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• Why pass by const reference instead of by value?

  - by Maulrus

  From what I understand: when you pass by value, the function makes a local copy of the passed argument and uses that; when the function ends, it goes out of scope. When you pass by const reference, the function uses a reference to the passed argument that can't be modified. I don't understand, however, why one would choose one over the other, except in a situation where an argument needs to be modified and returned. If you had a void function where nothing is getting returned, why choose one over the other?

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• Android internet connectivity check problem

  - by Chaoz

  Hello, I'm new to Android development and working on an Android application that requires the phone to be connected to the internet, through either Wifi, EDGE or 3G. This is the code that I'm using: public static boolean isConnected() { ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE); return cm.getActiveNetworkInfo().isConnectedOrConnecting(); } I've also set these permissions in the manifest file: <uses-permission android:name="android.permission.INTERNET" /> <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" /> This works fine in the emulator running version 1.5 of Android when 3G is enabled, but it crashes when I disable the 3G connection. My application throws a null pointer exception when I call isConnectedOrConnecting(). Hope that anyone knows the solution to this. Thanks in advance!

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• Apply function to one element of a list in Python

  - by user189637

  I'm looking for a concise and functional style way to apply a function to one element of a tuple and return the new tuple, in Python. For example, for the following input: inp = ("hello", "my", "friend") I would like to be able to get the following output: out = ("hello", "MY", "friend") I came up with two solutions which I'm not satisfied with. One uses a higher-order function. def apply_at(arr, func, i): return arr[0:i] + [func(arr[i])] + arr[i+1:] apply_at(inp, lambda x: x.upper(), 1) One uses list comprehensions (this one assumes the length of the tuple is known). [(a,b.upper(),c) for a,b,c in [inp]][0] Is there a better way? Thanks!

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• Nullable types and ?? operator C# [en-US]

  - by ruimachado

  Nullable types vs Non-nullable types   While developing our C# projects its frequent the null comparison operation to avoid null exceptions. This simple operation is mainly coded using the "var x = null" code example inside an if clause. However not all types of variables are nullable, which means that setting a variable to null is not allowed in every cases, it depends on what kind of type are you defining. But what if there was an extension to your non-nullable type that would convert your variable types to nullable? This extension really exists. As I said before in C# you have nullable types which represent all the values of an underlying type, and an additional null value and can be declared easily using "T?", where T is the type of the variable and for example the normal int type cannot be null, so its a non-nullable type, however if you define a "int?" your variable can be null, what you do is convert a non-nullable type to a nullable type. Example: int x=null;     Not allowed     int? x=null;   Allowed     While using nullable types you can check if a variable is null the same way you do it with nullable types:     But what about setting a default value when a certain variable is null?   In this cases the c# .net framework let you set a default value when you try to assign a nullable type to a non-nullable type, using the ?? operator. If you don't use this operator you can still catch the InvalidOperationException which is throw in this cases. For example  without the ?? operator :     Using the ?? operator your code becomes cleaner and more easy to read and you get a bonus, you can set a default value for multiple variables using the ?? in a chain set.     That’s it,   Thanks, Rui Machado rpmachado.wordpress.com

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• Retrieving data from database. Retrieve only when needed or get everything?

  - by RHaguiuda

  I have a simple application to store Contacts. This application uses a simple relational database to store Contact information, like Name, Address and other data fields. While designing it, I question came to my mind: When designing programs that uses databases, should I retrieve all database records and store them in objects in my program, so I have a very fast performance or I should always gather data only when required? Of course, retrieving all data can only be done if it`s not too many, but do you use this approach when you make sure that the database will be small (< 300 records for example)? I have designed once a similar application that fetches data only when needed, but that was slow (using a Access database). Thanks for all help.

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• WCF net.tcp server disconnects - how to handle properly on client side?

  - by RoastedBattleSquirrel

  I'm stuck with a bit of an annoying problem right now. I've got a Silverlight 4 application (which runs OOB by default). It uses WCF with net.tcp as means of communicating with the server. The client uses a central instance of the wcf client proxy. As long as everything keeps running on the server side, everything's fine. If i kill the server in the middle of everything, i drown in an avalanche of exceptions on the client side (connection lost, channel faulted etc etc). Now i'm looking for a way to handle this in a clean and centralized way (if centralized is possible). The SL app has one central client object sitting in App.cs (public static MyClient Client { get;set;}), which gets initialized on application start. Any idea how to properly handle any connectivity problems on the client object?

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• Using the same modules in multiple projects

  - by Andreas Vinther

  I'm using Visual Studio 2010 and coding in VB.NET. My problem is that I've collected all the modules I've written and intend to reuse and placed them in a separate folder. When I want to add a module from the above folder to any given project, it takes a copy of the module and places in the project's source code folder, instead of referencing the module in the folder containing all the other modules. Is it possible to include a module in my project and leave it in the folder with all the other modules, so that when I improve upon a module, it'll affect all the projects that uses/references that module. Instead of me having to manually copy the new module to all the projects that uses/references the module. Right now I have multiple instances of the exact same module that i need to update manually when I improve code or add functionality?

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• Detect if PCRE was built without the --enable-unicode-properties or --enable-utf8 configuration switches

  - by Mark Baker

  I've a PHP library that uses a number of regular expressions featuring the \P expressions for multibyte strings, e.g. ((((?:\P{M}\p{M}*)+?)|(\'[^\']*\')|(\"[^\"]*\"))!)?\$?([a-z]{1,3})\$?(\d+) While this works on most builds, I've had a few reports of the regexp returning an error. Depending on Operating platform, the error messages from PCRE are: Compilation failed: PCRE does not support \L, \l, \N, \P, \p, \U, \u, or \X at offset n or Compilation failed: support for \\P, \\p, and \\X has not been compiled at offset n I know that I can probably test a regexp at the beginning of my code that uses \P, and trap for a returned error, then use that response to set a compatibility flag and provide a degraded (non UTF-8) regexp without the \P within the main body of my code based on that compatibility flag; but I was wondering if there was any simpler way to identify whether PCRE had been built without the --enable-unicode-properties or --enable-utf8 configuration switches. PHP provides access to PCRE_VERSION constant, but that won't help identify whether \P support is enabled or not.

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• php sessions and cookies

  - by gautam kumar

  when should we use session and cookies in php?please specify seperately their uses,pros and cons.

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• Using texture() in combination with JBox2D

  - by Valentino Ru

  I'm getting some trouble using the texture() method inside beginShape()/endShape() clause. In the display()-method of my class TowerElement (a bar which is DYNAMIC), I draw the object like following: void display(){ Vec2 pos = level.getLevel().getBodyPixelCoord(body); float a = body.getAngle(); // needed for rotation pushMatrix(); translate(pos.x, pos.y); rotate(-a); fill(temp); // temp is a color defined in the constructor stroke(0); beginShape(); vertex(-w/2,-h/2); vertex(w/2,-h/2); vertex(w/2,h-h/2); vertex(-w/2,h-h/2); endShape(CLOSE); popMatrix(); } Now, according to the API, I can use the texture() method inside the shape definition. Now when I remove the fill(temp) and put texture(img) (img is a PImage defined in the constructor), the stroke gets drawn, but the bar isn't filled and I get the warning texture() is not available with this renderer What can I do in order to use textures anyway? I don't even understand the error message, since I do not know much about different renderers.

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• Trouble creating a makefile

  - by catia

  Hi everyone! I'm having some trouble making a Makefile. Write now I just compile everything every time. Although, the professor is ok with that, I do want to get it working faster and to avoid unnecessary compiling. Here's what I have. FILES= p6.cpp SetIter.cpp Node.cpp Set.cpp CFLAGS= -ansi -pendantic -Wall -Wextra CC= g++ MakePg6: p6.cpp SetIter.cpp Node.cpp Set.cpp $(CC) $(CFLAGS) $(FILES) -o pg6 Node.cpp - node class Set.cpp - uses nodes. Friend of Node. SetIter.cpp - gets a set and uses a pointer to iterator through I'm confused with some of the depencies arising from the friends thing and the point of lib.o being included in the Makefile as some sites have. Any help is greatly appreciated. Thanks in advance.

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• How does Ruby's Enumerator object iterate externally over an internal iterator?

  - by Salman Paracha

  As per Ruby's documentation, the Enumerator object uses the each method (to enumerate) if no target method is provided to the to_enum or enum_for methods. Now, let's take the following monkey patch and its enumerator, as an example o = Object.new def o.each yield 1 yield 2 yield 3 end e = o.to_enum loop do puts e.next end Given that the Enumerator object uses the each method to answer when next is called, how do calls to the each method look like, every time next is called? Does the Enumeartor class pre-load all the contents of o.each and creates a local copy for enumeration? Or is there some sort of Ruby magic that hangs the operations at each yield statement until next is called on the enumeartor? If an internal copy is made, is it a deep copy? What about I/O objects that could be used for external enumeration? I'm using Ruby 1.9.2.

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• How to grab all cookies in Flash

  - by Leticia Meyer

  For a site I'm developing with a user login that uses cookies to store the session ID, a separate section of it uses Flash to provide content and such. Is there some way it can access the cookies that were set the by login? The name of the cookie will not the be same every time, as it is randomly generated, as well as its value. I then need to send the name and value of the cookie back to a page on the server to do additional stuff. Anyone know how to do this? Note that I didn't write the Flash interface, an the person who did doesn't know how to do this. Please help me, and thanks in advance!

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• Log4net 1.2.10 running on .NET 1.1 and 2.0 not compatible

  - by Daniel Williams

  I have old code that uses log4net version 1.2.10 targeted for the .NET 1.1 platform. My current code uses lognet version 1.2.10 targeted for the .NET 2.0 platform When I mix the old and new code all hell breaks loose. Code written today on .NET 4.0 and VS2010 can use the 2.0 log4net dll just fine. but if I put in the 1.1 version, it breaks. Conversely, the old dlls will break if I use the 2.0 log4net dll. I do not want to force my old dlls onto 2.0. Is there a good solution? I guess what bugs me most is that the log4net has the same version number, but I cannot fool my code and dlls into working with a single version.

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• How can I prevent ADO from creating multiple SPIDs?

  - by stusmith

  I'm working on an application that creates a single ADO connection and keeps it open for the lifetime of the application. I have connection pooling turned off. (Please ignore the fact that this might not be best practice for the purposes of this question). If I spawn a new thread and use the exact same ADO connection, it uses a new SPID behind the scenes. Is there anyway to ensure an ADO connection always uses the same SPID, across all threads? (For reference the application is VC++ using ADO via COM to SQL Server).

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• INSERT SELECT Statement and Rollback SQL

  - by Juan Perez

  Im Working on a creation of a query who uses INSERT SELECT statement using MS SQL Server 2008: INSERT INTO TABLE1 (col1, col2) SELECT col1, col2 FROM TABLE2 Right now the excecution of this query is inside a transaction: Pseudocode: try { begin transaction; query; commit; } catch { rollback; } If TABLE2 has around 40m of rows, at the moment of making the insert on the TABLE1, if there is an error in the middle of the INSERT, will the INSERT SELECT statement make a rollback itself or I need to use a transaction to preserve data integrity? It is necessary to use a transaction? or SQL SERVER it self uses a transaction for this type of sentences.

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• Android/Eclipse: Creating multiple builds with different com identifiers.

  - by Dave

  Hi, I have an app that requires two builds - one is a demo app, the other uses the same codebase but uses a flag to introduce different functionality. The identifier must be different each time (e.g. com.siteA.appA and com.siteB.appB). However it doesn't appear to be trivial to use the refactor functionality in Eclipse to change the com identifier - all references change apart from the "import com.siteA.appA.R" reference. Is there a way to create different builds with different com identifiers/app name within Eclipse? Thanks

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• Android dictionary application

  - by mawia

  Hi, I wanted to develop an application on top of a dictionary i.e. an application that uses dictionary as a part of it.Is their any dictionary application available in the market for this purpose?Application which come under GPL is preferable.Also those which uses local database instead of using network connection is preferable. If not,is there any dictionary database available in the market on the top of which a dictionary application can be developed which can then be used for said purpose? Hope I am clear. Thanks in advance.

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• HttpTunneling a TCPClient application

  - by user360116

  We have a custom chat application(c#) which uses TCPClient. We are having problem on clients who are behind Firewall or proxy. We know that these client can browse the internet without a problem so we decided to change our TCPClient application so that It uses HTTP messages to communicate. Will it be enough just to wrap our text massages with standard HTML tags and HTTP headers? We need a long lasting connection. Does keep-alive have a limit? Do firewalls or proxies have time limits for "alive" connections.

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• Recommend a local LDAP store for development

  - by Paul Stovell

  Our project uses an LDAP repository for storing users. In production this will be Active Directory. For development, we seem to have a couple of options: Install an AD LDS instance that everyone uses Install an AD LDS instance on every developer machine We're trying to keep the 'F5' experience as lightweight as possible, so installing things or relying on a central AD store aren't my favorite ideas. There are other LDAP servers, like Open LDAP. I was hoping there might be an LDAP server that simply talks to an XML file. This would allow us to store the XML file in source control and have something that is fast and works. Our nightly builds would still use AD to pick up any differences, but the hope is since we're using LDAP it should Just Work. Can you recommend an LDAP implementation that works well for zero-config shared-nothing development?

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• Making uppercase of std::string

  - by Daniel K.

  Which implementation do you think is better? std::string ToUpper( const std::string& source ) { std::string result; result.reserve( source.length() ); std::transform( source.begin(), source.end(), result.begin(), std::ptr_fun<int, int>( std::toupper ) ); return result; } and... std::string ToUpper( const std::string& source ) { std::string result( source.length(), '\0' ); std::transform( source.begin(), source.end(), result.begin(), std::ptr_fun<int, int>( std::toupper ) ); return result; } Difference is that the first one uses reserve method after the default constructor, but the second one uses the constructor accepting the number of characters.

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• Linkage Error with Inherited Class

  - by metdos

  I have static library and another program which uses it. In the static library If I define header without inheretence it works fine. class TcpCommunication On the other hand If I use inheretence with a QT class, class TcpCommunication:public QTcpServer I'm getting linkage error when I compiling code which uses this static library. >MStoDKAPId.lib(TcpCommunication.obj) : error LNK2019: unresolved external symbol "__declspec(dllimport) public: virtual __thiscall QTcpServer::~QTcpServer(void)" (__imp_??1QTcpServer@@UAE@XZ) referenced in function "public: virtual __thiscall TcpCommunication::~TcpCommunication(void)" (??1TcpCommunication@@UAE@XZ) What can be the problem? Thanks.

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• How to input data into user defined variables into MySql query

  - by user292791

  Simple Shell script echo "Enter 1 for month of March" echo "Enter 2 for month of April" echo "Enter 3 for month of May" read Month case "$Month" in 1) echo "enter establishment name" read a; mysql -u root -p $a < "March.sql";; 2) echo "enter establishment name" read b; mysql -u root -p $b < "April.sql";; 3) echo "enter establishment name" read c; mysql -u root -p $c < "May.sql";; esac done In this i have three other query files March.sql, April.sql, May.sql. i'm linking this in shell script . Example of .sql file: SELECT DISTINCT substr( a.case_no, 3, 2 ), b.case_type, b.type_name, a.case_no into outfile '/tmp/April.csv' FIELDS TERMINATED BY ',' ENCLOSED BY '"' LINES TERMINATED BY '\r\n' FROM Civil_t AS a, Case_type_t AS b, disposal_proc AS c WHERE substr( a.case_no, 3, 2 ) = b.case_type AND a.date_of_decision BETWEEN '2014-04-01' AND '2014-04-30' AND a.case_no = c.case_no AND a.court_no =1; I have to alter the .sql script every time. Is there any method to read the variables from shell script and use it in mysql. For example:- echo "enter date" read a #input date Now i have read a "date" and i want to use it in March.sql query in where clause. Is there is any method of using this variable in .sql query.

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• Subversion repository type

  - by hs

  How can I tell if a respository uses BerkeleyDB or FSFS?

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• Array.Reverse Algortihm ?

  - by ManojTrek

  What kind of algorithm Array.Reverse(string a), uses behind the scene to reverse the string?

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