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• Double Negation in C++ code.

  - by Brian Gianforcaro

  I just came onto a project with a pretty huge code base. I'm mostly dealing with C++ and a lot of the code they write uses double negation for their boolean logic. if (!!variable && (!!api.lookup("some-string"))) { do_some_stuff(); } I know these guys are intelligent programmers, it's obvious they aren't doing this by accident. I'm no seasoned C++ expert, my only guess at why they are doing this is that they want to make absolutely positive that the value being evaluated is the actual boolean representation. So they negate it, then negate that again to get it back to its actual boolean value. Is this a correct? or am I missing something else? Thanks, Brian Gianforcaro

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• gdb: SIGTRAP on std::string::c_str() call

  - by sheepsimulator

  So I've been trying to use gdb to return the value of a string I have by calling > print <member variable name>.c_str() But everytime I do so, I get this: Program received signal SIGTRAP, Trace/breakpoint trap. <some address> in std::string::c_str() from /usr/lib/libstdc++.so.6 GDB remains in the frame where the signal was received. To change this behavior use "set unwindonsignal on" Evaluation of the expression containing the function (std::string::c_str() const) will be abandoned. Two questions: Why/how is the standard library throwing SIGTRAP? I checked basic_string.h and c_str() is defined as: const _CharT* c_str() const { return _M_data(); } I don't see any SIGTRAP-throwing here... is there a way to get around this SIGTRAP? How can I read the text value of the std::string out (without getting some crazy extension library) in gdb?

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• Making your class an event source in Java

  - by Crystal

  I'm making a custom button in Java that has two states, mousePressed, and mouseReleased. At the same time, if I wanted to reuse this button, so that other event listeners can register with it, are these the appropriate steps I should do: override addActionListener(ActionListener action) override removeActionListener(ActionListener action) have a private variable like List <ActionListener> list = new List <ActionListener>() to keep track of when events get added and some sort of function with for loop to run all the actions: public void runListeners() { for (ActionListener al : list) { al.actionPerfomed; } } I'm not really sure if this is the way you can do it or if there are other things I am missing. Like does my custom class have to be implements ActionListener? Thanks.

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• logging in scala

  - by IttayD

  In Java, the standard idiom for logging is to create a static variable for a logger object and use that in the various methods. In Scala, it looks like the idiom is to create a Logging trait with a logger member and mixin the trait in concrete classes. This means that each time an object is created it calls the logging framework to get a logger and also the object is bigger due to the additional reference. Is there an alternative that allows the ease of use of "with Logging" while still using a per-class logger instance? EDIT: My question is not about how one can write a logging framework in Scala, but rather how to use an existing one (log4j) without incurring an overhead of performance (getting a reference for each instance) or code complexity. Also, yes, I want to use log4j, simply because I'll use 3rd party libraries written in Java that are likely to use log4j.

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• C# - Convert Implict Type to ObservableCollection

  - by user70192

  Hello, I have a LINQ statement that returns an implicit type. I need to get this type to be an ObservableCollection in my Silverlight 3 application. The ObservableCollection constructor in Silverlight 3 only provides an empty constructor. Because of this, I cannot directly convert my results to an ObservableCollection. Here is my code: ObservableCollection<MyTasks> visibleTasks = e.Result; var filteredResults = from visibleTask in visibleTasks select visibleTask; filteredResults = filteredResults.Where(p => p.DueDate == DateTime.Today); visibleTasks = filteredResults.ToList(); // This throws a compile time error How can I go from an implicitly typed variable to an observable collection? Thank you

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• Numpy modify array in place?

  - by User

  I have the following code which is attempting to normalize the values of an m x n array (It will be used as input to a neural network, where m is the number of training examples and n is the number of features). However, when I inspect the array in the interpreter after the script runs, I see that the values are not normalized; that is, they still have the original values. I guess this is because the assignment to the array variable inside the function is only seen within the function. How can I do this normalization in place? Or do I have to return a new array from the normalize function? import numpy def normalize(array, imin = -1, imax = 1): """I = Imin + (Imax-Imin)*(D-Dmin)/(Dmax-Dmin)""" dmin = array.min() dmax = array.max() array = imin + (imax - imin)*(array - dmin)/(dmax - dmin) print array[0] def main(): array = numpy.loadtxt('test.csv', delimiter=',', skiprows=1) for column in array.T: normalize(column) return array if __name__ == "__main__": a = main()

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• How to invoke a delegate with a null parameter?

  - by Rodney Burton

  I get a null exception if I try to pass a null parameter to a delegate during an invoke. Here's what the code looks like: public void RequestPhoto() { WCF.Service.BeginGetUserPhoto(Contact.UserID, new AsyncCallback(RequestPhotoCB), null); } public void RequestPhotoCB(IAsyncResult result) { var photo = WCF.Service.EndGetUserPhoto(result); UpdatePhoto(photo); } public delegate void UpdatePhotoDelegate(Binary photo); public void UpdatePhoto(Binary photo) { if (InvokeRequired) { var d = new UpdatePhotoDelegate(UpdatePhoto); Invoke(d, new object[] { photo }); } else { var ms = new MemoryStream(photo.ToArray()); var bmp = new Bitmap(ms); pbPhoto.BackgroundImage = bmp; } } The problem is with the line: Invoke(d, new object[] { photo }); If the variable "photo" is null. What is the correct way to pass a null parameter during an invoke? Thanks!

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• pointer to member function question

  - by Steve

  Hello, I'm trying to replicate a template I've used before with a member function, and it isn't going very well. The basic form of the function is template<class T> T Convert( HRESULT (*Foo)(T*)) { T temp; Foo(&temp); //Throw if HRESULT is a failure return temp; } HRESULT Converter(UINT* val) { *val = 1; return S_OK; } int _tmain(int argc, _TCHAR* argv[]) { std::cout << Convert<UINT>(Converter) << std::endl; return 0; } For the life of me, I can't get this to work with a member variable. I've read up on their syntax, and I can't seem to figure out how to make it work with templates. The class would be something similar to class TestClass { HRESULT Converter(UINT* val) { *val = 1; return S_OK; } }

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• Object's field cannot be accessed after $.ajax call in success function - it is undefined

  - by dragonfly

  I have a $.ajax call and and server returns JSON. This is my call: var result; // tmp variable just for playing with Chrome console $.ajax({ type: "GET", url: "ashxJSON.ashx", data: { name: "some sample data" }, contentType: "application/json; charset=utf-8", dataType: "json", success: function (msg) { result = msg; console.log(msg); $("#output").append("<p>" + msg.message + "</p>"); }, error: function (jqXHR, textStatus, errorThrown) { console.log(textStatus); console.log(errorThrown); } }); Server returns exactly this string: { "messsage": "Hello World to ..."} And now, when I: console.log(msg) I see: Object messsage: "Hello World to..." proto: Object But when I access msg.message or msg["message"] I see: undefined What is wrong with me / that msg object?

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• Java variables -> replace? RAM optimization

  - by poeschlorn

  Hi guys, I just wanted to know what happens behind my program when I declare and initialize a variable and later initialize it again with other values, e.g. an ArrayList or something similar. What happens in my RAM, when I say e.g. this: ArrayList<String> al = new ArrayList<String>(); ...add values, work with it and so on.... al = new ArrayList<String>(); So is my first ArrayList held in RAM or will the second ArrayList be stored on the same position where the first one has been before? Or will it just change the reference of "al"? If it is not replaced...is there a way to manually free the RAM which was occupied by the first arraylist? (without waiting for the garbage collector) Would it help to set it first =null? Nice greetings, poeschlorn

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• tsql proc logic help

  - by bacis09

  I am weak in SQL and need some help working through some logic with my proc. Three pieces: store procedure, table1, table2 Table 1 stores most recent data for specific IDs Customer_id status_dte status_cde app_dte 001 2010-04-19 Y 2010-04-19 Table 2 stores history of data for specific customer IDs: For example: Log_id customer_Id status_dte status_cde 01 001 2010-04-20 N 02 001 2010-04-19 Y 03 001 2010-04-19 N 04 001 2010-04-19 Y The stored proecure currently throws an error if the status date from table1 is < than app_date in table1. If @status_dte < app_date Error Note: @status_dte is a variable stored as the status_dte from table1 However, I want it to throw an error when the EARLIEST status_dte from table 2 with a status_cde of 'Y' is less than the app_dte column in table 1. Keep in mind that this earliest date is not stored anywhere, the history of data changes per customer. Another customer might have the following history. Log_id customer_Id status_dte status_cde 01 002 2010-04-20 N 02 002 2010-04-18 N 03 002 2010-04-19 Y 04 002 2010-04-19 Y Any ideas on how I can approach this?

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• How to reset Scrapy parameters? (always running under same parameters)

  - by Jean Ventura

  I've been running my Scrapy project with a couple of accounts (the project scrapes a especific site that requieres login credentials), but no matter the parameters I set, it always runs with the same ones (same credentials). I'm running under virtualenv. Is there a variable or setting I'm missing? Edit: It seems that this problem is Twisted related. Even when I run: scrapy crawl -a user='user' -a password='pass' -o items.json -t json SpiderName I still get an error saying: ERROR: twisted.internet.error.ReactorNotRestartable And all the information I get, is the last 'succesful' run of the spider.

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• Thread local storage with __declspec(thread) fails in C++/CLI

  - by EFrank

  I'm working on a project where we mix .NET code and native C++ code via a C++/CLI layer. In this solution I want to use Thread Local Storage via the __declspec(thread) declaration: __declspec(thread) int lastId = 0; However, at the first access of the variable, I get a NullReferenceException. To be more precise, the declaration is done within a ref class (a .NET class implemented in C++/CLI). I have already read something about __declspec(thread) does not work with delay loaded DLLs. Am I using delay loaded DLLs automatically if I use .NET?

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• Grails deploy on Tomcat6

  - by Jack

  Hello, while trying to deploy a Grails application into tomcat6 I ran into some problems: I used the grails war command to build up a war, then copied it to var/lib/tomcat6/webapps and tried to restart the container. I had to change default Tomcat policy to skip security exceptions, since I couldn't access environment variable (like grails.env), then tried again but it gives me an exception related to instantiating something, but it's not clear where should I try to fix the error, according to tomcat6 logs the problem is: SEVERE: Exception sending context initialized event to listener instance of class org.codehaus.groovy.grails.web.context.GrailsC$ org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'pluginManager' defined in ServletContext$ at java.lang.Thread.run(Thread.java:619) Caused by: org.codehaus.groovy.grails.exceptions.NewInstanceCreationException: Could not create a new instance of class [Hiberna$ ... 1 more Caused by: java.lang.NoClassDefFoundError: org.hibernate.cfg.Environment It seems like it's unable to load org.hibernate.cfg.Environment class. I checked the applicationContext.xml and it refers to grails.xml to search for plugins, in this last file I actually have HibernateGrailsPlugin. Where should I look to find if the plugin is present?

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• Puzzled with nib files...

  - by Michael

  I know nib files are serialized objects and they have owner, outlets to make connections. Using XCode Navigation window template I created application, which in its order created 2 nib files - MainWindow and SecondView. I can't understand how MainWindow is referring to SecondView, there is no connection between those two as far as I can see. SecondView's owner is UIViewController and in MainWindow there is a navigation tab which is also UIViewController. But how they are connected in IB I can't understand... Also I don't understand who is instanciating MainWindow's owner object and where that object is being kept, where is the variable which is UIApplication myApp = [[UIApplication alloc] init]. If I create 10 nib files with UIViewController owner, who will trigger their deserialization? If some class is nib file's owner, what is the essential responsibilities of that class? Is it deserializing nib file into memory? Sorry for unorganized questions, I've been reading numerous articles and docs about nib files, but it is still confusing.

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• Rails: how do you access RESTful helpers?

  - by Ethan

  I'm trying to work through this guide to Rails routing, but I got stuck in section 3.3: Creating a RESTful route will also make available a pile of helpers within your application and then they list some helpers like photos_url, photos_path, etc. My questions: Where can I find the complete list of helpers that is "made available?" Is there a way to call the helpers in the console? I created an app, then opened up the console with script/console. I tried to call one of the helpers on the console like this: >> entries_url But got: NameError: undefined local variable or method `entries_url' for #<Object:0x349a4> from (irb):8

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• Entity Framework How to specify paramter type in generated SQL (SQLServer 2005) Nvarchar vs Varchar

  - by Gratzy

  In entity framework I have an Entity 'Client' that was generated from a database. There is a property called 'Account' it is defined in the storage model as: <Property Name="Account" Type="char" Nullable="false" MaxLength="6" /> And in the Conceptual Model as: <Property Name="Account" Type="String" Nullable="false" /> When select statements are generated using a variable for Account i.e. where m.Account == myAccount... Entity Framework generates a paramaterized query with a paramater of type NVarchar(6). The problem is that the column in the table is data type of char(6). When this is executed there is a large performance hit because of the data type difference. Account is an index on the table and instead of using the index I believe an Index scan is done. Anyone know how to force EF to not use Unicode for the paramater and use Varchar(6) instead?

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• Types in Bytecode

  - by HH

  Hey everyone, I've been working for some time on (Java) Bytecode, however, it had never occurred to me to ask why are some instructions typed? I understand that in an ADD operation, we need to distinguish between an integer addition and a FP addition (that's why we have IADD and FADD). However, why do we need to distinguish between ISTORE and FSTORE? They both involve the exact same operation, which is moving 32 bits from the stack to a local variable position? The only answer I can think of is for type-safety, to prevent this: (ILOAD, ILOAD, FADD). However, I believe that type-safety is already enforced at the Java language level. OK, the Class file format is not directly coupled with Java, so is this a way to enforce type-safety for languages that do not support it? Any thought? Thank you.

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• Pressing "Home" in Vim on an Indented Line

  - by Reid

  I have a bad habit of using the 'home' key to go back to the beginning of a line. As I recently started using vim (and loving it!) I noticed that when I press the home key on a lined that is indented, it returns me to the very beginning of the line. In Notepad++ (the editor I used to use) it would return me to the beginning of the code on that line, right after the indent. Is there some way to replicate this behavior in vim? Usually, when I'm pressing home it's in the Insert mode for me to (usually) stick a variable there. I have set smartindent in my vimrc, with set noautoindent as a "tips" page told me to make sure to disable autoindent (although it didn't seem to be enabled in the first place - perhaps that option is extraneous.) Thanks in advance.

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• Cursors vs Procedures in SQL

  - by CogitoErgoSum

  So, I just learned about CURSORS but still don't exactly grasp them. What is the difference between a cursor and procedure or even a function? So far from the various examples (DECLARE CURSOR ... SELECT ... FROM ...) It seems at most its a variable to hold a query. Is the data real time, or a snapshot of when the cursor was declared? i.e. I have a table with one row and one col with a value of 2. I do DECLARE CURSOR ... SELECT * FROM table1 I then insert a new row with a value of 3. When I run the cursor, would I Just get the one row from before the cursor was declared, or both rows? Thanks

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• Making ofHideReadOnly work with UseLatestCommonDialogs

  - by Jan Goyvaerts

  In Delphi 2007 and later, the global variable UseLatestCommonDialogs causes TOpenDialog to use the new Vista-style dialog on Windows Vista and 7. That's cool. Unfortunately, the Vista-style dialog does not seem to support the ofHideReadOnly option of TOpenDialog. The read-only checkbox never appears regardless whether this option is set to True or False. How can I make TOpenDialog show a read-only checkbox on the Vista-style dialog? TOpenTextFileDialog adds a combo box to the dialog regardless of whether it's Vista-style or not. It should be possible to add a read-only checkbox in the same way, but I can't figure out how to do it, even when looking at the source for TOpenTextFileDialog.

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• watchpoint in GDB

  - by Tim

  Hi, If I set a watchpoint for a variable local to the current scope, it will be auto deleted when going out of the scope. Is there any way to set it once and keep it auto alive whenever entering the same scope? Is there anyway to set conditional watchpoint, like "watch var1 if var1==0"? In my case, the condition does't work. gdb stops whenever var1's value is changed, instead of untill "var1==0" is true. My gdb is GNU gdb 6.8-debian. Thanks and regards!

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• Creating New Objects in JavaScript

  - by Ken Ray

  I'm a relatively newbie to object oriented programming in JavaScript, and I'm unsure of the "best" way to define and use objects in JavaScript. I've seen the "canonical" way to define objects and instantiate a new instance, as shown below. function myObjectType(property1, propterty2) { this.property1 = property1, this.property2 = property2 } // now create a new instance var myNewvariable = new myObjectType('value for property1', 'value for property2'); But I've seen other ways to create new instances of objects in this manner: var anotherVariable = new someObjectType({ property1: "Some value for this named property", property2: "This is the value for property 2" }); I like how that second way appears - the code is self documenting. But my questions are: Which way is "better"? Can I use that second way to instantiate a variable of an object type that has been defined using the "classical"way of defining the object type with that implicit constructor? If I want to create an array of these objects, are there any other considerations? Thanks in advance.

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• Exporting Eclipse project with a reference to native library

  - by TacB0sS

  I have an Eclipse project, that uses JMF, I found out I could skip the JMF installation process and still to use the CaptureDeviceManager of the JMF, and to receive the list of devices if I could point my project to the native lib of the JMF. I've managed to add the native lib to the IDE run/debug, but once I export the application to an external runnable Jar, the application cannot find the native lib. the files are located in c:\JMF*.dll I tried to add the folder path to the environment variable in windows - didn't work. I tried to add them into another Jar and add it to the project - didn't work. I tried to add the files into the project - didn't work. I tried to add the path to the class path - didn't work. I tried to add the path to the library path - didn't work. does someone have any sort of a solution? Thanks in advance, Adam Zehavi.

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• Rotate a feature Image in Open Layers

  - by Ozaki

  I have an open layers map. It adds and removes my "imageFeature" every 10secs or so. I have a JSON feed that gives me the rotation that I need, I have a request to get that rotation and set it as a variable of rotationv. Everything works but the fact when the image is recreated it does not update the rotation. My code is as follows: JSON request: var rotationv = (function () { rotationv = null; $.ajax({ 'async': false, 'global': true, 'url': urldefault, 'dataType': "json", 'success': function (data) { rotationv = data.rotation; } }); return rotationv })(); Creating image feature: imageFeature = new OpenLayers.Feature.Vector( new OpenLayers.Geometry.Point(mylon, mylat), { rotation: rotationv } ); The image is set in the styling elsewhere. Why does this not rotate my image?

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