another is it work doing ... [self setStatusValue: currentValue]; or should I use the property again and use [self setStatusValue: [self currentValue]]; I suppose the latter (although maybe overkill) does tell the reader that we are using one of the objects instance variables and not some local variable. just curious really ... gary

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• Facebook writing on a wall problem - retrieves only null value.

  - by Viral

  hi all friends, I am making a game application in that I want to pass my score on wall of face book. I've completed all the things (the log in and message passing part) but when I passes the score via global variable, I am getting only null as a value and not the score that I want. Is there any way to pass data or string to Face book and write on a wall? My code is (void)viewDidLoad { static NSString* kApiKey = @"be60415be308e2b44c0ac1db83fe486b"; static NSString* kApiSecret = @"4f880c7e100321f808c41b1d3c813dfa"; _session = [[FBSession sessionForApplication:kApiKey secret:kApiSecret delegate:self] retain]; score = [NSString stringWithFormat:@"%@",appDelegate.myTextView]; [_session resume]; [super viewDidLoad]; } whre score is NSString and myTextView is NSString in other viewcontrollerfile, And appDelegate is global variable. Any help?? thanks in advance.

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• Creating many new instances vs reusing them?

  - by Hugo Riley

  I have multiple business entities in VB.NET Windows Forms application. Right now they are instanced on application startup and used when needed. They hold descriptions of business entities and methods for storing and retrieving data. To cut the long story short, they are somewhat heavy objects to construct (they have some internal dictionaries and references to other objects) created and held in one big global variable called "BLogic". Should I refactor this so that each object is created when needed and released when out of scope? Then every event on UI will probably create a few of this objects. Should I strive to minimize creation of new objects or to minimize number of static and global objects? Generally I am trying to minimize the scope of every variable but should I treat this business logic objects specially?

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• What does 'unsigned temp:3' means

  - by Munir Ahmed

  Hi, I'm trying to map a C structure to Java using JNA. I came across something that I've never seen. The struct definition is as follow, struct op { unsigned op_type:9; //---> what does this means? unsigned op_opt:1; unsigned op_latefree:1; unsigned op_latefreed:1; unsigned op_attached:1; unsigned op_spare:3; U8 op_flags; U8 op_private; }; you can see some variable being defined like unsigned op_attached:1 and I'm unsure what would that mean: would that effect number of bytes to be allocated for this particular variable? any help? Thanks, Munir

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• The C++ 'new' keyword and C

  - by Florian

  In a C header file of a library I'm using one of the variables is named 'new'. Unfortunately, I'm using this library in a C++ project and the occurence of 'new' as a variable names freaks out the compiler. I'm already using extern "C" { #include<... }, but that doesn't seem to help in this respect. Do I have to aks the library developer to change the name of that variable even though from his perspective, as a C developer, the code is absolutely fine, as 'new' is not a C keyword?

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• Find order of data inside an array

  - by user271619

  I have a simple array of stuff: $array = array("apples","oranges","strawberries"); I am trying to find the order of the stuff inside the array. (sometimes the order changes, and so do the items) I'm expecting to get something like this: "apples" = 0, "oranges = 1, "strawberries = 2 The end result has something to do with database sorting. Something like this, inside a foreach loop: UPDATE tbl SET sortorder = $neworder WHERE fruit = '$fruitname' The $neworder variable would be populated with the new order, inside the array. While the $fruit variable comes from the item inside the array.

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• The use of IN OUT in ada..

  - by maddy

  HI all, Given below is a code in ada with TYPE_VECT_B; use TYPE_VECT_B; Package TEST01 is procedure TEST01 ( In_State : IN VECT_B ; Out_State : IN OUT VECT_B ); function TEST02 ( In_State : IN VECT_B ) return Boolean ; end TEST01; The TYPE_VECT_B package specification and body is also defined below Package TYPE_VECT_B is type VECT_B is array (INTEGER range <>) OF BOOLEAN ; rounded_data : float ; count : integer ; trace : integer ; end TYPE_VECT_B; Package BODY TYPE_VECT_B is begin null; end TYPE_VECT_B; What does the variable In_State and Out_State actually mean?I think In_State means input variable.i just get confused to what actually Out_State means? Thanks Maddy

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• C++ Sentinel/Count Controlled Loop beginning programming

  - by Bryan Hendricks

  Hello all this is my first post. I'm working on a homework assignment with the following parameters. Piecework Workers are paid by the piece. Often worker who produce a greater quantity of output are paid at a higher rate. 1 - 199 pieces completed $0.50 each 200 - 399 $0.55 each (for all pieces) 400 - 599 $0.60 each 600 or more $0.65 each Input: For each worker, input the name and number of pieces completed. Name Pieces Johnny Begood 265 Sally Great 650 Sam Klutz 177 Pete Precise 400 Fannie Fantastic 399 Morrie Mellow 200 Output: Print an appropriate title and column headings. There should be one detail line for each worker, which shows the name, number of pieces, and the amount earned. Compute and print totals of the number of pieces and the dollar amount earned. Processing: For each person, compute the pay earned by multiplying the number of pieces by the appropriate price. Accumulate the total number of pieces and the total dollar amount paid. Sample Program Output: Piecework Weekly Report Name Pieces Pay Johnny Begood 265 145.75 Sally Great 650 422.50 Sam Klutz 177 88.5 Pete Precise 400 240.00 Fannie Fantastic 399 219.45 Morrie Mellow 200 110.00 Totals 2091 1226.20 You are required to code, compile, link, and run a sentinel-controlled loop program that transforms the input to the output specifications as shown in the above attachment. The input items should be entered into a text file named piecework1.dat and the ouput file stored in piecework1.out . The program filename is piecework1.cpp. Copies of these three files should be e-mailed to me in their original form. Read the name using a single variable as opposed to two different variables. To accomplish this, you must use the getline(stream, variable) function as discussed in class, except that you will replace the cin with your textfile stream variable name. Do not forget to code the compiler directive #include < string at the top of your program to acknowledge the utilization of the string variable, name . Your nested if-else statement, accumulators, count-controlled loop, should be properly designed to process the data correctly. The code below will run, but does not produce any output. I think it needs something around line 57 like a count control to stop the loop. something like (and this is just an example....which is why it is not in the code.) count = 1; while (count <=4) Can someone review the code and tell me what kind of count I need to introduce, and if there are any other changes that need to be made. Thanks. [code] //COS 502-90 //November 2, 2012 //This program uses a sentinel-controlled loop that transforms input to output. #include <iostream> #include <fstream> #include <iomanip> //output formatting #include <string> //string variables using namespace std; int main() { double pieces; //number of pieces made double rate; //amout paid per amount produced double pay; //amount earned string name; //name of worker ifstream inFile; ofstream outFile; //***********input statements**************************** inFile.open("Piecework1.txt"); //opens the input text file outFile.open("piecework1.out"); //opens the output text file outFile << setprecision(2) << showpoint; outFile << name << setw(6) << "Pieces" << setw(12) << "Pay" << endl; outFile << "_____" << setw(6) << "_____" << setw(12) << "_____" << endl; getline(inFile, name, '*'); //priming read inFile >> pieces >> pay >> rate; // ,, while (name != "End of File") //while condition test { //begining of loop pay = pieces * rate; getline(inFile, name, '*'); //get next name inFile >> pieces; //get next pieces } //end of loop inFile.close(); outFile.close(); return 0; }[/code]

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• How to store local variables in jQuery click functions?

  - by Geuis

  I'm trying to figure out how to store external variable values in the functions created during jQuery's click() event. Here's a sample of the code I'm working with now. for(var i=0; i<3; i++){ $('#tmpid'+i).click(function(){ var gid = i; alert(gid); }); } <div id="tmpid0">1al</div> <div id="tmpid1">asd</div> <div id="tmpid2">qwe</div> So what's happening is that the events are attaching properly, but the value of 'gid' is always the last incremented value of 'i'. I'm not sure how to setup the private variable in this situation.

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• Use javascript variables in Rails view helpers

  - by Horacio

  Using jqGrid I want to generate delete links for each row in the grid. The standard way to do this is to add the links in the gridComplete callback like shown below: gridComplete: function() { var ids = jQuery("#jobs_table").jqGrid('getDataIDs'); for(var i=0;i < ids.length;i++){ var cl = ids[i]; be = '<%= link_to(image_tag("delete.gif", :border=>0, :size=>"20x22", :alt => "delete"),· { :action => 'destroy', :id => 'cl', :method => :delete}, :class => 'ajax') -%>'; jQuery("#jobs_table").jqGrid('setRowData',ids[i],{workflow_state:be}); } }, Using getDataIDs I get a list of IDs that I can use to generate the delete links. The problem is that this is a javascript call that results in a javascript variable. The question is how can I use this variable "cl" inside rails link_to view helper?

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• Best practice with respect to NPE and multiple expressions on single line

  - by JRL

  I'm wondering if it is an accepted practice or not to avoid multiple calls on the same line with respect to possible NPEs, and if so in what circumstances. For example: getThis().doThat(); vs Object o = getThis(); o.doThat(); The latter is more verbose, but if there is an NPE, you immediately know what is null. However, it also requires creating a name for the variable and more import statements. So my questions around this are: Is this problem something worth designing around? Is it better to go for the first or second possibility? Is the creation of a variable name something that would have an effect performance-wise? Is there a proposal to change the exception message to be able to determine what object is null in future versions of Java ?

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• Python module seeing a full list as empty in another module

  - by Nick

  I'm working on a pygame project and have the main engine layed out. The problem is I hit a bug that I just can not seem to figure out. What happens is one module can't read a variable from another module. It's not that the variable can't be read, it just sees an empty list instead of what it really is. Instead of posting the entire source code I reproduced the bug in two small snippets that hopefully a skillful python-ist can interpret in his\her head. Code: main.py (This is the file that gets run) import screen screens = [] #A stack for all the game screens def current_screen(): #return a reference to the current screen return screens[-1] def play(): print'play called' current_screen().update() if __name__=='__main__': screens.append(screen.Screen()) play() screen.py import main class Screen: def __init__(self): print'screen made' def update(self): print main.screens #Should have a reference to itself in there Thanks!

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• How to check value of stored procedure output parameter

  - by Anna T

  I have a stored procedure that: A. inserts some rows into a "table variable" based on some joins B. selects all values from column x from that table into a string with comma separated values C. selects all from the "table variable" If I execute the procedure like this: EXEC CatalogGetFilmDetails2 2,111111; a table is returned as instructed per step C above. How can I execute it so that also the output parameter value is displayed? (see point B above). I need to check if it's calculated properly. And since the second parameter is of output type, meaning it's calculated inside the procedure, why is it mandatory to specify a value for it when executing the procedure? I normally use a random value for it, it anyway doesn't matter/impact the result. On the other hand if I try to execute it without the output parameter, it returns an error) Thank you very much! This is how the procedure starts: CREATE PROCEDURE CatalogGetFilmDetails2 (@FilmID int, @CommaSepString VARCHAR(50) OUTPUT) AS And this is how @CommaSepString is calculated: SELECT @CommaSepString = STUFF((SELECT ', ' + Categ FROM @Filme1 FOR XML PATH('')), 1,1,'')

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• Problem while configuring the file Delimeter("\t") in app.config(C#3.0)

  - by Newbie

  In my app.config file I made the setting like the following <add key = "Delimeter" value ="\t"/> Now while accessing the above from the program by using the below code string delimeter = ConfigurationManager.AppSettings["FileDelimeter"].ToString(); StreamWriter streamWriter = null; streamWriter = new StreamWriter(fs); streamWriter.BaseStream.Seek(0, SeekOrigin.End); Enumerable .Range(0, outData.Length) .ToList().ForEach(i => streamWriter.Write(outData[i].ToString() + delimiter)); streamWriter.WriteLine(); streamWriter.Flush(); I am getting the output as 18804\t20100326\t5.59975381254617\t 18804\t20100326\t1.82599797249479\t But if I directly use "\t" in the delimeter variable I am getting the correct output 18804 20100326 5.59975381254617 18804 20100326 1.82599797249479 I found that while I am specifying the "\t" in the config file, and while reading it into the delimeter variable, it is becoming "\\t" which is the problem. I even tried with but with no luck. I am using C#3.0. Need help

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• Why in Ruby, a || 1 will throw an error when `a` is undefined, but a = a || 1 will not?

  - by Jian Lin

  When a is undefined, then a || 1 will throw an error, but a = a || 1 will not. Isn't that a little bit inconsistent? irb(main):001:0> a NameError: undefined local variable or method `a' for main:Object from (irb):1 from c:/ruby/bin/irb:12:in `<main>' irb(main):002:0> a || 1 NameError: undefined local variable or method `a' for main:Object from (irb):2 from c:/ruby/bin/irb:12:in `<main>' irb(main):003:0> a = a || 1 => 1

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• C# socket blocking behavior

  - by Gearoid Murphy

  My situation is this : I have a C# tcp socket through which I receive structured messages consisting of a 3 byte header and a variable size payload. The tcp data is routed through a network of tunnels and is occasionally susceptible to fragmentation. The solution to this is to perform a blocking read of 3 bytes for the header and a blocking read of N bytes for the variable size payload (the value of N is in the header). The problem I'm experiencing is that occasionally, the blocking receive operation returns a partial packet. That is, it reads a volume of bytes less than the number I explicitly set in the receive call. After some debugging, it appears that the number of bytes it returns is equal to the number of bytes in the Available property of the socket before the receive op. This behavior is contrary to my expectation. If the socket is blocking and I explicitly set the number of bytes to receive, shouldn't the socket block until it recv's those bytes?, any help, pointers, etc would be much appreciated.

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• How does dereferencing of a function pointer happen?

  - by eSKay

  Why and how does dereferencing a function pointer just "do nothing"? This is what I am talking about: #include<stdio.h> void hello() { printf("hello"); } int main(void) { (*****hello)(); } From a comment over here: function pointers dereference just fine, but the resulting function designator will be immediately converted back to a function pointer And from an answer here: Dereferencing (in way you think) a function's pointer means: accessing a CODE memory as it would be a DATA memory. Function pointer isn't suppose to be dereferenced in that way. Instead, it is called. I would use a name "dereference" side by side with "call". It's OK. Anyway: C is designed in such a way that both function name identifier as well as variable holding function's pointer mean the same: address to CODE memory. And it allows to jump to that memory by using call () syntax either on an identifier or variable. How exactly does dereferencing of a function pointer work?

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