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  • Is it true that in most Object Oriented Programming Languages, an "i" in an instance method always r

    - by Jian Lin
    In the following code: <script type="text/javascript"> var i = 10; function Circle(radius) { this.r = radius; this.i = radius; } Circle.i = 123; Circle.prototype.area = function() { alert(i); } var c = new Circle(1); var a = c.area(); </script> What is being alerted? The answer is at the end of this question. I found that the i in the alert call either refers to any local (if any), or the global variable. There is no way that it can be the instance variable or the class variable even when there is no local and no global defined. To refer to the instance variable i, we need this.i, and to the class variable i, we need Circle.i. Is this actually true for almost all Object oriented programming languages? Any exception? Are there cases that when there is no local and no global, it will look up the instance variable and then the class variable scope? (or in this case, are those called scope?) the answer is: 10 is being alerted.

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  • Declare Locally or Globally in Delphi?

    - by lkessler
    I have a procedure my program calls tens of thousands of times that uses a generic structure like this: procedure PrintIndiEntry(JumpID: string); type TPeopleIncluded = record IndiPtr: pointer; Relationship: string; end; var PeopleIncluded: TList<TPeopleIncluded>; PI: TPeopleIncluded; begin { PrintIndiEntry } PeopleIncluded := TList<TPeopleIncluded>.Create; { A loop here that determines a small number (up to 100) people to process } while ... do begin PI.IndiPtr := ...; PI.Relationship := ...; PeopleIncluded.Add(PI); end; DoSomeProcess(PeopleIncluded); PeopleIncluded.Clear; PeopleIncluded.Free; end { PrintIndiEntry } Alternatively, I can declare PeopleIncluded globally rather than locally as follows: unit process; interface type TPeopleIncluded = record IndiPtr: pointer; Relationship: string; end; var PeopleIncluded: TList<TPeopleIncluded>; PI: TPeopleIncluded; procedure PrintIndiEntry(JumpID: string); begin { PrintIndiEntry } { A loop here that determines a small number (up to 100) people to process } while ... do begin PI.IndiPtr := ...; PI.Relationship := ...; PeopleIncluded.Add(PI); end; DoSomeProcess(PeopleIncluded); PeopleIncluded.Clear; end { PrintIndiEntry } procedure InitializeProcessing; begin PeopleIncluded := TList<TPeopleIncluded>.Create; end; procedure FinalizeProcessing; begin PeopleIncluded.Free; end; My question is whether in this situation it is better to declare PeopleIncluded globally rather than locally. I know the theory is to define locally whenever possible, but I would like to know if there are any issues to worry about with regards to doing tens of thousands of of "create"s and "free"s? Making them global will do only one create and one free. What is the recommended method to use in this case? If the recommended method is to still define it locally, then I'm wondering if there are any situations where it is better to define globally when defining locally is still an option.

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  • How to load the environment variables at boot time before X11 on Ubuntu Precise?

    - by Fnux
    Using Ubuntu Precise 64 bit, I'm facing a problem that I'm unable to solve and that I'll try to describe below: I'm using a console mode program (let's say abc) that uses Go, NodeJS, Java and Scala. In order for abc to work with these languages, I've to declare the following statements: a) within /etc/environment: PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/go/bin" CLASSPATH=$CLASSPATH:/usr/share/java/scala-library.jar b) within /etc/login.defs ENV_SUPATH PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/go/bin ENV_PATH PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/go/bin c) a) within /etc/sudoers: `# env_reset Defaults secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/go/bin"` Then, when I start abc from a terminal, all is fine and I can use any of the 4 languages described above. However, if I put a script within /etc/init.d that starts abc during the boot process (i.e. before to start the GUI), using Java from abc still is fine, but using Go, NodeJS or Scala doesn't work anymore. Then, I guess that during the boot process, the script within /etc/init.d that starts abc is executed before that the different environment variables set within /etc/sudoers, /etc/environment and /etc/login.defs are loaded. So, my question is: how to force the environment variables to be loaded before that my script starting abc is launched? Any help and advice on this topic would be trully appreciated. TIA. Cheers. Thanks again to Mark and Danila. Below is the current "abc" script file that I put within /etc/init.d `#! /bin/sh ### EDIT: ADD THIS VARS DEFINITIONS: PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/go/bin" CLASSPATH=$CLASSPATH:/usr/share/java/scala-library.jar "ENV_SUPATH PATH"="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/go/bin" "ENV_PATH PATH"="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/go/bin" "Defaults secure_path"="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/go/bin" ##### EXPORT this VARS so they are accessible to children:" export "PATH" "CLASSPATH" "ENV_SUPATH PATH" "ENV_PATH PATH" "Defaults secure_path" `### BEGIN INIT INFO `# Provides: abc `# Required-Start: $remote_fs $syslog `# Required-Stop: $remote_fs $syslog `# Default-Start: 2 3 4 5 `# Default-Stop: 0 1 6 `# Short-Description: abc initscript `# Description: This iniscript starts and stops abc `### END INIT INFO `# Author: Fnux, fnux.fl at gmail dot com `# Version: 1.2 `# Note: (edit ABC_PATH if abc isn't installed in /opt/abc) NAME=abc ABC_PATH=/opt/abc START="-d" STOP="-k" VERSION="-v" SCRIPTNAME=/etc/init.d/$NAME STARTMESG="\nStarting abc in deamon mode." UPMESG="\n$NAME is running." DOWNMESG="\n$NAME is not running." STATUS=`pidof $NAME` `# Exit if abc is not installed [ -x "$ABC_PATH/$NAME" ] || exit 0 case "$1" in start) echo $STARTMESG cd $ABC_PATH ./$NAME $START ;; stop) cd $ABC_PATH ./$NAME $STOP ;; status) if [ "$STATUS" > 0 ] ; then echo $UPMESG else echo $DOWNMESG fi ;; restart) cd $ABC_PATH ./$NAME $STOP echo $STARTMESG ./$NAME $START ;; version) cd $ABC_PATH ./$NAME $VERSION ;; *) echo "Usage: $SCRIPTNAME {start|status|restart|stop|version}" >&2 exit 3 ;; esac : So, where and how should I write the needed environment variables for: a) Go needs the following statements (ie: PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/go/bin" ENV_SUPATH PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/go/bin ENV_PATH PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/go/bin `# env_reset Defaults secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/go/bin") b) and Scala needs this one: (ie CLASSPATH=$CLASSPATH:/usr/share/java/scala-library.jar). TIA for an explanation how to do so. Cheers.

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  • Strategies for when to use properties and when to use internal variables on internal classes?

    - by Edward Tanguay
    In almost all of my classes, I have a mixture of properties and internal class variables. I have always chosen one or the other by the rule "property if you need it externally, class variable if not". But there are many other issues which make me rethink this often, e.g.: at some point I want to use an internal variable from outside the class, so I have to refactor it into a property which makes me wonder why I don't just make all my internal variables properties in case I have to access them externally anyway, since most classes are internal classes anyway it aren't exposed on an API so it doesn't really matter if the internal variables are accessible from outside the class or not but then since C# doesn't allow you to instantiate e.g. List<string> property in the definition, then these properties have to be initialized in every possible constructor, so these variables I would rather have internal variables just to keep things cleaner in that they are all initialized in one place C# code reads more cleanly if constructor/method parameters are camel case and you assign them to pascal case properties instead of the ambiguity of seeing "templateIdCode" and having to look around to see if it is a local variable, method parameter or internal class variable, e.g. it is easier when you see "TemplateIdCode = templateIdCode" that this is a parameter being assigned to a class property. This would be an argument for always using only properties on internal classes. e.g.: public class TextFile { private string templateIdCode; private string absoluteTemplatePathAndFileName; private string absoluteOutputDirectory; private List<string> listItems = new List<string>(); public string Content { get; set; } public List<string> ReportItems { get; set; } public TextFile(string templateIdCode) { this.templateIdCode = templateIdCode; ReportItems = new List<string>(); Initialize(); } ... When creating internal (non-API) classes, what are your strategies in deciding if you should create an internal class variable or a property?

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  • What are the pro and cons of having localization files vs hard coded variables in source code?

    - by corgrath
    Definitions: Files: Having the localization phrases stored in a physical file that gets read at application start-up and the phrases are stored in the memory to be accessed via util-methods. The phrases are stored in key-value format. One file per language. Variables: The localization texts are stored as hard code variables in the application's source code. The variables are complex data types and depending on the current language, the appropriate phrase is returned. Background: The application is a Java Servlet and the developers use Eclipse as their primary IDE. Some brief pro and cons: Since Eclipse is use, tracking and finding unused localizations are easier when they are saved as variables, compared to having them in a file. However the application's source code becomes bigger and bloated. What are the pro and cons of having localization text in files versus hard coded varibles in source code? What do you do and why?

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  • How to set user environment variables in Windows Server 2008 R2 as a normal user?

    - by likm
    In older versions of Windows, it was just open the Control Panel, select the System applet, select the Advanced tab, and then hit the Environment variables button. As a normal user, you could edit the "User variables" but not the "System variables". In Windows Server 2008 R2, if I try to hit the Advanced System settings option in the System applet, it prompts for the Administrator password.

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  • Will my shared variables loose value? (asp.net vb)

    - by Phil
    I have a class includes.vb that holds some variables (sharing them with other pages) like: Public Shared pageid As Integer = 0 I then have a function that does some work with these variables returning them with values; Return pageid When I step through the code, the variables have values (while stepping through the function), but when they are returned to the page, they come back null. Do they loose value everytime a page is loaded? Can you suggest an alternative method? Thanks a lot.

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  • SSIS Basics: Introducing Variables

    In the third of her SSIS Basics articles, Annette Allen shows you how to use Variables in your SSIS Packages, and explains the functions of the system-defined variables. Are you sure you can restore your backups? Run full restore + DBCC CHECKDB quickly and easily with SQL Backup Pro's new automated verification. Check for corruption and prepare for when disaster strikes. Try it now.

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  • Using Variables Within Crystal Report Formulas

    This article demonstrates how to create formulas in a Crystal Report and use the Crystal scripting language to create variables, use built in functions, perform conditional logic, and manipulate dates. After a brief introduction, the article provides the steps required to create the database, the website, and the report, including how to add fields and formulas to the report. Near the end, the article examines the steps required to create formulas with variables.

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  • More Server Variables in ASP.NET 3.5

    The first part of this series served as a basic introduction to server variables and their application in ASP.NET 3.5. You learned how to output server variables using classic ASP tags and using ASP.NET visual basic code file. This article will pick up where the previous part left off.... GoGrid Cloud Center Connect Cloud and Dedicated Servers on Your Private Data Center

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  • More than 5 custom variables across multiple websites using Google Analytics

    - by brakes
    We have multiple websites using the same Google Analytics account number so we can track visitors across multiple websites. One of these websites has set 5 custom variables. We want to introduce a new custom variable to track logged in users for our single sign-on (SSO) system to find out what parts of which website they are accessing. Is this possible or is it a case that all the custom variables have been used up by 1 of the sites?

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  • MySQL – Introduction to User Defined Variables

    - by Pinal Dave
    MySQL supports user defined variables to have some data that can be used later part of your query. You can save a value to a variable using a SELECT statement and later you can access its value. Unlike other RDBMSs, you do not need to declare the data type for a variable. The data type is automatically assumed when you assign a value. A value can be assigned to a variable using a SET command as shown below SET @server_type:='MySQL'; When you above command is executed, the value, MySQL is assigned to the variable called @server_type. Now you can use this variable in the later part of the code. Suppose if you want to display the value, you can use SELECT statement. SELECT @server_type; The result is MySQL. Once the value is assigned it remains for the entire session until changed by the later statements. So unlike SQL Server, you do not need to have this as part the execution code every time. (Because in SQL Server, the variables are execution scoped and dropped after the execution). You can give column name as below SELECT @server_type AS server_type; You can also SELECT statement to DECLARE and SELECT the values for a variable. SELECT @message:='Welcome to MySQL' AS MESSAGE; The result is Message -------- Welcome to MySQL You can make use of variables to effectively apply many logics. One of the useful method is to generate the row number as shown in this post MySQL – Generating Row Number for Each Row using Variable. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: MySQL, PostADay, SQL, SQL Authority, SQL Query, SQL Tips and Tricks, T SQL

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  • Need help eliminating dead code paths and variables from C source code

    - by Anjum Kaiser
    I have a legacy C code on my hands, and I am given the task to filter dead/unused symbols and paths from it. Over the time there were many insertions and deletions, causing lots of unused symbols. I have identified many dead variables which were only being written to once or twice, but were never being read from. Both blackbox/whitebox/regression testing proved that dead code removal did not affected any procedures. (We have a comprehensive test-suite). But this removal was done only on a small part of code. Now I am looking for some way to automate this work. We rely on GCC to do the work. P.S. I'm interested in removing stuff like: variables which are being read just for the sake of reading from them. variables which are spread across multiple source files and only being written to. For example: file1.c: int i; file2.c: extern int i; .... i=x;

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  • How should I group these variables?

    - by stariz77
    I have a shape that will be defined by: char s_type; char color; double height; double width; These variables are scanned in from a request string sent to my server and passed into my printing function, which then prints out the shape. Currently they are just local variables sitting in my main(); however, I was wondering if there would be any advantage in creating a struct containing these variables, and then passing the struct to my printing function? or how else might I improve my program's structure/style, would passing a struct by reference have any kind of performance benefit if there were many requests and therefore many printing function calls? printer(char st, char cr, double ht, double wd); int main() { // Other main functionality. char s_type; char color; double height; double width; sscanf (serv_req, "GET /%c/%c/%lf/%lf", &s_type, &color, &height, &width); printer(s_type, color, height, width); // Other main functionality. return 0; } It seemed "neater" if I had a struct or something that didn't leave me with declarations in the middle of everything else going on in main. I'm interested in structure/style as well as performance. EDIT: didn't mean to put printer declaration inside main.

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  • How can I pass environment variables to a WSGI script, using uWSGI?

    - by orokusaki
    I've added the following line to /etc/environment: FOO_DEPLOYMENT_ENV="vbox" Upon logging in via SSH, I can echo $FOO_DEPLOYMENT_ENV and, of course, see vbox output to the shell. If I open a Python shell and run os.getenv('FOO_DEPLOYMENT_ENV'), it will return 'vbox', but the same code in my Python application, when run by uWSGI (as the www-data user), it does not see the environment variable. Clearly, this isn't a problem of uWSGI, and is rather a problem with my understanding of environment variables, or how they're properly set, and the contexts in which they can be retrieved. What am I doing or understanding incorrectly?

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  • NullReferenceException when accessing variables in a 2D array in Unity

    - by Syed
    I have made a class including variables in Monodevelop which is: public class GridInfo : MonoBehaviour { public float initPosX; public float initPosY; public bool inUse; public int f; public int g; public int h; public GridInfo parent; public int y,x; } Now I am using its class variable in another class, Map.cs which is: public class Map : MonoBehaviour { public static GridInfo[,] Tile = new GridInfo[17, 23]; void Start() { Tile[0,0].initPosX = initPosX; //Line 49 } } I am not getting any error on runtime, but when I play in unity it is giving me error NullReferenceException: Object reference not set to an instance of an object Map.Start () (at Assets/Scripts/Map.cs:49) I am not inserting this script in any gameobject, as Map.cs will make a GridInfo type array, I have also tried using variables using GetComponent, where is the problem ?

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  • Clean Code says to avoid protected variables

    - by Matsemann
    I have a question to a statement in Clean Code. I don't fully understand the reasoning to why we should avoid protected variables. It's from the chapter about Formatting, section about Vertical Distance: Concepts that are closely related should be kept vertically close to each other. Clearly this rule doesn't work for concepts that belong in separate files. But then closely related concepts should not be separated into different files unless you have a very good reason. Indeed, this is one of the reasons that protected variables should be avoided.

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  • Missed environment variables in Eclipse Juno

    - by hara
    I recently moved from Eclipse Indigo to Juno. I installed the IDE in my Ubuntu 12.04 by downloading the archive from here. Then I created an entry in the unity launcher for Juno as I done before for Indigo. Here is what I wrote in ~/.local/share/applications/eclipse-juno.desktop: [Desktop Entry] Type=Application Name=Eclipse Juno Comment=Eclipse Integrated Developmentm Environment Icon=~/.eclipse-juno/icon.xpm Exec=~/.eclipse-juno/eclipse -vmargs -Duser.name="my name" Terminal=false Categories=Development;IDE;Java; When I run eclipse from the unity launcher, eclipse does not see environment variables that I set in ~/.bascrc. Instead, if I run eclipse from shell, it can see all the env variables. How can I fix the problem? Thanks a lot.

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  • Unable to access A class variables in B Class - Unity-Monodevelop

    - by Syed
    I have made a class including variables in Monodevelop which is: public class GridInfo : MonoBehaviour { public float initPosX; public float initPosY; public bool inUse; public int f; public int g; public int h; public GridInfo parent; public int y,x; } Now I am using its class variable in another class, Map.cs which is: public class Map : MonoBehaviour { public static GridInfo[,] Tile = new GridInfo[17, 23]; void Start() { Tile[0,0].initPosX = initPosX; //Line 49 } } Iam not getting any error on runtime, but when I play in unity it is giving me error NullReferenceException: Object reference not set to an instance of an object Map.Start () (at Assets/Scripts/Map.cs:49) I am not inserting this script in any gameobject, as Map.cs will make a GridInfo type array, I have also tried using variables using GetComponent, where is the problem ?

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  • Naming conventions used for variables and functions in C

    - by Zel
    While coding a large project in C I came upon a problem. If I keep on writing more code then there will be a time when it will be difficult for me to organize the code. I mean that the naming for functions and variables for different parts of the program may seem to be mixed up. So I was thinking whether there are useful naming conventions that I can use for C variables and functions? Most languages suggest a naming convention. But for C the only thing I have read so far is the names should be descriptive for code readability. EDIT: Examples of some examples of suggested naming conventions: Python's PEP 8 Java Tutorial I read some more naming conventions for java somewhere but couldn't remember where.

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  • Conceptualisation des variables tableau en VBA et optimisation du code sous Excel, par Didier Gonard

    Bonjour, Ci-dessous, le lien vers un nouveau tutoriel : "Conceptualisation des variables tableau en VBA et Application à l'optimisation du code sous Excel" Le but de ce tutoriel est :? De proposer une conceptualisation graphique des variables tableau en 1,2 et 3 dimensions en VBA général (vidéo animation 3D pour visualiser le concept) . ? De présenter les analogies avec Excel ainsi que des champs d'applications. ? De démontrer les gains de rapidité que leur approche génère sous Excel (avec fichier joint). ? De proposer une fiche mémo téléchargeable. Lien vers...

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  • SSIS 2008 Configuration Settings Handling Logic for Variables Visualized

    - by Compudicted
    There are many articles discussing the specifics of how the configuration settings are applied including the differences between SSIS 2005 and 2008 version implementations, however this topic keeps resurfacing on MSDN’s SSIS Forum. I thought it could be useful to cover the logic aspect visually. Below is a diagram explaining the basic flow of a variable setting for a case when no parent package is involved.   As you can see the run time stage ignores any command line flags for variables already set in the config file, I realize this is not stressed enough in many publications. Besides, another interesting fact is that the command line dtexec tool is case sensitive for the portion following the package keyword, I mean if you specify your flag to set a new value for a variable like dtexec /f Package.dtsx -set \package.variables[varPkgMyDate].value;02/01/2011 (notice the lover case v in .value) You will get errors. By capitalizing the keyword the package runs successfully.

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  • How to access variables of uninitialized class?

    - by oringe
    So I've gone with a somewhat singleton approach to my game class: #include "myGame.h" int main () { myGame game; return game.Execute(); } But now I need to define a class that accesses variables in the instance of myGame. class MotionState { public: virtual void setWorldTransform (...) { VariableFromMyGameClass++; //<-- !? ...} }; I'm trying to integrate this class into my project from an example that just uses globals. How can I access variables of myGame class in the definition of new classes? Should I give up on my singleton approach?

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  • What is meant by Scope of a variable?

    - by Appy
    I think of the scope of a variable as - "The scope of a particular variable is the range within a program's source code in which that variable is recognized by the compiler". That statement is from "Scope and Lifetime of Variables in C++", which I read many months ago. Recently I came across this in LeMoyne-Owen College courses: What exactly is the difference between the scope of variables in C# and (C99, C++, Java) when However a variable still must be declared before it can be used

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